[Blackhawk36]

Has anyone had to replace their serpentine belt tensioner on an N54 yet? What were the symptoms? I think I have isolated a knock on start up to the tensioner. Interested to find out if anyone else has experienced this.

Joe

[Tzu]

Yes, replaced due to squeaking from loss of packed grease.

[oddjob2021]

i had to replace mine because i shredded the belt which then ate into the wheel of the pulley. i believe it's called a hydraulic tensioner.

[dominick]

Mine got changed due to the subframe breaking.

[Blackhawk36]

Thanks. I think mine makes a clunking noise when starting the engine. It deflects over an inch when I hit the start button then everything is fine. I checked everything else for looseness and the subframe for contact. Nothing there. I guess it is my next project.

[Tzu]

Originally Posted by Blackhawk36

Thanks. I think mine makes a clunking noise when starting the engine. It deflects over an inch when I hit the start button then everything is fine. I checked everything else for looseness and the subframe for contact. Nothing there. I guess it is my next project.

Yea, I'd replace that, like tongiht.

[marv85]

I'm going to replace it this Saturday. Loud squealing noise especially when cold, along with a plastic rattle at low rpms.

I do have a weird clunk at start up!! Never could find out the cause of it, you're saying it has to do with the belt??

[marv85]

SO have you changed it yet ?

[Blackhawk36]

Originally Posted by marv85

SO have you changed it yet ?

I will be doing it this Thursday night. Part isn't in stock at Tischer (getbwmparts.com) I settled on the tensioner by process of elimination. I will post Thurday night after I change it out.

[Blackhawk36]

I did some feeling around with a stethascope. The noise is definitely coming from the tensioner.

[Tzu]

Just slip off the belt and check the pulley. 10 min job.

[marv85]

Belt broke yesterday! It's at the dealership, i'll let you know how it goes...

[Blackhawk36]

I changed the tensioner. I still have the noise. Pretty discouraging. I spent couple hours on the lift this morning hunting and couldn't find anything.

[Dave W.]

Clunking at startup could be a loose starter, loose flywheel, or loose motor/trans mounts. When starting the engine usually rocks a little more, so it might even be the exhaust hitting something.

Have you checked the motor mounts? I've seen a few break, although it's hard to tell. Usually it's the rubber part that breaks inside the housing, the pieces stay together but it has more movement. You might be able to see it since the engine sits about 1/4" lower when the rubber comes apart.
HTH

[Blackhawk36]

Originally Posted by Dave W.

Clunking at startup could be a loose starter, loose flywheel, or loose motor/trans mounts. When starting the engine usually rocks a little more, so it might even be the exhaust hitting something.

Have you checked the motor mounts? I've seen a few break, although it's hard to tell. Usually it's the rubber part that breaks inside the housing, the pieces stay together but it has more movement. You might be able to see it since the engine sits about 1/4" lower when the rubber comes apart.
HTH

Dave, thanks for the input. I checked all mounts this weekend. Had it up on a lift with all covers on the bottom off and someone starting it to create the noise. All mounts are sound. I checked the starter when I cleaned my intake valves. It is good. On the flywheel, I don't think it is loose. My car is a manual so if the flywheel was loose enough to cause a clunk when starting, I would definitely have a vibration in the clutch. The noise is up front in the engine. It is worse when the engine is warm. Next stop is the timing chain tensioner.

[oddjob2021]

Originally Posted by Blackhawk36

Dave, thanks for the input. I checked all mounts this weekend. Had it up on a lift with all covers on the bottom off and someone starting it to create the noise. All mounts are sound. I checked the starter when I cleaned my intake valves. It is good. On the flywheel, I don't think it is loose. My car is a manual so if the flywheel was loose enough to cause a clunk when starting, I would definitely have a vibration in the clutch. The noise is up front in the engine. It is worse when the engine is warm. Next stop is the timing chain tensioner.

i admire your persistence. many would either: a) just give it to the dealer to worry about (warranty/lease return/etc), or b) give up on the car and try to sell it as is. so kudos. hope you can figure out your gremlin.

[marv85]

Originally Posted by Blackhawk36

Dave, thanks for the input. I checked all mounts this weekend. Had it up on a lift with all covers on the bottom off and someone starting it to create the noise. All mounts are sound. I checked the starter when I cleaned my intake valves. It is good. On the flywheel, I don't think it is loose. My car is a manual so if the flywheel was loose enough to cause a clunk when starting, I would definitely have a vibration in the clutch. The noise is up front in the engine. It is worse when the engine is warm. Next stop is the timing chain tensioner.

The dealership said my steering pump was loose causing the belt to shred so they changed the bolts and put a new belt. I'm not sure we had the same clunk, but mine was getting very loud and happens only at startup. Sounds like two thick piece of metal are touching each other at startup. When I picked the car up from the dealership that noise was not there. A couple of days later it came back but is very benign to the point I'm not sure I want to spend time to debug.

Keep us updated!

[Blackhawk36]

Originally Posted by oddjob2021

i admire your persistence. many would either: a) just give it to the dealer to worry about (warranty/lease return/etc), or b) give up on the car and try to sell it as is. so kudos. hope you can figure out your gremlin.

I will find it! Thanks for the encouragement. I will post the fix when done.

[JamesM3M5]

Originally Posted by Blackhawk36

Dave, thanks for the input. I checked all mounts this weekend. Had it up on a lift with all covers on the bottom off and someone starting it to create the noise. All mounts are sound. I checked the starter when I cleaned my intake valves. It is good. On the flywheel, I don't think it is loose. My car is a manual so if the flywheel was loose enough to cause a clunk when starting, I would definitely have a vibration in the clutch. The noise is up front in the engine. It is worse when the engine is warm. Next stop is the timing chain tensioner.

When you have the belt off, check the 6 bolts that hold the vibration damper to the crankshaft. One member here just had his break/fall off last week. Vibration in the clutch pedal could be a bad vibration damper coming apart/falling off the crank, too.

Bad timing chain tensioner sounds like a bad rattle at startup that doesn't go away until oil circulates to the tensioner - about 5-15 seconds. Haven't heard of a bad tensioner causing a startup rattle since the E30 M3 days.

[BMV///M3]

Glad I came across this, don't mean to thread jack but I noticed a squeaking at cold start this AM. I've been noticing it a bit more lately. Called BMW (under warranty) and dropping it off next Tuesday. Possible belt tensioner? I'll post back with the dealer diagnosis.

[JamesM3M5]

There are several idler and tensioner pullies that all have bearings in them. They eventually lose their grease and get noisy. Simple procedure to replace them.

[Tzu]

FWIW, I had a squeak which occured when cold. After checking the pullies, turned out to be the rad fan. Still squeaks sometimes after turning off the car.