Belt change - running in?

[stjohnsmythe]

Just had the belts changed on my Lux. I know that it will need re-tensioning in 1000 miles but apart from that do I need to take it easy for a bit for the belts to bed-in, etc?

 

[TTM]

No []

 

[xenon]

As long as you re-tension, which is often overlooked, I've never heard of running belts in.

 

[stjohnsmythe]

Excellent, I can see myself enjoying the car somewhat over the coming months []

 

[mr brightside]

I didn't bother with the re-tension, it's done about 3k so far, do i need to see to this asap?

 

[xenon]

Because the belt when fitted from new will have kinks and curves from storage and will straighten out and stretch very slightly as it begins its work. The reasoning is that it will stretch as far as it will ever stretch after 1000 miles and then that's it.

Is it necessary? I don't know for sure. Is it a myth? Nope, 'cos I had mine done after a belt and rollers swap.

However, when my indie checked the belt tension he decreed that no further adjustment was required.

 

[berg944]

A new belt has a different tension setting to a used belt.

If you are lucky the belt will have stretched slightly and falls within the tolerance of the used belt setting.

Some do not need retentioning but all need checking. A visual check to make sure there are no other problems with alignment (especially if you have changed water pump or pulleys) is always a good idea.

Belt stretch is not an exact science but pistons meeting valves is always very very bad[]

Mike[:'(]

 

[geoff Ives]

Also, the sharp edges to the teeth wear slieghtly round. That is why a new belt whines but after a few thousand mailes it goes quiet.

 

[944 man]

M44/07 onwards 944s (1987 model year) have automatic tensioners too: Id still have it checked if I were you.

 

[rcsalmons]

They have auto tensioners but once they are set they are bolted in position.

Rich

 

[Neil Haughey]

Wouldn't the spring tensioner as it is a spring also go out over the years? Ultimately the best solution is an oil fed tensioner like on the 968.

Different question but is it worthwhile rechecking belt tension after a couple of years? I am thinking about the balancer shaft belt in particular as this doesn't have an auto-tensioner.

 

[xenon]

Rich's comment is correct - the tensioner does not dynamically adjust the tension, it's bolted in a fixed position once the tension is taken up. Which is a bit crap, but there you go.

 

[TTM]

ORIGINAL: xenon
Rich's comment is correct - the tensioner does not dynamically adjust the tension, it's bolted in a fixed position once the tension is taken up. Which is a bit crap, but there you go.

... but it still is miles better than the 968 tensioner than actually isn't dynamically oil fed and eventually wears out.

 

[AntB]

Remember the balance belt also needs checking which I believe is a manual tension - and they are 'supposed' to stretch in the first 2k

 

[graham.webb]

Thanks Geoff...a useful comment. Wondered why mine was wining after the last belt change.

BTW I see you've been promoted since last weekend. I enjoyed Blenheim...ticked all the boxes for me, in spite of what others may have said!

ORIGINAL: geoff ives

Also, the sharp edges to the teeth wear slieghtly round. That is why a new belt whines but after a few thousand mailes it goes quiet.

 

[vitesse]

Is it true that the balance belt tension is set approx half that of the cambelt ie.manual method--twist through 180 degs rather than 90 degs?
When I changed the belts only 2 yrs plus ago,the new balance belt was the same width as the cam belt so I have had lots of whistling because the pulleys were unworn & unpolished on part of their width where the previous narrower belt hadn't been running.I have never re-checked the tension since having only done 2-3000 miles a year anyway.Before anyone dives in over that comment,I should say that in my past I have been a power transmission engineer specialist.

 

[barks944]

The balance shaft is slacker than the cam belt. I always leave quite a bit of slack then just adjust it if it makes any horrible whining noises .

I guess im not scared about the balance shaft belt. After I found it to be in pieces when I first bought the car and had driven about 500miles.

 

[AntB]

I recently had my Cam / balance belts done - and they made an awful wining noise... Took it to a porsche specialist who used the tensioner tool and the balance belt was too tight.. They set it at the correct tension and no noise after that []

 

[ChasR]

If you look carefully in Clark's Guide, when he didn't change the belts using the tensioner tool, he said to pretension the balance belt so that the slack is just taken out of the belt. I know when I saw a 968 having work done on it at a Porsche workshop (front end was off) the balance belt seemed looser than cambelts (could easily twist through 90 degrees , but I wouldn't want to twist it more than that!). I am still only new to 944s!

The cambelt (on the 968) could just be twisted to 90 degrees via the tension I normally put on belts from changing the Peugeot 306 XU10 belt and CVH (although the Peugeot like the Porsche has a semi-automatic tensioner done by aligning marks on the tensioner pulley). The belts all whine to a very small degree I found, but I think you'll know how they whine when they are too tight (sounds like a washing machine whine).

Hmmm, when I get enough cash (I.e after I have an new engine...) I may join the club and get the tensioner tool.