Rob Edwards

I picked up a black '90 GT on Saturday, the car is GORGEOUS! But- the timing belt warning was lit up on the digital dash. Drove carefully home, and borrowed a Kempf tool (Thanks Carl!!!!) Anyway, I' ve had a great day pulling the engine apart, and I'm finally at checking the tension. The balancer is at TDC and you can see the cam marks in the picture. SO- obviously this belt is way loose. The car's got 108K, the belt was done at 97 and retensioned at 100K (have the receipts) BUT- the tensioner was not rebuilt.
Question #1 : Can I just adjust the tensioner to get the belt in spec and drive it until I get all the bits together for a TB/WP and rebuild the tensioner, or would you not drive it? (This assumes that the tensioner's not so bad that I CAN'T get it adjusted)

Question #2: How does this cam gear look? I think they're worn but I have never seen what I'm looking at before. Thanks for any input and I hope to meet the SoCal and NorCal folks soon!

-Rob

928ntslow

Cam gears are worn. Tensioner is probably bone dry, belt is very loose. You have a catastrophe awaiting. For the hassle of trying to get it "just" safely drivable, do it right.

You have it that far apart, why put it back together? Borrow the money! Get the parts, do it correctly. No sense in taking chances.

Spend about $1200 now or spend $7000 later. I have done this job several times, I can tell you this car is over due!

wds928

Passenger side cam sprockets will usually wear faster than the other side. I just finished my WP/TB/Cam Gear job one week ago tonight. Mine were a lot shinier than yours, with 134,500 miles on them.

I replaced them with new cam sprockets, rebuilt the tensioner, replaced the tensioner and idler rollers, bushings, etc. I posted some pics a couple of weeks ago. Just search on my name to see them.

If you can tighten the belt to spec, drive it and recheck in 1500 miles, just for grins. Make sure the sensor wire is connected, as this could also be a problem. Then start accumulating parts and tools to do the job

You can do it yourself. Should be plenty Rennlist members nearby to lend a hand. Good luck.

Jim R.

I would park it and just replace it all if it was my car. I liked starting with a clean slate in the TB related area-one less thing to worry about.

If you feel lucky and like to gamble, you could probably retension the belt towards the 3/4 point of the window on the tool, try to add oil to the tensioner if the boot is intact, and recheck it in 300-500 miles to see if it is loosening up. The belt should have been done stretching already, but who knows how the last retensioning was done (hot vs cold, measuring device/technique etc.).

Your cam gears need to be replaced. Get ready for the gears and whatever else you may feel the need to replace. I replaced all my gears, rollers, bushings, WP etc with my TB change. At least I have some TB peace of mind, although all the parts $$$ do add up......

Good luck with the car, with the shop manuals, Rennlist, and some patience they are not too bad to work on.

Jim

AO

Based on age alone, I'd say you are due for everything. You've gone this far, it's not that much further to get the rest of the engine apart and ready for a full TB(&WP) job. Good luck.

Rob Edwards

Thanks for the input! I already have Jim's CD's and have been reading non stop for a week. I've already got a pretty exhaustive list of what I (think I) need for the TB/WP, and already had the cam gears on it . I'll probably do the crank seals, the whole nine yards. For now, is it ok to fill the tensioner with 30-weight, and adjust the tension?

AO

Use gear oil... 70-90w-ish.

Alan

Yes those cam gears are pretty well shot - many worn all the way across - they start eating up the belt when they wear that far - speeds the degradation up. Given its old & loose that's a particularly bad thing... I would be inclided to do everything ASAP... Belt, cam gears, crank gear, oil pump gear, belt idlers & tensioner & water pump- they almost certainly will all need to be done...

Alan

worf928

Rob, you can fill the tensioner with either gear oil (as specifiied in the WSM) or motor oil (as specified in a later TSB.)

Do the teeth of the cam gears feel sharp (even a little) to the touch?

With a loose timing belt, sharp sprockets, unknown tensioner condition, and timing off - I would do the whole job now. Unless I absolutely had to drive the car I would park it.

Bill Ball

Motor oil is fine in the later tensioner.

The gears are worn and should be replaced, However, if there is no dishing or sharp edges, these are livable for a while. I've seen far worse with no effect on the belt. The belt only has 11K miles, if I read your post correctly, and should be in good shape.

The belt losing tension this badly after a retension only 8K miles ago is concerning. I had that occur with one belt. I believe my tensioner had gone dry. A dry tensioner does not warm the internal washers as well, and the tensioner does not compensate for expansion of the block when warm, thereby overtensioning and stretching the belt. I corrected the dry tensioner but I still replaced the belt even though it looked like new.

Rob Edwards

I will be ordering everything for a complete R&R tomorrow. The issue tonight is getting it buttoned up so I can get it back in the garage. I can't seem to loosen the locknut on the tensioner. It's cooking in PB blaster right now. How much force should it take? And how many turns on the tensioner bolt should I give it before rechecking?

AO

It shouldn't be THAT tight. Cook away! To bring tension up to spec, probably at least 2 or 3 full turns or more. Once you get it in the window, turn the crank by hand 2 full rotations (clockwise) and recheck. Adjust, repeat, until you get her just right.

khalloudy

Yup yup... don't even think of driving this GT... would be a shame!!! have it hauled to a 928 mechanic you trust and change the belts, waterpump and all those tensioners, and rollers and cam gears. Your cam gears are so worn that they are most probably eating into the belt too. Only advice is like everyone else. Spend $1200-$1500 now or pay later this is definitely a disaster waiting to happen and it would be a shame.

P.S. Welcome to the 928 world, the GT is a supercar in all form - it will rape a new M3 if you know how to drive it ;-)

Sincerely,
Khaled

morganabowen

Congratulations That is a very nice car, that has been neglected. It is good to know that a real enthusiast now owns it

pmotts

Rob,

Do it yourself, you will be glad you did.
As for raping a new M3 with your GT, ain't gonna happen unless the M3 driver is clueless. 60mph plus would be very close but from a standing start the M3 would cause you some grief.