I've read that this is a common complaint with these engines. How difficult is it to replace the plastic intake and gasket? I bought the car used and just replaced the radiator, water pump, ECM, and crank position sensor. Now that all the external leaks are plugged, it'* swilling coolant internally. It'* only got 85,000 miles on it and could run long enough to justify some of the repairs I have put into it, if I can get the coolant loss under control. A friend said that someone makes a retrofit intake for these engines out of metal. Any helpful suggestions would be appreciated.

Alright. For the UIM, you'll want to replace it with either an APN or a sleeved UIM from Bob Dillon (pm him for more info).

While you're at it, you'll want to replace the LIM gaskets with aluminum ones.

You should take a few minutes and read this techinfo article.
http://www.bonnevilleclub.com/forum/...e=article&k=38

difficulty depend on experiance and tools. If you have air tools, and have everything prepared you can have in done in 2-3 hours.

some have mentioned swapping the oe UIM off an 04+. but mop, it is NOT worth it. do a lil search, and you will soon find out why. but, im not aware of an aftermarket aluminum intake. if you find one, let me know.

**edit, heres a thread that explains the L26 swap a lil better.http://www.bonnevilleclub.com/forum/...t=aluminum+uim


P.*. dont forget to get new injector o-rings.

Did my UIM/LIM work last summer on my 95.

Just take your time, dont force anything.
Ask if you have any questions, as almost all of us has done this at least once.
PM me if youre stuck....

Oh, and make sure you do a good job of cleaning everything..

Bob

Internal coolant consumption could be the upper or lower gaskets or the EGR pipe has burned through. You will have to cover all bases.

You guys have been a great help and more knowledgeable on this topic than my first mechanic.

I changed the oil yesterday to prevent any antifreeze from destroying the bearings in the engine and the oil was perfectly clean, no anti-freeze visible in it at all. I may be guilty of wishful thinking, but my current plan is to keep a careful eye on the coolant level for the next week or so and see what happens. Is there a danger that this course of action (or inaction about not replacing the UIM and LIM) could destroy the engine?

Also, I've got to replace the tensioner pulley for the serpentine belt. Does that simply bolt on or does the whole tensioner need to be removed to replace the pulley and the bad bearings?

Yes, it can cost you a motor. Could be today, could be in a month. Is it worth the risk for something you can fix for 200-250 right now?

I can't count the number of L36'* we've lost on this Forum to this problem. Even those that THOUGHT they caught it and reacted quickly enough.

If you're already sucking it internally, it'* only a matter of time before it breaches a gasket and enters the oil.

Tensioner: Assuming yours is the same as 93 non-SC; of course, remove the serpentine belt. Then the LEFT HANDED bolt that the pulley rotates on. Check the replacement part close. Some places are bad about giving you the wrong one. I ate up a plastic one when there was not proper clearance between it and the big washer.

constructone,

I thought my car was doing fine too, green coolant, "oily" oil.
One day my coolant dropped 2 quarts, thats when I knew to check it out.
My UIM was falling apart at the EGR area, just like everyone elses. I picked at the mud around there and found "daylight". My lower manifold gaskets were also brittle and leaky, particularly in the center of both sides.

Cost me about $275, and a weekend to complete, and I goofed off alot.
As Ive posted before, take your time, and CLEAN everything well.
You can also remove the sensors and clean up the throttle body, it makes a difference.

I also changed the coolant/oil(obviously) I ran cheap Advance auto brand oil/filter for 500 miles after to purge out any nastiness, then back to Quaker State 10w30.

Happy Hunting!!!
Bob

It'* been two and a half weeks since my last full day off and I got a chance to work on the Bonneville. You guys have been a great help. With time pressure to get the car running and my not being sure if I could get the UIM and LIM gaskets replaced and still have a running car, I took it to a mechanic and asked them to replace the UIM and LIM gaskets and the plenum. First they called and said they couldn't find a problem, suspected the head gasket. After sharing what you have all said, they checked again and agreed to replace the plastic-plenum with a Dorman unit but did not see any reason to replace the lower gaskets. Since you guys have consistently been ahead of the curve, I insisted that they replace the lower gaskets as well.

Once I got it home, I replaced the tensioner pulley (thanks again for your advice) and the serpentine belt (could've taken three days or more money to the mechanics without your help) and plug wires. Now it runs great. You've helped a lot with great advice on things I can do and by helping direct me to forcefully suggest that my mechanics benefit from your experience.

My car is not supercharged. It has been suggested that platinum plugs are bad for supercharged engines. GM put platinum plugs in my 97 Transport new at the factory and it ran perfectly for 11 years until someone totalled it. Are platinum plugs bad for non-supercharged Bonnevilles? Do they burn up the coil packs prematurely even in non-racing applications?