So.... That sketchy 740GLE I bought with the cam seal leak broke its timing belt within 300 miles of me buying it. I had a new belt and was waiting for a weekend and tensioner tool....

Anyway, I was decelerating at about 1500 rpm and heard what sounds like a large electric circular starting (HRRRRk). Engine died... belt was obviously broken.

Obviously some valves are definitely bent. I haven't looked yet to see if any pistons are holed, but I have a borescope that hooks to my laptop and I'll take a look before I remove anything.


Is the damage probably just to valves and the head and tops of the pistons? Am I looking at more than fixing the head and grinding off some gouges in the piston tops? Can the rods have bent from a valve/piston collision?

If the lower end is 99% likely just fine, I may pull the head and fix it. If we're talking piston, rod, or rod bearing problems, I'm just going to sell the car.

I'm going to sell the car in a few months either way. I have a nice interior to put in it, but the engine trumps all of that.

Cheers

As part of your evaluation, drain and inspect the oil for debris, and cut the oil filter open and do the same.

Will,

So I don't have an answer for you, but from reading the other responses, your rods should be fine.

I currently have two 16-Valve heads in my garage that are awaiting funds to go on engines that will eventually be turbo'd.

Of the the two, the one failed because the crank gears single small tooth that holds it into the crank shaft sheared off. My recommendation to you is while you are in there, remove this and check it out, you may even want to go as far as having it milled and keyed so that this failure can never happen again, or at least not from a crank perspective. I plan to do this, but have not gotten around to it yet.

Best of luck,

Matt

seen a few b234s that lose belts and never seen a bent rod. valves and guides are the worst i've seen. good luck, chuck.

Agreed, I've never heard of rods being damaged. Especially on a Volvo engine! Most likely just valves and guides.

Possibly. Depending on RPM at the time of the timing components failure.

The valves will have contacted the piston crowns. How many times? So, valve stems can bend.

Some will have encountered, after a failure such as yours on the much-fabled B234 quattrovalve (yes, a VW term) a half moon imprint on the piston crowns. I would be concerned the pistons would distort because of the impact.

The weight of the rotating lower engine mass (up to cone rods) will push at the piston end, distorting it.

A view inside the engine using your borescope (how cool is that!) may help. Yet engine tear down will fully reveal the damage. The head can also suffer damage.

You are aware of the weak bolt used to secure one or more of the overhead cam gears or the intermediate cam on B234. I believe there is a Volvo TSB to replace it. Though more likely an old or loose belt cause the issue, I guess.

http://volvoforums.com/forum/volvo-240-740-940-12/1990-740-b234-broken-timing-belt-damage-55720/

You Bube Toob Video:

Volvo 940 b234f engine repair after timing belt failure, first startup
https://www.youtube.com/watch?v=skNQvswAAgs

It may help to search here and also try a search for the term:
volvo b234 broken timing belt

The turbobricks site can help.

Hope that helps.

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