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1998 dleta 88 3.8 coolant leak

02-03-2008, 10:16 AM
I have recently inherited a 1998 Delta 88 LS with 61 k miles . It is slowlty loosing coolant . I do think that that it not internal yet but anticipate at least the upper intake problem . Has anything changed with the GM policy on repairing this under a "secret warranty" or am I on my own ?

I guess this is my DIY alternative - http://www.automotiveforums.com/t288707.html

Any other tips to R&R the fuel rails etc are appreciated (my Haynes manaul is pretty weak) .


02-04-2008, 08:51 AM
Welcome to your worst nightmare with this model and year of vehicle.

I too have a 1998 Olds 88 LS with the purported "one of the best ten engines in the world" - the now infamous 3.8 liter V6. That sucker comes with a composite plenum (engine cover) which incorporates tiny channels for antifreeze coolant liquid to flow through. The EGR valve then goes into that plenum and the heat of the gases flowing through it is too high for the composite material to handle so the material cracks leaking coolant into the engine's V and flooding the engine with coolant. When it happened to me, the engine would not start (had to get the car towed to get it fixed), but before that, I was losing about a half gallon of coolant every 100 miles or so!

The mechanic did a pressure test and everything seemed OK, so he figured it was a leak through the gasket between the plenum and the engine block and the leak was so slow that the heat of the engine evaporated it. So he replaced the gasket after cleaning up the mess inside the engine. Took the car home only to find a few days later that the leaking persisted. Took the vehicle back and he then replaced the plenum ($500!) and gasket again after cleaning up the mess in the engine a second time. Total bill was over $1,600!

A few years later, the coolant loss started again.....

These plenums are of poor quality materials unable to handle their task and GM should have recognized that and fixed this problem a long time ago. Instead they keep pumping out the same old crap destined to fail. I complained to them and didn't even get a response back! Aluminum plenums on cast iron blocks caused problems at the gaskets due to the different contraction/expansion rates of the two metals. So they went to composite, and now this! Why didn't they go to all aluminum engines?

To make a long story short, the second time around, I dumped some Prestone granular stop leak into the rad. That was years ago and it's still holding - my theory is that the tiny particles of stop leak are filling in the cracks in the plenum and stopping the coolant from leaking into the engine and mixing with the gasoline.

There are class action lawsuits in most States and Canadian provinces over this. Some are at the negotiation stage, and, I am not sure but, you may need to register your name to become a beneficial member of the legal action in your particular State or Province. Just Google GM class action and it should all come up.


04-17-2008, 10:06 PM
There is a kit out there that you can retrofit existing plenums with if not warped or melted. see...


I made basically the same thing 50k miles ago and it worked to 175K. Today, however, the power steering pump locked up, I think, threw the belt, and blew all the coolant out. Towed it home to deal with this weekend.

04-17-2008, 10:09 PM
Just a reminder there are all kinds of posts on AF concerning this issue. Just search for coolant plenum olds for plenty of reading.

04-18-2008, 07:07 AM
I wound up replacing the lower intake manifold gaskets with the new aluminum type and replace the upper intake manifold with the Dorman upgraded unit . It is rediculous that GM has gotten away with this . Many people have paid
$800-$1200 for this repalir .

04-18-2008, 08:49 AM
I purchased a 1998 Olds LS Vin k 3800 series 2 and the owner had a tap that we thought might be a lifter. The tap got louder and not long after I had to have the engine replaced because apparently he had the repair done to the intake manifold a little too late and coolant had destroyed the rod bearing. That little coolant leak isnt enough to usually cause much of a problem so it goes undiagnosed for a long time. Meanwhile there is a small amount of coolant mixing. *Otherwise* one of the best engines ever.

04-18-2008, 09:09 PM
I wound up replacing the lower intake manifold gaskets with the new aluminum type and replace the upper intake manifold with the Dorman upgraded unit . It is rediculous that GM has gotten away with this . Many people have paid
$800-$1200 for this repalir .

I don't think they have gotten away with it yet, although that's what they had hoped for. Class action law suits are expected to be successful. Should cost GM many $$$$.

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