Urgent, timing belt tensioner moves.
10-05-2006, 01:43 AM
#1
Drifting
Thread Starter
Urgent, timing belt tensioner moves.
Well I'm a little worreid. I have basicly finished my timing belt / water pump / seal replacement and just instaleld my rad hoes etc and used a .5 mm feeler gauge to set the balance belt roller and have followed all of Clarks directions and I'm using all the correct tools.
Here is what is worrying me. I wanted to make sure that the timing belt tensioner was tensioned to 33 ft-lbs correctly (double checking ) so I held the eccentric nut with the thin spanner and used my torque wrench until it clicked without moving the nut so it was already tightened, however as I was turning the torque wrench, I applied counter torque to the wrench on the eccentric nut and the timing belt tensioner moved slightly counter clockwise.......
now I was shocked that the roller could still move when it is torqued down. so this time with the torque wrench I just put the thin spanner on the eccentric nut and tried to turn it and again I could move it a little counter clockwise and a tiny bit clockwise. Is this normal?
the tensioner , nut / washer are all properly installed and when I turn the motor over by hand the tensioner does not move or anything just when I try and turn it with the spanner on the eccentric nut you could still move it when applying some pressure.
now I wanted to also check the balance shaft tensioner so I tighened that up to just less than 30 pounds and then torqued it to 33 ft-lbs until the wrench clicked and it was pretty tight , however with the think spanner on the eccentric nut I was able to turn it counter clockwise a little at a time until it loosened up fully and the belt fully went slack......
now it is again installed properly and torqued to 33 ft-llbs.
so is this normal? I'm scared that the pressure from the belt could do the same but I'm hoping I'm wrong and this only happens with the spanner.
I want to start the car tomorrow but I don't want to have a nice suprise when the belt comes out.
Here is what is worrying me. I wanted to make sure that the timing belt tensioner was tensioned to 33 ft-lbs correctly (double checking ) so I held the eccentric nut with the thin spanner and used my torque wrench until it clicked without moving the nut so it was already tightened, however as I was turning the torque wrench, I applied counter torque to the wrench on the eccentric nut and the timing belt tensioner moved slightly counter clockwise.......
now I was shocked that the roller could still move when it is torqued down. so this time with the torque wrench I just put the thin spanner on the eccentric nut and tried to turn it and again I could move it a little counter clockwise and a tiny bit clockwise. Is this normal?
the tensioner , nut / washer are all properly installed and when I turn the motor over by hand the tensioner does not move or anything just when I try and turn it with the spanner on the eccentric nut you could still move it when applying some pressure.
now I wanted to also check the balance shaft tensioner so I tighened that up to just less than 30 pounds and then torqued it to 33 ft-lbs until the wrench clicked and it was pretty tight , however with the think spanner on the eccentric nut I was able to turn it counter clockwise a little at a time until it loosened up fully and the belt fully went slack......
now it is again installed properly and torqued to 33 ft-llbs.
so is this normal? I'm scared that the pressure from the belt could do the same but I'm hoping I'm wrong and this only happens with the spanner.
I want to start the car tomorrow but I don't want to have a nice suprise when the belt comes out.
10-05-2006, 09:44 AM
#3
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Hi,
If this is an 86 or older you have to be extra careful of the belt tensioner design. I just went though this with an 86 turbo so I think I know what's happening with yours. Porsche designed the tensioner using a stud that screws into the block and is held in place with a jam nut. If during loosening of the tensioner pulley (to loosen the belt) you do not get a good hold of the eccentric nut on the pulley while loosening the nut on the outer tip of the stud you can easily unscrew the stud directly from the block.
Then you will have the situation you are in now; the outer stud nut will be tight at 33 foot-pounds but the stud itself will be loose inside the engine block and able to turn. The reason you are able to reach 33 foot-pounds on the outer stud nut is because you are actually using the jam nut on the other side of the pulley (against the block) to react the force but the jam nut itself is not up tight against the block.
What I suggest you do is take the tensioner pulley off the engine and look for the jam nut that's against the block and check it's torque. I couldn't find a torque listed in the manual for this jam nut but set mine to 33 foot-pounds and that seemed to work fine.
Also make sure that the stud is engaged deep in the block and has not worked its way out over time (from other belt changes) reducing the amount of thread engagement. You do not want to strip out the block when doing this so be extra careful. There may be someone else here that knows better on what this torque should really be but the way the torques are usually determined is based on some percentage of the material yield strength of the stud and there is already a torque of 33 foot-pounds used on that stud.
I couldn't believe Porsche actually set this tensioner up this way when I saw it. It's something that everyone on here needs to be aware of, as I didn't find much written on it when I did a search for the problem.
I hope this helps!
If this is an 86 or older you have to be extra careful of the belt tensioner design. I just went though this with an 86 turbo so I think I know what's happening with yours. Porsche designed the tensioner using a stud that screws into the block and is held in place with a jam nut. If during loosening of the tensioner pulley (to loosen the belt) you do not get a good hold of the eccentric nut on the pulley while loosening the nut on the outer tip of the stud you can easily unscrew the stud directly from the block.
Then you will have the situation you are in now; the outer stud nut will be tight at 33 foot-pounds but the stud itself will be loose inside the engine block and able to turn. The reason you are able to reach 33 foot-pounds on the outer stud nut is because you are actually using the jam nut on the other side of the pulley (against the block) to react the force but the jam nut itself is not up tight against the block.
What I suggest you do is take the tensioner pulley off the engine and look for the jam nut that's against the block and check it's torque. I couldn't find a torque listed in the manual for this jam nut but set mine to 33 foot-pounds and that seemed to work fine.
Also make sure that the stud is engaged deep in the block and has not worked its way out over time (from other belt changes) reducing the amount of thread engagement. You do not want to strip out the block when doing this so be extra careful. There may be someone else here that knows better on what this torque should really be but the way the torques are usually determined is based on some percentage of the material yield strength of the stud and there is already a torque of 33 foot-pounds used on that stud.
I couldn't believe Porsche actually set this tensioner up this way when I saw it. It's something that everyone on here needs to be aware of, as I didn't find much written on it when I did a search for the problem.
I hope this helps!
10-05-2006, 01:56 PM
#4
Good point Nick. A few years ago I had that stud break off right where it exits the block. I believe the jam nut was loose which allowed the stud to flex more (as it was effectively longer) and it finally fatigued in half. Luckily it occurred in my garage when I started the car and I heard the 'funny' sound of the tensioner pulley hitting the belt cover and shut it off before the timing belt slipped. A close one indeed...
10-05-2006, 03:03 PM
#5
Drifting
Thread Starter
okay that sounds scary so take the tensioner out and check the stud but it should be alright.
when I took it out the stud was pretyt damn tight. I can't see how I can use a torque wrench on the nut on the stud, I don't think there is a socket deep enough to go over the stud and reach the nut.
maybe I'll just make sure by hand that it is good and tight but i would probably not be able to reach 33 ft-lbs with a tiny wrench on that little nut.
when I took it out the stud was pretyt damn tight. I can't see how I can use a torque wrench on the nut on the stud, I don't think there is a socket deep enough to go over the stud and reach the nut.
maybe I'll just make sure by hand that it is good and tight but i would probably not be able to reach 33 ft-lbs with a tiny wrench on that little nut.
10-05-2006, 03:05 PM
#6
Drifting
Thread Starter
okay that sounds scary so take the tensioner out and check the stud but it should be alright.
when I took it out the stud was pretyt damn tight. I can't see how I can use a torque wrench on the nut on the stud, I don't think there is a socket deep enough to go over the stud and reach the nut.
I also have 2 torque wrench one is a beam type so I can double check the tq. I'm guessing it might be normal to be able to move it as you can easily exeed 33 pound on the eccentric nut.
when I took it out the stud was pretyt damn tight. I can't see how I can use a torque wrench on the nut on the stud, I don't think there is a socket deep enough to go over the stud and reach the nut.
I also have 2 torque wrench one is a beam type so I can double check the tq. I'm guessing it might be normal to be able to move it as you can easily exeed 33 pound on the eccentric nut.
