91 6cyl timing belt questions, please help!

civilnerd · 07-22-2007, 04:10 PM

Hello all. I'm totally new here and am seeking some advice. I recently purchased a 1991 325i sedan, automatic. Its pretty rough around the edges, but i really like the car.

anyway, i had been driving it to work a couple of days a week. Its a very easy drive from my house, almost all highway miles and no traffic lights along the way. I was pulling off the highway onto a county road right beside my office. I was slowing down to make the turn, maybe 20mph and the engine was at idle speed as i was braking when it completely died. No noise from under the hood or anything, just died. It had been having some rough idle issues, but had never stalled before. i attempted to restart it, but it wont even turn over.

After reading these boards and other web pages, I'm afraid that the timing belt is broken. I ordered the "super kit" last week and started to tear into things today. I figured I wouldnt know if the belt is broken until I can get the timing belt covers off. If its not broken, then it still needs to be replaced.

well, just as things were moving along nicely, i realize that my engine does not look like the ones in the pictures. i removed the hood, the grill, the radiator and hoses, the fan (with clutch), the belts and was down to removing the 3-in-1 pulley when it dawns on me that there is a large, steel, toothed wheel/pulley/thing that the 3-in-1 is bolted to. Its not in any of the pictures.

I removed the upper timing belt cover. The belt is not visibly broken. Neither end can be pulled free from under the lower cover. On the side where the belt goes around the tensioner, its very tight. The other end of the belt is much more loose. There's one place where i can see that there are a couple of teeth missing on the belt.

I'm guessing my engine is not the same as the older ones. Can anyone lend me hand or point me in the right direction for how to proceed?

If the belt is broken, can I rotate the engine to TDC? Wont that cause the pistons to hit the valves?

I have pics if needed.

Nostril Cheese · 07-22-2007, 08:13 PM

pics would help.

the toothed wheel thing could be the sender wheel for the fuel injection.

civilnerd · 09-01-2007, 09:40 PM

Hello all, it's me again.

I took a break from working on the car, but decided to use the holiday weekend to get back at it. I managed to get the large, toothed pully off the crankshaft. It was just a press fit wheel with a dowel to align it.

Anyway, now I have the lower timing belt cover off as well, and can see that the timing belt is not broken, but does have some teeth sheared off. I removed the spark plugs and attempted to rotate the engine to TDC, but as I turn the crankshaft, the belt does NOT turn with it. Although I can't really see at this point, it appears that there are no teeth on the timing belt as it goes around the crankshaft.

Here's the question: is it time to put down the tools and either tow it to a shop or part out the car and look for a new project?

Any help or opinions are appreciated.

e30m20 · 09-01-2007, 10:03 PM

hmm - doesn't sound too good. Get yourself a new belt and carefully try to line things up again. Keep in mind that, for every turn of the cam, the crankshaft turns twice - so even if the timing marks on the cam and crank align with their respective marks, you could be out by one rotation of the crank. turn the engine by hand to make sure nothing hits. You might be lucky.

Bjornb · 09-08-2007, 05:42 PM

Before you do anything pull the valve cover off and inspect all of your rockers and make sure nothing looks out of place, it is possible to break rockers when jamming pistons into valves. If everything appears to be normal do like e30m20 said try to carefully rotate the engine to the tdc position. You will have to rotate the cam as well as the crank the keep things from jamming up. I would suggest rotating the crank counter clockwise a small amount to back the pistons away from the valves and unjam the engine. once you get things moving you can use a long screw driver to feel if the number 1 piston is at tdc when the marks on the crank pulley are lined up. If you can get the crank and cam lined up correctly install the new belt and then turn the engine over a few times by hand. With the spark plugs out the engine should turn freely without any sudden resistance. If everything feels ok you may have gotten lucky and not done any damage. At this point you can put everything back to normal and try starting the engine. If you do feel more than slight resistance when turning the engine over you will probably have to pull the head off and have it rebuild with new valves. You could still put the engine back together and try to start it if you like. You cant really hurt anything as long as you get everything lined up and installed correctly. I have seen an engine that broke a timing belt at low speed and survived so there is hope. I hope this helps you and good luck!

BMWCowboy · 09-09-2007, 05:50 PM

If the belt wasnt broke I would look elswhere~~>like cam sensor or even Harmonic balancer coming apart

TOTALLYBMW · 09-15-2007, 04:37 AM

Are there no teeth left on the belt where it meets the crankshaft? If so the crank has rotated without the camshaft, so you will have to at least get the rocker cover off and spark plugs out to line things up again, and to check that nothing broke!!!

David Bevan · 09-17-2007, 09:29 AM

i have just replaced the belt on my E30 that i noticed had missing teeth. it seems that the cheap belts tend to shed teeth when they get on a bit, not ideal! it had 12 teeth missing in 4 locations.
By a BMW belt they last the distance.
You may be very lucky and possibly got away with snapping a rocker or 2.