Interference Engine Timing Belt Survival

[John Ramsey]

Last week while driving down the Interstate at 65 in my 1997 Acura Integra LS and the timing belt stripping out a bunch of teeth stranding me along side the road. I was being a bone-head pushing the timing belt interval as long as I did (90-95K at least), but I’ve always been daunted by the prospect of doing anything as in-depth on an engine as a timing belt and it wasn’t convenient to be without a car while I learned.

I felt so bad afterwards because I was certain that I’d ruined the engine, and worse there were warning signs that I overlooked. Here are some things that I learned.

1. Know if your engine is interference or non-interference and keep tabs on the last time that the timing belt was changed. If you break a belt on an interference, you just might be lucky but I’ve learned enough to know that you certainly shouldn’t count on it.

2. There were warning signs. My Integra has run so well for so long that I’ve never had to get into the engine to do anything beyond routine maintenance. That said, I did break the teeth on 2 distributors this winter. I chalked that up to poorly manufactured aftermarket distributors. The reason that I bought 2 aftermarket distributors? There was a marble rattling noise coming from it leading me to believe that it had a bad bearing. I now know that the timing belt was loose causing irregular movements of the camshaft turning the distributor. I can’t imagine that the motion was good for the valve train. Beyond this though the engine ran excellently.

3. After I had it towed to my apartment, I had to make a judgement call about whether to invest in a new timing belt. I know the proper way is to do a blow down test or even remove the head from the engine but my resources were limited and removing the head seems like more work than changing the timing belt. I decided to go forward in faith based upon 3 pieces of information. That information being a) I didn’t hear any metallic clatter or noise of any kind at the moment the timing belt broke, b) I removed the valve cover and turned the cam shaft and saw what appeared to be normal motion of the valves, and c) I took a feeler gauge and felt for any excessively loose valve clearance with the logic being than a bent valve wouldn’t close to proper clearance. All the valves were tight if at all out of specs.

4. The job wasn’t as bad as I thought it would be. Just a plug for Eric, I bought the V-Manual for my car and it was great for sizing up the job before I actually had to jump into it. It was really nice to see step by step what was left to do and where everything went on reassembly. The amount of space to work in wasn’t a lot but the job wasn’t too bad, just time consuming.

I changed the timing belt and it is running strong again. I still haven’t done a blow down or even a compression test but I got around 33 mpg running through a full tank of gas. I can’t imagine that I’d get normal efficiency if everything was not as it should be.

I’m sharing this just in case anybody else does the same thing that I did and is looking for hope. With 16 valves, dual overhead cams, and interstate speeds I wouldn’t have thought that my motor stood a chance, but it appears to have made it. My best guess about what happened was that the inertia of the cam pushed the cam off lob to close the valves that were open at the time of the break but didn’t have enough inertia to open up another set of valves, but that is just speculation.

I’d be interested to hear about anybody else breaking a timing belt with an interference engine, and hearing anymore ways of know the extent of the damage or lack of damage without resorting to engine dis-assembly.

Topic

[Bill]

That’s a good story and sometimes you do get lucky. It’s not unusual but unlikely. Most times interference engines have catastrophic results when the timing belt breaks IMHO.

Ummm…could I borrow your horse shoe? :silly:

[Jamie]

I know a guy who heavily modified a 1.9L TDI engine with a combo turbo charger set up. It was backyard style but he was quite the genius. Worked really well. Lots of torque, went fast and blew so much coal dust…..of you’re into that.

Bad part of the story. He didn’t tighten the belt properly. Pulley loosened off and it jumped a lot of teeth. All valves bent, head killed, pistons trashed. I’m surprised a piston didn’t go through the block with how off the injection timing would have been off.

Either way, the engine is now laying on a tire in the back of his yard.

Never skimp on a belt interval. And if you do it yourself make sure you torque the bolts properly.

[Nick]

With some inline 4 cylinder motors you can pull the valve cover off and check for bent valves. If you can see the valves are bent you know you at least need new valves. Which means the head needs to come off and you can see if the pistons are good when the head is off. Had a Honda where the tensioner broke and the belt jumped. Took the valve cover off all the exhaust valves were open. Bent just the exhaust valves. Don’t remember which motor it was.

[Lorrin Barth]

As makers go in search of more power engines get cams with more lift. So, you hear about valves surviving mostly in older engines.

[Author]

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