I have 200 k on my 98 Bonnie and NEVER had any problems, is this something on these years that go bad an if so how often ??

95 and newer L36 engines (which you have). The mileage it fails at varies greatly. 200k is well past the average point, though.

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

is this a problem that was ever fixed, if so what year ? Do they ALL fail or just some ? With over 200k can I consider it is not going to fail ? What are the signs of impending failure ?

Read the link I posted in my last reply. It'll explain everything.

It WILL fail.

Sounds like it was replaced before you bought the car. I am pretty sure about that since the UIM'* haven't lasted that long unless your car was owned by a old lady that drove it to the store and doctors once a month. I would get it replaced again since you are pretty close to the 2nd mark on where they fail.

I looked at mine and it shows 1/1/01 as the date of manf. it is a 1998 so it must have been replaced. Is this replacement better than the orignal ? Is there any signs that it needs to be replaced BEFORE it goes ? With 200k I hate to just replace it because it MIGHT go ???? Doesn't loose any coolant etc. When they go do they just let loose ??

When they go, they can just let loose or you'll notice coolant loss. It can go either way to my understanding.

If it does let loose, you'll have a cloud of white smoke and the engine typically stalls. Don't try and restart it. pull the plugs and get the coolant out of the cylinders if theres any there, get the oil drained asap. The coolant and oil mixed will form and acid that will eat at the bottom end of the engine (bearings and crank)

Honestly, if you've got the money, you'll want to get the UIM replaced before it actually fails. If you develop a sudden, catastrophic coolant leak, you'll wish you had replaced it sooner. If you wait until there'* coolant in your motor or mixed in with the oil, you're putting your main bearings at risk, any of which require an entire engine disassembly to replace (unless you would elect to buy a different motor). Getting coolant in your oil doesn't automatically ruin the mains, but you're taking a chance by waiting until the UIM actually fails. It'* much less painful to be preemptive with the UIM.

is it possible that when this was replaced in 2001 that they put a sleeved one on ? How many miles do they usually go before they let loose ?

Doubtful that you have a sleeved upper. I don't think we've ever heard of shops that offered homemade sleeved units to customers, and until recently I don't believe there were any widely available on the market (unless your mechanic invested in a Kenco kit). Check receipts for the work done, or try to contact the mechanic that performed the repair and ask him if he would have used a sleeved UIM.

Again, mileage before failure can vary enormously. Sometimes they go after 50,000, and sometimes they last 100,000 or more. Pretty big window of opportunity for failure.