Tensioning Belts - An Introduction

Owning a 944 pretty much means knowing something about the timing belts. This page is intended to provide some insight on tools & methods for setting the belt tension.  

Its funny how these belts exist in countless other cars but on the 944 they take on a whole new level of dread. Some feel the belt failures are the 944's Achilles heal while others see them as no big deal. No matter where you stand in this mix,  there is no question that the 944's belts require a bit more maintenance than other cars.  Belt maintenance, and specifically the tensioning of the timing belts, is not as straight forward as you might hope. The specialty tools, particularly for Porsche's recommended method, are expensive. There are alternatives but as you might expect there are also problems with these approaches and this page is an attempt to highlight exactly what those problems are.    

Below is an options diagram to illustrate the different approaches. 

Notes for chart above...

1. The Krikit will work reasonably well on the cam belt (83 through 86 944 only) but is not well suited to the balance belt. The Krikit's operating range will just barely read the low tension setting needed for the balance belt. Is this a show stopper? Not usually, one casual method of setting the balance belt is to set the belt by feel and then observe how it tracks with the engine running - too loose and it will flop against the belt cover, too tight and it will make an irritating whine. Some "ball park" adjustments can be made with the krikit and this approach.

2. Deleted Note.

3. The balance belt can be set by feel. 

4. Here is a link to the steps for using the Porsche 9201 tool.

5. The 920X can only be used on engines that have the updated waterpump. Here is a link for using the 920X.    

Above is a sketch to illustrate the options available to you. The method that you use is based on which specialty tools that you have on hand. The 9201, is a Porsche tool that is roughly the size of a pack of cigarettes and, with a little practice, will provide a reliable reading of your belts. The 9201 price is approximately $680. The 920X is a tool that I make. It costs approximately $150. The Krikit is about the size of a marker pen and costs about $25. It can only be used on some Porsche models and is not well suited to the balance belt. Still, it is very popular with some.

Tensioning Belts - More General Info

First, getting access to the belts is a challenge in itself. Above is a photo of an 85.5 NA, the other models are slightly different but equally difficult. 

Here is a drawing of the belt layout used in the 83 through 86 944. Porsche recommends these belts be replaced every 30,000 miles and be re-tensioned at about 1500 miles following replacement. Porsche offers a couple of tools to set the belt tension and you should be able to pick these (below) up at your local dealer for about $700. If this seems reasonable, get the maintenance manuals while you're there (for another $430) and forget about trying to do this little job on the cheap. 

The Twist Method

This method uses no special tension measuring tools. It is really for the more casual mechanics but any discussion of the various tensioning methods must include at least a mention of this procedure. Essentially, we are going to set the cam belt tension to a point where the belt can be twisted to 90 degrees from its normal tracking position. This is done with the thumb and index finger of an average strength man. This should be done at a point along the belt midway between the cam gear and the crankshaft gear, along the upper span and the timing belt idler pulley must first be removed.

Do I recommend this approach? Umm no, but if you're going to guess at your cam belt tension, this beats nothing. 

Which cars will this work on? Only the 83 through 86 944s and 924S.

Using the Krikit

Here is a link to information on using the Krikit. 

Other Notes:

This is the belt layout for many others of the 944 series. In the center is a device known as  an auto-tensioner. If it has a fresh spring, it will get your cam belt "in the neighborhood" of a correct re-tension setting. Be aware though that the springs on 20 year old cars are often way out of tolerance. 

Here is the video clip of a a too-tight balance belt.

Here is a link to more info on the balance shafts.

Above, I mentioned the Porsche recommendation for belt change intervals. There is some controversy concerning how often the belts should be changed, Gates (a company who make belts) recommends a longer interval. This clipping (below) is taken from Gates' manual on  recommended belt change intervals.