danglerb

The belt is under tension whether the motor is running or not. Its rubber, and things like the tensioner that get looked at during a belt change are worth looking at on more than just a pure mileage interval. Lots of really short trips are murder on a car, so no general plan. Inspect the specific car and then move forward with what it needs. Things that are easy to replace as they are to check, replace.

I mean how do you know the guy that replaced the belt 4 years ago did everything he should have?

Bill Ball

You never know anything for sure.

Jim bailey - 928 International

The tensioner only picks up the slack on the loose part of the belt. (think 10 speed bicycle chain)The crank gear pulls down on the belt turning the oil pump left side cam water pump and then the passenger right side cam then the belt gets to the tension roller/tensioner. So the load on the tensioner typically is far less than the actual loading on the belt during running and when stopped depends on how many valve springs are being compressed and the net energy stored by the camshaft since some are plus some are minus in the eyes of the tensioner. Which is why Porsche cautions you NOT to turn the crankshaft backwards (counter clockwise) or you may overload the cup shaped bi mettalic washers in the tensioner and smash them.

Bill Ball

Thanks for that, Jim. I thought the countercloskwise caution had something to do with the cam chain tensioner, but I was only guessing.

y33trekker

I only mentioned the 4 year interval since last TB change because I had read here on Rennlist recently that some say it's best to change the TB every 4 years, regardless of mileage.

Is that considered exceedingly safer than sorry? Considering the possible consequences of a TB failure, I can see why some might opt for that interval.

Do most just replace the WP at the same time because it's right there anyway?

Bill Ball

Some have suggested 5 years or 45k miles. The factory interval is 60k miles. Considering the consequences of a broken belt, some people feel that shorter intervals are better. I check the TB system every 15k miles. I did change my second TB at shorter than the 60k interval when I found it losing tension. It looked fine but it had stretched after 30k miles. I wouldn't expect significant stretching beyond the first few thousand miles. The replacement belt is still fine after 50k miles.

I really shouldn't argue with someone who is just being cautious, but I just don't like to see it become standard procedure.

deliriousga

I used all OEM parts, but will use the Porsche belt next time. The Continental belt (tried two of them) has a deflection in it that looked scary at first and I have had to re-tension it more than others have with the Porsche belt. I don't think the Continental was the OEM belt so it's worth the extra $$ just for the belt. Everything else (including the rebuilt Porsche water pump from 928Intl) has been holding up beautifully.

perrys4

Mine was six years and around 20k miles and it looked brand new. I was more worried about the WP after seeing the belt and cogs were perfect.

oups59

Thanks to all of you.

I had some time this week and I began the TB/WP on Wednesday. I removed the timing belt that night. No problems so far . About 3-4 hours to do it. The crankshaft bolt was very tight.Need the pipe to removed it.

The timing belt was like new

The tensioner boot was crack all around.

I have a couple of questions:

1.camshaft sprocket wear : Should I replace mine? or is this normal wear?

2.the tensioner look to be stuck to the block : Any advice on how to get it out?

RyanPerrella

smack the tensioner with a rubber mallet. Also make sure the smog pump is free, it mounts to the tensioner.

Your cam gears should probably be replaced as well, they are due.

borland

tensioner-- Like Ryan said, looks like you need to remove the bolt for smog pump too. It should pull free with little effort.

cam sprockets --- They look excessively worn. Looks like your crank sprocket may need replacement too.

Bill Ball

The cam gears are shot. Once the wear through the anodized coating is anywhere near full width and the teeth are starting to dish out at the top, they are done. Those are probably original gears. How many miles on the car? If those are not original gears then the tension may have been too high.

You need to very carefully mark the position of the cam gears relative to the camshaft before you remove them. On the passenger side you can see the trigger plate for the Hall sensor through the cutouts in the cam gear. Use a thin marker to outline the cutouts on the trigger plate. On the driver side there is no Hall trigger plate, So, you need to mark the position of the bolt holes on the cam spider visible through the slots that the rotor bolts go into.

Look carefully at the oil pump gear as the original gear is the same material as the cam gears. The crank gear is steel, but look it over as suggested.

There seems to be a lot of what looks like belt dust around the tensioner area. What condition was the belt in? At 22k miles, it should have looked very close to new and the PN lettering should have still been readable.

The tensioner should come off unless the air pump bracket still has the long bolt in. That goes through the tensioner and into the block. Also, there are 4 other bolts that hold tensioner on. I can see 3 of them. One more is tucked above the adjuster, as well as the air pump bracket bolt.

I see you have the cam gears at TDC. Normally the crank is locked at 45 BTDC and the cams rest at about 22 BTDC, about 3 teeth away from TDC. No biggie that the cams moved, but the crank should be at 45 BTDC, although some argue that you don't need to take that precaution.

oups59

Ryan,

I did just that and got the tensioner out

Bill,

The belt looks very good

oups59

Bill,

I did lock the crack at 45 BTDC. And here a look at the crank and oil pump gear.

Thanks again for your help

borland

Very good. Belt looks almost new.

The crank sprocket is easily removed now that you have dampener off. Try matching the belt to the crank sprocket. I can see some corrosional wear on the top of the teeth, simliar to the cam sprockets. The crank sprocket is steel, so you wouldn't expect it to wear as fast, but yours is quite worn.

Oil pump sprocket looks almost as bad as the cam sprockets.