T-Belt Tensioner Adjustments at the Trigger?
03-21-2004, 01:14 PM
#1
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T-Belt Tensioner Adjustments at the Trigger?
It's interesting that some people say their tensioner runs dry and there are no t-belt light problems and others say the opposite. Would that not be an adjustment issue?
My question is.....if the electronics of the tensioner and the tensioner mechanics/seals etc. are OK, but the light still comes on when you let off the gas at redline...are there adjustments to the Tensioner that would make it slightly less/more sensitive...like add or delete a washer to increase or decrease the trigger sensitivity? Or would that not even work? This question is retorical and presupposes that the Tbelt is always meticulously and properly tensioned. I also understand that this topic is potentially controversial since doing anthing that resembles modifying the existing Porsche Tbelt safety system is sacrosanct. I'm curious about tolerances and adjusting for sensitivities in triggering more than anything. I haven't seen anything posted on this.
I had a Tbelt lite problem and a mechanic did something to fix the problem. Although he rebuilt the Tensioner...the oil quickly ran out (The boot clamp was loose)....but there was no Tbelt light anyway...but it still worked correctly and passes all the electrical tests.
I'm sure there are more factors involved with Tbelts than perhaps any other single 928 issue but, back to my question....are there adjustments that can be (or maybe should be) made to a tensioner?
Harvey
85S
My question is.....if the electronics of the tensioner and the tensioner mechanics/seals etc. are OK, but the light still comes on when you let off the gas at redline...are there adjustments to the Tensioner that would make it slightly less/more sensitive...like add or delete a washer to increase or decrease the trigger sensitivity? Or would that not even work? This question is retorical and presupposes that the Tbelt is always meticulously and properly tensioned. I also understand that this topic is potentially controversial since doing anthing that resembles modifying the existing Porsche Tbelt safety system is sacrosanct. I'm curious about tolerances and adjusting for sensitivities in triggering more than anything. I haven't seen anything posted on this.
I had a Tbelt lite problem and a mechanic did something to fix the problem. Although he rebuilt the Tensioner...the oil quickly ran out (The boot clamp was loose)....but there was no Tbelt light anyway...but it still worked correctly and passes all the electrical tests.
I'm sure there are more factors involved with Tbelts than perhaps any other single 928 issue but, back to my question....are there adjustments that can be (or maybe should be) made to a tensioner?
Harvey
85S
03-21-2004, 02:42 PM
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Harvey,
I don't know of any adjustments to the tensioner. What i have found (using the J Kempf tool) is that 16v engines should be adjusted to the midfdle of the "window" and 32v at the tight end of the window.
Keeping the oil in the tensioner should help reduce "flutter" on the tensioner due to varying loads on it. This will alos help any tendency fro the light to be trigerred. The whole contact system is not well engineered, relying on a number of electrical contacts through unplated steel etc. I always assemble after cleaning the surfaces and using some contact grease to stop oxidisation
Regards
I don't know of any adjustments to the tensioner. What i have found (using the J Kempf tool) is that 16v engines should be adjusted to the midfdle of the "window" and 32v at the tight end of the window.
Keeping the oil in the tensioner should help reduce "flutter" on the tensioner due to varying loads on it. This will alos help any tendency fro the light to be trigerred. The whole contact system is not well engineered, relying on a number of electrical contacts through unplated steel etc. I always assemble after cleaning the surfaces and using some contact grease to stop oxidisation
Regards
03-22-2004, 06:44 AM
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Thank you, John, for your input on this. In fact, I've had my Kempf tool re-checked by Jay. It was fine (and Jay's a great guy by the way and the tool is a great buy) I did this because of some comments made by a mechanic who has a 9201 tool and compared it to my Kempf. However, just to be absolutely sure on future settings, I also bought myself one of the expensive 9201 tools and you're right about the settings. It's pretty obvious that for 32V motors you should use the upper end of the Kempf tool window (or perhaps even slightly more).
One thing is for sure, the Kempf tool is way easier to use and get consistent and replicated readings. The 9201 requires a lot of practice to get it down for the tight quarters of the t-belt. However, on the alternator belt where there's plenty of room, it's a piece of cake to use.
Harvey
One thing is for sure, the Kempf tool is way easier to use and get consistent and replicated readings. The 9201 requires a lot of practice to get it down for the tight quarters of the t-belt. However, on the alternator belt where there's plenty of room, it's a piece of cake to use.
Harvey
03-22-2004, 12:02 PM
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I have never seen anyone say that they deliberately ran the tensioner dry, and I certainly would not recommend that anyone do so.
The oil serves three functions, all important.
Heat transfer - The oil is critical for transferring the block heat to the bi-metallic Belleville washers that correct for block/head thermal growth.
Damping - The oil drastically reduces belt flutter.
Lubrication - The oil reduces tensioner internal wear.
The tension warning "sensor" consists of a short, stout coil spring around the tensioner plunger. As long as the belt tension is sufficent, the coil spring is compressed enough for the plunger to bottom out. This transmits the force for the belt tension, and also makes electrical contact from the sensor wire to ground.
When the tension falls off, the coil spring pushes the plunger off its seat, breaking the electrical contact.
There is no "adjustment". You could change the coil spring, but there doesn't appear to be any reason to do so.
The oil serves three functions, all important.
Heat transfer - The oil is critical for transferring the block heat to the bi-metallic Belleville washers that correct for block/head thermal growth.
Damping - The oil drastically reduces belt flutter.
Lubrication - The oil reduces tensioner internal wear.
The tension warning "sensor" consists of a short, stout coil spring around the tensioner plunger. As long as the belt tension is sufficent, the coil spring is compressed enough for the plunger to bottom out. This transmits the force for the belt tension, and also makes electrical contact from the sensor wire to ground.
When the tension falls off, the coil spring pushes the plunger off its seat, breaking the electrical contact.
There is no "adjustment". You could change the coil spring, but there doesn't appear to be any reason to do so.
03-22-2004, 09:07 PM
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Is there some chance that a car that had been run with too high a belt tension (say 8.0) by some previous user could possibly now have a shortened spring or premature wear on the plastic (phynolic?) washer, etc...causing the tensioner light to be particularly sensitive? Or would spring length not matter?
Harvey
Harvey
