so prior owner paid to get it done. Question is always WHO did it and what did they KNOW ??? Many "professional" mechanics have no clue , do not have manuals or any kind of tension measuring tool but just guess at what it needs or keep tightening until the light goes off or they snap the end off the camshaft....

 

I'm sure this is a newbie question. But does anyone have a link to a step by step of checking tension. If searched all over and can't seem to find a step by step for my MY85... Sorry for the bother.

 

Bought a kempf.. Checked tension today. Tension was on point.

 

Did you make sure to check tension at TDC? Also for 32v engines the Kempf tool should be set at high end of window.

If the tension light is coming on when you open throttle wide then it's more likely problem is with the belt or associated parts than the tension warning circuit. Can you post a photo of the Kempf tool notch measuring the tensioning, and a head on pic of the passenger side cam that you have exposed?

It sounds as if the belt just hasn't been retensioned since installed (or maybe it was but it's a ContiTech belt, which have reputation for stretching more continuously in service so need more frequent checks. Likely all is fine but you just need to set tension to that high end.

 

Didn't take a picture but. It was set just on the high side of the kempf tool. I'd say "max" in the window. Thing runs like a dream. one thing I noticed was maybe the cam seals leaky? How hard are those to change out?

 

The engine need to be cold, not warm and crank set at 0 TDC to check the tension.
Also is the Tensioner full of oil, if not it needs to be filled.

How did the inside of the belt cover look, was it clean or belt dust dirty?

If all of the above is good, then check the wire that runs from the tensioner to the T belt cover and back to the engine compartment, make sure it is a good connection.

edit: forgot to ask How do the Gears look?

 

Re-read my post from the beginning of the thread and thoroughly check the tensioner warning circuit for continuity to ground by unplugging the warning circuit wire at the center cover and attaching your multimeter to the plug end with an alligator clip. Continue to check for continuity while manipulating the spade connector for the center cover plug to test for intermittent connectivity. If loose at the spade end you will need to either re-crimp the female connector on the plug wire and/or bend the spade end of the connector so that it doesn't contact the center cover. You can also check the copper strap to make sure it hasn't broken (even after it breaks it may have enough contact to work most of the time.) If it has you can't really do anything about it until the next time you change the belt.

 

Holy **** folks - DO NOT TRY THIS AT HOME!
Mark, that may be an ok quick and dirty at the track for an exceptionally experienced eye, but anyone else - I would never do this as a reliable tension check!

 

MK's hillbilly method is good for checking to see if the belt is still there. I'm sure he uses a carefuly-calibrated thumb and a precision-graduated pin to do his test. For the mere mortals, consider that the cost of doing it right is substantially less than the cost of doing it wrong.

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To the OP's question, after properly checking the belt tension, consider that the function of the factory tensioner is to adjust to maintain a somewhat consisten pressure on the belt as the block expands and contracts with temperature change. There are spring washers (technically, they are Belleville washers) inside that do the duty of keeping pressure on the tensioner roller. There is a piston inside that includes a check valve, and a little bypass passage that limits how fast oil moves around inside. The purpose of the piston and the oil is allow the piston to extend quickly but retract relatively slowly.

You must have oil in the tensioner for that dampening to work right. Although the piston will extend correctly with no oil in the tensioner, it will retract/compress just as easily. There are two bleeder ports on the tensioner, used for adding oil. The oil recommendations vary from 30wt motor oil to 90wt gear oil. The Good News is that those are in fact very close to the same viscosity despite the difference in numbers. There's a growing group of folks (me included) who suggest using STP oil treatment in the tensioner. It's thicker than the other oils, so it tends to leak out more slowly/less. Also a bit harder to get it in through the bleeder ports. Stan (Mr Merlin here) suggests using a Visine dropper bottle. I've had good luck using a grocery-store ketchup squeeze bottle with a bit of hardware-store vinyl hose. It's still a chore to get it full. I need to make a filler out of a bit of pipe and some threaded fittingss, so I can add a little air pressure to force-feed the tensioner.

The tensioners tend to leak the oil out if they aren't in good shape. The threads on the adjuster bolt come originally with a ring of sealant on the threads. The factory sealant used there is pretty much a one-time-use product, meaning that you'll want to replace at least the sealant, preferably the whole bolt with new, every time the belt is replaced. There's an o-ring on the piston inside, and a rubber boot on the business end of the tensioner to keep the oil inside and the crud out. The o-ring wears if the tensioner is dry, while the boot seems to crack from engine heat over time. Both will ultimately inhibit proper function of the tensioner.

The tensioner rollers ride on the belt just downstream of the crankshaft sprocket that pulls the belt around, so any stretch shows up as slack right where the tensioner roller supports the belt. The belt itself can't tell the throttle position, but it can see the effect of higher RPM's as the load on the belt increases. A momentary reduction in pressure applied by the roller results in an internal spring pushing a couple contacts open, setting the warning light.


There's a third-party tensioner option that does away with the spring washers and the oil and check valve, instead using modern rollers and a tensioner originally fitted to Audi engines. The maintenance issues go away, and you just replace the Audi tensioner and the bearings at each belt change. It also eliminates the warning light, since the new design maintains a much more consistent belt pressure across the range of operation. Many owners have installed these tensioner packages, and enthusiasm for them is pretty high. You might decide to change yours out next time the front of the engine is apart for a belt and water pump service.

For now, I'd try refilling the existing tensioner with oil, and see if that helps. Keep in mind that you'll risk oil on the belt (not good!) if you start adding oil to a tensioner that leaks through a cracked boot. Watch carefully for signs of leakage after you refill. You've seen how the belt cover comes off for inspection, so you can look for signs of oil on the belt if you start getting dribbles of tensioner oil on the floor. If the belts gets oily, it's time to consider a new belt and tensioner rebuild or replace before the oil damages the belt itself.

 

Wally's write up with pictures explains the tensioner well-

http://www.928gt.com/t-wallytbelt.aspx

 

If that's the case then you know what you have to do.


This...

.

 

I knew there was a reason I subscribed to this thread (and no, it wasn't to read Dr. Bob call Mark a hillbilly).

Thanks for explaining this Dr. Bob. I've had the same problem since I re-built my stock tensioner and replaced the belt awhile back. Downshifting or hard acceleration near red line sets off the idiot light. All I have to do is pull over, turn off the key and start up again, problem solved. The ECU holds that alert until a key off reset near as I can tell.

I'm using 90w gear oil in mine, new boot. The belt has over a 1000 miles on it now and the Kempf tool says it's right on. I may be talking to Ken soon if STP doesn't fix it. I've been chaising this problem for over a year now and I really need to be able to trust the tension light.

 

Otto --

I didn't call him a hillbilly. That might be considered an insult. Instead, I suggested that the method he promotes is commonly attributed to hillbilly mechanics. Mark has worked out some shortcuts and simplified procedures that are different from what I recommend. His are a little too, um, casual for what I think most folks need. The biggest concern about most of them is that there's so much that's subjective. He's worked out the guesstimated forces and measurements that work for him. It's impossible for the rest of us to duplicate his results by feel or by eyeball. By the time I drag out the proper tools and go through the effort to try and verify a by-touch adjustment I might have made, I might as well have just done the adjustment with the proper tools.

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To your situation:

You don't share what year your car is. The S4+ cars seem to like a tension setting at the snug end of the window on the Kempf tool. If you have one of these, you may want to make a slight adjustment to bring the tension up ever so slightly. This preference on tension range may also apply to other 32V cars. Remember that Jay Kempf had/has an OB (a true OB, terminology obviously validated by him when he coined the "OB" term.) Anyway, the Kempf tool is an available replica of the original tool that Porsche recommended for tensioning the 16V belts. I know that a lot of effort was made to get it to work well on all engines, even the ones for which Porsche recommended use of the later tool. Anyway...

Each car is different, but... On my car, the difference between mid-range on the Kempf tool and the tighter end of the range works out to less than one flat (<60º rotation) on the adjustment bolt. I cringe when I hear folks recommend a field adjustment of "just a few flats" on that bolt, because when properly set up with the washers and all, it's amazingly sensitive. Since you have the tool handy, of course you would use it for your procedure.

 

Or a jest amongst friends. I've traded similar banter in the past. Had you not been at least mildly entertained by the epithet perhaps you would have controlled yourself? After all, Mark is a little famous for his colorful ways and his opinions on brakes...

Mine's an '85. It doesn't complain unless its under stress and then only once in awhile. Next time I have it apart I'll give it a tweak and check, but your explanation of the actual mechanism and it's dependence on oil viscosity tends to move me in the direction of an experiment with STP.

 

Thanks.... then ill take that as a complement.

Look, im not saying to start adjusting, tension loose and tight and use the "poker" techicque to calibrate your thumbs.... but, its a great way to see if the engine should be started. i use a drill bit..... i drilll a hole in the cover..... i then mark the drill bit as it makes contact with the belt..... then i push as hard as my thunb can and mark the drill bit again. that distance is a normally adjusted belt tension...... Then, if im ever wanting to check it out at the track before i start the car, i can see if it has tension. a loose belt , shows a significant distance of those two marks. So, its really for guys that want to drive the car ot the shop or put off doing a "real " check, to have piece of mind that its not going to slip under normal driving.

However, it doesnt take too long to do it the right way, with the kempf tool.. but remember, 1/4 in the window, not mid window looks to calibrate with 5.0 on the porsche too. (mid window looked like near 6 on the porsche tool)