540/6 piston slap

[spitfire]

For all you experts out there. My 540 has developed a knock at idle after a start with a cold engine. This knock comes from the bottom of the engine, you can't hear the knock from opening the hood, only from looking underneath. This knock can sound like a clattler when the engine decelerates from a quick blip of the throttle. Once the engine is at operating temp's, all is well. A BMW Tech sugested that it is probably piston slap and that if the problem goes away after the engine warms up that not to worry(which is the case). Yes it's a NIK with 183,000 kms, uses no oil and had a leak-down test at 120,000kms with excellent results. Any comments?
Cheers
Spitfire

[632 Regal]

type oil? Oil pump could be loose or low pressure.

[SRR2]

Yeah. Oil pump. Check it out NOW.

[DueyT]

Spitfire, get some extra bolts for the oil pump, and have a machine shop drill them to accept lock-wiring, a la aircraft style...I'll be doing that this summer...

Cheers,
Duey

[blaise]

Yeah. Oil pump. Check it out NOW.

I have a 95 540 six speed and I'm experiencing the same thing. What did you find out? Was it the oil pump?

[Elekta]

They'll drive a long time with one bolt and the pump just barely hanging, so when it does go....it will GO.

I had one bolt in the pan when they checked mine. Like a 6yr old's loose tooth it was.

[yaofeng]

For all you experts out there. My 540 has developed a knock at idle after a start with a cold engine. This knock comes from the bottom of the engine, you can't hear the knock from opening the hood, only from looking underneath. This knock can sound like a clattler when the engine decelerates from a quick blip of the throttle. Once the engine is at operating temp's, all is well. A BMW Tech sugested that it is probably piston slap and that if the problem goes away after the engine warms up that not to worry(which is the case). Yes it's a NIK with 183,000 kms, uses no oil and had a leak-down test at 120,000kms with excellent results. Any comments?
Cheers
Spitfire

As others said, drop the fron sump to check for loose oil pump bolts. And do it now.

[BillionPa]

Eek

[yaofeng]

Eek

That's inside of the engine of the 144k one. I have since gotten one 66k miles on the stand to replace it. Waiting for free time to do it. Too busy.

[Spasso]

Found an oil pump bolt in the pan of my Touring at 116k. Judging from the wear marks in the pan from the bolt and the oil pick-up strainer it had been there a while. The other forward bolt was finger tight.

ALL of the bolts on my sedan were finger tight but still in there at 115k.

Lockwire is a great idea. I settled for a thorough rinse of the holes with carb cleaner and red loctite. Hopefully that will hold for another 116k

I heard piston slap when cold was a common and "acceptable" occurance in many newer GM products. "They" say, "Nothing to worry about". Yeah, maybe from them, as long as it holds together past warranty expiration.