3800 hydro-locked, cont'd.

My son's Bonneville had about 80k miles when we did it as a preventive measure. Didn't see anything wrong with the upper. No melting at all. The LIM gaskets looked ready to fail, but who knows. We put in a new upper, since the original design is known to fail. Dorman from Amazon. They have it for $78. Despite some saying they always fail, you can see they don't. Maybe it has to do with EGR operation in different cars, and different circumstances causing a hotter tube. Make sure you use the metal-clad LIM gaskets. The originals are known to be failure prone. No experience with hydro-lock. You could have possible damage, but you're in far enough now to finish up and find out. What I would do is re-use the old upper to get it running so you know you have a engine that works. Then, if you are good, decide whether to put on a new upper or roll the dice.

--Vic

What i would have done (too late now for you) is drained the system coolant, and tried to start the car after you blew the coolant out the plug holes. if it ran without major mechanical "I am going to self destruct" noises, then replace the intake gaskets. If the motor was shelled at this point, you would not have waste the time on the gaskets or new intake parts.

If

I posted in here a few weeks ago about a 3800 with about 160K, which hydrolocked overnight after running normal the previous day. Removed the plugs and cranked it and it blew coolant out of both banks (which I figured ruled out a head gasket). Finally tore into it today and removed the plastic UIM, expecting to see it burned where the EGR pipe passes through he bore in the UIM. It appeared to be original since it had the larger diameter pipe which pretty much is in direct contact with the bore in the plastic. Upon inspection, I was surprised that I could see no evidence of any such charring or burning there... Thinking it had apparently been replaced before, I looked at the mfg date stamped into the UIM and it was March 1998 -- the same mfg date of the car according to the door sticker ('98 Olds Intrigue). UIM gasket looked unharmed as well. The LIM was covered with coolant, and I was going to replace the gaskets anyway while I was doing the upper. Upon removal of LIM the gaskets didn't look very straight or pristine and possibly been the cause of the problem. But to my untrained eye I find it hard to really tell by looking at them if they had actually leaked or not. Questions:

1. It seems unusual that the UIM doesn't show any wear or signs of failure, given the fact that they are pretty much expected to fail -- especially with that hot EGR pipe in direct contact with the plastic bore for 160K miles. Either my untrained eye doesn't know what I'm looking for, or there is nothing wrong with the UIM. Would it be unreasonable to simply re-use it -- perhaps with a smaller diameter EGR tube if available? Trying to save money here. Or could it have damage not visible from the outside or something like that?
2. Would the LIM gaskets failing result in the condition of hydro lock and coolant in both banks -- same as a failed UIM would?
3. Would most people feel confident ruling out a head gasket issue?

I had to wait to get the time to start on this job, as it appeared to be rather involved, as there is a lot of stuff needing to be removed on this car to get at the problem. And so after doing all that I was a little bit concerned that the problem wasn't what I was expecting at all. TIA.

***************************** Vic wrote: My son's Bonneville had about 80k miles when we did it as a preventive measure. Didn't see anything wrong with the upper. No melting at all. The LIM gaskets looked ready to fail, but who knows. We put in a new upper, since the original design is known to fail. Dorman from Amazon. They have it for $78. Despite some saying they always fail, you can see they don't. Maybe it has to do with EGR operation in different cars, and different circumstances causing a hotter tube. Make sure you use the metal-clad LIM gaskets. The originals are known to be failure prone. No experience with hydro-lock. You could have possible damage, but you're in far enough now to finish up and find out. What I would do is re-use the old upper to get it running so you know you have a engine that works. Then, if you are good, decide whether to put on a new upper or roll the dice.

--Vic

************************

I have been confident from the start that I don't have engine damage, because of the way it let go after it was parked. I drained the oil and there was NO trace of anti freeze in the oil. And when I removed the LIM there was no anti-freeze in the valley below it, so lifters, etc are untouched. I think that is pretty good advice, to re-use the upper and go from there. I would feel more comfortable and confident re-using it, however, if I could first install the smaller diameter EGR tube which is available in many of the upgrade kits (new UIM's). Does anyone know if these are available individually, or can you only get one with the upgrade kits?

In my experience., those gaskets look like shit and then they fail. I have seen some of the sorriest looking gaskets you can imagine that had not yet failed, but IMO they will, in time.

Vic wrote: "What I would do is re-use the old upper to get it running so you know you have a engine that works. Then, if you are good, decide whether to put on a new upper or roll the dice. "

***********************

Since the UIM-to-LIM gasket is the type that's about 1/4" thick plastic with the soft silicone insert in it for sealing, would you anticipate any problem re-using it as well -- if it looks OK? There was no such gasket included in the LIM kit I just bought, which would suggest to me that the old one is re-usable if in good cond.

I think you said your old UIM gasket looked good and the plenum looked good. I would use them just to get it running and make sure the hydro lock didn't kill the engine. No sense buying the new stuff until then if you get a good gasket seal using the old stuff. If the engine is good I would then put in the new improved plenum and a new gasket. The new gasket comes with the plenum. That's what I would do, because I'm that way. But the old stuff might work. I just don't take chances on that. Here's another thing. I'm just taking your word that the upper plenum is good. I don't remember exactly the passages on that upper plenum, or even what the failure modes are, if I ever knew. Like I said, I did it as a preventive measure. Are you absolutely sure there isn't an internal crack in the plenum that allowed coolant to enter the cylinders? So far you are guessing it's from LIM failure. Maybe it is. But I would find out if that upper plenum could have caused it before I would reuse it. You can look at the Bonneville forum for better advice on all this than you'll get from me.

--Vic

Upon closer inspection of the plastic upper plenum, I found a potential problem, a small piece missing (broken off) inside the recess where the gasket sits where it interfaces with the throttle body. It probably didn't cause the original problem but could very well cause a sealing problem, immediately or down the road. I am not sure how it could have gotten broken like that, kind of a strange place to be broken. It looked like it had a small amount of RTV sealer at that spot. I actually got the impression that the UIM had been removed in the past, but I don't know why that would have been. I don't know about performing this job on any other car, but on this model I thought there was a surprising amount of stuff to remove to get at the manifolds. Kind of a big hassle. For that reason I wasn't too inclined anyway to try re-using the original first to make sure it still ran -- plus I am almost 100% sure the engine is undamaged as the hydrolock condition occured as the engine sat overnight and no antifreeze got into the lower engine. I am going to go ahead and get the new plenum, which is the best way for peace of mind and not that much money anyway. Thanks to all for your responses.