I'm hoping someone can help me with a serious problem I have with my engine.

I am driving a 2003 Mazda 3 with a 2.0 litre with a 5 spd tranny with about 158,000km [100,000miles] on it. I am the second owner of this vehicle for about a year now. It was purchased as an accident vehicle [ front end damage].

My problem is, the car would not start first thing one morning. I can't even boost it, the engine will not turn over. Took the car to shop, told me the engine is seized, they pulled the plugs and could see something in the cylinders. I told them to pull off the cylinder head to find out what happened.
Turns out ALL 8 exhaust valves have broken apart, the valves themselves have broken about a 1/4" above the seat . How is this possible. the timing chain was still on and tight, no broken guides, or any other signs of failure.

Can somebody help me understand this

 

From the outside looking in, I'd suggest taking a look at the lower end of the engine. My bet is that you'll find damage there as well, and that in turn will indicate a lubrication related issue.

 

more or likely depending on how hard the engine got hit it cracked the exhaust valves and it was a matter of time till they completely finished off. unfortunately for you the person who checked the car before didnt do a thorough check before accepting it to be road worthy. because if they had checked it. they would have realized that it would have been a write off, however sorry for your luck and it looks like you may have to bite the bullet and pay for a new engine. or take it back to the place you got it from and explain what may have happened. good luck/

 

thanks for the quick responces

shipo - we tor the rest of the engine down - no signs of any other damage and there is oil throughout the entire engine with no signs of oil starvation.

jaimie08mazda3 - all exhaust valves breaks are perfectly clean and shinny, no signs that the cracks were there while the engine was running. you would expect to see some exhaust blackening in the breaks. all are broken almost exactly the same.

 

How long did you drive it before this occurred?

For all 8 valves to be broken, that sounds like a timing issue to me. Chances of all 8 valves being damaged by anything other than the pistons is slim to none.

That's a wierd failure.

 

sstlaure - was driving for a couple of months. i am figuring a timing issue on the exhaust cam as the pistons are showing signs of impact from the valves. my main concern is how does the one cam jump?? the timing chain was still tight and the guides are not broken.

 

I think you're on the right trail....

Any damage to the cam where the cam gear attaches? Missing teeth on the cam gear, etc?

Maybe that engine had work done to it and was initially improperly timed (maybe long enough for them to crank over) which caused some cracking of the valves and it took time to fatigue?