new UIM is now leaking coolant... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 07-12-2006, 03:48 PM   #1
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Default new UIM is now leaking coolant...

I posted recently about a gap between the throttle body and UIM, which I finished installing this morning. When I filled the radiator, it immediately started dripping from the point where I placed a masking tape "pointer" in the following pictures. Any suggestions? I tried tightening the UIM bolts a little tighter, and it seemed to leak faster. Any chance the JB Weld (or whatever was used to close off the coolant passages) is causing the gasket to not seat properly? Anyone else had this issue?

http://i71.photobucket.com/albums/i1...6/102_5182.jpg
http://i71.photobucket.com/albums/i1...6/102_5181.jpg
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Old 07-12-2006, 03:58 PM   #2
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If I could make a somewhat related suggestion regarding your posts...

I did a search to find out what your repair issue was and noticed that you have four different threads related to this same basic repair problem, the UIM failure. It would certainly be easier for folks to help if you kept the whole repair and all it'* related questions and issues in the same thread. That way, we could follow what has happened so far and try to relate that to what your current question is. OK, off my soapbox.

Anyway, I for one need for you to be a little more descriptive as to what is happening.

One question I have for you is:
What torque spec did you use for the UIM bolts?
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Old 07-12-2006, 04:49 PM   #3
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Default Re: new UIM is now leaking coolant...

Quote:
Originally Posted by laff66
I posted recently about a gap between the throttle body and UIM, which I finished installing this morning. When I filled the radiator, it immediately started dripping from the point where I placed a masking tape "pointer" in the following pictures. Any suggestions? I tried tightening the UIM bolts a little tighter, and it seemed to leak faster. Any chance the JB Weld (or whatever was used to close off the coolant passages) is causing the gasket to not seat properly? Anyone else had this issue?

http://i71.photobucket.com/albums/i1...6/102_5182.jpg
http://i71.photobucket.com/albums/i1...6/102_5181.jpg
It is difficult to tell definitively from the pictures, but it appears that the sealing surfaces for the blocked coolant passages may be not smooth enough for the top side of the UIM gasket to seal properly. The two small round coolant passages on either side of the EGR bore are the source of the coolant. It just runs out at the low spot you have marked with the arrow. If you are going with blocked coolant passages anyway, you could plug the passages in the LIM, and thus remove the source of the coolant, or you could try block sanding the throttle body end of the UIM with 100 or 150 paper until those sealing surfaces around the coolant bores are smooth and flush with the surrounding sealing surfaces. To see where these surfaces are, just examine the UIM gasket.

BTW, with blocked coolant passages, it will be very difficult to remove air trapped under that area of the LIM, especially the back (firewall) side, unless some additional provision for bleeding is made.
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Old 07-12-2006, 04:58 PM   #4
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sorry, thought the other posts were too far gone to be viewed. In regard to the "four posts" comment, only the last one or two dealt with installing the new one.
Anyway, to be more descriptive, water is leaking out between the upper and lower intake manifolds at exactly the point where I placed masking tape in the pictures I posted. I have not started it yet, as it began to leak immediately upon filling the radiator.

Torqued to 89 in lbs.

I removed it again, and it does look like there are some really rough edges and gouges where the two coolant passages were filled. I am thinking about filling the holes in the gasket with RTV so that coolant never even gets to the UIM.
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Old 07-12-2006, 05:04 PM   #5
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Not a problem. I was just commenting to try and make it easier for you to get help in the future, not trying to pick on you or anything.

Bill Buttermore has the best take on this issue from what I can tell. He is also one of the folks here with the most experimental and personal knowledge of the UIM, and it'* problems with respect to your question, so I would follow his lead if I were in your situation. We'll all happily chime in if we have better or more info.

EDIT: I asked about the torque just to make sure that it wasn't over-torqued.
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Old 07-12-2006, 05:16 PM   #6
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okay, thanks for the help. I am curious about the trapped air, though. What would be the consequences of that? If they are severe, what would I do to alleviate the problem?

Thanks again!
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Old 07-12-2006, 06:58 PM   #7
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You can alleviate the problem by plugging the holes in the lower manifold.
Something like in this picture will work.

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Old 07-12-2006, 07:11 PM   #8
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Quote:
Originally Posted by laff66
I removed it again, and it does look like there are some really rough edges and gouges where the two coolant passages were filled. I am thinking about filling the holes in the gasket with RTV so that coolant never even gets to the UIM.
Generally speaking, the sealing surfaces for the coolant passages on the UIM need to be flat, flush with the other surfaces on that plane, and without an imperfection (like a gouge) that would allow for a leak between the silicone bead and the UIM surface. Don't know...you might get away by overfilling the gasket holes with RTV, but unless you do it perfectly, you may still leak. Also use a straight edge to look for high or low spots on the UIM sealing plane that may prevent a good seal.

Re trapped air, take a look at your lower intake manifold while the UIM is off. You will see two coolant holes adjacent to the EGR pipe. If yours is like mine, the rear coolant hole (nearest to the firewall) normally serves as the air bleed (through the throttle body) for that rear chamber. That path is now blocked on your engine. The only other passage allowing coolant to flow out of the back chamber of the LIM is that little cover on the Driver'* end that connects the rear chamber to the front chamber. Notice the front chamber is also the thermostat housing. Also notice that the little cover is a good bit lower than the top of the chambers. Normal coolant flow might be expected to eventually displace any air in the front chamber. (This would be facilitated by providing a bleed hole in the highest part of the thermostat flange.) But in that back chamber, you will almost certainly trap a slug of air that will sit under and adjacent to half of the EGR passage near where the stovepipe is installed. Maybe it won't make any significant difference. But air won't conduct heat away like liquid, and if air is trapped, that side will be hotter. Anyway, to re-establish coolant flow under the top of that back chamber, you would need to drill into it at a high point and maybe install a bleed like is used on the thermostat gooseneck.

Also, you may want to consider this method when you re-fill to minimize the chance of trapping air.

http://www.bonnevilleclub.com/forum/...ic.php?t=57407
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Old 07-13-2006, 03:27 PM   #9
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I tried sanding down the JB Weld or whatever was used to fill the "new" UIM, and its a total mess. I should have bought a new one, which I am probably going to do right now. I think the metal sleeve in the EGR hole is set too low and not allowing the UIM to tighten all the way.
Any recommendations on sources for new ones?
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Old 07-13-2006, 03:42 PM   #10
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Do a quick search on UIM.

There are at least three good sources for replacements. Two are: Dorman and our member Bob Dillon (if he has any, they are rebuilt and may be the best option). The third I can't remember right now, but do that search. 'cause I know it'* been posted a few times in the past month or so and it seems to be a great option.
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