M42 chain tensioner bolt stuck

Wed Jan 07, 2009 5:42 pm

I'm having some difficulty removing the timing chain tensioner cap on my M42, the bolt seems to be stuck solid! I left it to soak in WD40 overnight but I still couldn't shift it this morning, and am getting a bit worried about ending up with a rounded bolt.

Does anyone have any ideas as to what I could try next? Would applying a little heat around the bolt help, or is this risky given the alloy head?

And there was me thinking this would be a 15 min job!

Wed Jan 07, 2009 5:51 pm

Not sure whether the bolt is stuck or not. My son replaced the tensioner on his 318is and to be frank it was a real pig to undo the bolt. We had to put an extension arm on the socket that was about 3 feet long to get enough leverage to undo the bolt. When it came undone it went with a real 'crack' initially we thought something had snapped. Not sure what the torque should be on this when replacing and tightening up, but to be frank we just tightened it upo using a normal socket extension then ran the motor at 3000rpm to pressurise the tensioner. There have been no oil leaks and timing chain seems to run sweetly. But as your finding a bit of a pig to undo.

Wed Jan 07, 2009 6:18 pm

it is a cap not a bolt.go at it from under the car with a hex socket and an extension bar for more leverage.
or slide a pole over your ratchet handle,,,let the engine run first up to temp then no need to add heat..

you can get the cap from bmw with the tensioner and the washer,all cheap,,under £40

if the correct socket is too big as the cap head is rounded,beat on the next sized down socket till it's home'
and it will come out.

Wed Jan 07, 2009 7:58 pm

Cheers guys, i'll warm up the engine then get a piece of scaffolding tube over my ratchet and give it hell!

Wed Jan 07, 2009 8:14 pm

job done m8,let us know the result m8

Sun Jan 11, 2009 11:31 am

Got the cap off eventually (took quite some force to remove!) and popped in a new tensioner. My engine's still a bit noisy between 3.5k and 4.5k rpm when warm though, so i'm guessing the sprockets and chain could be to blame!

Sun Jan 11, 2009 12:01 pm

haw many miles on the clock jek?

Sun Jan 11, 2009 12:09 pm

Jek318is wrote:Got the cap off eventually (took quite some force to remove!) and popped in a new tensioner. My engine's still a bit noisy between 3.5k and 4.5k rpm when warm though, so i'm guessing the sprockets and chain could be to blame!

i'd say so yeah. I replaced the tensioner on mine and it was still a tad rattle. Replaced everything (because im like that

) and its no longer rattley!

Sun Jan 11, 2009 12:12 pm

Sure its the chain? I had a customer a couple of weeks ago ask us to replace his tensioner, which we did, but the noise was infact a broken heatshield. Its the one bolted above the axhaust manifold around the HT leads. Its only around £3-£5 from BMW too.

Sun Jan 11, 2009 12:14 pm

Jek318is wrote:Got the cap off eventually (took quite some force to remove!) and popped in a new tensioner. My engine's still a bit noisy between 3.5k and 4.5k rpm when warm though, so i'm guessing the sprockets and chain could be to blame!

I did exactly the same, I'm just hoping it lasts til the next engine swap...

Mon Jan 12, 2009 11:58 am

I've got 122k on the clock right now, Magpie. My funds are quite low and don't think i could afford to replace the sprockets etc. Not doing many miles in her just now tho, so hopefully she'll last untill i can afford the parts!

Good tip Sheps i'll check that one out. I must admit, i'd describe my engine noise as more of a vibration (from inside the car, it sounds like its coming from behind the wheel/speedo) than a rattle if that makes any sense, i.e its higher pitched. Also when i first noticed the noise, i took the car to a mechanic who did the screwdriver on the chain cover test and he didn't think it was chain related, he's not a bmw specialist tho!

Mon Jan 12, 2009 7:57 pm

Jek318is wrote:I've got 122k on the clock right now, Magpie. My funds are quite low and don't think i could afford to replace the sprockets etc. Not doing many miles in her just now tho, so hopefully she'll last untill i can afford the parts!

Good tip Sheps i'll check that one out. I must admit, i'd describe my engine noise as more of a vibration (from inside the car, it sounds like its coming from behind the wheel/speedo) than a rattle if that makes any sense, i.e its higher pitched. Also when i first noticed the noise, i took the car to a mechanic who did the screwdriver on the chain cover test and he didn't think it was chain related, he's not a bmw specialist tho!

Yes, definately worth checking that heat shield. It vibrates quite loadly and sounds similar to a chain hitting the housing lol.

Good luck mate