UIM replacement - symptoms, comments - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat

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Old 05-15-2007, 09:23 AM   #1
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Default UIM replacement - symptoms, comments

I did the upper at 150K mi with a Dorman from Advanced with the reduced size EGR pipe that just presses in and it also has special o-rings at the seals for the water tubes on the LIM. If GM had done thisfix in 2002 and 75K I wouldn't have had to do the job a second time.

Dorman tech was very good to talk to. He explained how the Dorman is much thicker int he problem area than the GM design was/is. He explained the o-rings instead of thin press seals like the GM had. He also said if it weren't his car he wouldn't change the LIM since I had always kept the DexCool changed and never let it go bad or acidic like coolants do.

The whole replacement would be a 6 hour job now that I see how things snap in and out on the motor.

inch pound torque wrench. Loaned from PepBoys-only store that had one in the area including those know for loaning tools. Atta Boy PepBoy.

I notice a symptom that I thought was age but might help someone thinking water loss is UIM relaced. On cold starts the car fired instantly but didn't catch and cranked more for up to 1 second and then would catch. I suspect that was related to the water sitting on the floor of the plenum area or what was on the plugs. But it'* gone. Car catches as fast as my newer car. It also is touchy on takeoff. I just tip the throttle slightly and it'* moving engine speed up; that wasn't true before.

Hope this may help someone with coolant loss that'* not sure about the reasonfor the loss.

Does anyone know if I can chemically soak the iridium plugs that had about 10 K at most on them and put them back in. They were coolant covered and had black color to the ceramic. Someone suggested the old sandblasting but I suspect the ceramic is coated these days.

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Old 05-15-2007, 10:08 AM   #2

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While I wouldn't do anything to the plugs but put them in and take them out for a little "carbon blow off" on the highway.

I'm interested in the LIM gaskets. You mention the Dorman Tech said he wouldn't have because you kept up on changes etc. What did your lowers look like when you changed them? I personally don't blame Dex for the caving of the gasket around the intake runners that are air/fuel only. Therefore I can't hold the water jacket collapsing on the Dex either. Add that to the fact that I swapped out to Prestone LL coolant and still saw this after 1.5 years... hmmm no Dex was present. GM changed the gasket design to a stronger aluminum frame, interesting track I'm on here isn't it?

How about your lowers?
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Old 05-15-2007, 10:12 AM   #3
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imidazol, please don't tell us you took Dorman Tech'* advice and did NOT change out your LIM gaskets.

RE plugs: I would not use any abrasive on them. I'm not sure about the effect of the iridium alloy, but platinum is very soft. I would not consider sandblast. You might spray or dip them in methyl or ethyl alcohol, then let them dry. Any coolant will mix with the alcohol, then evaporate.
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Old 05-15-2007, 12:16 PM   #4
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I'm the "guilty party" on the "sandblasting" when I mentioned in your other thread that in the old days, a tool similar to a sandblaster was used to clean the plugs. There are several places (JC Whitney, Northern Tools, etc) that still sell them. I'd stick with what Bill Buttermore said, or what I did in the original. A little wire brushing, and maybe a spray with intake cleaner. I apologize if the wording was misleading.

I also do hope that you didn't listen to the Dorman rep., and replaced the LIM gaskets!
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Old 05-15-2007, 06:11 PM   #5
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I've always keep mine flushed regularly too. My fist failure was at 130K and all I did was my upper like you. Well the lower failed at 185K and I had to do it all over again. I wish I had known at the first repair that the lower should have been done too.
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