Belt tensioner and other issues

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03 Oct 2012 22:07 #11640 by tedder
I was told that I needed a new or rebuilt belt tensioner by Randall Kara Techniques. I occasionally have a warning light come on the dash, sometimes accompanied by belt tension warning. I believe that belt is not being held at an even amount of tension pressure. Please offer me up some options - how about a PKtensioner? The car is coming together pretty well. Last major project for probably next year is AC system rebuild - probably need new seals and other parts replaced. I believe system compressor is OK though. For some reason the front lights are too far back on my car. They need to be moved a inch or two to be in proper position. Car was probably damaged in the front and someone did not position the lights properly - may have had problems with bumper shocks. Always something to work on these cars! Thanks - Ted

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03 Oct 2012 22:25 #11641 by wallyp
It always helps to give info on the car, especially model year.

The belt tension warning light operates thru a grounding switch on the tensioner. The tensioner adjustment compresses a stout spring on the tensioner push-rod. If the belt tension goes below spec, the spring relaxes, pushing apart the contacts on the push-rod, breaking the ground contact between the block and the warning computer input.

But - anything that breaks the ground contact will also set the warning, regardless of belt tension, so there are sometimes false belt tension alarms.

The problem is that the consequences of timing belt failure are usually catastrophic, so it is not a good idea to ignore a tension warning.

The best approach is to make a knowledgeable inspection of the timing belt, rollers, cam sprockets, tensioner and tensioner warning system.

It is very, very rare that you would need a new tensioner. The tensioner should be rebuilt every time that the belt is changed. This includes a new boot, clamp, gasket, O-rings, and oil.

Any loss of belt tension requires a close inspection of the entire system, and the inspector must know the system well.

There are mixed opinion on the PKTensioner. While it adapts to changing tension better than the stock system (which is actually a "detensioner", maintaining the proper tension on the belt when the engine block and heads expand from normal operating heat), the PKTensioner does not have any warning system to show loss of operating tension. There are ardent supporters and concerned doubters of the system.

It is very important that you get accurate information about why you are getting belt tension warnings.

Wally Plumley
928 Specialists
www.928gt.com

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04 Oct 2012 09:57 #11644 by the flying scotsman
The Porkensioner also provides a far more robust roller and bearing, elliminates the idle roller, long pin,wear out bushings and the oil leaks.

Have had this system on my S4 for 1000s of kms..........will never go back to stock.

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04 Oct 2012 11:19 #11645 by xstepson
Tedder,
If Randy Kara says you need to rebuild the tensioner, then that would be good enough for me. You can either rebuild the tensioner or install a Porkensioner. Your choice.

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07 Oct 2012 14:00 #11705 by ROG100
Randy is a well know 928 mechanic and his advice should be listened to.

Most use the PKensioner as it is so much more reliable than the old detensioning system. Been in use on the 928 for over six years with ZERO issues and hundreds and hundreds in use. The system is used on Audi cars with millions in service. Porsche went to this type of system on the 968 in 1992 and had the 928 stayed in production I am sure would have used a similar system.

Nothing wrong with the 1970 detensioning system but requires regular checks, prone to leak and become ineffective and even with a warning light know to fail.

If you want total peace of mind go with the PKensioner.

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09 Oct 2012 18:15 #11743 by pcar928fan
Roger,

I didn't know that about the PKensioner! That is good info! I never looked at nor studied it so that is great info for me! Thanks mucho!

James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black

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31 Oct 2012 19:17 #12223 by ROG100
James,
Sorry I missed your question. Trying to visit more often.
The PKensioner is the way to go and most of my customers Worldwide use it.
Lets talk about you getting one fitted so you know how it performs.
Roger

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