I am doing some work on my newly aquired turbo including doing the belts. To my surprise when stripping it down I found the spring was missing from the cambelt tensioner. Obviously it has been running for a number of years like this, the last belt change was 10 years ago!! So the question is do I just set the initial belt tension manually, I have a tool to check it. Once the the tension is set the tensioner is locked in position anyway.
Auto belt tensioner spring missing
- Thread starter JM1962
- Start date
bmnelsc
New member
That might do as long as you keep an eye on your tension. IMHO the spring takes up slack as your belt stretches (which they do) so as your belt wears in- you will get decreasing tension on your belt with no spring to take it up. If I were you - I'd look for a new/used tensioner with a functioning spring.
Mine was exactly the same! Someone, somewhere has a pile of springs!
I replaced it with a second hand tensioner.
Have to disagree with Bruce though... when the tensioner bolts are torqued properly the spring does nothing... it's just there to set the initial tension. When the belt stretches you have to manually loosen the bolts and let the spring take up the slack, hence the 1500 mile belt retension rule.
I replaced it with a second hand tensioner.
Have to disagree with Bruce though... when the tensioner bolts are torqued properly the spring does nothing... it's just there to set the initial tension. When the belt stretches you have to manually loosen the bolts and let the spring take up the slack, hence the 1500 mile belt retension rule.
Nearly right, Rob - very nearly.
The spring is a guide to setting the initial tension, but no more than that. In my case (and most cases, as far as I can tell) the spring slightly over-tensions the belt, and you need to slacken it off a smidge before locking the tensioner. The belt tension gauge exists for this very reason.
There is a school of thought that says that you run the belt on the spring tension and don't lock the tensioner at all, but I can see no logic to this argument at all.
Oli.
Who ever have worked with your cars belt earlier have done job a wrong way. Spring does not come out without putting tensioner into the pieces. Working tensioner usually put the belt as it should be and when it is tighten up spring does not do nothing. So, you can manually set up your belt if you wish.
Veerzigzag
New member
Better swap it quick - 4 years max belt life and most people change at 3 years. Probably needs the oil seals changing too, and maybe a new water pump - lots of postings about this.
Oli is correct ref the function of the tensioner - as ever this is outlined well on the Clark's Garage web site.
Clark's site also has photos of bent valves and gouged pistons if you need some incentive to get the belt changed before it breaks!!
924nutter
PCGB Member
FFS do not EVER contemplate running the engine relying purely on the spring in the tensioner to keep the belt tight. It wont. Rev it much past idle and the dynamic forces on the belt will make it jump teeth. As I suspected there are many people on this forum who do not know what they are talking about, and in this case I am happy to insult them if it will help prevent a beginner from damaging their engine by trying such a stupid stunt. Porsche are not known for engineering extraneous mechanisms and if the bolt wasn't necessary it wouldn't be there. I know I sound quite vehement about this but get this wrong and it wont be about taking off a caliper to replace pads instead of compressing the centre of the spring with the caliper in situ (my own personal mistake); we are talking two orders of magnitude worse in terms of expense and I wish I hadn't done that!
Veerzigzag
New member
Not at all - I don't think you can be too vehement about mis-using the tensioner like that; leaving the bolts loose and allowing the spring to fight the belt is a guaranteed self-destruct plan.
As ever with Porsche engineering, RTFM, and RTFM again.
bmnelsc
New member
Oops! Thanks for the correction. I better review how this thing actually works before I do my belt change (coming soon). I ASSumed [
] the spring was there to take up a little slack (obviously the range of motion is limited) otherwise not much point in having a spring at all. Thanks for setting me straight.That is exactly what I'm doing. I had to drive the car 150 miles to get it home and haven't driven it since, in fact I can't because I have removed the head. Plan was to do the belts, then I thought I would fix the cam tower oil leak, then I thought I may as well remove the head, so things have snowballed a little.
... but even this doesn't work reliably as the tensioner may not set the tension correctly. They seem to slightly over-tension the belt; mine does, and I have heard of others that do the same.
As I said in my last post, the tensioners exist for a reason!
(However, as an aside, I don't know how critical the tension is. I have never come across any other marque of car that is so fussy about setting the tension up, and the engineering on a 944 is no different to that on any other car with a toothed belt to drive the camshafts. I suspect there is a huge latitude of 'acceptable' tension on a 944, as there is on everything else.)
Oli.
924nutter
PCGB Member
I too subscribe to the myth that the 944 engine has to be worked on with a voodoo doll hanging from the bonnet light. The service interval on my Citroen Ax GTI is 70,000 miles for the belt. Half the engine I know, however, the belt is only half as wide, but drives the water pump and red lines at about 6,400 and I always set it up with the quarter turn twixt thumb and forefinger, as I did on my golf GTI and all iterations of my 924. When I sent the 944 to my local indie for MOT and tension check he said one of the belts was too tight, but I didn't think to ask if it was the cam belt set by the tensioner.
I seem to recall getting all this set up infromation from the data reproduced on Clark's Garage, and now we are starting another myth that the factory tensioner sets the belt too tight when used,
There is a different belt for the 16 valve engines, I have not seen one but given the extra load driving two camshafts, especially as the inlet drive is taken from the exhaust cam by chain, my guess is it would be wider so Porsche have got this covered too.
When all said and done it is called the automatic belt tensioner, not the automatic nearly gets it right. close but no cigar tensioner. If anything due to metal fatigue of being constantly compressed for five years I would have thought that subsequent use would put too little tension in the belt. More when I check up with Clark's.
I seem to recall getting all this set up infromation from the data reproduced on Clark's Garage, and now we are starting another myth that the factory tensioner sets the belt too tight when used,
There is a different belt for the 16 valve engines, I have not seen one but given the extra load driving two camshafts, especially as the inlet drive is taken from the exhaust cam by chain, my guess is it would be wider so Porsche have got this covered too.
When all said and done it is called the automatic belt tensioner, not the automatic nearly gets it right. close but no cigar tensioner. If anything due to metal fatigue of being constantly compressed for five years I would have thought that subsequent use would put too little tension in the belt. More when I check up with Clark's.
Not quite sure what you are saying here, but I'd disagree with the 'starting another myth that the factory tensioner sets the belt too tight' bit. The fact that the spring in the factory tensioner sets the belt on my S2 too tight is no myth, it's a fact! I have read that some others have found the same, although I don't know whether this is a common occurrence or not.
Oli.
924nutter
PCGB Member
Actually Oli I am not sure what point I am trying to make now.
I have faith in the auto tension if set up properly.
I had the bolt come loose on mine after a belt change
Tension may be more critical on the 944 because the post for the idler can flex, we know of members who have sheared them off.
Tension may be more critical becuase of harmonic vibration of the belt
The club has two belt tension gauges available for members to use, providing one hasn't taken up permanent residence with Tref (lol)
The 16v engine uses a diffrent belt, and i was just about to check on the pulleys to see if the were different.
I have faith in the auto tension if set up properly.
I had the bolt come loose on mine after a belt change
Tension may be more critical on the 944 because the post for the idler can flex, we know of members who have sheared them off.
Tension may be more critical becuase of harmonic vibration of the belt
The club has two belt tension gauges available for members to use, providing one hasn't taken up permanent residence with Tref (lol)
The 16v engine uses a diffrent belt, and i was just about to check on the pulleys to see if the were different.
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