300TDI Alternator problem

Hi, i have a 300 tdi disco on an N plate, an the alternator nut keeps coming loose on it, once the nut come loose it causes damage to both the pulley and the shaft from the alternator resulting in having to replace the unit! this is now the 3rd time in 6 months it has done it!! i have checked and checked that everyting is running in line, i have tightened the nut with a big bar and put alot of locktight on the nut and the shaft from the alternator and left over night to set before installing the unit. I have also replaced the fan belt and the tensioner as i though the tensioner had a whisper of movement in it!! it just seams to do about 2000 miles and then goes again its extreamly frustrating and expensive as its a new alternator every time!! has any one had similar issues??

use locktite bearing fit it wont come undone again

I would start to suspect the pulley itself (slightly too big ID), is it the right one? I have seen incorrect pulleys fitted to 300tdi alt's in the past.

Are all the pieces there, there are a few variations, some have the pulley a big thick washer and a nut, others have a spacer, pulley and a nut. If you don't have all the bits in the right order they do tend to work there way loose.

I usually just horse the nut up as hard as I can with a big ratchet and counter hold the pulley so the alt doesn't turn.

Is everything sitting in line OK.

yea pulley is right one, the new units came complete with pulley and is a brit part unit bought from land ranger services. it has both nut and a spring washer holding the pulley on. i used a lock tight not a bearing fit as i didnt have any, but i still find it odd why it keeps doing the same when i cant see anything out of line and there isn't any vibrations

There is your problem! BRITPART!

Not being funny, they are probably messing something up, making the pulleys incorrect size or generally making a mess of something.

For example pulleys must be made from the correct metal, they are designed to stay put, if they get the metal wrong expansion and contraction rates can throw the whole thing - this is more so on a taper fit pulley, but it gives you an idea of how they can balls things up.

I am almost certain at this point that it is down to poor workmanship.

I would get onto them ASAP, letters to supplier and Britpart and have a good moan, they supply it with the pulley fitted, therefore it's not something you can make a mistake with while fitting, their fault.

Please note that it should be possible to even make Britpart parts work OK. C'mon a pulley on a shaft - its not rocket science! There are numerous grades of Loctite. The common grade is for easy undoing but you can also purchase the High Temperature Retainer grade (also sold by Vapormatic in a nice sized bottle) The retainer is really intended for fitting loose type cylinder liners but it is extremely versatile. I'm now beginning to wonder whether there is something wrong with your engine. Is the cam timing or injection timing out? If the engine is running roughly, unexpected problems may appear in other places. I seem to recollect over the years that some alternators had a fine thread holding on the pulley. Others had a coarse thread which IMHO is not so good. As a last resort why not try a pair of locking nuts? If the thread is not long enough the pulley could be bored deeper. Some vehicles use a free-wheel pulley to save gear changing shocks but in practice the free wheel mechanisms have been more trouble than they were worth. If you have a friend with a lathe it might be possible to produce a THREADED pulley. This with a nut fitted as well should never come off as any reverse rotation on the over-run would just drive it into the retaining nut. I actually suspect that a sloppy fit and a coarse thread is causing the trouble. Good luck!

Davey1000 said:

Please note that it should be possible to even make Britpart parts work OK. C'mon a pulley on a shaft - its not rocket science!

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cmon this is ****part they could fcuk up almost anything