cschou

Hi everyone...

I'm writing to you since I'm conserned about a "mis"-noice coming from the front of my engine, suspecting it to be something to do with the TB.

The short version:
The car: 928 S4 1989
Complete new TB, rollers, waterpump etc. After approx 150 miles, re-tension the TB. Afterwards a mis-noice coming from the front of the engine in the middle. Suspecting the TB to touch something under the cover. Noise is like a schriek only appearing in the rev-range 1000-1500 rpm.
Anyone got similar experience or idea what this could be?


The Long story:
The car is a 928 1989 5,0 S4. I have spent the last 3-4 years restoring the car and of course the engine has been restored too. This includes a complete TB-job, with all the rollers, waterpump, new TB, cam sprockets, oil pump sprocket etc.
After the restoration the car started nicely and have run properly ever since. I have now done about 150 miles since the restoration (and TB-job).
A few days back the TB warning light came on. (Animated picture saying Zahnriemen Service!). I gently drove the car home, and pulled the right TB-cover (passenger side). I'm aware that re-tensioning of the TB can be nessecary. I checked the tension, and it was a bit too loose. I readjusted the tension and put it back together.
When fired back up, It now has a mis-noise in the very short rev-range of approx 1000 - 1500 rpm. The noice sounds a bit like a schriek or a belt touching something, but a bit hard to explain. I'm not entirely sure that the noice wasn't there before the re-tension. The sound seen to be coming from the front of the engine somewhere in the midle. (could be the waterpump?)
I pulled the TB-covers on both sides but everything seems nice and clean. The tension is right, and i have tried to let a bit tensin of without any change.
The TB looks fine, no tattered sides or anything.
I haven't yet pulled the center cover, but will do tomorrow or in the weekend. I'm therefore asking you guys if anyone has ever had similar experiences or has an idea what might be causing the noice.

Not sure if i missed any important info...

Hope somebody can help.

Sincerely
Casper Schou, Denmark

Landseer

What brand water pump was used / how much $ / from what source?

Can you please provide pictures that show the tracking from several angles?

Do you remember the orientation in which you re-fitted the belt guide washers that sandwich the crankshaft gear?

You are very wise to slowly disassemble and review!

cschou

Thanks for your reply...

All the parts were purchased at 928gt.com (928 specialists). I'm not sure of the particular brand of the waterpump, can't see from the receed, but perhaps a rebuild? The price I can't see, since it was part of a TB and waterpump kit.

Regarding the sandwich plates at the crank-sprocket, I'm 99,9% sure I put them on correctly, as they had clear markings from the sprocket itself.

I can supply pictures, but unfortunately it'll take a little while.

cschou

UPDATE**

I knew I would forget something in my initial description and I did. :S

On the backside of the belt (the side without teeth) there is a black line (approx 2-3 mm wide) running the entire length of the belt. The line is placed about 1/3 of the width from the engine-side.
At first I thought the line was a light scratch (very hard to feel the line), but investigating it further I found that I was able to remove it from the belt, which means it was somekind of dirt. It didn't seem like oil, much more high viscous almost solid.... like soft rubber or compacted dirt+grease of somekind. Underneath the belt looks as new.

Sorry for forgettting as this info might help...

SteveG

It shouldn't be loose at only 150 miles. Recommendation is to check at 1500 miles and it might need 1/4 turn tightening of the adjusting bolt.

Mrmerlin

that line may be the belt touching the guide rollers under the crank
and the bearings of one or both of the rollers are too tight to turn freely.

I had a similar line on my belt after the waterpump got loose,
I replaced the pump with a new Laso from Roger no problems since .

your belt is still OK to use

giddyupp

Did you replace the tensioner ? Seems like it's not holding tension, if it was loose after just 150 miles. I think I would start there. If you did not replace or rebuild it, I would totally recommend porken's tensioner. Once installed no need to re tension.

NoVector

I had a similar noise when my waterpump was going. I started by removing belts one at a time to confirm where the noise was coming from (wanted to make sure it wasn't the A/C or the alternator, etc.)

I looked down through the vent holes on top of the timing belt covers and watched the belt as the car was running. Every time the noise occured, the belt would track differently and move to the front of the cam gear and then when the noise stopped, move back to where it was before. That's how I knew I had a pulley or something dragging the belt down--in my case, the water pump.

Hopefully you don't have to pull all that crap off the front of the engine again! Good luck and keep us posted! / Bruce

cschou

Hi guys and thanks for the many replies.

I am also a little concerned that the belt already need tensioning...

I did completely rebuild the tensioner and it is still FULL of oil...

I can reach under the plastic surrounding and touch one of the rollers underneath the crank, and that one is running fine. But this also implies that the belt ain't touching it. Both these rollers were also changed.

If the new waterpump, which actually isn't that new, bought it some years ago and had it lying around, is giving up, could that explain the loose belt?` It was never unpacked, an felt fine as I fitted it.
Also i tried watching the belt through the holes, it seems to be running fine. Maybe moving back and forward (as in the length of the car) less than 1 mm, but that happens independent of the noise... Is that a problem?`

Thanks a lot
Casper

cschou

Oh, and regarding the line on the TB... I don't see how (if its the waterpump) it could make that line?? The waterpump pulley doesn't have any signs of a line.

Landseer

There has been a major realization in the last couple years that rebuilt waterpumps were not being held to proper tolerances by multiple rebuilders. Multiple. Search and you will see that some of these would fail and machine the block. So we had to get away from using rebuilts.

We as a group have pretty much switched to one of three pumps.
1. New Porsche 2. Ed's (O'behave's) special design 3. (for the masses) A brand new casting Laso w/plastic impeller (developed by Laso at urging of Roger Tyson)


Probably not your immediate issue, but you'd do well to consider making the switch now, not waiting.

NoVector

cschou - So the noise only happens when you rev the engine up to `1500 rpm and it doesn't do it at idle? Have you checked your other belts and stuff? Sometimes it's hard to hear where a noise is coming from...

Bilal928S4

The pulley you are feeling does not touch the belt when the engine is not running.
Bilal

WallyP

Use a spray bottle, child's squirt gun, or water pipe to spray a little water between the belt and pulley on each of the accessory belts (power steering, A/C, alternator, air pump) with the engine running and see if the noise changes. If the noise changes, it is very likely that the problem is one of the accessory belts.

cschou

Okay, thanks... didn't know about the waterpumps... :S Is there any way to see on the waterpump if it's a rebuild? any signs, special colors or anything?

NoVector - Yes only when i rev the engine or hold constant revs at approx 1500... I have though tried to manipulate the acc.-belts (pressing on then with a wrench) without any change in noise. Didn't know about the water-spray, but will definiatly try that once assembled again...

Unfortuniatly I have not yet had the time to do any more work on the car, but will return to it this weekend.