207D camper - fan belt loosens

[jacesmith]

I have a 207D based camper, the fan belt goes loose very quickly. I know how to adjust it, loosen the 3 bolts securing the alternator and then wind the adjustor nut until the belt tightens. Then do up the three securing bolts. After doing this the belt will slcken again after only 100miles or so, even new belts. I cant work out what is happening. Has anybody experienced the same ?

 

[Sprint'n'Go]

I had a 1986 307D up until 2001 and I put about 250k on the clock during my ownership. I can't specifically remember how all the bolts go but I do recall the threaded adjuster as this was a different set up to any I had seen before (normally place a lever between the alternator and engine to tension then nip up the bolts). I changed the belt a couple of times just as a preventative measure and had to fit an exchange alternator at some point and seem to remember it being fairly tight on access and a bit dark to see what you were doing.

I cant think of any specific reasons why the belt would self slacken but from memory I think the bolts have 17mm heads? so make sure they are tightened adequately (they should stand a fair amount of torque but were not talking wheel nuts so don't go mad and it shouldn't really be necessary to do more than a standard 'tight'). I think the belt was a thick one at 12.5 or 13mm? Make sure you haven't inadvertently fitted a narrow 9mm one as this will run in the bottom of the pulley groove and soon wear giving you the slipping problem you describe. Alternatively, are any of the pulleys excessively worn or pitted/corroded (due to long periods parked up?) They should have a definite straight sided V profile. The alternator pulley is most likely to be guilty here as it is often from pressed steel while the crank pulley is usually cast.

Apart from that I can't think of anything obvious. If you have any other info that may help please post it here and if these ideas point you to the problem also let us know the outcome.

 

[Sprint'n'Go]

A vague memory has just surfaced and i am not certain about this but -

the securing bolts are not a push fit but are screwed through the alternator casing/bracket at least for part of the way. However, this is not what completely holds the alternator and there are locknuts on the ends of the bolts as well?

As I say it was a while since I last saw this vehicle so I can't be certain but the above sounds right.