False Tensioner Warnings
 

I've been dealing with intermittent belt tensioner warnings on my 90 S4.

It seemed to be related to the tensioner leaking. I would refill, they'd go away. Then when they started up I'd repeat.

A couple of weeks ago pulling into my subdivision the tensioner warning came on. I reset and it came back several times.

I nursed the car into the garage and parked it thinking it was telling the truth.

Got a chance to check the belt tension and it was at the tight end of the gap exactly where I left it.

I'll refill the tensioner and see if that clears the warnings.

But, the leak really has to be addressed. I already use STP and it leaks out. Feh!

Do I really have to take everything apart to replace the the tensioner gasket? This is beyond frustrating.

Has anybody clamped the right and left cam gears to the belt, loosened the tensioner bolt, removed the tensioner and replaced the gasket and then put it back together?

Kevin

I've heard you can also use grease in the tensioner it doesn't leak out.

Oil or grease in the tensioner just helps transfer heat from the block it shouldn’t trigger the warning if it’s empty, have you checked there isnt an electrical issue?

yes, the oil should have nothing to do with it. Instead, your manipulation on the tensioner to fill it is likely causing it to temporarily function, then later vibration throws it back out again. Look at the bi-metal peice and make sure it is aligned properly. For others following along, you'll need to remove the right side timing belt cover to access and see everything clearly. Something is loose or out of alignment.

How do you reset the warning?

I have a similar issue with my 89 GT.

I was told that false warning could also be due to shorting of batttery on lid.

Yes confused me too, but did appear to clear an issue I had. Of course i also checked the belt anyway

When the battery shorts to the lid it instantaneously welds the two together, everything electrical fails instantly including the motor, the battery knackers itself and it is better fun than Hamilton and Verstappen when it happens in the outside lane of a busy motorway doing 140 kph at night with the wife and two [at the time] kids in the back- ask me how I know!

No idea whether it is possible to have an instaneous flashover as it were and if so what the consequences might be.

Ok very current false warning. IMHO, it is certainly, the electrical wire that cause the intermittent warning.

The warning happens when the electrical wire is relied to the ground. So, look at it, you certainly have an issue on it. It certainly accidentally contact the ground by a defected wire so you have that intermittent warning.

The oil in the tensionner has really no function of tension, it is only made to transmit heat from the motor to the bi metalic washer and compensante the extent of the motor. At a certain point the bi metalic washer would have eated even though there is no oil in the tensionner.. The lack of oil can't cause an intermittent lack of tension and then a warning of belt tension. Otherwise, the belt tension warning may be caused by the belt itself.

Considering that the factory tensioner lowers tension when warm, I would suspect the wire.

Remove the connector to the TB warning plug at the belt cover and check for continuity to ground there while you manipulate the center cover. I used this method to chase down random false alarms that eluded Bill Ball and me for over a year caused by improper orientation of the warning circuit spade connector at the tensioner which caused the plug connector to work its way slightly loose.

There's a detailed troubleshooting guide in the Factory Workshop Manual.

Book G, page 33.

Note that one of the things that can make the light come on is a lack of oil in the tensioner....

The tension is at the far end of the Kempf tool. In the years since I did the timing belt it has not stretched at all. Never had to adjust the tension.

I filled the damn thing again, took it for a drive no warnings.

I tested continuity from the center belt cover connector to ground.

I really want to test from the harness to where ever it goes but I lost consciousness looking through the wiring diagrams. :-)

But, it more likely the tensioner lost its contents.

Building two custom harnesses, so I know this, without having to look it up.

Wire runs from belt cover, through injection harness, to W25. It's brown/white, as I recall.

Comes out the other side of the relay board and comes out on P21.

There's something really wrong in your first sentence. It is technically impossible to not have to readjust a timing belt after "years", unless that is less than 2,000 miles....or the belt got insanely overtensioned, out of the gate.

With new gears and factory belts, we are currently not able to get 1500 miles on a belt, before the tension light comes on. (This has been occurring since the "new" cam gears were introduced.)

The "new" gears apparently "knock off" the high spots much quicker or are more abusive on a brand new belt....something changed!

With the old gears (and obviously older production run belts) it was rare to have the light come on before 2500 miles.

The belt light is extremely accurate, contrary to common "Internet Myth".
Always between 3.0 to 3.2 "belt units" on a 9201 tool and will always "normally light" on a long deacceleration event, like getting off the freeway.

I do not own/have never owned/never have used a Kemph tool, so nothing it says means anything to me.

For some crazy reason, I currently have five 9201 tools, two of which need me to machine a new part and one that needs me to calibrate it....
I try to always have two 9201 tools functional and accurate, in case I don't trust a reading.

Being OCD can be a curse....

Greg, how often should the tension be checked? Assume original cam gears, but new belt. Was checked after 1500 miles after initial installation, but then driven regualrly since then, with another 5 or 6K miles. (1985MY)

I totally agree. Given the constant annoying loss of tensioner oil I've been in there at least twice and each time the tension was fine.

I'll wait until I get the warnings and then measure again. Probably another month or so. Sadness.

The fact that I went from warnings every other minute (yikes) to none at all after filling the tensioner points to the tensioner loosing all its contents.

I will trace the wire back the CE panel.