I have noticed a knocking sound on my 500i that I thought I'd toss out to see if anyone else has heard this, or knows what it might be.

The knock appears at mid rpm's, under a load, usually when pulling a moderate grade hill. Sounds a lot like a rod bearing, but it seems to go away at higher rpm's. I can reproduce it by putting in 1st, holding the brake, and running the engine up to put a load on it. Doesn't sound like a skid plate, it's a little too heavy sounding for that. And it does appear to be coming from the engine.

Does this ring a bell with anyone? The cat goes in for service/joints in a week or two, so I'll be asking the dealer about it as well.

--John

 

Try running a tank of high test thru it, it may have a little to much timing.

 

I have a 98 500 and it does the same thing. Ive seen people ask this question on the forum and never really see any good reasons for why it happens. But im told they pretty much all do it. I may run a tank of high test myself as suggested and see what happens. Couldnt hurt it im sure.

Mark

 

This has been asked many many times. Don't worry about it. My 500 does it, my old quadrunner did it and all 500's do it. Its some sort of compression release thing in the motor. I'm not exactly sure what its called but it has something to do with that.

 

Yea this is the reply ive seen most often. Its just kind of a disturbing sound, kinda like the crank is getting bad or whatever. I remember these sounds from my early 4-stroke MX days and it was never good news hehe.