Timing Belt Re-Tension
08-14-2018, 10:02 PM
#1
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Thread Starter
Timing Belt Re-Tension
Does a newly installed timing or balance shaft belt need to be re-tensioned after 1500 miles on a 1989 951? I thought the re-tension only applied to the models before 1987.
Thanks
Thanks
08-15-2018, 12:00 AM
#2
Burning Brakes
Yes.
Check the belt tension first, (gauge or twist) then follow the shop manual procedure for the belt tensioner and you're done. Balance shaft not so critical since the belt is loose to begin with.
Glad to hear you are retensioning the belts, many ignore the extra hassle and get broken belts, and/or bent valves. ;(
Check the belt tension first, (gauge or twist) then follow the shop manual procedure for the belt tensioner and you're done. Balance shaft not so critical since the belt is loose to begin with.
Glad to hear you are retensioning the belts, many ignore the extra hassle and get broken belts, and/or bent valves. ;(
08-15-2018, 09:37 AM
#3
Double yes... the timing belt may have a self tensioning device but the balance shaft does not, and I have found that both typically need a tweak after the first 1500mile run-in to get back into proper range.
By the way, make sure you use the proper tool to measure. I’ve had way too many experts tell me they can “feel” the right level of tension, but when I measured my own after having a self proclaimed expert tell me he had done me a favor and tensioned my belt by hand, I found that he had it three times higher than Porsche recommends. On the other hand, a real expert named Don Istook, who has done more timing belt jobs than most over the years, told me he would refuse to do a job if he can’t use the factory tool to measure it. If he can’t do it by hand, trust me, no one can.
By the way, make sure you use the proper tool to measure. I’ve had way too many experts tell me they can “feel” the right level of tension, but when I measured my own after having a self proclaimed expert tell me he had done me a favor and tensioned my belt by hand, I found that he had it three times higher than Porsche recommends. On the other hand, a real expert named Don Istook, who has done more timing belt jobs than most over the years, told me he would refuse to do a job if he can’t use the factory tool to measure it. If he can’t do it by hand, trust me, no one can.
08-16-2018, 08:04 AM
#4
Drifting
The tensioner on later cars isn't dynamic (i.e. it doesn't automatically move to keep constant tension on the belt like most newer cars with tensioners fed by oil pressure). You will need to loosen the adjustment nut, let the tensioner retension, then retighten the bolt.
See Tom McGuinn's excellent article in a recent Panorama issue, where he compared the accuracy of various tensioning tools and methods. He found the factory tensioner slightly undertensioned the belt.
See Tom McGuinn's excellent article in a recent Panorama issue, where he compared the accuracy of various tensioning tools and methods. He found the factory tensioner slightly undertensioned the belt.
08-16-2018, 11:20 AM
#5
Any chance we can get that article reposted here, maybe with a picture of Tom's Corgi, Gizmo? 
08-25-2018, 05:13 PM
#7
Burning Brakes
Which tension do I use when retensioning the belts? That is, a newly installed belt after 1500 miles. I assume I use the "Used Belt" specs but just want to be sure. I'm using the Arnnworx tension gauge.
Thanks.
Thanks.
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08-25-2018, 07:24 PM
#9
Drifting
Never laid eyes on the factory tool. I check the cam belt tension on a warm engine. Same water pump has been on the engine for years...
