Bad rep for automatic belt tensioners

[89-944NA]

I have seen many posts here where people have said not to trust the automatic belt tensioners (ABT) on the late model cars. I am wondering if I missed some study that was done that says they are not reliable.

I have always trusted the ABT, and never had a problem with belt tension, and I have done many many belt jobs in my 20+ years of 944 ownership.

[kdjones2000]

I have only used the auto tensioner in mine, and have had no issues.

The last time I retensioned it, I threw a Kritit tool on the belt to see where it was, and it seemed to be within range.

There are many stories out there about the auto tensioner not providing enough tension, but the other people I know with late cars ('89) have also not worried about it, and have had no issues.

Cheers, Keith

[89-944NA]

That's my point, it's almost like one person posted that theyhad a problem with one, so everyone starts posting that they are unreliable or don't work properly. There are so many posts that say that after installing the belt to double check the tension, because the ATB's are worn out, have weak springs, etc.

I have even seen one or two posts where a reply has been posted to buy the Arnworx kit because the ATB's don't tension properly.

[kdjones2000]

By the way, who did you sell your '89 NA to? I know someone here who bought one from somewhere a year or two ago....

'89 Glacier Blue....

[89-944NA]

Don't remember the guys name, that was 3 1/2-4 years ago, but he was a younger guy that lived in Chino Hills. Does it have Linen (white) interior? NO airbags? And that big center piece that says "PORSCHE" where the license plate is supposed to mount?

[nize]

i've used the auto tensioner on 8 different 951's about 2 dozen times and it worked perfectly every time, verified with the arnworx tension gauge afterwards.

i think the people complaining that the auto tensioners didn't work or had worn springs, probably forgot to put the slack on the belt where it spans the tensioner so that the auto tensioner can do its job. you have to 'tick' the crank counter-clockwise to get the slack on the correct side of the belt for it to tension properly.

[kdjones2000]

Originally Posted by 89-944NA

Don't remember the guys name, that was 3 1/2-4 years ago, but he was a younger guy that lived in Chino Hills. Does it have Linen (white) interior? NO airbags? And that big center piece that says "PORSCHE" where the license plate is supposed to mount?

Nope, must be a different one...

[AaronM]

My issue with the auto-tensioner isn't that it's unreliable, it's that people who aren't familiar with the cars assume that the automatic tensioner maintains tension over the life of the belt as with some other, newer, cars that have hydraulic tensioners which maintain constant tension over the entire belt life.

They're useful, but you still need to re-check at 1,500 miles and 15,000 miles and a lot of people assume that the automatic tensioner eliminates that.

[nynor]

i use my auto tensioner. i checked it a couple times in a row against the 9201 porsche tool and it was spot on. i reset the tension on the belt with it about every 8 months (because i am paranoid).

[wild man]

I think that most peoples' problems are the result of not using it correctly. Like nize said, you need to turn the crank back a certain amount (I forget exactly how much, but it IS in the book) to get the tension right.

[nynor]

Originally Posted by wild man

I think that most peoples' problems are the result of not using it correctly. Like nize said, you need to turn the crank back a certain amount (I forget exactly how much, but it IS in the book) to get the tension right.

10 degrees.

[wild man]

There you have it! Thanks.

[89-944NA]

Now all this reply needs is some input from the people who don't trust the ABT, as to why they feel they don't work properly.

[nynor]

what i have read in the past on the forum here: the spring gets weak with age, or they aren't calibrated properly at the factory, or people mess with the setting (and then it really is off), etc. mainly, its been anecdotal.

[wild man]

Originally Posted by wild man

I think that most peoples' problems are the result of not using it correctly. Like nize said, you need to turn the crank back a certain amount (I forget exactly how much, but it IS in the book) to get the tension right.

The number provided later (by nynor) was 10 degrees, BUT...

After finally completing the job yesterday, I think that there is a BIG mistake here, which was apparently overlooked by others!

IT IS THE CAMSHAFT, NOT THE CRANKSHAFT, which must be turned back 10 degrees, in order to get all of the slack on the tensioner side, so that it can take it up, before tightening the bolts.

Or maybe it's 10 degrees FORWARD, on the crank?

[nynor]

it is ten degrees CCW on the crank.

[wild man]

I apologize for being so blunt, butt here's NO WAY that can be right! If you go CCW on the crank, you pull tension on tensioner pulley, drawing the spring in, and creating slack on the side of the crank where the tensioner is NOT located. If the bolts are then tightened up, the belt will have so much slack in it, that it probably won't even engage the teeth on the crank pulley.

Bottom line: To make sure there is no slack in the belt, you either need to go CW on the crankshaft, or CCW on the camshaft.

I know, I just went though this yesterday.

[89-944NA]

I go 10 degrees (about 1 tooth) CCW on the camshaft, release the tensioner, and it takes up the slack and draws the cam back to the index line. Then tighten the ABT

[nynor]

with all due respect, you are incorrect. CCW 10 degrees at the crank. this puts slack at the tension pulley.


now you all have made me doubt myself. i am looking it up in manual. be right back.

[wild man]

Before this gets out of hand, do you mean CCW from the driver's perspective?