I have a 99 Bonneville -3800 seriesII - 180,000 miles. Intake replaced at 95,000 by previous owner. Now the problem - It appears I'm losing a little coolant, but have no leaks, no white smoke and can't smell any antifreeze burning at the exhaust. Motor seems to run fine. i pulled the plugs and the first plug on the left bank appears whiter than the rest. The uim was replaced 80k miles ago. Do I have another uim failure and what would be your recommended repair sceniaro? i.e, is it necessary to replace the lim? I'm a decent mechanic... how long does this take?



i looked at the aftermarket intake manifold that is listed on this site. what do you recommend?

just read Bob Dillion'* post on a need for UIMs. Bob,what do you charge for repair?

Thanks and appreciate the advice and knowledge!
Bob

Bob doesn't do the repairs, he simply sells improved UIMs.

You need to get that oil drained out ASAP. There'* coolant mixed in with the oil. Coolant will eat away at the lower end bearings.

Your UIM may have failed. If it didn't, then your lower intake manifold gaskets are to blame. If those hasn't been replaced in 180,000 miles then I'm sure they're pretty toasted. I've replaced my LIM gaskets and UIM 3 times in 155,000 miles on my 99. GM now sells an aluminum frame LIM gasket set. They should hold up much better than the plastic composite. Also replace the coolant by-pass elbow between the LIM and belt tensioner. They're known to crack with age.

DIY job? If you have a Chilton'* manual, a torque wrench and some patience the job isn't too bad. Count on 4-5 hours to do the whole job (including the LIM gaskets). Cleanliness is VERY important during the reassembly.

Joe, I agree on the UIM repair, as well as checking the oil at once (by draining it) and seeing if you have chocolate milk.

Check your PMs, please.

I've checked the oil and it still is just a little low and does not indicate water present, i.e no whitish color or foaming. The oil just looks normal dark color. Do I still have water in the oil?
Now I'm afraid I might have bearing damage. What do you think?

While it is certainly possible (likely even) that you are experiencing
another UIM failure, I personally always recommend that you eliminate other
possible coolant loss areas first.

To do that bring your car up to temperature so that the water pump comes on
and the system pressurizes. Then carefully review all hoses and water
connections for leaks. Sometimes hoses will only leak through a pinhole
while under pressure.

Then if you've found no leaks in hoses or connections, you move on to the
UIM. I do recommend the APN (I believe that'* the name) aftermarket UIM
kit. This kit takes into account all the things we have learned about why
the UIM fails and how to best avoid future failures. Plus the price is
right.

I also recommend replacement of the LIM gaskets, especially if they've never
been replaced before. Even if they have, unless they were replaced with the
new aluminum framed style that just came out in 2005, they could probably
stand to be replaced again. You're in there already... ; )

Use the write-ups in TECHINFO for instructions. Once you do these, you
should be good to go!

Please read the Techinfo article on this.

http://www.bonnevilleclub.com/forum/...e=article&k=38

For those who want to buy a new one, I recommend the APN sleeved upper that comes with a 1/2" diameter stovepipe. You will want to have the shoulder on that little pipe turned down to slightly under 0.625 to fit it into your LIM. Do the aluminum LIM gaskets and a metal bypass elbow and you should not have to do the repair ever again.

If you want to repair your own upper (very inexpensive option) PM me for a stainless steel repair sleeve.

I still say don't panic until you know what your problem really is.

Certainly drain your oil and see what you find. It won't hurt and will help if indeed you do have an internal failure.

But do the simple tests first.

It'* true that a white plug is a pretty good indicator of an internal coolant leak, but it never hurts to walk your way into a problem diagnosis, IMO.

Well... I haven't torn anything down yet, but looks like a UIM &LIM job. Any advice is appreciated. I like Bob Dillion'* theory of bolcking the coolant passages to prevent this in ths future. Will drain oil and take a look. It appears ok on the dipstick... just a liitle low and dark... not creamy.

Here'* a thread from when my brother and I did the UIM and LIM. About half way down the page you can see a series of pictures of the job. I also asked a bunch of questions in this thread and got great answers.

http://www.bonnevilleclub.com/forum/...f7623028c0c94b


LeifW

Thsnks for the help. We have a big family reunion this weekend, so I probably will not start tear down until next week. Will post what I find.