944S and Timing Belt - Not Happy

[kdjones2000]

So I saved an '87 944S from the scrapper back in late 2018.

I had to have the head redone as there was an issue with a valve guide, went through all the mechanical systems, and my daughter used it for transportation through college.

Jump to 2022, about a month ago, and she tells me that the car died as she was pulling into her workplace. I go take a look and lo and behold, the timing belt had taken a crap. This is the Gates OEM timing belt purchased through our host here.

3-1/2 years.....

Not something that I was expecting. So I get the car home and tear into it and it is obvious that this particular timing belt is just GONE. The usual teeth were stripped from around the crankshaft (how every timing belt has failed for me, ever).

It looks like the vulcanization of the teeth to the belt was just defective or something. I am wondering if this is due to the extra drag / inertia of the 16V setup compared to the NA/Turbo cars and their single cam/8 valve setup?

Here are the pictures:











The good thing, if there even is one, is that only 2 exhaust valves were bent, since the car was essentially at idle when it failed. $600 and 8 hours of work and it's back up and running - something that I should not have had to do, IMO.

This time I went with the Gates RPM racing timing belt, as it is supposed to have 2X the tooth strength than the OEM.

We shall see, but actually maybe not, since the car is going on the market soon.

[944 S2]

Wow that sucks! I’m on 6 years on my S2. Wonder how/why other OEM can last so much longer than ours.

[pfarah]

Sorry to hear about this, glad you fixed the car.

[kdjones2000]

This engine was never abused, or really even revved high. It was driven by a young woman for daily transportation.

Maybe it's the 110+ heat out here. I need to check out my turbo's belt, as it's a lot older than this one.

[djnolan]

When I did my belt on my 87S I used a stethoscope to fine tune the tension to reduce the whine. Particularly the whine in the WP and the tensioner pulley. I was definitely concerned. I also made sure the tensioner arm was lubricated and free to move. I was more concerened about longevity of the belt and rollers and WP bearing than performance. However if I was going to track the car I would have maybe used the recommended tension using the P gauge.

PS: Thanks for sharing, I may upgrade to the kevlar belt after seeing this.

[944 S2]

I just got off the phone waiting on a quote to get my timing/balance shaft belt replaced. I only have 6K miles and it was replaced 6 years ago. I was told since it’s a newer belt it good for 10 years/90K miles! Not so sure about that!

[TibetanT]

Originally Posted by 944 S2

I just got off the phone waiting on a quote to get my timing/balance shaft belt replaced. I only have 6K miles and it was replaced 6 years ago. I was told since it’s a newer belt it good for 10 years/90K miles! Not so sure about that!

^^ This does NOT sound correct to me, but I am no expert.
I have always been in the camp of changing belts, water pumps at or before 50K miles on the clock. In some cases, while I was in there, I chose to change out belts and water pump at 32K miles.

Ten years and 90K miles is way too far outside the Porsche specifications, IMHO.

Kevlar belt is a good bet for track, so I will be looking into that option with my next timing belt change. Expensive I know, but I do like to sleep at night.

[944 S2]

Originally Posted by TibetanT

^^ This does NOT sound correct to me, but I am no expert.
I have always been in the camp of changing belts, water pumps at or before 50K miles on the clock. In some cases, while I was in there, I chose to change out belts and water pump at 32K miles.

Ten years and 90K miles is way too far outside the Porsche specifications, IMHO.

Kevlar belt is a good bet for track, so I will be looking into that option with my next timing belt change. Expensive I know, but I do like to sleep at night.

Right! That recommendation was based, they said on the newer technology. Interesting tho many Japan OEM do recommend 90K miles/10year.

[Jfrahm]

If the problem is the teeth shearing off, I'm not sure that the kevlar helps.
My S8 I think is 105K for the belt, I do not think age is specified. There is a big difference between the narrow 944 8v belts and the wider 16, plus the constant tension in the 968 which is typical as of the early 90's in most cars.

Teeth shearing off seems like a common failure on 944-type cars. I wonder if it's tension related. Too much? Not enough? On the 928 there are concerns with the sprockets getting worn sharp also.

[djnolan]

Newer rubber compounds should be more durable than older ones. Even if the manufacturer date is recent it could be an old design and old rubber compounds. No creditable data on this except this CarTalk post, just a musing. https://www.daytondailynews.com/classifieds/cars/preventive-radiator-hose-replacement-thing-the-past/CLHhvOKR3JlL02mQgrVA3L/

Some old fashioned methods:

Well run the heck out of a car and check the pulley temps with an IR gun to see where the hot spots are. Heat has to be one of the causes of the teeth sheering off. Also if one of the pulley bearing is bad it could seize and strip teeth off of the belt. the smaller pulleys could do this but the cam pulley is large and distributes the stress over many teeth. The WP pulley could get hot but it is smooth and not toothed. Just thoughts...

On the other hand inspect belt regularly for cracks and replace.

[kdjones2000]

Kevlar belt has TWICE THE TOOTH STRENGTH than the OEM.

Or so they claim...

[Jfrahm]

That's good, looks like they integrated a mesh into the teeth or something.

[Fast Freddy 944]

I always have a qualified shop do my belts. Can I do it, probably, would I do it, nah, ya needs special tensioner tools, and if I mess up, it might drop a valve or something. If I hire a mechanic and something breaks, I have a reciept and somebody to blame.

[zedsn]

I have my timing/balance belts done every 4 years even though they still look good and have low miles and I use continental belts and have never had an issue with them on my 89 944 turbo in over 15 years of ownership and I run my car hard.