The timing belt on our 1990 failed Saturday night. Am in the process of replacing it. Engine is a B230F, which is a non-interference design, so there are no problems with that issue, but a couple of questions arise:

1. Since the crankshaft and camshaft are free to rotate, do I just align everything with the marks on the rear timing belt cover and the block (for the crankshaft), then align the belt like normal, or is there some other procedure to line things up when a belt has failed?

2. This is the fourth time I have used the "rope trick" to hold the crankshaft still while removing the harmonic balancer. This time, as I applied counter-clockwise force to loosen the bolt, the crankshaft passed what looked like top dead center, and rotated all the way around nearly to the index mark again before it hit the rope and stopped. It usually does not do that, and hits the rope only a few degrees from when I start applying force. Is something fishy in there? I was trying to align it at TDC by using the mark on the harmonic balancer, and will now go check the alignment marks on the gear and shaft with the mark on the block. But even if they match, it seems suspicious. BTW, there was no internal noise or rattling, or anything that would indicate any internal failure of the block or head.
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1955 Human, Scott; 1991 745 Turbo, Thunderbolt; 1990 745GL, Posideon

to all those who said that you need to make sure the marks line up after you replace the belt and rotate it a couple of times, this is totally wrong and not helpful, and cuased me an extra 3 hours of work. just line them up carefull initially and you are fine. the white out trick works great.

Two full rotations and two of the three will line up.

"align cam timing mark, and align intermediate shaft at timing mark."

As mentioned in a reply by another to your other rather hostile post "BS" post, these actually have to line up.

White lines on the belt are designed you help you get it set up right. Few belts have them. The purpose of doing two full rotations is to make sure you are not a tooth off once the slack has been taken up...by checking the timing marks.

Thanks to all that answered.

The car was back together yesterday afternoon, and ran like a champ.

Taking out the #1 spark plug for the rope trick even led me to the loud and annoying exhaust leak so I could fix it. Somehow the nuts that hold the exhaust manifold to the head were very loose for the #1 cylinder. Bumping them accidentally caused them to rattle and caught my attention. They were that loose. Several of the manifold nuts were loose, but none were as loose as the two on the #1 cylinder, they were about a half of a turn loose, maybe a bit more. All are tightened down to about the right torque now.

The car now runs quietly, like a 740 should, and seems to be much better and smoother. More power when accelerating from a stop too. I think that may indicate that the belt may have slipped a tooth before it failed. The failure was not splitting apart, but a bunch of teeth that were stripped clean off of the belt, so it may well have slipped a tooth or two before enough teeth let go to stop it dead in its tracks.
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1955 Human, Scott; 1991 745 Turbo, Thunderbolt; 1990 745GL, Posideon

I did my timing belt last dec(2012) .It had just about 50k on it and I believe it was a Conti. It looked darn good guys and I believe I could have gotten another 10k easily . Just wondering how many miles you had on yours before some teeth became "missing" and what brand belt it was. Regards

I've had the car for just about the last 100,000 miles and did not change the belt since I have had it. Heaven alone knows what kind of belt it was. The lettering on it had long ago worn off, and the back side of the belt was nothing but a network of cracks that went all the way through the rubber to and through the teeth. Come to think of it, the front, or toothed side looked like that too. Literally the only thing holding it together were the cords in the belt. I should have taken photos of the old belt and posted them. It may still be somewhere where I can find it. If it is, it is possible that I'll post some photos.

Normally I am much better at maintenance, and would have changed it long ago. I certainly don't recommend that you try to get 100,000 miles from your new belt. Not even 75,000. Change it in accordance with the recommendations in the user manual, or the Brickboard FAQ, or an average of the two if they differ. That your belt was still in good shape is the whole point of the change interval. It is like cleaning, vacuuming, and dusting your house: You do it regularly, even if it does not look like it needs it. It is much easier that way. You certainly don't wait until it is covered in a foot of dust and there is schmootz all over your carpets.
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1955 Human, Scott; 1991 745 Turbo, Thunderbolt; 1990 745GL, Posideon

If you weren't slightly passed TDC, then when you went CC, the piston would be dropping.
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Post Back. That's whats makes this forum work.

Exactly right! You are both right. The crud on the lower timing belt cover had partially obscured the "0" Deg. line, and I was lining up on the "0" part of the "20" before TDC mark. Oh DUH!
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1955 Human, Scott; 1991 745 Turbo, Thunderbolt; 1990 745GL, Posideon

the REAL '0' is not on the High section of the cover .. forgetting that used to get me crazy.

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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html http://cleanflametrap.com/tony/

1. Yes, that's the procedure. Get crank motor to TDC, align cam timing mark, and align intermediate shaft at timing mark. Then get the belt on there with the timing marks on the belt lined up, should be good to go.

Unless...

2. Sounds like your crank pulley may have slipped. I'm not sure how to determine this, as I've never had it happen on any of the motors I worked on, but getting the motor to TDC now could be tricky. And, you'll need to remove the crank pulley now too to see if it did slip and why.

Good luck.