timing belt, bent valves

4Him Asked:

1999 300M Broken Timing Belt

I was driving my 1999 3.5L 300M when steam started coming out of the engine compartment and I immediately pulled over and turned off the motor. After waiting about 45 minutes, I tried to restart it and it was obvious that the engine was spinning too freely. I didn't get any noises that were really concerning me but I figured out later that the timing belt had broken.

My question - since there have been no obvious signs or sounds of valves hitting pistons and the I can turn the crank and the cam shafts fairly easily (I have the front of the engine taken apart to replace the timing belt), what are the chances I have not bent any valves?

Would I have heard metal on metal contact when trying to start the car if valves were being bent? Thanks in advance for any input.

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2 Answers

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kitt Answered:

You'll have to do a compression test in order to be sure that no valves were bent. You should have heard if a valve wold have hit a piston.

Posted 5 years ago

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billtech Answered:

I have 43 year experience as an automotive tech. I was looking for posts to answers to this same question. I have never done this particular engine, and would like to know before I spend customers money.

However, It's Listed As An Interference Engine In Autodata Tech Series Timing Book, And, One Online Post Quoted Factory Proceedure As Needing To Remove Valve Covers And Loosen ALL Rocker Arms Before Working On The Timing Belt. This Is Very Unusual, So Factory Knows That Valve To Piston Contact Is Most Likely To Happen.

By the way: I can't hear pistons hitting valves when a timing belt breaks. it is not loud enough. It usually just bends some valves a little. The only one I saw where it can be heard is on a Kia 4cyl. where the valves actually BREAK off. clattering around sounding like broken glass until the engine comes to a stop. (for the last time.)