Question-------------------------
Followup To
Question -
is there an inexpensive way to tension a drivebelt if it does not need replacing? what are the signs that it needs replacing (either visual or sounds)? how much is too much to pay for this service? this is on a 1987 porsche 944 8 valve, non turbo with a manual transmission. the belt has been replaced once to my knowledge and looks to be in good condition (no cracks or fraying)
Answer -
Hi Travis, good to hear from you again.
I don't want to make an error here on terminology and assume you're talking about one kind of belt when I'm talking about another. So... when you say "drivebelt" I'm going to assume it means: the easily accessible belts that turn the alternator, power steering pump, and air conditioner. The number of belts is a function of the accessories installed and the pulley arrangements. What you are NOT talking about and I won't be discussing unless you write back specifically...is the camshaft belt and the balance shaft belt, both hidden deep inside the engine, both not readily accessible and both extremely critical and expensive to the owner if they fail.
So...with respect to the drivebelts...and your query: "is there an inexpensive way to tension a drivebelt"...there is no cost involved in tensioning them. That's why I want to make it perfectly clear which belts we are talking about. Each drivebelt is tensioned by moving the belt driven accessory, like the air conditioning compressor, on its bracket. This is accomplished by loosening the pivot bolts and pressure rod locknuts...adjusting the length of the pressure rod to tighten or "tension" the belt, and then tightening all the loosened nuts/bolts.
As for their condition, you're right on track looking for cracks and frayed edges. Keep in mind that the belt would be best examined off the car...but if you're THAT worried about it you might as well put a new one on at that point. You are perfectly capable of changing it yourself, so I won't comment about shop charges.
If you're talking about the camshaft belt or the balance shaft belt, that's for another time. Write back to me if you have any questions. Thanks. Hope I hear from you soon.
Dave
dave it was good to hear from you, unfortunately i was talking about the camshaft drivebelt. i am actually in the middle od changing it right now. i believe that the 1987 944 has a self tensioner and that it will work out alright, i would still appreciate your input and advice.
AnswerTravis,
Hi...I had a hunch that's what we were going to be talking about. The rule of thumb is to begin worrying about the condition of the TWO belts...the camshaft timing belt and the balance shaft belt when they reach 25,000 miles. Each mile after that will increasingly add stress to your heart...and by the time you reach 30,000 miles, if you do...you'll be ready to change the belts, just so your blood pressure can go down.
You see, these two belts, which are subject to oil contamination, heat checking, and the out of sight, out of mind syndrome, WILL break... and when they do the pistons will hit the valves. Oops, time for another engine rebuild.
I'm sure you'll find guys who've said they got 55,000 miles out of their belts...well, do you want to be the guy to try and eek out some more mileage to save a buck or some time? I'm notorious for trying to get just a bit more mileage from my tires, but they're easily seen and checked every moment and when one pops, I won't have to rebuild my engine, like when a belt snaps.
OK, as you may be able to tell, I'm not all that keen on the design the Porsche engineers came up with here. And then to use a belt they can't guarantee for any certain mileage. DUMB! Oh...I almost forgot...if you don't really know the mileage on these two belts, I wouldn't drive the car one foot without re-newing them both!
I'd suggest spending some time at this website: (http://www.clarks-garage.com/)...which is really very cool...and this particular page dealing with the belts themselves: (http://www.clarks-garage.com/shop-manual/eng-10.htm).
I've done the belt replacement and tensioning myself without the special$$$$$$ tool and I know from forums I visit that a lot of folks feel the say way I do, that it's perfectly possible to do so as a home mechanic. The risks the factory or the dealer, or even the Haynes manual discusses are very real...if you don't get it right...so each of us has to choose whether to do the work or have it done. Not having had it done professionally, I don't know the costs, but some estimates I've seen range in the $200-$400 area. And the belts are way less than $50.
This is going to sound hokey...but if I were doing it again I would test feel prod measure and study the tension (the movement of the belts when you press them with your thumb) of the old belts first and foremost. Other than some slack from age that should be taken up by the tensioner, the tensions you see and feel are right...right? So duplicate them as best you can and you're done. It' really the same notion as the power steering belt tension...how do you know it's right???
Here's another way to think about it: too loose will cause a noticeable squeal...a tiny bit will cause a noticeable squeal on start-up, just till the belts warm-up...and they warm up very quickly. Too tight? Well it seems the ONLY problem with too tight is that the belt may fail prematurally, UGH! Remember, if Porsche wanted no slack (too tight) then they would have used timing chains like the rest of the modern world.
So...now that I have imparted all the wisdom I could regarding how tight is too tight...here's the last idea for you. When you are done, for the first 250 -500 miles your heart will be going pitter-patter becasue you really won't know if you adjuted it right...will you? So rather than "re-check the tension after 1000 or 1500 miles"...re-check your work at 250-500. Get in there again, by now it'll be easy to get the engine apart enough to see the belts. Put your thumb in there, put your nose in there, shine that flashlight down into the deep dark recesses of that valuable engine and then smile...'cause the tension "feels right" and you won't have to do this job for another 25,00 miles. Mark your calendar!
Dave
