3800 coolant leak - "repaired" but still leaking -

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e-dad wrote

Did you replace the "plastic upper plenum"? You've mentioned everything "but" it....and it's the most important piece you have to replace. The plastic upper plenum is what actually leaks. If you didn't replace it, don't drive it any further until you go get a new one and install it. You should be able to use the upper plenum to intake gasket that you just installed again with no problems.

That's what happens when the upper plenum lets go. The EGR tube either burns a hole in the upper plenum or warps it so badly that it will leak.

Another wonderful feature of this GEN II engine was a nasty habit of leaking oil from the rear main seal housing to engine block gasket.

Ian

"" wrote: > e-dad wrote > > Ok, First I count my blessings that I made it all the way to > 243,000 > > miles on my 1998 Grand Prix before it developed the dreaded, > yet > > expected coolant leak problem on the 3800 series II (non > Super). > >

Thanks for the info/advice Ian.

Kind of ticks me off. I mean the reason one would put the egr repair kit in is so they would NOT have to replace the upper plenum. However, if the thing is still warped or damaged beyond the egr pass through area, then it kind of makes the whole repair thing a moot issue and a waste of time and money.

I really didn?t want to buy a new upper.

For clarification:

1. There should be NO oil pooling on top of the intake. If there is, then the plenum is shot. Oil in there, also means water in the oil?

1. The only penalty I pay for not repairing the rear main seal housing gasket is a continual oil drip. I mean it should be ok as long as I keep the oil level up.

It just sounds like the rear seal issue would be more than I would want to tackle.

Rats.

Thanks again. I?ll have to make a decision before it gets cold here and the motorcycle is no longer a backup option.

Thanks.

Obviously, you must have done some research about this, but somehow you weren't told what really is the problem. The EGR tube in the original intake manifold is too large....it overheats the plastic upper intake plenum and as I mentioned before, it either burns a hole in the plenum or warps it. So the very least that you have to replace is the upper plenum. If you wanted to save money, you can "just" replace the upper plenum, as it takes another 50 thousand miles to burn/warp the upper plenum.

If you mean on top of the intake "once you take the upper plenum" off...then, yes.....you will see oil there...that is normal.

This is what you see when you take the upper plenum off and there has been a "bad" coolant leak.

Note: if all you see is oil in the same cavity that the green antifreeze is in...that's "normal".

Yep.

You have to remove the subframe and transmission....or it might be easier for the DIY'er to pull the engine out. You then need a couple of special tools to line up the rear main housing covering and install the rear main seal. Failure to use these tools will be a virtual guarantee that you will have another leak.

The leak is actually from the paper gasket between the block and rear main housing. The one piece rear seals rarely leak anymore. The paper gasket shrinks and splits and you get a good leak.

Ian

For what it's worth, most of the upper intake failures can be "repaired" without replacing either the upper manifold or the gasket. Simply remove the upper intake, tap the two coolant passages in the lower intake and install threaded pipe plugs. Reinstall and retorque per factory specs. (I've never actually seen a gasket failure on these engines, it's always been the upper intake itself). I believe that 3/8" NPT plugs are the closest fit. This will cure the coolant leak, but may cause a slight loss of cold weather driveability in very cold climates. It is a favorite ploy of the backstreet used car dealers.

Also for what it's worth, I did not use this method on my own '97 Bonny, which made the 130,000 mile mark before suddenly burning a hole through the upper intake via the EGR tube.

Which frankly makes this repair totally undesirable. Kinda like stuffing sawdust in rear ends.

Ian

stuffing sawdust in rear ends.

Ian

"" wrote: > For what it's worth, most of the upper intake failures can be > "repaired" without replacing either the upper manifold or the > gasket. > Simply remove the upper intake, tap the two coolant passages > in the > lower intake and install threaded pipe plugs. Reinstall and > retorque > per factory specs. (I've never actually seen a gasket failure > on these > engines, it's always been the upper intake itself). I believe > that 3/8" > NPT plugs are the closest fit. This will cure the coolant > leak, but may > cause a slight loss of cold weather driveability in very cold > climates. > It is a favorite ploy of the backstreet used car dealers. > > Also for what it's worth, I did not use this method on my own > '97 > Bonny, which made the 130,000 mile mark before suddenly > burning a hole > through the upper intake via the EGR tube.

So Steve, you are saying ?plug? the two coolant inlets that are adjacent to the EGR stove pipe in the lower intake?

I mean I understand the ?why? part, just identifying the ?what/where?.

Not my first choice as I DO live in one of those colder climate regions and I like the heat to work well. But it?s a consideration.

Dave.

adjacent to the EGR stove pipe in the lower intake?

I mean I understand the =92why=92 part, just identifying the =92what/where= =92.

Not my first choice as I DO live in one of those colder climate regions and I like the heat to work well. But it=92s a consideration.

Dave.