951sickness

Hello Everyone, as you might have guessed by the time stamp of this post I spent my Christmas changing my timing and balance shaft belts. To set the ground work here is what I did. The belts were changed as well as all the rollers. The car is an 88 944 Turbo. The timing belt was set to 3.9 and the new style balance shaft belt (18mm) was set to 4.0. I had to manually force the tension adjuster to get the 3.9 figure as it is factory set to only go to 2.7. The serpentine belt was set to 9.5 and the power steering belt was tightened until there was about 1/8" deflection. The problem is that now at idle there is a metallic rattle/vibration noise. It comes and goes depending on the engine speed. Any ideas what this could be? My first thought was the new rollers as they are a bit tight and not free spinning as the ones I replaced. Also I thought the additional tension on the new belts could be causing the vibration. Has this happened to anyone else? If so, does it go away after a few heat cycles and the belt stretching? Any help would be appreciated...I just don't want to take it all apart again. Thanks.

Jerry Ljung

The bad and the good... Had similar symptoms after replacing belts on my 88 NA this summer. someone with more experience than I took one listen and said "*! we should have replaced the water pump while we were in there". Re-tensioned belts, let it go for a couple weeks, didn't go away (stretch/set theory). replaced water pump. noise went away.

The good? your noise may be different. and similar symptoms can have multiple causes. mayhap someone can suggest a diagnostic that will attribute it to a harmless harmonic flapping (remove cover and observe?) at low rpm or other. maybe it will go away next week

Good Luck!

Thaddeus

Good call Jerry. Changing the belts and rollers could certainly make a weak bearing in the water pump become audible. That's where the smart money is.

Thaddeus

951sickness

Hmmm, that makes sense since the belt is now at 3.9 instead of 2.7 there is definitely more pressure on the waterpump. The reason I did not replace the pump is that the current one only has 9,000 miles on it...although it is five years old (the reason for changing the belts...age). I guess I'll have to release the tensioner so it reverts to 2.7 and see if the sound goes away....ugh.

Greg Hammond

If you have the luxury or time to re-adjust the belt tension every few hundred miles, you can just let the timing belt slack to 2.7 and re-adjust as it stretches. At any rate, you should be able to better discern the noise with the covers off.

How the the car run otherwise? Any possibility you have one of the balance shafts 180 degrees out of phase?

Greg

951sickness

The car runs great other than the noise. I am sure the balance shafts are timed correctly as I checked everything three times and there is not any increase in vibrations. The rattle is noise only. The more I think about it, I am beginning to believe that it is the waterpump. I'll find out tommorrow when I set the belt back to 2.7 Unfortunately the car does not get driven much (only 900 miles last year). I might have to set it at 2.7 and adjust every few months. Thanks for all your inputs.

951sickness

Here is an update. I loosened the cambelt to 2.7 and the noise is lighter now. I guess the water pump is the culprit. You guys were right. Any suggestions on where to get a new (rebuilt) pump? I have to get some new plug wires and Zims has a great deal on them...any experience with their waterpumps? Oh boy more fun with the Porsche. Thanks.

Jerry Ljung

Ger, I have no complaints with the pump or the price I got from Zim's. They were quite helpful (get the right version for your car). Something you may want to do while your in there (again ) is replace the thermostat, seal and snap ring. If you are tracking the car, considering the low-temp (71 deg C) stat may be a good thing. I never get above 1/3 on the temp gauge (excepting when a little air in the system, another story...)

Went to your website, say hi! to the cats, from Maryland (I'm sure they'll be impressed). Could not find pix of your P-Car, but the Volvo is a trip! (friend of mine has an ongoing P 1800 restoration, the chrome logo on the rear is missing the middle letter:

V O V O

... for his Xmas card, he took a picture of the logo, with a little snow hanging over the (lock/handle?) above...)

It's all worth it.

951sickness

Hey Jerry, thanks for your advice on the waterpump. I'm going to check the dealer first as I have a $100 gift certificate if I send at leat $200. My webpage is alittle old and the P-car is a bit buried but here is the url to the Porsche
http://home.pacbell.net/gchar/951.html

Still mentally preparing for the waterpump change. All I need to get is a cooling system pressure tester. I would hate to get it ll back together just to have a leak. Speaking of Volvo...I have to go and run that car....it's been a few months.

951and944S

Keep in mind that a "rebuilt" pump will require a core or a core deposit.. A new one while more expensive does not.

John Anderson

THe factory manual specifically says, there are no tensioning proceedures for the auto tensioner other than releasing the spring. It soundslike you pushed the tensioner past the flex of the spring to make the belt read the desired tension (as far as the gauge goes) for the timing belt and your roller is kind of floating and rattling. This is confirmed by your post that said you released the auto tensioner to the factory spring rate (you said your spring rate was 2.7 on the gauge) and the noise got lighter. You may have just damaged the tensioner. Please know this, there is no further adjustment to the auto tensioner other than simply releasing the spring. Read the manual, the great part of owning a later car is the auto tensioner and lack of special tool required to change the timing belt :-)

951sickness

Well, I have finally returned to the Porsche. For the last month I just let it sit as I looked at it with disgust. I find it mind boggling how difficult it is to work on the 944 vs. my Jetta. Progress is being made...although very slowly. Getting the crankshaft pullt bolt losse was an ordeal in itself. Let's just say that I have a Craftsman 1/2" breaker bar in four pieces, the thing literally shattered...bolt...still tight as ever. Once the bolt was loosened, getting the pulley off the crank was the next hurdle. All in all a royal PITA. Now the engine is void of all belts, rollers, and waterpump. No broken bolts if you can believe it. Now the fun of putting it all back together...maybe I'll be on the road by next weekend. Anyway, sorry for the rant but as it turns out it was the waterpump that was making the noise. Damn Euroselect parts

951sickness

Here is an update. After spending two pretty solid days working on this car it was finally back together. Filled with fresh coolant and fired her up....the noise reappeared within five minutes. Ever seen a grown man cry...come on by. I have just about had it with this car. What I did next was to take one belt off at a time and see when the noise stops. With only timing belt on the car the noise remains. The waterpump is new so I'm sure (kinda sure) that it is not the culprit. I swapped both the idler roller and the toothed roller with the old ones and the noise was still there. I took the car to a European Car Repair shop and they thought it sounded like a bad water pump. At that point I agreed with the shop and figured it must be a bad pump as if it were the crank or camshaft making this noise, the engine would have seized after ten minutes. So the place where I bought the rebuilt pump sent out another one and guess what....noise is still there. Just out of frustration and to make sure I wasn't missing anything, I took the car to yet another Porsche only shop and after poking around using a stethoscope they concluded that the noise was from the water pump! This mechanic says that they will never use rebuilt water pumps for this very reason. He stated that the rebuilt water pump failure rate is really high....around 60-70%. Okay, I call the palce where I got the pump and they sent out a brand new one...no more rebuilt ones. The new pump arrived and it it now installed in the car, pump change number three. Five minutes after startup the noise returned. Now I am positive that the waterpump is not making the noise although it sounds like that is where the noise is coming from. The only other place which it might be coming from is near the camshaft gear, but I keep believing that if it were coming from the camshaft, the engine would have seized by now. Anyway, I asked a neighbor what he thought (he works on old Detroit iron, and does frame up, big motor type stuff). He listened to the car and used a yardstick to listen to the waterpump bearing....said it was sounding nice and quiet. Here comes the interesting part. He asked what side of the T Belt runs on the waterpump pulley. When I said the smooth side (w/o teeth) he said "you likely have crud on the belt". Apparently serpentine belts which have idlers which run on the smooth side of the belt will make the same noise at idle when there is crud on the belt. What makes this more interesting is that the first rebuilt pump had a bunch of rubber bits stuck on the pulley. I'm going to run with this theory and buy a new T Belt at the dealer on Monday. I figure if there is crud on the pully there must be crud imbedded on the belt as well. I guess the "bumps" cause the belt to resonate in some way. At this point I just hope this is it and that I got a bum belt. Wish me luck, I'll keep you posted.

Lizard944

Did you try running it without the alternator or power steering pump belts on? You can eliminate two more bearing type noises this way ( at least you'll rule out two more potential noise sources)
My ps pump makes a noise that sounds like a ball of aluminum foil rolling across a tile floor (sorry, best description I could come up with )
and I swore it was coming from under the belt cover. Also, when I changed my belts, and a few rollers, I had a noise like arcing electricity. Went away after a couple hundred miles.


Lizard

951sickness

Actually I ran the car with only the cambelt and the noise persisted. So it can only be coming from either the camshaft, crankshaft, waterpump, idler, or the tension roller. Being this is the third waterpump and this one is a new one and not a rebuilt, I think I can eliminate that part. The ilder and tesion roller have been exchanged between a set of three. That leaves the cam or crank which I think would have seizedthe engine by now(250 miles). The Belt on the other hand has not been swapped out. That is what I'll be trying next.