marc abrams

We all read here how the timing belt is the Achilles heel of the 944. How it must be treated with due diligence, replaced often, change everything, tension must be set with tools just calibrated to .01% 15 second prior to use by the top engineers of NASA or it will break for sure. Every other car that uses a timing belt doesn't have this problem. Take the timing cover off of a 944. You see a camshaft sprocket, crankshaft sprocket, and a belt-no different than any other car. So why do these cars have a bad reputation of breaking belts?

ramius665

Because they used to break timing belts with no warning and more often than they should have. Belt technology has come a long way and they're much more reliable. But just like the M96 motors on the 986/996, a couple of failures can result in a permanent black eye.

Humboldtgrin

A big four cylinder engine puts more stress on that belt. The stiffer valve spring, and the 2.5 or 3.0 is a big four cylinder engine. And these are interference engines, if the belt brakes the valve will take a little sliver off the piston and jam it between the piston and cylinder wall wasting the engine. That's why we do a timing belt every 45K no matter if your using a Kevlar belt or not. I got very lucky on the last car I bought with a bad timing belt. The tried starting it and it didn't start because it stripped the teeth on start up. Well the engine had the little sliver piece stuck to the top of the piston in the carbon deposits when I took off the head. You won't get that lucky if the timing belt brakes while driving at higher rpm's.

Van

Also remember that rubber timing belts were a pretty new thing 32 years ago... The world just hadn't seen that many - so any failures were big news.

Now, many years later, if a timing belt breaks, the cost for repair exceeds the value of the car... So they continue to get a bad rap with dire warnings, and all that.

V2Rocket

I don't know why the 944 goes through belts so much.
But I know that they do need to be done every 3 years. The "recommended mileage" varies from 30k to 45k or even more depending who you ask.

But I would say 3 years is the max life for a belt on the car. The belts are very visibly worn after 3 years worth of regular driving, very consistently. The belt cording almost always starts to show through the rubber by the time the belts are removed. 3 year old belts are dry, starting to get tiny little cracks, and they are "hard".

I think the bad reputation is because "by the book" a timing belt job is a pretty expensive service to have to do every 3 years, so people skip it, which inevitably leads to failure and a broken head, and cars sold for parts due to the "timing belt problem". This is because, by the book, you have to remove the crank pulley and rear belt cover to do the timing belt, which is not actually necessary, but it adds extra labor time at $100+/hr at a typical shop. Back in the day (and still for many shops now) a timing belt is a $1500 job...which is why I get so much business doing it for $600 including parts ([/self-promotion])

So there is some internet folklore involved, but you really should change them every so often. And honestly, with the right tools (and I don't mean the belt tensioner gadget) it only takes 2-3 hours start to finish to change the belts and rollers...can you spare 2 hours every 3 years?

Humboldtgrin

I just told you all why... It's a big four cylinder engine!!! The stress that is applied to the belt is much more then a small four cylinder engine. The power band of any piston in any engine is 120 degrees. That leaves 60 degrees for the next piston going up for compression to slow down the crankshaft creating the vibration of the four cylinder engines. The bigger the pistons and stroke the more the vibration. A v6 or flat 6 engine will have less vibration because it fires right at 120 degrees on each cylinder and a v8 or flat 8 has 30 degrees of power band overlap which is why a v8 is a smooth running engine as any engine with 6 cylinders and more will be smoother then any four cylinder. Can you see it now? The bigger four cylinder will put more stress on a timing belt then a small four cylinder engine.

odonnell

Marc, I agree with you that the problem is over-hyped...it's just mechanical parts, no voodoo.

But on the other hand there are so many real-world failures that we always see it pop up on forums relatively frequently.

marc abrams

Chrysler had a 2.5L engine both turbo and naturally aspirated with a timing belt and they don't have timing belt problems.

Humboldtgrin

If you think the problem is over hype then change your belt at 105 to 110 thousand miles like Honda does on there v6 cars and see how that works out. Personally the $25 or less for a regular timing belt and a little time every 45k is worth not replacing the engine.

Jay Wellwood

2-3 hours for a belt change is a lot less than a belt change on a 928S4.

Humboldtgrin

Yea they made a LOT less power too!!! That also plays into affect.

V2Rocket

Yea, we only have half the s*** to line up lol

marc abrams

For me the belt is no biggie to do. So l will do it at the 3 year mark just for the peace of mind. But l also believe it could go twice that. I'm not sure about doing the tension recheck at 1500 miles, l felt "well that's a hour of my life l won't get back" the first time.

V2Rocket

its worth re-checking.
but you can wait a bit longer than 1500 miles.

marc abrams

Sorry, I mean no disrespect to the 944 guy's hear, but my Chrysler powered, 2.2L Turbo ll Daytona would eat my n/a 944 with it's 7 year old timing belt.