You are correct about this being a common 3800 issue. Dorman makes a kit to fix this. The issue is caused by the hot EGR gasses eroding the plastic. The kit comes with a new upper intake, gaskets, and a little metal tube that goes in the EGR hole. While you were doing this it would have been wise to replace the lower intake gaskets with Fel Pro Perma Dry gaskets. Valve cover gaskets too. There are also 2 plastic elbows on the front of the engine that crack and break. You can get aluminum upgrades cheap. When this is all done your engine won't leak anything again for a very long time.
Be careful with the Dorman kit. I am a technician who works at a reputable shop in STL and I have spent a week going through Dorman upper intakes and having to send them back because the gasket won't fit the intake properly. Not the gasket but the intake being the issue. I did eventually get a good one and it is made by Dorman and had a different part number than the first common one the parts store pulls for a customer. It was so bad that Dorman had gotten back to us to help them work on a fix for the issue.
As a mechanic I can honestly say I've never worked on an engine before with plastic on it like the 3800 series GM.... Until I bought a Buick LeSabre. Couldn't believe my luck, a car with less than 125k miles for less than $1200! Then the problems started. After replacing plastic elbows, radiator, battery, plugs, wires, pump, and hoses, I thought I was good. Then the problem the one you're working on here happened to mine. I know why it was so cheap now. Thanks for the video. Saved me some time and head scratching 😅
What were the symptoms? My LeSabre won't go past 40 mph with the pedal down, it idles rough, and it stalls. Brand new fuel pump and filter, brand new plugs and wires, EGR valve, PCV valve, MAF sensor, O2 sensor, and coil packs with ICM, none of it fixed the issue. Mechanic did pressure test and believes all gaskets are good so they want to replace the motor.
I’ve got a 1998 Buick riviera 3800 series super charged v-6 that had been sitting for 2 1/2 years so the first thing I done was replace the fuel pump then I started replacing sensors and I still couldn’t pass smog it’s just one thing after the other so it started missing so I started in the front checking the new plugs and on the #3 cylinder firing order the plug had been burnt off so I replaced it so my question is does anyone know what causes the diode on the spark plug to burn off??
The Ford 4.6s had issues like that too, the geniuses made the complete intake out of composite and hung a alternator off of it,lol,well the harmonics of the alternator spinning and the million cooling and heating cycles ended up making a 5 inch crack where the alternator bracket was hung on the intake,they way it would occur would be that you would be driving and maybe goose it a bit and all of the sudden every light in the dash would be on and you would have a sea of coolant under the car. The way they fixed this was they installed a aluminum crossover that bolted to the intake and hung the alternator off that, that fixed the problem after a million cracked intakes, ha ha ha, another bright idea they had was to get the oil and coolant millimeters from each other where the oil filter bolted by using this really weird angled plastic and rubber gasket that would fail after a few years and you would think you had a cracked head when it was just that gasket but its a bitch to replace. Gotta love car designers and what makes me laugh all the time is the people that think that "their brand " doesn't do this, THEY ALL DO. every car brand has issues.
Man....have been losing coolant for a hot minute now and didn't know why coolant was coming out the top of the motor. I've been searching RU-vid for hours on this gasket and that but none explained this issue. Took all night but now I'm sure I've found the right video. Thank you.
Great! I am experiencing a coolant leak in 3800 Series 2 engine (2001 Chevy Impala) with 68,000 miles. Worried about the head gasket. Had coolant leaking down the right/rear side of the engine, what looked like the gasket just below the lower intake manifold. After closer examination, it looks like it is coming out above the EGR heater hose going into the lower intake. Looks like it fits your description to a tee. I will be removing the plenum. I also understand there is a metal tube (EGR riser pipe) that can be added into the hole of the lower intake EGR port which extends up and through the plenum. This would prevent the same from happening in the future. Saved me some time I hope. !
Excellent explaining the problem. I'm getting ready to work on my 1995 Oldsmobile 88, same thing. Thank you for not having a filthy mouth in this video.
05 LeSabre...Appreciate your investigative effort...Gave me an additional inspection point before reinstalling the lower and upper manifolds. Your gift keeps on giving!
This is informative for sure. I cannot say I enjoyed it though because my room mate has a car with this engine and i am thinking, "when will the fateful day come when..." It is like hearing bad news you do not WANT to hear yet need to.
EXCELLENT video / tutorial Dave. Nice job indeed. Many thanks for sharing. I have a '94 Regal so this is related, i.e., an L27 family member. PS: I can see how the plenum was causing "plenty a problem", thus ... becoming a 'Plentum'. (^_^)
Do not use a salvage plenum for this repair unless you are going to sell the car, thereby passing the problem to the next owner. The salvage part will end up in the same condition, probably a lot sooner than the original did. As noted, this is a VERY common issue on the 3800 with the plastic intake. The cause of the problem is hot exhaust gasses going through that hole from the EGR. It literally melts the plenum. An after market kit replaces the plenum with a redesigned part and an aluminum insert that goes in the engine block which protects the plastic from hot exhaust gasses. Buy the after market kit for a permanent repair.
I've seen in manuals 3800s with an aluminum intakes plenums for the same year as the plastic ones. So that's a series 3 motor? And they swap over to a series 2 without any hassle? I'd appreciate any info on this please....
Besides the adapert plate for thottle body your factory air box will not fit very well with the aluminum one idk why no one has made an aluminum one for the series 2 engine
Thanks for taking the time to make this video. We are a GM family and with my four daughters and now the grandkids are getting cars I think this newfound knowledge will come in handy.
I just had the intake gaskets, thermostat, and water pump replaced. Drove it home from the shop no problems. The next day (Saturday and shop is closed until Monday) it started overheating and lost heat in the cabin. So I topped off with coolant and tried to bleed it. Left coolant all over my driveway and can’t find where it’s coming from. Add some more coolant and make it 18 miles where the shop is this morning. Parked it and handed them the keys while coolant leaks on the ground in front of the showroom. I’m sure they’ll make it right but it’s extremely frustrating and expensive. On the other hand I’m sure management is loving a brand they sell leaking coolant all over the ground in front of the showroom window where customers walk in and out. Btw it’s a 2006 Buick LaCrosse 3.8L series 3, well maintained and cared for.
*UPDATE* they took it back for another two days and replaced the radiator cap. This morning I found a puddle of coolant again after getting it back the second time. I noticed a bolt on the upper plentum wasn’t tightened. So I’m taking it back AGAIN. So far they’ve had it six days all together
You're video is GOOD and informative.... My mother was southern, she said "warsher", NOT washer. I dunno why, but in school, in spelling class, I spelled washer, "warsher", and was told I was spelling it wrong because I was pronouncing it "wrong"... I still SAY "warsher". PLENUM.... NOT PLENTUM... There's no T in the word.... Say "PLENTUM" all you want, but I now know my spelling teacher's pain, and my own hearing it mispronounced quite regularly.... GREAT video otherwise. :)
I have been having a leak on the same side of the motor. replaced thermostat and gasket and still leaking over there. I think I will be tearing into this project and see if mine is the same. Great video, very well detailed
This guy put a used stock manifold back on!!!! The original gm intake is the issue. The aftermarket manifolds fix the failing issue with them failing. Once you put a new fixed manifold on with new aluminum lower intake gaskets that motor is good for ever.
Are the series 3 known for this too? 2008 Buick Lacrosse. No visible leak, coolant loss is extremely slow, and car drives great, besides a rough start sometimes. Otherwise no rattling, vibrations, etc.
Also I want to add the intake on the left is a original part the one you have from the salvage yard is the problem solver one (Dorman) also I'm surprised you didn't replace the lowers? If not you Will eventually as well
I had a '92 Buick where that whole manifold was metal. Then later on the Series II 3800 noticed it was plastic and did have a coolant leak issue that was mostly gone by the time I replaced the radiator but some coolant did slowly disapear. Now I have a Series I 3800 car again but it is a '93 and unfortunately it has the damned plastic manifold. Tiny bit of oil found in the coolant but it runs almost too cool. I suspect the plastic manifold might be to blame. Would love to find a '92 car with the metal manifold as it's the only year of the Series I with it, though perhaps the earlier 3800s would have the same one.
great video. very informative. thanks for your help. one question... did you ever dream of putting a fender cover or a towel on the trunk lid of that car so you wouldn't scratch the damn paint???
I've an '04 Lesabre with what may be the same problem. Started with those junk plastic heater hose elbows on that piece above the water pump (the main structure for mounting the alternator). Replaced those with the aluminum ones, only to have it blow a leak now somewhere under the front, under the exhaust manifold. I suspected a head gasket, but I don't have any problem with white smoke, just doggy performance.... wonder if I'm not getting coolant sucked into the manifold? I can't see down there, and it's fucking winter now, no shop, no garage.. Ready to just find another $900 Buick...lol (But then I'll be replacing the plastic hose again, probably plus this problem, plus probably head gaskets and coil packs, and mass airflow doohickey, and the tail lights will be full of water...etc etc
Christian is 100% correct, its PLEN--um. Not PLEN-TUM. Good video though--why on earth would you mess around with junk yard plenUMS when you can buy a new one with steel sleeves for under 100$? Then you never -ever have to change this again.
Could I do a simple reroute/bypass of water rather than replace plenum? What does the plenum heat matter as water passes by? Yes, an unautherized mod. What do you think, Workable?
I have owned 30 of these cars from repair and resell or repair and drive and I only had 2 with blown head gaskets why because of the intake gaskets the owner went too far on it I have also never had to replace a timing chain as well I had to replace EGR tube, lower intake, and upper intake including intake plenum crank sensors ignition control modulator valve cover gaskets coolant elbows, because factories are plastic Napa, are aluminum really all common 3800 issues also the intake gasket thing was a common fault in 1996 simple because of dex coolant because nobody maintains their radiator fluid that simple and in the end with dex coolant becomes corrosive switch, in the end, result is what gasoline does to foam slowly just eating at that gasket that's why a lot of people flush their entire cooling system and run regular green antifreeze switches non-corrosive even if you go over or you don't maintain it regularly now 1995 and older all used the green stuff from factory so u didn't have intake issues as common #dexcool been pissing gm owner off since 1996
Hey i have 06 lacrosse 3800. Car overheats. Changed leaking elbows. Changed thermostat. Flushed radiator. I can now hear water behind dash while i drive. Could this be the issue?
I have a 95 buick Riviera supercharger that is having this exact issue. Exactly what parts do I need (i was using captions and it said plenum?) and Were the parts expensive?
Hey guys!!! I've got a 99 Regal with the 3800 series 2 motor. What mileage are you guys noticing this intake plenum gasket problem happening at? I've got 146,000 on mine. Thanks.
Lee Jones: you are due, keep an eye under the throttle body at the egr tube for leaks. I just bought one (ATP brand) to fix mine. Mines a 2004 with 198K not visibly leaking but hard starting. Good luck
Damn..yall doing better then me..2000 buick regal with only 74,000 miles..found puddles if oil coolant mix on top of engine..and most importantly..the dipstick!😢 800$ fix
@@edubb2491 you ain’t gonna believe this but at 374,568 miles (yes, I’m dead a$$ serious) the intake plenum still hasn’t gone bad, most likely it’s already been done by the older lady who had the car before me but I’m not sure on that, car runs fine and doesn’t burn/leak any fluids that I can see, but then again the oil is changed every 2,500-3,000 miles whether it needs it or not, etc.
@@leejones1072 daaamn! Well thats good..i gotta long ways to go with only 74000 and me too..i change oil every 2500..looken to get it fixed in a couple weeks..😢
every gasket was leaking at some point on my girlfriends current 3800 engine , those 90s gm engineers must have been doing too much coke or something. Heat and plastic aren't a good combo.
I've 2004 buick lasabre 3800 Series 2 coolant leaking between the back engine block and the transmission looking for advice on the best way to fix coolant before I just dropped another engine hopefully this can be an easy fix without a new engine
My buddy Radiator was had a crack and I replace the radiator for him and after he started it up is started smoking and had a small misfire but went away after a certain rpm he drove the car home which is about 20 minutes and he checked the oil this morning and it did not have a milkshake color looks like regular oil Could this possibly be the issue
Yeah. Unfortunately, he did. It's *ple-num*.......not 'plen-tum'. Reminds me of an idiot I used to know who would say 'al-blum' instead of album and 'trem-lo' instead of tremolo. I imagine this guy is probably good at math because in my experience, people who are good at math can't spell, pronounce shit correctly, use bad grammar and generally can't do anything BUT math with any degree of competence, including basic communication or socialization with humans.
Often the original parts on these cars are way better then new aftermarket ones. If you can find a low mileage donor, you can be ahead of the game. I think the cheap AC Delco in Canada was like $177 and one made to OEM spec is closer to $400 in Canada. You take your chances with offshore stuff.
My Regal went from running great to dying instantly. My wife started it up and it was rough so she parked it and called me. Couldn't turn the engine (#6 cylinder full of coolant). Pulled of the plenum and coolant all over the (lower) intake manifold. I am not a mechanic but the old plenum and gasket look good to me. I thought some of the plenum bolts were too loose. Will do a leak test this afternoon to check the head gaskets. Don't want to replace intake manifold gaskets if not needed. Does it make any sense that coolant would be on the intake manifold if there is an intake manifold gasket failure?
Ended up that the throttle body has a channel for the coolant and it was clogged. In the intake manifold, there are 2 coolant channels, one on each side of the EGR chimney. These channels are to source and return for the throttle body channel. Coolant couldn't pass through fast enough so it ended up spilling on the plenum. Fix was cheap.
@@edubb2491 I fixed it on my driveway in January when it was really cold. Some people thought my mechanic (me) was nuts. The tow cost me $60. The plenum gasket was cheap. I think I spent about $125 total. New plugs. Changed oil and coolant while I was at it. I made my own tool using my compression tester to verify that it was not a head gasket. I am not a mechanic. Never took any courses or training. I am handy and I enjoy this kind of stuff because I don't have to think too much so it is really relaxing. A mechanic would have told me the cost to fix exceeded value of car and tried to dissuade me from fixing it.
I checked the oil on my 98 Buick century 3100 the other day and there was coolant on the dipstick. The oil had consistency of water more than it did oil. Can you or anyone who reads this tell me what the issue may be. Keeping in mind I have already swapped out the intake gaskets on the motor to remedy the notorious dexcool issue.
okay so I agree that DEX-COOL becomes corrosive over time, but I still cannot figure out why GM put those 2 coolant holes up top like that to just barely touch the throttle body? that doesn't make a lot of sense to me, can anyone plz explain? I need to replace the upper plenum on my GM 3800 & now that I see this is one of the underlying issues, what if I just plugged those two holes up in the lower manifold altogether with like a spot weld & then grinded down everything to spec? thoughts?
In THEORY it regulates air temp on cold days. It will help cool the throttle body in the desert also. Its the 3 ps in ction right here. The workaround "problem solver" kit will do the same thing. Plastic will melt back until it leaks. 95 Bonny has had 4 intakes on it now. 1st one took 10 years to leak. Last one made it for 11 mos. Still under warranty. They will replace it one time from the original purchase date. If it didn't run so good and get descent fuel mileage I would get a new car. THis time Im trying some epoxy in the center hole since that is were it leaks first.
It will. For a time. My best time was about 6 years, Its still HOT air from the EGR and the plastic can not take it. Follow the direction. Stake it in really well with the RED Loctite. My Bonneville had 370K+ on her when she moved to my nephews garage. They do not make the aftermarket plenums as strong as GM did. My first clue was always white smoke billowing from the exhaust...
Plenum, not plentum. And that’s a very common problem on the series 2 3800s due to the plastic/phenolic plenum design. It’s not a matter of if it’ll fail, but when. I worked for Pontiac 20 years ago, and I can do an intake job on a 3800 in my sleep. The 3100/3400s were common for manifold base gasket failures, as well as the R motors in the trucks. Horrible designs. The series 3 manifold can be swapped onto a series 2, but it’s not a bolt on deal.
Ahhh i had an Oldsmobile with this engine if only all my mechanic friends didn't think it was the most reliable engine maybe I wouldn't have welded the pistons to the cylinders because it overheated Hella because my coolant leaked out. But hey all of them tell me that's crazy I was able to blow up the engine that could drive with a hole in the block
Maybe... Maybe not if the the cat was up to temp it would clean it out if it was straight water. But coolant is somewhat sticky when heated. This would make a great debate. Thanks for the comment!
Does anyone know if the 3.8 Gen 2 with aluminium plenum has this issue. Have an 06 grand prix that has a mysterious coolant leak. Thinking it is along the lines of this problem.
It's not likely that an aluminum plenum would be subject to the same failure here where the hot gases from the EGR melt thru to the coolant passages in the plastic plenum. The next most common source of coolant loss on the GM 3800 would be the plastic elbows that channel coolant thru the belt tensioner to the heater hoses. These can be replaced with aluminum elbows from the Dorman help rack part #47065HP and will last forever. Another weak point is the gaskets between the lower intake and the cylinder heads. Replace these with Felpro Perma Dry aluminum gaskets and your good to go. Head gaskets on this engine are almost bulletproof. These 3 are specific to the 3800 be sure to check all the usual suspects for all cars; upper & lower radiator hoses, heater hoses, heater core, radiator, cracked overflow reservoir, and radiator cap.
jared key I bought my 2004 Pontiac Grand Prix in November. It has an “aluminum plenum.” Is that original or do you think someone put the aluminum one there instead of plastic?
Just setting yourself up for a world of hurt. Need the 3rd party replacement kit which includes a new intake and a new EGR insulated nipple that shields the plastic from melting and warping again. It will fail again because the dill holes that designed this intake couldn't believe that plastic and heated exhaust gases don't do well together. They had an opportunity to redesign this from the previous model year because it had similar problems. They knew going in that they had to redesign the EGR so the plastic wouldn't melt. Those brainiacs redesigned the plastic only. Why they thought moving the plastic would fix the problem is beyond any common sense. Idiots in action. I found even though I bought the new kit the machining wasn't that flat and would leak when driven with hard acceleration. Had to flatten the gasket surface near the input and output coolant ports on the intake just a little. Used a new exacto blade with a scraping action with a light behind it to see I not go too far. Watch for that.
I have a 2001 Pontiac Bonneville 3800 series 2 I was loosing coolant wasn’t leaking ever did some research and replaced the plenum. Thought it was the problem my car was running better and smoother until I floored it and I started burning coolant like a mf smoked up the whole street. It was burning coolant but eventually stopped and before the plenum was replaced my car would start smoking once I got in high rpms or floored it. I replaced plenum and I think if I floor it again it starts to smoke again. So before and after replacement of plenum they both started making my car smoke up anyifreeze after I floored it so it is replaced and I come to the conclusion it’s not the plenum it’s something else much more expensive considering it was replaced and still smoked and burned coolant. Anyone know what could be the problem I’m not leaking antifreeze I replaced my upper plenum my throttle body is fine my whole car is fine until I floor it then it begins to smoke.
Used plenum is not a good idea, buy a new one they are not expensive a new ''Plentum'' only costs $50 Rockauto or $75 1a auto. putting on a used one is only asking for more problems.
