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3S-Fe Engine Cam Belt Tensioner Failed!

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I wonder if I can pick the forums thoughts?

I have a Year 2000 (W reg) 2.0 auto Avensis, with the 3S-FE engine in it, thats done 99K miles. I've had the car 3 years and never had a problem.

10 months ago the Cam belt, water pump and tensioner were all replaced as the water pump was starting to make noises.

Yesterday, after 4000 miles the car started fine (it was cold -4C) and I drove to work as usual.

I was approaching some traffic lights (20 mph) and suddenly no power the engine sounds like a bag of bolts. 3 seconds later it stalls. I try restarting just sounds awful like a set of brearings been shaken in a tin. Luckily I'm on a side road.

Call AA and short while later AA man pops over and checks cam belt and says there's no tension so either belt's failed (but at the bottom end of the engine) or tensioner has gone.

Clearly I'm a bit miffed as I specifically had the work done to avoid just this! All the parts were bought by me from Toyota and fitted by an independant who has his own Avensis. The rest of the car is perfect, everything works and bar a water leak at the back (common issue) no problems. I was hoping to run it for ever and look after it

My question is I have read the 3S-FE engine is non-interference meaning in the event of this issue I may be in with a chance of not bending values etc? Or has the Avensis run its last mile?

I just want to check as the car is back at the same independant that fitted the belt etc and I want to be fully informed as to background before I talk again to the mechanic. He is going to look at it next week (weather permitting) and I was hoping its fixable for reasonable money ...

Any thoughts / comments gratefully received!


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I don't know if these enines fail safe but I bet they do. What I would bet on is that your independant mechanic is feeling a little nervous just now. If something he fitted has failed after so few miles you may be in with a chance of getting him to put it right. As you paid him your contract is with him. If a part has failed that's his problem to take up with his supplier and not your problem.

Good luck.

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  • 1 month later...

Thanks for your reply (and soory so long in coming back)

The 3s-fe is non interference and it turned out neither the belt or the tensioner failed its just the belt slipped off! The belt is all fine (no teeth missing) and tensioner all looks OK.

The question now is why?

Toyota suggest maybe its the wrong water pump been fitted ...


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the timing belt has slipped off?

isnt it enclosed with a timing cover and at least a couple of pulleys with edges to keep the belt running true.

sounds as if a tensioner securing bolt has worked loose and the garage that did the work are lucky it isnt an interference engine and can remedy the work

as you have an auto it isnt as if you can go from 5th gear to 2nd gear and really put opposite forces on the belt yo make it jump a tooth.

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not sure where u stand... as its with in 12 months somone should be responcable for the damage. however as u supplied the parts urself i susspect the fitter will have some wiggle room. You said u got the parts from toyota maybe someone on here with a parts list can see if there is only one waterpump for ur car etc etc. but i susspect that both will blame the other and u will be left in the middle with a big bill either way.

Having said that if all the parts u supplied r mechanicaly sound. then it has to be the fitter. for a belt to "come off" it had to be on too loose in the first place unless there is a mechanical reason if came off. ie component failure or some other reason.

do u use kick down alot? do u drive the car hard?

u said it sounded like a bag of bolts when u tried to restart it somthing must of happend for it to sound like that

sorry for the double sided argument but cant think how else to put it


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From what I have read so far, it sounds like the bolt securing the tensioner has come loose. If the tensioner itself was faulty then Toyota who supplied the part, will have to replace it under guarantee. But you stated that the part is fine.

The mechanic will have to refit everything, making sure the tensioner bolt is well secured this time.

I would check the belt again and if any sign of damage due to tensioner issue, get him to pay for a replacement!

For the bolt to work loose after 10 months is unusual. I wonder if the bolt was part of the kit you bought? If not, maybe that should be replaced too.

Another thing to note that the cam belt is well protected from the outside world, so a foreign object should not got have through unless a cover has not been replaced properly.

Hope it is sorted quick and don't loose faith in the car due to what appears to be an error or fluke incident.

The car will serve you for a long time. :thumbsup:

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