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:
- 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?
- Would the LIM gaskets failing result in the condition of hydro lock and coolant in both banks -- same as a failed UIM would?
- 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.