1989 Civic Timing Belt

[tblake]

Yeah, just by reading the subject, you already know the inevadable has happened. The timing belt jumped, Since it killed in traffic, I really didnt know what happened at the time, so I kept cranking on it out of stupidness, and not thinking, and blew the starter. I replaced the starter, and it cranked, then ripped apart the engine, replaced the belt, and attemped to start it. Its either still a little out of time, or being an interference engine, (correct?) I have valve damage, and major engine repairs. Any suggestions? Thanks a lot. BTW, its a 1989 Honda Civic with roughly 200,000 miles on it.

[91civichatch2571]

Definitly is an interference motor. Easiest way for you to tell if you have bent valves is to do a leakdown test. Its like a compression test but pinpoints where you are losing compression (rings, headgasket, valves). If you dont know how to do it, find a friend that does or take it to a shope and throw them a few bucks to do it.

[jeffcoslacker]

Put a vacuum gauge on it, if the needle shakes when its' running, the valves are bent. If the reading is absurdly low, cam timing is off.

[91civichatch2571]

where would you hook the gauge up to?

[jeffcoslacker]

Any vacuum source below the throttle plate (i.e. the intake manifold) The line for the brake booster is good. Has to be an unregulated vacuum source. Should read 17-21" at idle and steady. Should drop to zero when the throttle is popped. Low reading indicates bad cam timing or ignition timing retarded, or low compression overall. Shaky reading indicates compression imbalance. A wandering reading can be indicative of a carb problem. A rhythmic drop, consistant with each revolution indicates a single cylinder affected. If a restricted exhaust is suspected, the reading will slowly drop at steady throttle opening as the backpressure builds. The most useful and timesaving diagnostic tool you can have.

[jeffcoslacker]

Suction at the throttle plate is a mirror image of the compression in the cylinders. Once you look at it that way, it's easy to picture what the gauge is telling you.

[91civichatch2571]

good to know

[tblake]

thanks guy's, but, what if its so out of time that it doesnt run? How do I check for bent valves then? Thanks

[91civichatch2571]

then you'd do a leakdown test

[tblake]

lets pretend for a second I have no idea what your talking about. What do I do now?

[jeffcoslacker]

Originally Posted by tblake

lets pretend for a second I have no idea what your talking about. What do I do now?

You should be able to tell if your timing marks are properly aligned, if not, you gotta pull the belt and redo it. What's it sound like when you crank it? Is it notchy and straining, or smoothly turning? Maybe too smooth? You have to verify that the cam timing is correct (marks are lined up) or a compression test will be false information. A leak down test is a little involved. I think you should just get your cam timing correct, and do a standard compression test. If you get variations of more than 20% in your readings from one cylinder to another, it's junkyard cylinder head time.

[tblake]

Yeah, before when the belt initially jumped, it would crank really fast, and sound like there was no compression, then it would slow down, and backfire, and then speed up again, with no compression, and slow down, over and over again. Now, its a little more normal, sounds like its chugging air, if that makes any sense, but it still kind of slows, and speeds back up, which has gotten better, but thats why I believe it is still off time. Thanks, does this help any?

[jeffcoslacker]

Originally Posted by tblake

Yeah, before when the belt initially jumped, it would crank really fast, and sound like there was no compression, then it would slow down, and backfire, and then speed up again, with no compression, and slow down, over and over again. Now, its a little more normal, sounds like its chugging air, if that makes any sense, but it still kind of slows, and speeds back up, which has gotten better, but thats why I believe it is still off time. Thanks, does this help any?

Yeah, if the marks are lined up and it sounds like that, you might be hearing compression coming through the intake, huffing back through bent intake valves. You could try having someone rotate the distruibutor slowly one way then the other while you crank the starter, if the cam timing is just a little off, that will usually get it to start, but it won't run strong. The cam and distributor are geared together (or I think it actually runs off the end of the cam on that car) so if the IGNITION timing was right before the belt broke, it still is. The problem is cam timing or bent valves. If your marks are correct, and you are getting push-back through the intake, the head is junk.

[jeffcoslacker]

Did the old belt actually break, or just rip a bunch of teeth off? If it stripped teeth, you've got valve collision almost for sure, as cam timing jumped while the motor was still running. Sometimes they break clean, and you get lucky enough that the cam stops with the valves mostly closed. The cam, being under spring pressure from the valves, will try to stop at the point of least resistance i.e. least amount of valves lifted. Did it seem to stumble or get weak just before it broke? If so, it was still running with cam timing jumped, and it probably crashed some valves.

[jeffcoslacker]

I'm assuming it is fuel injected? Put a piece of paper over the throttle body's intake side, and have someone crank it. If it alternates between sucking the paper into the intake and pushing away from it, you've got intake valves bent.