Anyone's timing belt snapped and bent valves?

M

mikebontoft

Member
:
02 Focus SE, 90 626 GT
Like I said, have any of your engines (which I'm assuming are FS-DE) snapped a timing belt or have you guys seen one that has, and bent the valves? If so, how much damage does it usually make anyway? still trying to decide if I should just junk the car or not.

If it helps also, I did a leakdown test (via compression checker hose hooked up to compressed air line, and cams loosened so all valves were "shut") and here were the results:

Cylinder 1: Leaked a good flow through the tail pipe
Cylinder 2: good leakage through intake manifold (when the TB was opened up it went away)
Cylinder 3: again, leaked a good flow through tailpipe
Cylinder 4: same as cylinder 2

What I can infer about this is that the engine went through only 1- 3 strokes, obviously considering only half the exhaust and half the intake valves are bent.

especially if anyone has pictures of it, we all love pictures :p

Thanks!
 
I thought that our engines were non-interference, so there would be no way for the pistons to hit the valves (unless the valve springs were ridiculously worn?)
 
I thought so too...... but I have an engine spec book from work that states all 2.0 DOHC 16v Mazda engines are interference type EXCEPT for the tribute :\
 
The book's wrong, son!

EDIT: It seems like the consensus is that the engine is non-interference, but that won't stop it from bending valves if the conrod cap comes loose and allows the piston to come higher than it should.
 
Last edited:
wow well that's nice. LOL

I'm willing to bet the piston (when I take the head off) will have a crap load of carbon deposits on it..... as I've heard that can take out valves as well. hope it's not the engine though. but if it is, it is I guess.
 
nothing happened if your timing belt snapped
the pistons have clearances for your valves in case that does happen, how many miles on the engine?
 
From the leak down test you describe - the valves were open. Do standard comp test first.
 
^^ I better hope so lol........ this was the instructors idea and I'm not a follower of his methods. I was gonna set the timing marks and put a new belt on and see if it will run.

edit: I mean, so can I DO a standard compression test without setting the marks and all that? probably not...
 
I'm not surprised it failed at all......... and I'm not the original owner but it IS the original timing belt.
 
^^ why would that matter? I thought by completely loosening the cams, all the valves would be shut regardless of piston position?
 
damn. lol. This has got to be THE worst engine to determine this on. LOL..

anyway, if anyone wants to check in around this time tomorrow, I SHOULD have the head off and be posting some pics.
 
Turning the crank wouldn't matter with the timing belt off. Not sure how you determined all the valves were closed? If you eyeballed them they may not be fully closed. Checking that the cam followers spin freely should work.

Years ago I did a leak-down test on a Isuzu Stylus XS that had a broken timing belt. At the time I thought it was an interference engine. When I did cylinder 1, I rotated the cams so cylinder 1 valves were all closed. To be sure they were closed, I checked that each cam follower/shim bucket rotated freely. I moved the cams to close the valves for each cylinder as I checked them. I had no leak-down and the car ran fine after the belt was replaced.

Clifton
 
did you loosen the camshafts or did you take them completely off?
if you took them off all the way then yea, the valves should have been closed
 
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