Timing belt?

[fmartinez1897]

I noticed this whirring noise from my 88' 924S a couple of days ago. To describe it exactly, after the car warms up I drive it and when I accelerate there's a whirring sound (loud) coming from the timing belt area. The whirring sound goes down very slowly. and around 2k rpms it holds there for about a second or 2 and drops to about 1k rpms where it idles. Also noticed when I revved the engine using the throttle cam it sounds like somethings hitting the timing belt cover. (Sounds like it). Wanna know if anyone's experienced this? Hopefully it's not as bad as I think it is.

[GreenWater]

I would take the black cover off the belts to see them. There could be something bad wrong, or maybe not. I would take that cover off before starting the car again. You don't want a belt braking. It might just be a roller, or it could be a belt coming apart, or many other things. Take the cover off to see what's going on.

[fmartinez1897]

Is it hard to take the cover off? can I run the car without it on?

[GreenWater]

The cover isn't very hard to take off, just make sure you get all the bolts, there is approximately 1 million bolts that hold the cover on. You will have to get under the car to get all the bolts. Trust me, it's worth checking. It's a lot less work taking the cover off to check, than putting new valves in the car after the timing belts brakes. Been there, done that.

The cover is actually two cover. A top and bottom cover. The top cover comes off pretty easy. To remove the bottom cover the PS and AC belt need to be removed first.

[fmartinez1897]

Ok so it doesn't sound too bad. can the car at least idle without the cover on?

[fmartinez1897]

The PO showed me the receipts of the timing belt changed. but I'm not sure if he changed the water pump or any of the rollers and what not. That was back last november. I've got the oil for a transmission oil change coming in the mail I figure I could get all that done in one shot if possible.

[9FF]

The PO showed me the receipts of the timing belt changed. but I'm not sure if he changed the water pump or any of the rollers and what not...

Whirring noise is more likely from the balance belt and not the timing belt, normally when it's too tight. As said you have to take the covers off, idle the engine and see exactly what's wrong. A failed balance belt will take out a good timing belt very quickly.

[fmartinez1897]

Update: Took off the Cover and the belts seemed to be fine. No dangerous wear on them. However, I was Changing out the power steering hoses since they've rotted pretty badly, took off the power steering pulley to get the belt out of the way. Afterwards I tightened the pulley to hold the belt in and the whirring noise was gone. Car runs a lot smoother now and it doesn't feel like the engine's straining to pick up speed. However I put the cover back on and noticed the belt was still hitting the cover. Also noticed while i was in there that the rear cover broke where this small hose goes into the air intake. Is this bad?

[fmartinez1897]

also seems like I have this triangular looking thing in there. Auto Tensioner?

[jwade944]

The hose to the air intake was deleted by Porsche in a Technical Service Bulletin. There are caps that go over the air intake port and the belt cover port in lieu of the hose. There's really no reason to put the cap on the belt cover port except for looks. The 1987 engine has a spring tensioner for the timing belt. With the engine cold, you set the belt tension by loosening the tensioner spring nuts (2) and then retighten. Do not leave the nuts loose on the tensioner. It is not intended to be an active device. I raced a 944 for ten years with no belt covers at all so don't worry about leaving them off while you sort things out.

[fmartinez1897]

Part numbers for those caps? Don't want anything unnecessary getting in that air intake box. lol

[jwade944]

944 106 103 3

[fmartinez1897]

any one have a picture of which nuts to adjust on the spring tensioner?

[fmartinez1897]

Jwade: You are the man bro.

[GreenWater]

Glad to hear that everything is fine with your belts. Better safe than sorry.

Like Jwade944 said, make sure you tighten both nuts back up on the tensioner. I forgot to tighten one of the nuts and bent 4 valves because of it. Triple check everything when it comes to those belts.

I just thought of something. The AC belt could be hitting the cover too. From the outside. I think mine does on one of my cars. Not a big deal, it just slightly touches it ever once in a while. You can see marks on the cover where the belts hits in. Maybe by removing everything and reinstalling it, it moved a little and the noise has gone away.

It shouldn't change the way the car performs. That sounds like another issue.

[Panzer909]

Originally Posted by fmartinez1897

Update: Took off the Cover and the belts seemed to be fine. No dangerous wear on them. However, I was Changing out the power steering hoses since they've rotted pretty badly, took off the power steering pulley to get the belt out of the way. Afterwards I tightened the pulley to hold the belt in and the whirring noise was gone. Car runs a lot smoother now and it doesn't feel like the engine's straining to pick up speed. However I put the cover back on and noticed the belt was still hitting the cover. Also noticed while i was in there that the rear cover broke where this small hose goes into the air intake. Is this bad?

So.....you simply tightened the PS pulley and now a strange noise is gone and the car runs significantly better(?)

[fmartinez1897]

yeah it was the weirdest thing. The noise SEEMS to be gone but then again I did all that this morning. In a rush to make it to work by 11. I didn't happen to hear any strange noises or the car took off at the slighest push of the accelerator. No slips. Nothing. But then again, these cars do have minds of their own, so maybe she's just in a good mood now that I fixed this stupid power steering leak. I did however take off the cover and the belts did seem to be ok. Not sure how to adjust the tightness exactly on the camshaft belt. I see the two nuts, but when I loosen them then what?

[GreenWater]

The timing belt tensioner is spring loaded. It's a very strong spring too. All you need to do is loosen the right bolts, and the spring will push the roller/gear against the belt to the right tension. Then tighten the bolts back up. Just don't forget to tighten the bolts.

The top arrow goes to a bolt that needs to be loosened to allow the tensioner to rotate. The bottom arrow lets the tensioner release the pressure onto the belt.(tightens it) Those are the only two bolts that need to be loosened.

[fmartinez1897]

ok so to sum it up. Loosen those two bolts (any order I'm assuming) the belt tensions itself and re-tighten. That's it?

[Chunkerz]

I would push down on the tensioner arm a few times to "wake up" the spring. They tend to stick after a while. Rotate the engine twice and tighten those 2 bolts down and you should be good to go. The spring is super strong, so compressing the spring is going to be a ***** unless you have the special tool.