katluke Posted May 19, 2015 Share Posted May 19, 2015 After having enough of the tensioner/ belt squeeling like a pig on my 300 tdi I decided to fix it. Firstly I bought a new bearing for the tensioner wheel but this didn't cure it so decided to investigate further. What I found was that the long bolt that fastens the tensioner unit to the casing was loose. Easy fix I thought get a 15mm socket and just tighten it up ! However the bolt just kept turning and I realised that the threads in the casing for the bolt were stripped. After calming down and getting over the shock I composed myself and searched the net for an idea how to fix this. There is a few ways from using heli coils a new casing or stripping casing from engine and putting a new bolt in from behind. What I did find was that people had just turned the bolt around and inserted the longer threaded part of the bolt into the casing and this had caught any remaining threads. I stripped the tensioner unit from engine and when I removed the bolt a broken helicoil and other crud came out from the bolt housing. Luckily I tried the bolt in reverse and it did indeed catch onto some remaining threads.I cleaned out the bolt housing then I put some Locktite onto the bolt and tightened it as much as I dared. I was waiting for parts to be delivered so had a bit time to think about fixing this bolt more securely as I wasn't 100% happy with it. I'm not sure if it has been done this way before but this is what I came up with. I drilled a 3mm hole at the 10'oclock posistion through the casing and through the bolt housing,through the bolt and out the other side of the bolt housing. I then slid a 3mm stainless dowel through the hole and then cut it off 10mm proud of the casing so I could remove it with pliers if ever needed. This should now hold the bolt very secure and allow me to torque the nut up on the tensioner to 45nm and with no chance of the bolt failing and the tensioner falling off. I will keep checking it from time to time just to be sure. Here is a photo of it . Edit to say could have probably used 2 mm stainless dowel but I didn't have any. Quote Link to comment Share on other sites More sharing options...
Blanco Posted May 19, 2015 Share Posted May 19, 2015 That looks like a great fix, always rewarding to think yourself out of a hole... quite a long 3mm hole to drill though, knowing my luck I'd have broken the drill doing that and doubled the trouble. Certainly wouldn't have attempted a 2mm hole, any drills I have would be way too short. Quote Link to comment Share on other sites More sharing options...
katluke Posted May 19, 2015 Author Share Posted May 19, 2015 I only drilled through the outer casing at the 10o'clock posistion and through the centre housing that the bolt fastens into. The length of the hole drilled is about 55mm. On the pic it looks like the dowel goes through the casing on the opposite side of the housing but it doesn't,the dowel is just pushed hard up against it. Quote Link to comment Share on other sites More sharing options...
PaulN Posted May 19, 2015 Share Posted May 19, 2015 Excellent lateral thinking! If only I could have such clarity of mind when in a jam! Quote Link to comment Share on other sites More sharing options...
Sheffield Posted May 20, 2015 Share Posted May 20, 2015 I think the failure of the thread in the alloy casting must be a common problem. I have wondered if I should get a spare one while they are still available. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 20, 2015 Share Posted May 20, 2015 A helicoil would fix it no problem, surely? Bit cheaper than a new casing, I suspect... Quote Link to comment Share on other sites More sharing options...
katluke Posted May 20, 2015 Author Share Posted May 20, 2015 This one had been repaired with a helicoil and when I stripped it down it was all broke up into little pieces so didn't fancy doing it that way again . Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 20, 2015 Share Posted May 20, 2015 Yeah I was talking to Sheffield really, I get your needs are different somewhat Quote Link to comment Share on other sites More sharing options...
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