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Old 05-28-2010, 10:49 AM   #1
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Default How to diagnose cracked UIM?

What is the easiest way to diagnose a cracked UIM?

For the past year my 96 bonne has been running a little rough and seems to be getting a little worse everyday. I tried numerous checks and replacements, including new 02'*, new plugs/wires/coil packs, cleaned MAF. Nothing seemed to fix the idle. Well last night, I found my radiator was low about 1/2 gallon. I am guessing this didn't happen over night and has been a slow loss over the last year or so. The reason I didn't notice the loss earlier was because the line to the overfill bottle was clogged, so the reservoir was full. I checked all under the hood, not really smelling coolant or seeing any leaks whatsoever. So I am thinking the UIM may be cracked again

The UIM was replaced about 7 years ago at around 95,000. Now I am at 188,000. I am thinking a cracked UIM may be blamed for the worsening idle and coolant loss. Any suggestions.
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Old 05-28-2010, 11:09 AM   #2
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The quickest and easiest way is to remove your throttle body (3 10mm nuts) and look in at where the EGR tube sits in the UIM. If the area around the tube and further in are wet with coolant, the UIM has failed.

I would suggest you replace the LIM gaskets again with the new aluminum version of them. The plastic ones you used back when are most likely in need of replacement again.
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Old 05-28-2010, 11:48 AM   #3
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What'* the date stamp on the the top of the UIM? These things have a date stamp with an arrow pointing to the year. If its anywhere below 2003, you need to replace it.

The problem with these is that you have a very high chance of it just completely letting go one day and hydrolocking your engine. Hydrolocking your engine while in gear going 70mph on the highway isn't a good thing. Its very easy to replace. Dorman makes a revised kit with a revised stovepipe which I have installed in the past. You can replace it a dozen times but if you don't fix the cause of the problem, you won't get anywhere.

Get the Dorman kit, which has all of the gaskets and o-rings you need, and as Bill mentioned, get the aluminum LIM gaskets.
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Old 06-01-2010, 10:36 AM   #4
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Thanks guys. The arrow at the hidden bolt is pointing at '03'.

I still need to take off the throttle body, but i am almost 100% certain the UIM is cracked. Just so I have this straight. I want to also replace the LIM gasket even though it may be the direct cause of the problem.
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Old 06-01-2010, 10:40 AM   #5
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Most likely the UIM is the problem. However in 03 the current metal LIM gaskets did not exist. The plastic LIM gaskets typically look bad, but may not be causing any issues at this point.
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Old 06-01-2010, 11:13 AM   #6
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I've never seen a LIM gasket fail to the point of loosing coolant in those amounts. They simply seep coolant. UIM failure is the cause of large coolant lose, however, if your going to change the UIM gaskets, go the extra step and do the LIM gaskets as well.
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