3.8L Engine, Loss of Coolant,No Visible Leak

I had to to fill my coolant reservoir a little each week. It was getting worse. There were no visible signs of coolant leak.

Additional Symptoms:
Power bog when making sharp turns
Accelerator pedal would stick slightly when starting car
When starting car it woukld run rough at begining, then smooth out
No white smoke out of exhaust

Problem solved:
The plastic intake manifold leaked coolant into the engine. There is a hole in the plastic manifold, where the EGR exhaust gases are routed through the manifold. With time (80K to 105K miles) the hot pipe containing the exhaust gases will deteriorate the plastic intake manifold, making in brittle and crumble. The deteriorated plastic area along the EGR pipe has resulted in a coolant leak. The plastic manifold has a coolant jacket near the throttle body. The coolant pooled in the lower manifold areas. The coolant entered my cylinders and caused the car to run rough and set the check engine light.

What a mess. I had to buy a new manifold and gasket set. Not once but twice! I hope GM Engineers are reading this. Once at 100K miles and then the same problem happened at 195K miles.

Start by taking off the alternator, brackets, fuel rail, plugs, wires, electrical connectors, and EGR Heat shield. Raise the plastic manifold a few inches to remove the bottom two nuts holding the throttle body.

What an experience! Not once, but twice. I'm getting to be a real pro at it. You also must take out all the plugs, they will be carboned up. Also blow air into the plug holes of each cylinder to bnlow out collected coolant.

I hope my experience will help others because it has been a real experience!

I'm a bit late here, but.... you can fix this with a short length of copper pipe (about the same O/D as an old craftsman 5/8 socket) and some JB weld. Mines been fine for nearly a year of city driving.

Thanks for the information. However, after all that work removing the intake manifold, I don't know if I would trust an adhesive in the problem area. Both times the plastic manifold material in the area where the EGR tube passes through was completely brittle and crumbled. You can easily see holes through the plastic wall where the plastic deteriorated allowing coolant to enter the intake.

In my opinion, this is a major design flaw. I would like to see GM reimburse me and other car owners for this problem. We have hot exhaust gasses passing through a metal tube in contact with plastic. How could they think it would not deteriorate over time?

Thanks for the information. However, after all that work removing the intake manifold, I don't know if I would trust an adhesive in the problem area. Both times the plastic manifold material in the area where the EGR tube passes through was completely brittle and crumbled. You can easily see holes through the plastic wall where the plastic deteriorated allowing coolant to enter the intake.

In my opinion, this is a major design flaw. I would like to see GM reimburse me and other car owners for this problem. We have hot exhaust gasses passing through a metal tube in contact with plastic. How could they think it would not deteriorate over time?

It is, in fact, a metal laden epoxy. There is, also, a kit sold for this specific purpose that does the same thing. It's important to note that the epoxy isn't what's butressing the plastic, it's the copper tube that fits snugly within. The epoxy merely prevents seepage and holds the pipe in place. I know about the plastic (composite) and had pictures at one time. GM has no interest because this failure is obviously a post warranty item and the car isn't guaranteed not to fall to pieces immediately after this period. There has been insufficient customer backlash to prompt action and newer models do not suffer from this mode of failure.

Thanks, your information is helpful

Wiseowl,send (hansnet) a private message and ask him for the artical on the upper plenum kits, good luck

Wiseowl,send (hansnet) a private message and ask him for the artical on the upper plenum kits, good luck

Who wants to spend eighty dollars on patching their ugly (on the inside it gets BAD) plastic intake? A new one is only fifty dollars more. If you'd rather not spend more than a few bucks for a temporary fix go here:
http://ironlizard.blogspot.com/

Thanks, your information is helpful

Wiseowl - I guess luck is with me; my leaks are external. Where did you get the plenum gasket for the upper intake manifold? I haven't found a source other than NAPA.

Wiseowl - I guess luck is with me; my leaks are external. Where did you get the plenum gasket for the upper intake manifold? I haven't found a source other than NAPA.
Autozone carries them as 'intake gaskets' :) Check online for the part number. They're felpro and quite good.

Autozone carries them as 'intake gaskets' :) Check online for the part number. They're felpro and quite good.

Thanks sideshowbob. I checked AutoZone and the part isn't available yet. Advance Auto Parts has them by FelPro also. Whoever designed that system should be put on the unemployment line. It would make more sense to have 2 separate gaskets so that the manifold wouldn't have to be removed. I may as well get used to it because I now have both 3.4 and 3.8 Olds engines to maintain.

Thanks sideshowbob. I checked AutoZone and the part isn't available yet. Advance Auto Parts has them by FelPro also. Whoever designed that system should be put on the unemployment line. It would make more sense to have 2 separate gaskets so that the manifold wouldn't have to be removed. I may as well get used to it because I now have both 3.4 and 3.8 Olds engines to maintain.


Which is having the problem? The Olds 88 (3.8) has a two piece intake that uses two seperate gaskets, and autozone did have mine (both!). Tell me more, I think I can help after dissecting mine and various others. What year, specifically?

Edit: Crap, you're right! They must have stopped selling them since I patched mine together, carrying only the lower set. Good luck with that and be careful of the plastic elbow on the lower intake, easy to break and irreplaceable (Well..... I had a quickfix for that too but let's hope you won't need it!)

Hell, while I'm babbling away: If you're experiencing external leakage between the upper and lower sections your problem might be warpage in the plastic or (god forbid) aluminum half of the damned thing. A good straightedge and a feeler guage will be just the ticket, there should be a max allowed warpage number in the manual, if you have it. If you don't, you'll want one quick! To check the plastic one, well I lay it on a table :)

Which is having the problem? The Olds 88 (3.8) has a two piece intake that uses two seperate gaskets, and autozone did have mine (both!). Tell me more, I think I can help after dissecting mine and various others. What year, specifically?

Edit: Crap, you're right! They must have stopped selling them since I patched mine together, carrying only the lower set. Good luck with that and be careful of the plastic elbow on the lower intake, easy to break and irreplaceable (Well..... I had a quickfix for that too but let's hope you won't need it!)

Sorry for the confusion. The vehicle I just started working on is a 1998 Olds 88 Royale LS with less than 70k miles. Being that the leaks are external I wouldn't have to remove the manifold if it had been designed to be in two sections. Where the EGR enters could have been a separate small gasket and metal cover. Anyway, I'd like to get the fuel rail off with minimal disassembly but the injectors are set at different angles so it looks like I'll have to remove them first.

Thanks for the warning on the plastic elbow. Did you know that the small rubber "Y" that's in line with the fuel pressure regulator hose/s is a dealer item and costs over $7.00 ? Mine split and I just put a small clamp on it. (I think I put a dab of silicone gasket sealer or tape on the split first.) The car would die any time it felt like it and would re-start O.K. The trouble was in the regulator which allowed excess gas to enter the fuel rail. A scan indicated trouble with the forward oxygen sensor so I bought one. I could have saved a bunch of money if I had brought the car to the dealer when I got the recall on the regulator but I've had too many bad experiences with dealers and repair shops, especially body shops. The dealership put new parts in the regulator and it hasn't stalled since. That is one of the rare times that I didn't get ripped off. Probably because it was a recall and the car was repaired in the dealership driveway while I was standing next to it.

The 3.4 is in a 1999 Silhouette which I just acquired. It had internal leakage and the lower manifold gaskets were replaced before I got it, thankfully. It has a little over 100k and runs great.

Yea, I replaced on of the L vacuum connectors on the TB with a spark plug wire boot (the coil pack end)! All temporary, of course :P . These cars cost more parts-wise than my datsun. I had an Aurora, the plug wires were over a hundred per set.

It is my opinion, GM should pay to replace defective intake plenums. The plastic deteriorates around the EGR pipe causing a coolant leak into the intake plenum. The coolant puddles at the bottom. It could cause the car to stall when making a turn (dangerous at an intersection). When the car turns , it can cause the pooled coolant to pour into the intake channels. This can cause the car to bog or even stall. This is my opinion. Anyone have similar experiences?

I have a 1998 88 Olds, I had to pay to have the upper manifold replaced, about $1,200. It was sucking coolant into the cylinders and pouring out of the exhaust pipe, talk about a hair-raising experience, I almost crapped myself because I thought the liquid was gasoline. I replaced the PVC elbow twice, once I did it; second time had it done. Had a '74 Olds Cutlass that did the same damn thing! Now, my 88 blows coolant when I start from cold, and my 'check engine light' comes on intermittently. Please help!

You'll have to get a leak down test done or tear it apart. Start with the upper manifold, inspect it and the gallery under it carefully. Any water on the plugs? Are they all nice and clean?Maybe just one or two are? Need more information.