I’ve been trying to get a 1978 Dodge Challenger running for SonO, who just turned 16. It’s been sitting unused for about four years, when his big sister parked it in my driveway and gleefully walked away from the heap.
No, it’s not a cool old Challenger; it’s the misbegotten gas-crisis model built for Dodge by Mitsubishi, with a 1600cc SOHC four-banger in it.
So, after much tinkering, swearing, and anguish, I get the thing fired up. Triumphantly, I pulled it out of the garage, ran it for a while, then turned it off and left it for a couple of days.
Yesterday, SonO goes out to drive to school, and Bam! - both timing belts broke. (Confirmed by subsequent teardown and autopsy.) The thing has two timing belts - a big one, which does the normal timing belt thing; and a smaller one, which runs a counterbalance shaft.
I thought it was odd that both belts would break at once. Now I understand that because it’s been sitting idle for four years the belts were probably dried out and funky, but still … hmmmm. So my question is: Is this normal - one belt goes, and it takes the other one out, too? Or is this perhaps indicative of an underlying problem that I should find before I slap the new belts in and try to fire it up?
Thanks in advance for helping me save what’s left of my sanity. This Demon Car is driving me nutz.
Four years idle, and the belts would be expanding and contracting with your summer and winter temperatures for four years, I can see the reason for them to break. Honestly though, I’d have done the same thing and not thought about changing them before starting it up. I don’t think there’s any other problem with the belts other than the wear, but my concern would be whether any valves were damaged as a result of the break. Timing belt snaps tend to do that to four-bangers, so I’d check those first before attempting to start it again.
And consider yourself lucky to have a car built before the 80’s. The engines today are too damn complex to make it worth getting your hands greasy. I’ll be looking for 70’s model soon just so I can have some fun on the weekends tinkering with it.
I don’t know, but you should by a manual. I know, by experience, that when the timing belt of a Ford Escort of that vintage breaks, it bends valve stems and can puncture pistons.
There is mechanical interference between the valves and the pistons when the valves are badly out of time.
To second the previous posters diagnosis, I think you could be…
Deep in the Do-Do.
The timing belts often drive other things, and one serious culprit is the water pump, whose bearing seals may have dried out over time and allowed moisture to seep out.
In short the water pump may have siezed bearings and this has taken out the timing belts.
Bad news. Very few engines are designed to not suffer damage when a timing belt breaks. The VW rabbit was this way, with clearance between valves and piston tops.
I’ve never seen an alternator or water pump that was run off a toothed timing belt, just V belts.
Well, I have. That is precisely what happened to my Escort. The valve timing belt also drove the water pump which siezed, stripped the timing belt teeth and BINGO! I was really disgusted with Ford engineering over that.
However, I suppose the decision was forced on them by some Value Engineering. After all we’ve already got a belt there, why add the cost of an extra one to run the water pump?
According to one of my books, this is an interference engine, meaning it can bend valves when the timing belt breaks. That doesn’t necessarily mean it DID bend them, but the odds against it are slim. And if any valves are bent, you’re looking at a major engine repair. Your choices here are: 1) assume the worst and forget it; 2) replace the timing and balance shaft belts and see if it will start and run normally; or 3) measure the valve clearance on all cylinders and see if any valves have wildly excessive clearance, indicating a bent valve.
For option 3, you can first remove the valve cover and see if any valves are obviously loose as it sits–if so, it’s valve job time. But in order to check ALL the valves, the camshaft must be rotated. Doing this without a timing belt in place requires first carefully setting the crankshaft to 90 degrees before or after top dead center, so all 4 pistons are down from the tops of the cylinders. If this isn’t done properly, it’s possible to bend valves in the attempt.
While a number of modern engines do indeed drive the water pump with the timing belt, I don’t remember anything of this vintage being designed that way. You can easily check that the water pump is driven by an accessory drive belt (“regular” belt).
Since the timing belt and balance shaft belt have only one sprocket in common, on the crankshaft, I doubt that anything seized and cause them both to fail. It is possible that some piece of debris got caught in there and messed up both belts, but if the timing belt cover was in place that’s very unlikely.* It’s also possible that one belt’s breaking caused the other to follow suit, perhaps by its loose end getting caught up in it. Nevertheless, it’s easy to rotate the various driven shafts (at least partly) to verify that they aren’t seized. DO NOT ROTATE THE CAMSHAFT UNLESS THE CRANKSHAFT IS POSITIONED AS DESCRIBED ABOVE.
Sorry that happened. Good luck.
*Once, I’d done a pre-delivery inspection on a Fiat 124 Spider, leaving it in the stall that night. The next morning, the car wouldn’t start. I found the timing belt had jumped several teeth. Huh? It ran great the night before. The explanation was evident when I reset the timing belt. I found corrugated mouse pelt. The poor thing found a warm place to sleep, but was still there when the porter tried to start the car.
I am a survivor of 3 Mitsubishi built Chrysler products, 2 1975 Dodge Colts and a 1981 Plymouth Sapporo. One Colt had the 1600 and the other 2 had the larger twin, the 2000. I found both the 2 liter cars to be very reliable and fun to drive, I put over 100,000 miles on each with only normal maintainance. The 1600 car those was a different matter. It broke it’s first timing belt about 5 blocks from where I bought it. I only gave $200 for it so I did not expect much. I replaced both belts and about 2 months later, same thing, except both belts broke.
Just before the belts broke, I would be willing to guess the car started running real crappy then about 3 seconds later, it died. With mine, the timing belt slipped on the timing gear then caught. This of course, cause the timing of the engine to change. If the timing jumps enough, the engine will fire on one piston at the wrong moment. This will actually cause the crankshaft to stop and change directions. Of course, the other engine components don’t know this and continue trying to spin in the correct direction. BAM. Both belts break.
If you can find one, replace the aluminum timing gear with a steel one. Mitsu engines are not close tolerance, the engine should have suffered no major damage. Also check the tensioner, they wear out too.
I had a timing belt break on a 2.0 liter Datsun engine I had in a 78 Datsun 210 race car. It let go at about 6000 rpms about half way down the back stretch at South Sound Speedway. The pistons and valves did a dance with each other. A hole about 6 inches long and 2 inches wide was blown through the hood of the car. I figured that was from the missing half of the camshaft I could not find. The head broke into 3 pieces, the #2 piston wedged itself sideways into the cylinder bore and a piece of a connecting rod went through the windshield of the car behind me. It was quite thrilling.
Thanks, thanks, thanks a million to all for replying!
Regarding the possibility that some valves got screwed up: Yeah, I’ve been sweating that out, too. Gary T, I’ll check 'em out like you said. I completely rebuilt that engine several years ago but for the life of me can’t remember if there’s enough clearance in the head for a valve down and a piston up. :::fingers crossed:::
racer72, I like your scenario about how both belts could have blown at once, especially if they were weak anyway like dreamlab said. I also got a laugh over the “survivor of Mitsubishi” line; and great story too. But dunne, I think a racing Datsun would use hamsters, not mice.
I’ve got the new belts on order. I’ll post a follow-up later, so if you’re interested in the outcome of this tale, watch for a bump of this thread at some point in the future. I have to go to Reno next week on business, so depending on when the belts get here it might be a while.
Thanks again! I’d love to have y’all over to the garage for a beer if I could. This board is amazing!
Not hamsters or mice, squirrels. Had 2 of them painted on the hood of the Datsun. The engine part that went through the hood took the tail off one of them
I’ve actually owned an interference-engined car that did have the belt break on it (stripped teeth) and did not, through some miracle, have the dreaded valve-piston collision. So you could be lucky…
