Automatic timing belt tensioner?

[geoffbateman]

Just been reading my workshop manual, the Porsche one, not the Haynes book of lies. It says in the engine section that cars after 1987 fitted with the M44/05 engine have an automatic (spring operated) timing belt tensioner and do not need the tension re-checking once the belt is fitted and the tensioner set up correctly. Can anyone verify this for me at all. I've not had the cover off to have a look, I must admit, so if anyone knows the answer before I take it off to have a look I'd appreciate the input. Thanks a lot.

 

[robwright]

It is true that they do have a spring loaded tensioner. The 968 has a hydraulic one I think. I think many do still have the belt tension checked 1 or 2K after fitting. I must admit that when I did mine I didn't bother and they are still fine two years on.

 

[bmnelsc]

Yes the 968 has a hydraulic tensioner (shouldn't they all ????). The S2 certainly has a spring loaded tensioner which is supposed to eliminate the need for re-tensioning. The tension must be set properly the first time around tho (I believe the spring is "locked" in the inbound position with a pin and once the tension is set, the pin is removed which allows the spring to take up the small amount of stretch you get in the first few k).

When I bought my S2, the belts had just been done by the local Porsche dealer and there was no instruction on the work order to return the car to have the belts checked. Its been 3 years now and nothing to suggest the belts are loose.

 

[geoffbateman]

Thanks for the information. That's certainly wetted my appetite to go and have a look. I've got an oil leak to sort out (oil pressure relief valve plug sealing washer) and a new oil pressure sender to fit so I'll have the cover off at the same time and have a look to see whether I've got the spring mounted one or not. Had the belts done about 8 months ago by Porsche Centre and they made no mention of it so here's hoping.

 

[Hilux]

Yes the 968 has a hydraulic tensioner (shouldn't they all ????).

I`m not convinced although they do work until (admitedly rarely) you get low oil pressure at high revs and instead of a possible bottom end rebuild your engine is toast as a few teeth are jumped.

Springs also `relax` over time so sprung tensioners should always be replaced in my book.

Modern composite belts dont stretch these days - they just dont. So any initial `release` once installed is tiny and a fixed tensioner is the norm. 90 degree twist is usually the only test they need once fitted.

 

[sulzeruk]

I always check the tension again. better being safe than expensively sorry!
Alasdair

 

[Hilux]

Agree but this is only needed on sprung tensioners. Any other check is to see if the fixed tensioner has moved. The belts arent the issue.

 

[sulzeruk]

The balance belts usually always need a tweak anyway as they seem to loosen slightly. The spring loaded cambelt tenisoner gets them close usually bt never spot on.
Alasdair