Dodge 318 Magnum Intake Plenum Leak Diagnosis 

Cheers bud! Glad I could help you out! This is why I make these videos; to help people :)

Glad i could help :) that's why i made videos

Did you fix it? Mine does smoke horrible

Would you happen to have a part number for that?

chvydrptop the blowby doesn't come out of just one side. It pressurizes the entire crankcase, including up in the valve area. The PCV valve is to allow some blowby to recirculate into the intake and be burned. Inside your combustion area (after the throttle body) is all vacuum. When the plenum starts leaking, it creates a vacuum inside the crankcase, and starts sucking in oil, which destroys your catalytic converter, fouls your plugs, and can cause a horrible running condition if it gets bad enough.

Just coded my truck last weak, cyl 8 had 'excessive misfire', a quick change of a set of plugs cured the 'money light' but I dug deeper and located several articles on the 'plenum' leak issue, made an adapter and hooked up my vaccumn guage to the oil cap opening, showed 8-10# vaccumn. I don't drive the truck on a daily basis so I plan to remove the plenum this weekend and pull 'forensics', depending on what I find I will decide then on either an after market gasket kit or either the aluminum plate mod kit. I like the little truck and it is currently my 'project truck'. It was a sorce of therapy for me as I was recovering from chemo and radiation treatment, after DEFEATING stage 3 lung cancer, 5-1/2 year survivor so the truck has a special value to me, even though I concider myself a chevy guy, lol.....gonna keep the lil dodge around for awhile..lol.....

@@jamesmoore3346 Once you get the plenum fixed, it will be night and day performance. Power like it left the factory. I used a Hughes kit to fix it. 1/4 inch plate.

Yep,,, I'm going to coat the gasket with permatex aviation form a gasket on both sides before I install mine. Makes it oil proof. That is what we did for the crank case on my brothers shovel head Harley Davidson engine block, and after 15 years it still works great without any oil leaks.

@@francisbrackney2061 That sounds like a great idea. I wish I had done that to mine. Also, I should have put some blue loctite on the bolt threads. They come with some on them, but I think more would help. The suggested torque is in the inch-lb. range, so there is not much force holding that plate down. I followed the instructions in the kit from Hughes and as I said, it worked until it didn't. I haven't taken it apart to see what failed, but I expect that some of the bolts worked loose and let the gasket fail.

@@francisbrackney2061 That's exactly what I used on my brother's 5.9L Magnum plenum gasket. I cleaned up the factory bolts and cleaned out the threads on the intake manifold with brake cleaner. I used blue lock tight on the plenum bolts and followed the tightening sequence and torqued it down exactly. It's been about 1.5yrs since I replaced that gasket and he hasn't bugged me to fix it again. Hopefully it's fixed for good,cuz I don't wanna do it again. 😆 But I think I may have to replace it on my 5.2L ZJ soon because it seems to be using a little oil. I looked down inside the intake manifold and it looks like there's a little oil in it. I figure that the plenum gasket is probably bad,just not bad enough yet to make the engine run bad.

Id start with basic maintenance. Change the fuel filter first. I had an issue with starting my 3.4L swapped 4runner after it was up to temp, ended up being fuel related. Fired up perfect when cold, but it struggled after id run it then try to start it again. I ended up changing the fuel pump, and it was fine

using a magnet on a stick, put it down your throttle body and see if it sticks. if it does, you've got a steel plenum base, and the gasket is probably breached. if your problem is only at 3k ripums or higher, it could be rings. check for vacuum in the crankcase like i show in this video, and go from there :) if you dont have vacuum, id suspect bad rings or something else.

I would do a leak down test on your cylinder heads, you could have multiple things going on.

Have a 98 doing the same, cloud of blue smoke when revved so high, you ever figure it out?

Id imagine an aftermarket intake would offer that option...

did it smoke at start and whenever you drove it smoked even more?

@@Toothless69420 mine does

@@marcovalle9410 same here still i think its the headgaskets

Our don't smoke. But has a rpm surge, and it misfires below about 2500 rpm, , just basically runs like a engine with a vacuum leak. Only I could never find any external leaks. The exhaust also has a strong odor of nitrogen like it is running too lean.

Jorge Bustillos security needs to be reset. The security systems on The 1st gen grand cherokees (ZJ) have a fuel system cut off for security. It’ll let it run for a second and then kill itt self. If you have the factory key or a key that works with the driver door and rear hatch, instead key into the hatch and cycle lock to unlock 3 full times and that should reset you’re security. If that doesn’t work, do it with the drivers door/ passenger door if it has a lock cylinder. I have a 96 with a 318 I fought those problem for a long time before I figured this out! Hope it helps!

mopars23 any transmission issues? Your lockup solenoid might be acting up? Does it just sputter and die, or bang and die?

bang and die,i can move it but it bucks.

mopars23 sounds like a transmission problem. Id guess theres an issue with your lockup solenoid. You have the 46re in your truck? I cant remember which wire it is, but you can cut it and it will disable your lockup. If that is not the issue, then its a simple case of reconnecting the wire. Ill see if i can find out which wire the lockup is.

i meant 98 but i do have a 97 parts truck.how would i know if its 46re? it has 2 driveshafts.thanks so much replyin back

mopars23 the lockup solenoid is the orange and black wire going into the connector on the driver's side of the transmission. If its 98 it will definitely have the 're' transmission. That would be the electric controlled trans. The 'rh' is hydraulically controlled.

if you have the steel pan, and you see oil or oily residue on it from the inside, id be willing to bet that the gasket is breached. when that gasket fails, it creates a vacuum inside the block and sucks oil into the intake.

@@analog56x Oil inside the Pentium, can also be a result of a bad Pcv too.

a line of engines produced for a decade.

Magnums are what terrorized you grandpa back in the day

Rofl, you obviously didnt watch the part where i said it was temporary to aid in diagnosis :P oh well, your loss.

@@analog56x not losing much. Your truck is an abortion

@@BlackCatFever2011 haha, i know, thats why i got rid of it.

@@BlackCatFever2011 but while you're out here taking shots at people, post up your truck bud. Easy to rip on someone when you're hiding your pos.