02 Rendevouz CX

[mlwtt]

Car regularly serviced. Gas filter replaced. At 55000 miles rapidly developing valve or piston noise. Going to trade. Have used STP. Is there an additive for the oil that might quiet the noise?

[rodeo02]

Originally Posted by mlwtt

.. Is there an additive for the oil that might quiet the noise?

It totaly depends on where the noise is coming from. Might be a simple rotating element like the serpentine belt idler, tensioner, water pump, etc... Have you been loosing engine coolant? If so, and you have not addresses the situation and only kept adding coolant, you could have worn connecting rod/main bearings (from coolant in the oil). If that's the case, the engine will self destruct shortly.

Joel

[mlwtt]

There is no coolant problem. All of the belts--rubber--seems to be fine. Fuel injection jets were replaced at 30000 under warranty. All new filters. It seems to be a piston noise--just a little different from the sound of a valve ticking. I've heard that Buick teflon coated some of the pistons on these cars and that it wears off causing a problem. I'm really looking for a temporary fix to the noise.

[rodeo02]

If it's piston slap, which is rocking of the piston(s) w/in the cylinder bores, this is a common and harmless annoyance. GM did add a nylon type material to the skirts of some of their pistons to 'absorb' the noise of the skirts rattling against the cyl walls. Many manufacturers have gone to this setup now. Different viscosities and brands of oils can supposedly reduce the noise for awhile. Some shops will insist the noise is due to carbon build-up in the combustion chambers & the pistons are actually 'hitting' a ridge of carbon. I don't buy that one at all. There's really no way to band-aid piston slap other than keep up on regular maintenance.

Joel

[mlwtt]

Found a GM mechanic who teaches in a community college. He says Buick teflon coated some--not all--of the pistons in this engine. Between 50 and 60,000 miles the coating begins to wear off and the piston slap develops. Because the car is also losing power on hills and harder to start with a 3-4mpg drop, his recommendation is trade before it loses more value, or rebuild and get another 50000 out of the vehicle. The partial coating sure doesn't make sense. I thought GM had a problem with a similar attempt some years ago. At any rate, it reinforces my inclination to trade a car we otherwise really like.

[rodeo02]

Power loss and reduced MPG are something unrelated to piston slap. You've probably got something else going on. There are million GM 'slappers' still cruising along with 150,000mi on them. Best off unloading your rondy if you are unhappy with it.

Joel