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Old 11-07-2011, 03:00 PM   #1
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Unhappy 98 pontiac grand prix gt 3.8 engine problems

Hello I am new to the forum

I would like some advice

my vehicle is hydro lock & about two year ago I had the LIM changed with the alum gasket...

Bad thing about it is that I did not have the UIM change....

I assume that is how my car is hydro lock...

Should I just change the UIM or Change both.....

I already took out the plugs & give it a couple cranks to push out the coolant & plan to take the necessary steps & hope for the best..

I just wondering about what to do with the LIM redue or not
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Old 11-07-2011, 03:07 PM   #2
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Hey!

Welcome to GMForum.com
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Old 11-07-2011, 10:41 PM   #3
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Welcome to the forum. Your thread has been moved to the Pontiac GP maintenance and mechanical section, where more "gear heads" will see it.
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Old 11-07-2011, 11:13 PM   #4
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Welcome to GM Forum!

Quote:
Originally Posted by Horseman12 View Post
my vehicle is hydro lock & about two year ago I had the LIM changed with the alum gasket…
Good call on installing aluminum LIM gaskets.

Quote:
Originally Posted by Horseman12 View Post
Bad thing about it is that I did not have the UIM change….
If the UIM wasn't damaged then, most people wouldn't bother replacing it. Still, if you're hydrolocked, it sounds like it finally gave out.

I'd replace the UIM. Your LIM gaskets should be fine. I don't think anyone has ever had a properly-installed aluminum LIM gasket fail on them.
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Old 11-08-2011, 10:34 AM   #5
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When you remove the UIM, check it by the TB. There is a single hole up into it for the EGR tube. Typically it will have cracked there. Filled the LIM with coolant and then filled the cylinders.

Clean up the mess in the LIM (shop vac) and you have two choices. Use 1/4" NPT headless pipe plugs to plug the LIM or install a new UIM and probably a reduced stovepipe etc.

Hopefully no one tried to crank it too much with the cylinders locked up and hurt the piston rod bearings.

One other note is that I've had to attached a piece of vacuum line to a compressor air chuck in order to blow out the cylinders enough to get it to fire back up. If it starts on 3 cylinders..keep it running until the other 3 clear. It really only takes about 3 though.
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Old 11-08-2011, 09:44 PM   #6
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does coolant pass through the uim? what if after i changed the lim would I be hydro locked....?



what is a reduced stove pipe ect?
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Old 11-09-2011, 08:07 AM   #7
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Coolant does pass through the LIM and UIM.

If you changed only the Lower Intake and not the upper intake, you will still have a problem. The upper intake is the part that goes bad. When it cracks inside that area I mentioned. You want to change the UIM, or plug the ports.

A reduced diameter stovepipe is this.. The EGR feeds hot gasses into the LIM under the throttle body. Then those gasses make a 90 degree bend to go straight up. That straight up goes up through the LIM and into the UIM. The UIM being a plastic/nylon composite can not take the heat of the exhaust gas. So they put a pipe in the LIM to channel the gas past the plastic. Well..the first few pipes were kinda large. Later on to give the plastic manifold more air gap to keep them from cracking, the pipe diameter was reduced.
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Old 11-09-2011, 04:41 PM   #8
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what is a TB

does the UIM kit come with reduced Stovepipe
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Old 11-10-2011, 08:01 AM   #9
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Throttle Body

Depends on which kit you buy. I know the Dorman kit does.
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Old 12-03-2011, 04:57 PM   #10
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I replace the uim gasket & put back together still got water in(hydro-lock) 1st time

then I went all the way down to the head gasket & put together & still got water in (hydro-lock) 2nd time note I did use the same uim gasket again because because I had just changed it out the 1st time......

what do I do now?
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