The 1977 Mack R model is back and it's still overheating. Let's get to the bottom of it. Send us a postcard: Watch Wes Work P.O. Box 106 Fulton, IL 61252 Send us an email: mail@watchweswork.com
I post guitar playing videos from time to time and a guy told me I was playing out of tune. Replied with "No, I checked before and after recording". Got an answer telling me "Well yeah but you were out of tune in between!" Internet commenters sometimes...sigh.
No one ever wants to believe its a headgasket. I once told a guy he had a dead cylinder, which you could clearly hear while cranking. He said it was the idle air control motor... seems legit!
Considering the weird vehicle issues you seem to readily attract, as added sanity insurance before replacing the head gasket, I would: 1) Make sure it still bubbles with the oil cap removed (i.e. over-pressurized crankcase + cracked block combo). 2) Use a radiator cap adapter and pressure gauge on a cold start and see if it quickly hits and continues past 20+ psi. With the compressor/turbo system ruled out, a liner/head/fire-ring leak should be the only way left to give it that much pressure. And if the pressure just levels off at some low psi... 1) Figure out how to be less attractive to weird vehicles 2) No idea. But I'm sure it will make an interesting video. ;-)
Hey Wes. You might want to disconnect the coolant lines from the compressor and run the truck to insure the head gasket on the compressor is not the issue. Even though you disconnected the discharge line, the compressor is still trying to build air and could be leaking pressure into the coolant system through a leaking compressor head gasket. You can also drain the wet tank to see if there is coolant present. You can also check the intake air pre-cooler by bypassing it In the cooling system. I’m not trying to tell you what to do. Just trying to help out. I watch your videos every week and think you do an awesome job. I’ve learned a lot of tips and tricks from watching your videos over a few years and its made me a better mechanic. Thanks for the great content and knowledge.
there is no coolant going through the head gasket area on that compressor. you can install stand pipes and fill them while running but its much easier to just pressure the intake of the air compressor since they are just reed valves
Compressor head gasket can cause some real problems. I had one go bad and backfill the fresh air supply line to the compressor which loaded the intake manifold. Starting the truck back up to pull it around into the shop bent the number 6 connecting rod. Learned my lesson quick on that one.
I like your theory about the gas bubble. My first thought while watching the temp needle drop is that NOTHING could take heat out of the coolant that quickly. All I could think of was some sort of intermittent restriction that blocked all flow, then allowed near-room-temperature coolant to suddenly flood in.
Actually, my first thoughts were to check to verify that the gauge is indeed working. Does the engine smell hot? You should be able to smell and feel the difference between 180º and 220º with the hood open, and perhaps even closed.
I’m thinking either a flakey temp gauge or a bad thermostat to start with. If it’s making cooling system pressure stone cold, & if it was setting off the Co2 tester then that’s bad news.
Perhaps you could do a reality check on that test fluid with the actual tailpipe exhaust of the truck too, just to have a better-controlled reality check that the actual combustion gasses from that truck would trigger it. Of course it should if human co2 does, but it helps rule out some weird variables/possibilities I suppose
The glove radiator cap was a classic move. A couple of taped down fingers could have summed up the issue. I always enjoy your content and sense of humor. Keep posting and I’ll keep giving a well-deserved thumbs up.
WES should have super glued the correct fingers down on the second take,THE video would have gone viral,at least as far as mechanics go.haha always enjoy his vids.
That truck is what is known in the Mack world as a "Pedigree" unit. Which means it's all Mack. It should have a gold bull dog hood pull on the hood as well. That truck is in great shape for it's age.
Its a head gasket, my father had a 1979 R model with a mack 285hp that did the same thing, we even used the same combustion gas tester with the same results, we replaced the head gaskets and had no problems with it afterwards.
I know I'm not a full-time mechanic but I've ran into the same problem had to rev it up to simulate a load and the test actually worked then. It ended up being a cracked head that only showed up under pressure of a load like driving. Good luck and keep up the good work
That was what I was thinking, under load the leak would open up and allow the pressure from the leak to stop the coolant from flowing. Remove the load the leak would close up and this would allow the cooler coolant to flow again.
Man I been trying to track down an issue similar to this on a 6bt for awhile now. I've tried the chemical but I can't get much pressure on the system sitting in the driveway just can't get the heat in the motor. I can drive it to town just easy cruising without much issues but once I lay into the throttle and get the boost up it starts pushing coolant into the overflow. And by the time I get in the driveway to pull the cap and try setting the tester up it's running normal and no pressure in the system. The only time it seems to start running above normal temp is when it pushes enough coolant out to do so. Pretty sure it's a head gasket but I was hoping I would have been able to positively diagnose it before ripping into it.
@BreatheScotland I had bubbles the first time I noticed the issue when I got home it was pure bubbling in the overflow but since I bought the test kit the three attempts I have tried I couldn't get it to bubble just signs of my reservoir level going up when I get it in the driveway. I haven't had much time lately to try another go at it I need to tho.
@@kmrjeep Oh, jeez - I just had this mental image of your hood removed and you sitting up on the engine doing the test tooling down the road while someone else is driving. Sometimes my mind just goes a little wacky! 😉🔧👍
My uncle used to take care of a fleet of 1930s rolls royces. One of those would over heat like this mack, it ended up being a huge glob of solder in the radiator would rattle around restricting the flow. Flowed enough at idle to keep the engine happy but got screaming hot at cruising rpm.
My friend had a Dodge Intrepid that did that. Wasn't the radiator though, the water pump impeller cracked and held on just tight enough to move coolant at idle. As you gave it throttle, the impeller would slip and slow the coolant flow to a trickle.
Love when that old truck is on. Couple of things, I’ve found the newer dual chamber combustion gas testers that take the blue fluid for both gas and diesel are a little more accurate. Ive also seen where even when unloaded the compressors have still pushed air into the system. The best way I’ve found to test a compressor is hook shop air at the discharge line and pressurize the compressor head. See if the cooling system builds pressure. Great video as always!
I encountered a similar problem on an old Mk2 Golf (VW Rabbit in the US) back in the late 90s. The problem turned out to be a loose water pump impeller. At idle everything worked as it should but increase the rpm and the water pump impeller started slipping on the shaft. I wager a small donation to Wes' favourite charity that the head gasket is good
Hello Wes.The guys at "BMT" big mack trucks forum, will probably be able to point you in the right direction as to particular head gasket tests that can be run on on that Mack engine , which looks to be an 2 valve e-6 ,with 237 hp or maybe 285hp.Just food for thought.great video as always!
That appears to be a sweetheart of an old truck, would really love to know if they wind up fixing it. Even with pilot bearing and a head gasket repair it would seem worth it. Thanks for showing us arm chair quarterbacks this video and the diagnostic process.
After graduating college at FSU , I packed up my belongings into my Mazda B2000 pickup and proceeded to drive home to Daytona Beach in the heat of the Florida summer. Head gasket gave out at Lake City, truck was overheating. I got home by driving with the heat on full blast and stopping at gas stations to hose down the engine.
Post an update on this issue or further findings if you can. The air leak you hear on the drivers side is from the reversing relay bolted to the intake manifold. Works with the rack as a puff limiter. SOP. Appreciate the content.
Jim that puff limiter only got supplied with air when the maxi brakes were released so assuming the maxi's were applied when he was working on the truck, probably not the leak !
@@mikesautotruckrepairinc.cr5621 Agreed. The way it should be. This truck has been touched by several hands and I bet some creative plumbing has occurred.
Those old R, RD, CH, and U model Mack's are true work horses. We have several at my company that are still in service. To this day you can still go to most Mack or Volvo dealerships and get OEM parts.
In the VW TDI world it's very rare that a combustion gas tester correctly diagnoses a bad head gasket... false negatives the vast majority of the time. No one uses 'em any more as a result. Also common for the issue to only show up when the head is under pressure and wanting to lift under boost... all is well in the driveway at idle. Pressure transducer method *might* pick up issues under boost? Hopefully never have to find out!
Am a retired mechanic in Land Down Under. Had similar very difficult to diagnose issues in the last few years. One was a diesel 2.4 litre transit van which was losing coolant, but very slowly and very inconsistently. I tested it with the combustion gas tester and came up empty. Another workshop did the same a few weeks later and came up negative as well. Owners limped the camper vehicle 600 kms home and then were told by another workshop about Rislone head gasket sealer (made in New Zealand). With nothing to lose except having to remove the head on a quite difficult job, they tried it in the cooling system. It fixed the problem. Don't know if it was a head gasket leak or porosity in the head or the block but the Rislone sealed it for less than A$100 for the bottle. Within the last 8 months, had issues with my own Toyota RAV4 V6. It would push out coolant from the pressure overflow bottle and the tester showed nothing. Again it was inconsistent with loss of coolant and temp gauge fluctuations. However a subsequent radiator pressure test showed that the coolant system pressure would rise when system was pumped up to the rad cap blow off pressure of 21 psi and then the pressure would rise to about 28 - 30 psi, with the vehicle at just above idle. That convinced me it was a pressure leakage problem from most likely the head gasket. A full engine removal is the only way to work on the V6 heads and we found that the head gasket had a minor tracking leak between two cylinders - the triple layer steel head gaskets have very little tolerance and require the head and block to be extremely flat and smooth. My heads and block surfaces needed about 0.002" off each face to get them dead flat (I have a milling machine at home with a diamond tipped insert on an appropriate fly cutter) and with new head gaskets all has been right since. However the work involved in removal, dismantling, repairing, motor reassembly and refitting was a lot, lot of work. Also job cost quite some dollars. Just glad it worked out. But moral of the stories is that the combustion gas tester (like yours) does not always pick up the head gasket of other combustion gas leaks. In the end it is an educated guess, one you hope you get right. If anyone else has a better method of diagnosing these issues I would like to know - think Wes would too.
Great Video, Wes. It would be nice content to see the head gaskets get changed out. Appreciate you sharing your adventures with us. That is a sharp old R Model Mack. Really nice farm truck.
I think your diag is spot on. I've seen that on Subaru engines. Running the engine at a different rpm works the gas bubble away from the temp sender. I've also never had much luck with those fluid testers. Same experience, I can't think of a single time it's changed colors even when every other sign points to a head gasket issue.
I thoroughly enjoyed the last minute of that. I propose a Watch Wes Wheelin' channel where you just drive different things and I get to watch. All in favor press 1.
I never trusted that fluid. I remember getting into an argument with my boss. (This was on a gas engine in a car). I was certain the head gasket was blown and I wanted to do a leakdown test. He said, the fluid stayed blue, no head gasket leak. I was so sure that I told him I'd do the leakdown test on my time. If it was the head gasket, he'd pay me. If not, no pay. He agreed to the deal, I did the leakdown, and sure enough, antifreeze started overflowing. Did the gasket job and problem fixed. He didn't question me as much after that....(Don't get me wrong, good man, but a little pig headed...)
2:45 You sound like you're from some alternate universe where in The Blues Brothers, instead of driving in an old Dodge cop car, they ride in an old Mack. "This truck has a Mack motor, Mack suspension, Mack tires, and it was made before the mid 2000s so it will run good on regular sulfur diesel"
once was pranked he cut a foam ear plug in half at a 45 degree angle then glued it to the dog on the hood drove around for most of the day before i saw the dog with a hard on thanks for bringing back memories of the rig i learned hoe to drive
My first thought was water pump with nearly eroded blades ... higher rpm they will cavitate and do nothing, low rpm they will move just enough to keep an engine cool... BUT .. that doesn't explain the 3 or 4 psi (how much psi does a glove take to inflate) of pressure at the rad cap ... a definite head scratcher!!! Thanks for sharing 🇨🇦
Yep, tough call. I used to get good results with a similar tester made by Snap-On- Blue point .It only used one liquid and changed a different colour depending whether testing Petrol or Diesel coolant. Also I was fortunate to have a gas analyser for carrying out emissions tests on petrol and diesel vehicles as part of the yearly U.K. MOT test. Even then it was not always cut and dried.
What did the gas inside that glove smell like? I've had some tricky head gaskets to diagnose but I always like to take a whiff of what's inside the radiator or cooling reservoir and I can usually tell if it smells like combustion gas or not. A lot of people don't realize it but as a mechanic your sense of smell is actually quite valuable.
@@steveschumacher5470 yes if it's only a minor leak, I have also smelled plenty that you could definitely tell the scent of exhaust gas in there. This is very subjective though because everybody has a different sensitivity to certain smells so what works for me might not work for other people and after the 19 disease that started with a "C" a lot of people have fucked-up sense of smell to this day.
@@CPthetooladdict Your not smelling the CO2, you're smelling the other hydrocarbon by-products and or raw fuel. Diesel exhaust and gasoline exhaust have a very distinct smell prior to going through after treatment devices.
@BreatheScotland A crack in the inlet port won't introduce gas into the coolant at idle, there is no pressure to do this. It would be more likely to leak coolant into the inlet port. The symptoms this truck is showing is typically either a bad head gasket or a crack in a cylinder wall or combustion chamber.
If you have a multimeter that has thermocouple ability then place a surface mounted thermocouple on the temp sensor and see if in fact the temps are fluctuating as quickly as the gauge tells you they are. The temps of the gauge and thermocouple probably won't match but you should still see if those wild fluctuations are true or not.
170 sounds hot for that truck and cooling system on idle . I had a fleet of freightliners with cats and series 60s and they all idled 120-140 during extended idles and they all had temperature controlled fan clutches with overrides. That thing is idling 170 with a continuous fan . BLOWN HEAD GASKET OR CRACK
BTW if you did not already know you can recycle the test fluids. Put them in a almost sealed container that will keep bugs or dust out but still vent and just set aside for a couple days, it will turn back to original color and work for years.
I also learnt don't just pour the used fluid back into the original container, even after the colour has returned to blue. The unused fluid in the bottle doesn't like it. Retired mechanic in Land Down Under.
@@bobhudson6659 unless your fluid supplied to you is dif than in the US whatever container it was in got contaminated, It is just the color change due to CO2 and it does not hurt fresh fluid. Might have gotten some antifreeze during testing.
One of the things I like the most about your content is I learn every single week. I do the shadetree mechanic thing. Your depth of kowledge is very impressive. I had no idea you cold do that with an oscilloscope!
The glove inflated as soon as the engine started with the air compressor venting, that was conclusive to me Wes. Your testing is valid and you made the right call. Don’t trust the fluid test, as you and I have experienced, it’s a fool’s errand.
Please do a follow up on this . We’d love to officially know what the problem was. And yes a big job it would be but what great content for your channel !
I highly doubt that the temperature of the motor and fluid can rise and fall that fast. A thousand pounds of steel and 12 gallons of antifreeze can’t cool down from 250 to 150 in 30 seconds. Plus the truck doesn’t sound any different from being so hot it should seize to running at regular temperature. The motor isn’t boiling over which at that temperature it should. An IR temperature gun should help diagnose the problem but I suspect it’s in temperature gauge, sensor or wiring. The glove thing doesn’t really tell me anything, the radiator cap holds 12 psi or so and the glove probably is showing less then 1 psi to blow up like that, normal expansion of the fluid would account for that.
Thanks Wes! Can’t wait to watch you dig into it! (If you decide to) In my job, lack of definitive evidence really frustrates me too. But its not always available, and calls still have to be made.
Ran across an issue on one of our Hagie wheel pullers. Gauge would erratically just climb in relatively short time. Originally the gauge grounded through the housing were was mounted. Over time corrosion and rust caused a bad grounding issue. Cleaned up gauge and housing and added a direct ground wire to the stud on the back of the gauge. It solved that issue
I would be inclined to remove the compressor just to completely eliminate it as a possibility before condemning the head gasket. Thanks for bringing us along on this head scratcher! 😅
On my om617, i used the blue colored test fluid Oreilly provides... it turns yellow from exhaust gasses. It worked on my diesel, but note, that it takes longer for it to react with diesel emissions that gas emissions. Blown head gaskets on a gas burner took less than a minute... testing the diesel takes like 8-10 minutes
Hi Wes, I worked on aircraft for a while and we used to do a differential pressure test on each cylinder, where you pump a maintained pressure in and it will also tell you the output, ie how much it is loosing, this is helpful because if it’s loosing too much you can find out where by finding the air leak, if you did the same test it would pressurise the radiator if it had a bad head
I'm glad I'm not the only one who's been frustrated by that tool. Scanner Danner did a good video about them. I think of it like a COVID test - if it's positive, assume you've got it, or your gasket is blown. If it's negative... well... could still have it, or have a blown gasket. You made a good point though that it's probably better to have false negatives than positives. Thanks for the video.
Hey Wes, just wanted to say I love your videos. I like the ones on machine work also even though I can’t do it it’s still interesting to watch machinist work. Best of luck with your journey.
Hey Wes. Thanks for the video. I can sympathize with you on the struggle of diagnosing gas in the cooling system. I recently had a 2020 model year Hino with a J series Diesel engine with the same symptom. Did similar testing to you and replaced head gasket. Same symptom existed. What ended up being the cause was the water pump sucking air into the cooling system through the weep hole. One of the more bizarre things I have seen as a mechanic.
Great video 👍🏻. I’ve never had any success using that combustion gas tester either. All it did was prolong my diagnostic time on the 2 engines I used it on. Both had blown head gaskets. After the second one, I quit using it.
In the past I've used a lisle coolant filling funnel and placed a household CO detector in it. Then cover with a grocery bag. If the alarm goes off you know its a leak and it can be a bit more sensitive when testing for CO vs CO2.
Wes I just wanna say I can not do collage for mechanics but when you teach me stuff I learn as much as I can. I'm not too smart but I am a good mechanic. Thanks for teaching me stuff.
Gold Mack! All Mack throughout. She’s a peach. Not just the Canadian trucks had the twin filters, the Mack engine with the tip turbine had a twin inlet too.
Do love your content. I also wish your content was longer and more frequent. But I understand why that’s easy for me to state and harder for you to do.
I picked up a MASSIVE engine and gad analyzer a few months ago at the scrap yard for about 4 cents per pound. I don't remember exactly but I know it was near or over 500 lbs. I don't work in this type of stuff but I couldn't stand to see it get crushed. I kept all of the test leads..... Of which there were nearly 100 pounds of complex purposefully designed test leads and probes. they're definitely something I will use or might come in handy with my day-to-day work with metrology equipment. (And all sorts of weird industrial stuff) I was actually super impressed at the test leads and custom probes (some of which were manufactured by Hewlett-Packard specifically for this company)... Even the little barcode scanning pen and book was super cool. Obviously as a photonics nerd the most interesting thing to me was the internal module... Of which weighs about a hundred pounds and is the size of a 50-gallon drum. It uses several optical mechanisms and techniques for measurements... Which are so fascinating and interesting. I can't even imagine all the crazy things it could do. I fell down the rabbit hole on some forums discussing the repair and restoration of them... I just had to stop reading. It's all Way over my head. Unimaginable how much engineering went into. Similar to why I enjoy specializing in testing metrology equipment so much. It is high art. I just couldn't stand to see the thing get trashed.
Reminds me of the mess we went through trying to find a coolant leak in an old CAT 3412 in a 500kw generator. Starting getting some coolant in the oil, but they weren't sure if it was a head gasket, or a cracked liner, downside was in order to fix it, they'd have to tear the engine half apart and due to EPA regs for generators like that it would have to be brought up to higher emissions standards if a major rebuild was done. Being the generator was 30 plus years old and rebuilding the engine would still leave the rest of the genset that age, it made more sense to pull it and replace the entire unit. Due to much smaller loads we replaced it with a 300kw Cummins unit for not a lot more than Cat gave us as quotes to rebuild the old one. I gather that 3412 was sold for reman as they are popular in marine and certain older trucks. Sometimes the repair just isn't worth the expense.
Man those 3412 and 3408 were such junk. At least in NG configuration they were just awful and ate heads for breakfast lunch and dinner. Hodge podge of parts from the CAT scrap bin. We dropped that junk and use cummins as well. Much more reliable and cheaper parts. Cat has the big HP market dominated but small and mid HP cummins is not a bad option at all
@@melvingibson4525 Yeah, the quote from Cat for a new generator same size as the Cummins we bought was almost double the price, made it easy to choose the Cummins and it's been flawless now for 5 years. And the support costs me half what I was paying Cat for quarterly maintenance. I don't miss that old Cat, it would always fail to start when you needed it most even with weekly test runs, not once has the Cummins failed.
A/F Ratio for a diesel at idle is really high so the fraction of CO2 in the even the fully homogenious downstream exhaust would be small. Plus the head gasket leak is way out at the perimeter of the combustion chamber, which at idle is very stratified, the fuel is injected and burned near the middle, and at the few jiffys at 'peak pressure' (when the leak is active) you might push basically fresh air out from the edge of the chamber. That's my theory as to why the tester did not work at idle. (This Mack need a head gasket or more...). Thanks for the content!
Also I’ve used that lisle kit successfully for years. I would say its working right. Doing a motor swap on a 2014 town and country minivan. Tested positive for exhaust in coolant. What a bastard job !!! And 3.6 engine for that matter.
Another good video Wes! I always look forward to seeing the notification of an upload from you! Electrical and the cooling system are probably the most complex components to diagnose and repair. In my experience anyway!
I work here in calgary alberta long time ago for inland cement yes wes is real trouble where is trouble on this on mack engine trouble shooting take time but I think you got problems good work wes.
I've used a 2 gas Hamilton smog analyzer for several decades on gasoline vehicles to detect a leaking head gasket. Worked very well. But never had a leaky diesel head gasket. Plus it never occurred to me to use the analyzer on a diesel. That would be interesting if it did work on diesels.
Vehicles can be so much fun. It would be nice it they would fail in predictable ways but they don't. Some things only fail when they are hot, that one is fun, some are intermittent. Absolutely hate those. You are so good at troubleshooting problems yet even you get stumped sometimes. I really enjoy your approach to troubleshooting and I do learn from you. Keep up the good videos.
To check if it's the compressor you need to feed the compressor intake with Co2 then it would show on the tester, you could also pressurise the individual cylinders with a shield gas bottle carefully and a flow meter, or pull the head or valve on the compressor so it just cycles, the air could easily being pulled in by the water pump if the seals were incorrectly fitted a wipe of grease would stop it temporarily, as would running a water hose over the water pump ....
First truck I ever drove looked exactly like that one. '74 with a Mack 12 speed. That thing had a crazy power band for being a little engine. Dragging a belly dump, a guy with a '06 550 cummins couldn't catch me on the hills. Sometimes bad head gaskets present in such odd ways. Your theory about the temp gauge has gotta be correct because there is no way that coolant can drastically change that quickly.
Great video. Cummins has best directions on using "block tester" fluid. Temp needs to be steady with T stat open, run for at least 30 min. Not a perfect test, just another arrow towards the bullseye.
Nice job Sir. I sorta think your video has the answer lurking in it... You say it sat outside & idled for 45 minutes... and it seemed fine... DRIVING it, the problem showed up.... Some of these head gaskets only show up under a load, with the engine trying harder.... Like going up a hill, or something like that.... I still sort of would have thought that the gas tester would detect that though... This was many years ago, but there used to be paper test strips you would dunk in the coolant, and it would change colors for "combustion by products" in the coolant.... I presume nobody does that anymore??? The gas pumper thing is supposed to be better???? Your theory about the gas bubble is what we all used to think, years ago.... If your temp gauge is bouncing, it's seeing a hot gas bubble.... The glove blowing up is classic head gasket.... I don't know. Why is the test negative??? I do not know.... Obviously, it's not my truck, and it's not my money.... But if they've been battling this for 2 years plus, it's time to pull the head, if they really want it fixed.....
I’ve had the debate over the combustion gas leak detectors many times. I think a lot of people expect them to give an answer every time when it’s not actually possible. In my career I’ve seen head gaskets leak in every which possible way, I’ve seen them leak oil externally down the engine but no other issue, I’ve seen them leak oil into the coolant but no other issue, I’ve even seen oil and coolant coming out an exhaust but no contamination in the oil or coolant, I’ve also seen combustion gases go from the cylinder to the cooling system. Head gaskets can leak any which way or a selection of them. The combustion gas leak detecting fluid is only designed to detect one type of head gasket failure and that’s combustion gases into the cooling system, it cannot detect any of the other types of head gasket failure. Personally I see the gas leak detector fluid as something to assist me find the issue and not something I expect to identify the problem for me. I can also agree, I’ve done plenty head gaskets and not yet has my fluid detector confirmed one yet. Although all the vehicles were fixed after the head job. I guess it’s one of those tools that will occasionally be a winner, and for £25 it’s not too bad. Also I very much agree that it can be hard to call, you never want to do that much work for nothing.
Check the air compressor again on a shop air compressor if you open the drain valve and let all the air out. if the compressor is still on you will still have a small amount of pressure building in the tank not all of it can get out of the drain valve that quickly. I would disconnect the compressor first before calling the head gasket
Hey Wes. Let me spin you a yarn of an experience I had with a Subaru. It came in with a blown up plastic radiator tank. Not uncommon. I did all the tests in the world to make sure it was okay. Ran perfectly, didn’t pressurise the coolant too much. No indication on the chemical leak test. Pressure tested perfectly. No air leaking from a leak down test. Was sitting on normal operating temp just fine. Cooling fans worked yada yada yada. Cool did a radiator sent it on its way. Came back a week later with the new radiator blown up like a banana, totally gone bottom tank this time. Ok cool maybe defective radiator no issues. Replaced it road tested it for about 45 minutes. Right at the end of the test it over heated, once it over heated it would stay like that and it was pressurising the coolant. Oh shit. Long story short we took the engine apart and there was a crack in the block around half way up the cylinder. At no point would the chemical leak tester indicate an issue. Only issue was the pressure in the coolant like the Mack you have got. We ended up putting a second hand motor in it and it was okay after that. I also saw this happen with a cracked cylinder head on my bosses xr8 falcon. Would only play up after running for about 3 hours. I share your experience with trying to chase these issues. My money is on a cracked liner. If these things have them. Happy hunting.
Wes! Don't leave me hanging!!! ;-) Funny, just as started to say something about using a scope I was thinking Eric O or Schrodinger's Box would have a scope-based solution. No dice on this one. Oh, well, at least I'm thinking. I still say using an IR thermometer all over the engine might tell you something you don't already know. Another thought - stick a regular thermometer in the radiator cap hole and see what happens while it heats up. I just have this sneaky feeling this could be an electrical issue or the gauge is faulty. Maybe the wrong calibration or the wrong guts for another gauge. Thinking outside the box at this point!
@@Netherlands031 I wondered about that! Normally that says there’s a head gasket leak, so I guess that was the first direction Wes was going in. He did start there by trying to analyze the gas coming out but it was inconclusive because the tester didn’t show CO2. That’s why he went on to look for other sources of gases (air in this case) getting into the the cooling system from elsewhere.
Hi Wes, you just earned a sub!!! You nake great videos and handle all the issues so professionally. Plus, my name is Wes too, so you get props for a cool name! 😎 👍
Have witnessed the same temperature fluctuations on a 70's vintage GM V8 diesel grafted into a landrover with a 350 auto, the temp would rise and fall when the engine was working and just idling along. Had huge radiator capacity, did not loose water, it was set up for competition off road and mud plugging. Also a 428 in a Thunderbird towing a trailer with a Camaro racecar on it.
When I worked for dodge the old 2.2-2.5 engines would overheat like that and you would also lose the heat out of the heater, if you pulled over it would cool down and might be fine for the rest of the day. Think your on the right track. Thx
Interesting man! For me this test worked every single time when we were suspecting head gasket or some crack in the engine head. But usually we were putting some higher rpm during the test
Those older Mack motors are tough. a guy had a dump truck from 1979 had the off center cab forgot what model it was. it was so beat down he was using it on a piece of land and it didn’t have coolant in it the whole time he would run it for 30 min at a time a day. It had fresh modern shell oil in it. But he didn’t want to take the time to find the coolant leak. When he was done with it. My bud and I put straight water in it. And it didn’t seem to have any issues. Mind you this dump truck was probably worth a grand it was so beat down. But the motors seem to be the last thing standing. This was all going on in the hot SC summers
In scenarios as this I usually place an adapter on the radiator filler neck and use long hose to another container containing water and get my samples from it. That way you can visibly see and gauge/measure how much gases are being expelled. Best to do this on a cold start and up and observe to operating temp if possible. A plain low pressure gauge can also be installed to see if the pressure exceeds cap relief pressure. Yeah, I do not have much faith in those chemical gas checkers either. I believe your theory holds water on the head, gasket or block. This is just the way I have done it. Results may vary. 😂
Hold your horses on 1977 being close to 50 years old. That truck wasn’t the only thing born that year. I know it’s not the same exact thing but way back when on Audi TTs we had a similar issue. The impeller of the water pump would spin on the shaft not circulate coolant. It could sit and idle all day and not overheat. Took next to no time when you started to road test it and it would start to shoot up in temperature. Took a while to figure it out because those were driven by the timing belt. You could reach the impeller on those through the thermostat hole and would be able to spin the impeller. Just a thought
Mack . Worked on a 1974 I think . Back in the 80's had somewhat of the same problem. If I remember. Bad cooler, bad water pump and bad head. Oh dang I'm old.
Yeah, it's got to be something intermittent to do with the flow. The very large amount of water in the cooling system could not change temperature that quickly. Physically impossible. So it looks like the temperature gauge is getting water from a hot spot and then a cold spot alternately, so to speak.
Brings back memories. Back in the day Freightliner had an air controlled bunk heater coolant control valve. The valve would go bad allowing air pressure to slowly feed into the cooling system thru the valve and make you think had a leaking head gasket.
