Front pulley 5 litre thought I had killed it

[jasoncook]

Hi all just been out for a blast and bang knock tap horrible sounding noises from the engine just as I was educating a boxter owner. Turns out the belt has shredded its self taking half of the right hand heat shied with it and jamming the power pump. Aprox 2K ago it broke the pulley bolt so I had it replaced the crank pulley is now loose again but i can still feel the bolt head. Should I change the pulley ??? part number ETC as I think it must be out of balance to break 1 bolt and shake another loose. What belt is fitted I tried ages ago to get a spare belt ordering for a Range rover with power and aircon but the belts were either too long or too short all ideas welcome the engine is a Serp 95 Thanks Jason cook

[tgriff]

The pulley comes statically and dynamically balanced so you can fit it to your crank. You should use a high tensile bolt available from TVR it is a common fault , but once a pulley has come off a new unit should be fitted
steve

[GreenV8S]

Sounds like the crank pulley bolt wasn't tight enough. They have to be done up 'kin 'kin tight because the front ulley acts as a torsional damper for the crank. At a minimum you should replace the bolt and do it up to the specified torque - which is a lot. Don't over do it though because the bolts can and do snap if done up too tight. Since the pulley is off it'd be sensible to check the condition of the outside of the crank and the inside of the bulley to see if either of them have been damaged. If the pulley is OK I would reuse it. If the crank is damaged it is new engine time.

The poly-V belts are specified by the width (number of ribs) and the length in millimeters. It will probably be marked on the outside of the belt. In any case, if you take these two bits of information to any decent motorfactors they will find a match for you.

[jasoncook]

The pulley bolt was at least the spetified torque plus a bit. When it was running loose it looked out of balance.

[shpub]

The fan belt is a TVR special. It is not a range rover etc part. Either get it matched or get one from a TVR dealer or specialist which is easier and often cheaper.

[shpub]

You may also find that there is a spacer behind the pulley which maybe made from pipe. This can collapse and cause the pulley to go loose. It should be replaced with a spacer that is up to the job.

[2munkys]

Yea, be careful here Jason.

My crank pulley bolt came loose causing some fretting between the keyway in the damper weight and the woodruff key; there was also a full depth crack along the keyway.

We still don't know whether the bolt came loose allowing for hammer resulting in the crack or the crack allowed for some micro-movement causing the bolt to loosen. Luckily the crank was undamaged (jeez, coulda been astranomically expensive). I only discovered this by chance too.

TVR Power supplied a new pulley/damper assembly which they dynamically balanced to that of the old item that I'd forwarded on. I think it came to £170. I had to sign a statement absolving them of responsibility should the crank break as it should be balanced as an assembly. Don't quote me but I think the revised torque load for the crank bolt is 170 lb ft. I gave it a good dose of thread-lock after thoroughly cleaning out the female thread in the crank.