86 timing belt tracking

12magnum · 07-23-2007, 07:16 AM

hey guys,

my 86 928s has a slight issue. my timing belt tracking is slightly off. When the car is cold, i can hear a slight rythmic squeaking. I removed the passenger side air intake hose, so I could look down in the timing belt cover while it is running. what i noticed is that the belt is wandering back and forth on the cam gear. Every time the belt wanders over towards the cylinder head, I hear a slight squeak, then the belt moves back out away from the head. It only does this when the engine is cold. I check the belt tension with my kempf tool and it's ok. I replaced my timing belt, water pump, rollers and rebuilt the tensioner about 4500 miles/2 years ago. I also don't see and wear on the belt so i don't think it is likely to shred the belt.

Do I have a problem or is this normal. Is there any way to adjust the tracking? I'm just asking because if this is a sign that my tensioner or something is about to give up, I will take it off the road and re-do the whole timing belt job. btw, I used a kit from 928specialists for my parts.

mike

12magnum · 07-23-2007, 07:30 AM

by the way, i did replace the plastic tensioner pivots, and the pivot bolt. I am thinking that I might have a problem with those plastic tensioner pivots, even though they are not very old.

porken · 07-23-2007, 02:34 PM

Are/were the cam gears in good shape? No shiny areas where the belt tracks? If the gears are not worn, I would suspect the (rebuilt?) water pump as the culprit.

12magnum · 07-23-2007, 05:04 PM

my timing gears looked perfect. I hope it's not the water pump.

porken · 07-24-2007, 11:30 PM

Did you check the belt tension when cold or hot? The tensioner could be dry/stuck, and only shows the correct tension when warm.

Did you use a torque wrench to install the shoulder bolt? It's easy to overtorque it. as it's only an M8 bolt. (15ft.lbs.)

12magnum · 07-25-2007, 10:29 AM

porken, last night I took some things apart to check the belt tension. My tension was at the loose end of the range on my kempf tool. I last checked it 3000 miles ago (belt now has 4000 miles) I did these checks cold as per the kempf tool instructions. I adjusted it up to the middle of the range on the tensioner tool. I put it all back together and fired it up. Still has the slight squeak. I put a drip of water on the back side of the belt while the car was running and it immidiately stopped chirping. I believe this confirms the belt is chirping and the noise is not a bearing squeaking. The belt looked ok, you can still read the writing on the back side. I now believe the chirp sound I'm hearing is coming from the belt slipping on the water pump. Does anybody know if the belt gets tighter as the engine heats up? because it stops after it warms up (either due to the belt getting tighter or stickier as it gets hot?) tonight I'm going to take apart again and raise the belt tension to the high end of the range on the kempf tool. I'm also going to carefully inspect the belt for contamination in case it is slipping due to an oil spot, then I hear a chirp as it regains traction. by the way my tensioner is not dry. Could the tensioner be sticking? possibly.

hughett · 07-26-2007, 08:08 AM

If the belt is not running "true"...and it's squeeking...something is wrong. Hopefully you don't have a bent shoulder bolt or one about to "go". The gear you took off is quite worn. Perhps other gears are worn too and contributing to this problems?

Harvey

jstobo · 07-26-2007, 11:10 AM

Do you have the flange washers on each side of the crank gear oriented correctly? They hold the belt pretty tightly at the crank end. Maybe if one is reversed it could allow enough slop for the belt to move. Just guessing. I don't think the belt should be moving that much. Good Luck.

12magnum · 08-08-2007, 02:57 PM

porken,

I looked at your website and i am interested in the tensioner bracket you build. when are you going to make more? I am probably going to install a new (rebuilt) water pump, continental timing belt and install the porken tensioner.

mike

porken · 08-08-2007, 05:10 PM

Mike,

I will hopefully be ordering a batch of tensioner brackets in a couple of weeks.

I just got the 32V'r cam timing tools (thread) back from laser cutting. After I get those mailed out, I will post a thread about a run of the brackets.