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1996 Toyota RAV4 Question: will a broken timing belt lock the engine

 

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Visitor, 2.0L 4 Cylinder, Independence, MO, October 09, 2010, 16:28

My car died while I was driving it. I thought it was an alternator or battery issue because the electical system was losing power. However the mechanic said my timing belt snapped in half, which caused the engine to lock and the vaalves are bent. Is that possible?

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  • Answer #1

    October 09, 2010, 18:29
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     Master

    The 3S-FE Toyota engine is a NON-INTERFERENCE engine, which means the piston won't contact the valves in the case of timing belt failure.

    You can find this technical explanation:
    Like the 3S-FE, the 5S-FE is a non-interference design to prevent the pistons from striking the valves if either of the camshafts were rotated separately from the crankshaft (A Situation most commonly found during a timing belt failure).

    At the below link, when you read about the 5S-FE engine:
    http://en.wikipedia.org/wiki/Toyota_S_engine

    So your mechanic is incorrect. I'd get a second opinion from an other shop.

    Just a note: In the last 20 years I have seen only one non-interference engine with valve damage after the belt broke due to an EXTREME amount of carbon deposit on the top of the pistons and the valves.
    Please let us know what happened!

    Zee

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    Visitor, October 09, 2010, 20:45

    When I told him this didn't seem likely, he stated that they had researched the issue on identafix.com and that was the only solution it was giving. Though they never tested my valves to see if they were damaged. And he couldn't tell me how/why the timing belt would cause the engine to lock (considering the oil change was done the day before by this same well-known national shop).

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    ZeeTech, October 09, 2010, 21:12
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     Master

    We love "well known national shops". They create a good revenue for us because of their mistakes. :) I could talk about this subject for really loooooong... but back to your problem.
    It's fairly easy to check if the engine is locked and if there is a problem with the valves.
    First see if the engine is actually is moving by turning it with a wrench, if it does it's not locked, as they said.
    Than the timing needs to be set correctly (turn the cam and crank shafts to the correct position), install a new timing belt and do a compression check. If the compression is low or zero, there is a damage.
    Now a bunch of questions, so we can help you better: do you know if the cylinder head was removed for any repair before?
    When it stalled, did you hear any chattering sounds? Did you try to restart it?
    If yes, was it cranking faster than usual or normal, like always? Did you see the broken timing belt? Do you have any record of timing belt replacement from the past?
    Some shop will put a timing belt service sticker -usually to the timing cover - with the mileage and date info for future reference- is there any?
    What did you decide with the repair? Will you get a second opinion?

    Zee

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    Visitor, October 09, 2010, 21:47

    The timing belt was replaced within the last 2 years and has been driven approx. 40,000 miles since it was replaced. I still have the receipt for the service and was given the old belt when it was replaced.
    While I was driving the car it just lost power. It stopped accelerating, the oil light came on but there weren't any noises at all nor any smoke. Once I was over on the shoulder I just let the car roll to a stop. I put the car in park, then tried to start it, it sounded as if it wanted to start but couldn't "catch". So I left it alone. The radio was still playing and the hazard lights worked, so I thought it was my alternator but then the electrical system started to fail (window wouldn't go up, the hazard lights faded out).
    I had the car towed to the shop and they called me later with a "changing" diagnosis of my car. At first it was the engine locked, the timing belt was frayed which bent my valves and the head gasket needed to be replaced. As I asked questions, their story became the timing belt snapped in half which cause the valve to bend and that locked my engine (the head gasket issue disappeared). After they couldn't get the car to start then they did a diagnostic and according to thier online source (identafix) that's how they were able to determine the problem. He did say that I was more than welcome to take it to Toyota for them to give me a second opinion and if the shop were liable for any damage they would fix it. (My guess is: when they did the oil change yesterday, someone made a mistake which caused my engine to lock today.)

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    ZeeTech, October 10, 2010, 07:35
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     Master

    Something is really fishy. This is not an interference engine, so there should be no piston to valve damage. If they wouldn't put oil in it, you should see the oil pressure warning on when you picked up the car. If they forgot to tight the drain plug or oil filter the car was losing oil while you drove it, however the oil pressure warning light should come on.
    I wish I could be there and check it for you. Now I'd really like to know what's going on.
    I'd take it to Toyota or another shop to get it checked.
    Even if it was an interference engine - which is not- you had the belt replaced 2 years / 40K ago. If the timing service was done correctly it shouldn't just broke.
    I strongly suggest to get that second opinion and please update us.

    Zee

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  • Answer #2

    Visitor, December 31, 2010, 06:37

    Crank shaft will still spin with broken timing belt but cam shaft wont because of bent valves.so yes a broken timing belt will lock the motor but only the top half. KnightHawk. yep something does sound very fishy real that fish back in.

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    ZeeTech, December 31, 2010, 07:38
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     Master

    Only on interference engine, the above engine is a non-interference.

    Zee

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    Visitor, April 03, 2011, 02:47

    I just got an oil change in an 97 Inifiniti J30 and then my timing belt broke. With the same story from above.

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