Litespeeds

I have a 1988 944 with about 154K miles that is in very good condition. I purchased it and the previous owner(s) kept records of most everything that was done to the car. The last timing belt change was around 123K miles.
Anyway, when the engine is running, I hear this knocking noise that is coming from the front of the engine. It sounds like it is coming from the timing belt area so what do you think might be causing this occassional knocking noise? Is it something that I should look into ASAP?

PorscheDoc

Pull the covers asap. I have heard knocks when the balance shaft belt was off a couple teeth, maybe your belt broke. Get in there asap, so if the belt is broke, it doesnt get wound up in the timing belt and cause that to break.

Yabo

It's getting semi-due for timing belt. Don't drive at all before you pull the covers. just a few 10 mm bolts. it could be broken balance belt or a loose timing belt slapping the cover.

xsboost90

last time i had a knocking noise from the timing cover it was a rod bearing. Check it out right away.

Dave in Chicago

As above, easy to peek at if you take your time and remove the 10mm bolts. Usually, such a knocking/slapping noise (especially if it is changes with warm up) is the balance shaft belt being just a bit too loose. Sounds like something knocking on a heavy plastic part.

The good news... You hear a noise and haven't had a co$tly failure.

The bad news... You have some work to do or get done.

Lucky find, let us know what it appears to be.

Techno Duck

As was mentioned, i had a knocking sound from my 924S. Ended up being the balance shaft belt actually slapping against the timing cover (way to loose). Your about due for a belt change anyway, you may consider just changing everything while you have the covers off.

jeff_944

I had the same problem, turned out to be a bad bearing in one of the rollers. Easy to check just grab a mechanics stethiscope(spelling?) and stick it on each roller.

Cass944

my timing belt was loose. it was slapping the inside of the cover. it has been replaced since then

Campeck

and remember to junk those covers once you've changed the belts.

M758

with 30k approx since the last belt change I'd do the belt and check all the rollers.

30k is about right for timing belt replacement anyway.

Mongo

My '84 made a knocking noise right before the bearing on the water pump failed. Check and see if there is any coolant also in the timing belt case. Sometimes coolant will seep out the covers or behind them and down the front of the motor too.

A good 'while you're at it' idea would be to do your water pump while the car is apart. Good luck to you.

jonnybgood

If the timing belt is way too loose it will contact the belt cover when the RPMs are declining. Sounds more like a chirping on my car. I have heard it twice. When checked the T belt was very loose. Near disaster loose. Remove the covers and check it quick. If it is the T belt you will know quickly by feel that the belt it too loose.