Belt Tension 944T

John Maddox · May 13, 2005

An old topic I know and I have looked through the archive. Just to get the up to date thinking - I am about to install new belts etc - can I rely on the auto spring tensioner looking after cambelt tension ?. I am not so worried about the balance shaft tension.

It looks very tight to get the cambelt in - should the spring tensioner be removed first ?

Clark Garage page indicates you can do it without removal but fiddly. Any experience on the forum.

Thanks

Fen · May 13, 2005

I have never changed my own belts but I do know that even with the latest tensioner the tension is set manually and should be rechecked after 1,500 miles, so I'd say no, the auto tensioner should not be left to look after tension itself.

berg944 · May 13, 2005

can I rely on the auto spring tensioner looking after cambelt tension

No.

I think the tensioner is only automatic while you set your belt in the correct position and undo the bolt to let the spring set the tension. It then must be locked in place.

I would not expect any body to over tighten a belt with this system, but you could have too much slack if the spring is weak, the tensioner sticks or the belt is not in the correct position.

As any of the above could damage an engine beyond economical repair, I would use the auto tensioner first them turn the engine over by hand a few times then recheck the tension with a gauge.

Mike

Diver944 · May 13, 2005

No

You must tension it correctly and then recheck it after approx 1500-2000 miles. Club HQ has the factory tensioning device that members can borrow, though there is a very cheap aftermarket version from suppliers in the States called a Krikit which I believe that Andrew at Promax is now stocking.

Guest · May 14, 2005

The spring tensioner won't pull a new cam belt tight enough. Period. If you do it, the new belt will be way under tensioned, i've tested it.

The Krikit tool actually works pretty good, though I don't trust it 100% so borrow a 9201 Porsche tool also. Loss of the timing belt would be a disaster.

Also note that the updated balance belts are 18mm wide rather than 15mm. They require more tension. Clark's has the figures I believe, but I have them in my files if you need it.

The BS belt should not be dismissed lightly, if you lose that it will probably take out the cam belt and your day is really ruined.

John Maddox · May 14, 2005

Thanks to everyone for the advice.

Just done the belts etc and made sure cambelt well tensioned and balance belt a little tighter than before. I will check tension with proper tool if I can locate it in the club.

Unbelievably I now have a coolant leak immediately on starting. Main hose from Waterpump to bottom of radiator failed where the jubilee clip is at the waterpump end !!

OPC Colchester has the only hose in the UK and is posting it to me.

Thanks again

Guest · May 15, 2005

You should retension around 1000 to 1500 miles. Make sure you use the used belt tension specs, not new.

The balance shaft belt is easy to overtighten. If you hear a whine which gets louder as the motor heats up you probably have overtightened.

John Maddox · May 18, 2005

Just received the Krikit belt tensioner tool as suggested only to find the instructions say it is not suitable for 1987 or later cars or turbo's with the spring tensioner arrangement so have had to send it back. Sods Law I think.

Guest · May 18, 2005

ORIGINAL: John Maddox

Just received the Krikit belt tensioner tool as suggested only to find the instructions say it is not suitable for 1987 or later cars or turbo's with the spring tensioner arrangement so have had to send it back. Sods Law I think.

Who did you get this from? This is the first time I have EVER heard such nonsense. The Krickit is made by Gates Rubber, the belt people, as a cheaper alternative to the more costly tools. Everyone uses them on cars with the spring tensioner as the belt's tension is the same as the older ones once you lock the tensioner down. If anything the instructions should say "Don't use this tool on any belt as it isn't as accurate as a $500 tool."

But it is usually accurate enough once you get used to it and can achieve repeatable readings.

John Maddox · May 18, 2005

IceShark - I was quoting directly from the instructions that came with the Krikit tensioner. Already sent it back and the supplier has confirmed not suitable for spring tensioner 944's and Turbo's.

Trying to locate the clubs tool now.

John Maddox · May 18, 2005

Just looked at the Gates website and they actually put in the Krikit information that it is not recommended for timing belts !!!! What is going on here? I think I am going to rely on my own judgement in future.

Guest · May 18, 2005

ORIGINAL: John Maddox

Just looked at the Gates website and they actually put in the Krikit information that it is not recommended for timing belts !!!! What is going on here? I think I am going to rely on my own judgement in future.

WOW! A lot are being used exactly for that. Thanks for pointing this out!

At least I have around 6 Porsche 9201 tensioners I know where to borrow.

Guest · May 18, 2005

Whenever replacing a t-belt on the 87+ cars I use only the factory spring loaded tensioner.
Never had a problem.
I *DO* however completely remove and disassemble the tensioner to inspect it and glass bead blast then lubricate all moving parts to make sure it functions properly (moves freely, etc.)
The srping is not actively setting tension once you lock down the adjustment and the heat that the spring encounters is not severe so I can't see it "losing tension" due to fatigue, etc.
If the tensioner is full of grit and crud, then yes I could see it being an unreliable source for tensioning but if it's in perfect working order.....no worries.

Just my .02..

TT

944Turbo · May 21, 2005

The srping is not actively setting tension once you lock down the adjustment

when you say lock down the tension do you use the correct guage at this point?
Tony

Guest · May 22, 2005

What I mean is that the spring is not actively setting tension after you're finished the job and have locked down the nut so it's not like the spring has a hard life of work that would cause fatigue like a diaphram spring in a wastegate for example- high heat, constant compression/decrompression.

To answer your question specifically though, no, I use no tool to check adjustment after following the refurbishing of the unit to make sure it's in working order as I described.

I've owned several 944s over the span of 12-15 years and have never had a problem with auto tensioners.

TT

chris_boyle33 · Jul 18, 2005

My car's coming up to its 2,500 mile re-tension and i fancied having a crack myself using the 9201 tool. Are you saying (a) you don't need to retension, and (b) don't need to use the tool?

Even if you were to confirm this i might prefer to play safe...[8|]

Guest · Jul 18, 2005

ORIGINAL: chris_boyle33

My car's coming up to its 2,500 mile re-tension and i fancied having a crack myself using the 9201 tool. Are you saying (a) you don't need to retension, and (b) don't need to use the tool?

Even if you were to confirm this i might prefer to play safe...[8|]

On the retension, which you do need to do, with an '83 you have no spring tensioner. The 9201 tool is usefull if you have access to one. Otherwise get a Krikit tool for cheap - like $10USD. It works OK. Real good mechanics can usually get tension close just twisting the belt by hand. But you better have done a lot of these jobs!

Also note the used belt tensions are lower than new. Common mistake using brand new belt tensions specs on a retension job. Your balance shaft belt will howl like crazy if you over tension it. You will know right away if you made a mistake on that.

berg944 · Jul 19, 2005

On the retension, which you do need to do, with an '83 you have no spring tensioner.

You must retension ALL MODELS

The auto tensioner is only automatic while adjusting the belt, It is then locked in place and and stays there like the earlier models.

I think it was redesigned to either do away with the tool or at least get it nearly right before checking with the tool.

Mike

Guest · Jul 19, 2005

No Mike,

You are sort of right but not totally. I think the spring auto tensioner was introduced in '87. You do lock and unlock it via the nuts so it won't change tension on the fly as it were.

However, the spring is far too weak to set tension on a new belt. Maybe OK on a used belt but no one I know trusts it 100% even for that and allways does another test.

The old blocks can be mounted with the spring tensioner and some do it but I think it is a waste of time.