About 18 months ago I did the LIM & UIM gaskets on a 1996 Bonneville SE witha 3.8 now seeing leaking of coolant and motor oil on the passenger side of the engine. I had never done anything so involved with an engine before. I did it in a marathon all-nighter type of session so I might have not done some things correctly. The car has only been driven 7,500 miles or so since it was done... I bought the car for my father-in-law and the LIM problem was a surprise to me. He is 87 and has decided to give up driving and the car is back with me. Now I am noticing leaks under the car and dropping coolant level. I have seen coolant on top of the silicon edge seal on the passenger side. I used Dorman parts upper & lower gaskets and a new dorman plastic upper intake manifold....not the GM aluminum framed LIM gasket.
I would say that coolant is leaking out of not into the engine. There was quite a bit of oil on the underside of the car the outside of the oil filter itself was wet with oil and the base it attached too was quite wet too.. It seems like after I cleaned it up with degreaser and brake cleaner that it is leaking oil faster?

I did review all the info that I could from this and the other old? bonneville club site and everything seemed to be okay car seemed to be running great...but it seems like I have a re-do to do.

Since I noticed the problem, I have re-reviewed the Bill Buttermore posts on the steps and have tried to remenber exactly what I did an did not do... I dont remember putting Hi temp sealant down the side rails...I did put some on the corners...but in re-reviewing it sounds like Bill says to put a little down on the corners then place the LIM gaskets in place and put a little more down on the corners again? I know that I attempted to tourque the LIM to the correct specs... but maybe I hosed that up? I can't remember if I used lock tight on the bolts or not...I sure should have. If I did not...the bolts would loosen? I know that I only replaced one of the 2 coolant elbows (the one from the LIM to the tensioner) I didn't realize what the 2nd one was for until I had it all back together. I have not taken anything apart as of yet., and would appreciate any advice you have to offer.

Will I need a new upper Gasket? Should I replace both elbows. Should I put hi-temp sealant on the top as well as the bottom of the edge seals? Is there anything else I should be looking at

Spit

Take a picture of where the leaking seems to be originating. Sure sounds like you did it all properly. There shouldn't be loctite on the bolts, however the lower intake bolts shoudl have a sealant on them to keep from having fluids seep up the bolts onto the lower.

In your year there is only one coolant elbow, the location where the other elbow would be in your year and 97 is metal and does not need to be replaced.

Bill, About no treadlocker on the LIM and UIM bolts? In the instructions I have from Bill Buttermore it says to use the Blue stuff?

What is correct?

Regards,
James

Right/wrong.. well that'* tough to say. No where in the FSM does it say anything about threadlock. I have a few buddies that are/were dealership mechanics during the run of these motors and they say nothing about threadlock. What they do suggest is using a dab sealer on each bolt on the threads.

Here is a pic of what they recommend using


Thread locker may seal the threads from oil and coolant wicking up them. It'* not a sealant though, and I've yet to come across any LIM or UIM bolts that were ever loose and seemed to need it. As with anything there are a few different ways to go about it.

I learned about the sealant after noticing coolant puddling on my LIM not long after a gasket change. That was not long after partly following Bill Buttermore'* directions at that time.

Thanks for the great info and photos. I will look again for coolant leaks.

What I saw last week was fresh coolant on the pass. side edge seal..I've not been able to see where it comes from only that a few drops had accumlated on the seal, and the coolant level was dropping.

When I looked for the leak on Saturday... and wasn't able to pinpoint any leakage... coolant or oil..
Again I ddn't see any leakage while it was running. Must have run it for 20-30 minutes...I parked the car in the street when I was done and next day I popped the hood and the coolant looked like it was down quite a bit more. There was 10-12 inch spot on street on the passanger side that seems to be more oil than coolant..

I had the front end up on jackstands and passenger side wheel off sprayed a lot of brake cleaner and degreaser...rinsed it with shop air.. I was underneath the car looking for leaks... never saw any. I did change the water pump 16 months ago, so I hope it'* not a problem...that may be when I broke a plastic elbow came in a 2 pack only replaced one...since you say the the tensioner elbow that goes into the LIM is aluminum

Where exactly is the oil sending unit is it on the filter mounting base?...where is the sending unit most likely to leak from

Spit

With coolant on the end seal I would suspect your coolant elbow.

The elbows do come two to a pack, although only one will fit in the tensioner to LIM holes. The other is meant for the lower elbow location on the newer tensioner assemblies and has one end that is larger than the other which will not fit into the other elbow'* locations

Here is a picture with the lower or second elbow that your tensioner has cast as part of it.

It does appear to be the elbow and I may be leaking at the tensioner connection more so than the LIM. . what is the best procedure to replace it? Would I remove the tensioner with elbow attached from the side of the engine? Replace/reseat the elbow into the tensioner then re-seat into the LIM and re-attach to the engine?

Yes, pull the alternator off, then there are uh.. 3 bolts left to remove the tensioner. Keep in mind there are lower and upper coolant elbows. In 96 and 97 the lower elbow was part of the cast tensioner with an o-ring on it. Use the large oring off the elbow you won't need to rering that cast piece.

Mission accomplished!

I changed the elbow last night and installed the rear/right side valve cover gasket, I had already done the front on Saturday. I ran it out on the expressway, got it good and hot parked on a clean sheet of cardboard overnight and no coolant leaks whatsoever!!! There was a small oil spot...not sure if it'* some run off from previous leaks and cleaning the engine. It was a real odd leak/splatter it maybe 2inches long and a 1/2 inch wide...not round.seemed like it was right below the front edge of the oil pan....I'm going to clean it up some more and keep an eye on it...and see if it coninues, stops, get worse. Thanks for all the good advice.

Spit

Spit,

Looks like my sons 96se has the same problem. We did the UIM/LIM almost exactly a year ago and replaced the upper coolant elbow. This morning went out in the driveway and noticed a big puddle under his car. After searching a bit I noticed a small leak around the LIM/Tensioner elbow. It'* only dripping slightly right down on the seal on the china wall. At this point I thought "Oh Boy" we get to pull the whole intake off again to replace a $4 part. I then got looking closer and thought that we might be able to just pull the alt and the tensioner and replace it that way. We put the car up on jack stands because it was leaking more coolant than what was seeping out of the upper coolant elbow. I looked everywhere I could see but I cant seem to see where the leak is coming from.

Then I see your post and get my question answered by Boost. Bill, you saved me AGAIN ! I'm guessing I have the same problem you had. I'll tear into it tomorrow and see what I got. From the sounds of it, we'll be up and running in a short amount of time.