Timing Belt Jumped

Help! What could have caused my timing belt to jump? I have a 2004 Toyota 4Runner with 20K miles. Never had a problem. Went to start it up one night last week and would not start. Dealership just called and told me the timing belt has jumped, BUT they still do not know what could have cuased the problem. They’ve had my SUV for a full week. Please help

If the timing belt has a tensioner, it could have failed and allowed to belt to jump.

Only thing I can think of is a faulty cam belt tensioner. Is there internal engine damage?

I’ll ask about the tensioner THANK YOU! Could it be weather related? It was below 0 with windshield the night the truck would not start.

My 2006 has a 5yr/60k powertrain warranty and a 3/36k bumper to bumper. Your problem should fall under powertrain. I would try and get more info from the dealer and maybe pass it on the regional office so they know what’s going on.

Good luck,

Ed B.

Where I live and work, -30F is not unususal; I have never heard of a timing belt jumping or failing because of 0F temperature.

The odds of a seized belt tensioner or a jumped belt at 20k miles are pretty darned slim.
The fact they’ve had your vehicle for a week, claim a belt has jumped, and do not know why this belt has allegedly jumped could mean that someone is WAGing (short for wild xxx guessing) and the belt has not jumped at all.

Were there any odd noises or anything out of the ordinary when the vehicle would not start? A jumped belt (if as claimed) should mean there was coughing, backfiring, sputtering, etc.
If a belt actually did jump, as odd as that is, then it should be a very simple matter to determine why.

Certainly will do let Toyota know.

My major concern was that the dealership could not find out what was wrong with the truck when it would not start. They’ve had it for four days. Finally, today they got it to start and got an error code that pointed them in the direction of the starting belt. As they got to it, they saw it had jumped but have not decifered what caused it. I’m concerned for the future now.

Thanks a lot to all.

That is what I am afraid of…that they do not know what is going on!

No particular noises as I went to start the truck. An immediate smell of fuel was noticeable. It cranked but would not catch.

The dealership first told me there was compression issue and fuel had gotten into the motor. Finally as they got it to start, the computer gave them an error code that pointed them in the direction of the timing belts. As they opened it up and got to the belt, they saw it had jumped but have not yet told me why. Does this make any sense?

I am now obvisouly concerned for the future.

Thanks a lot for any comments / ideas.

What they’re telling you does not make a lot of sense to me at all. The only way a belt can jump would be if some teeth sheared off the belt or for some reason the belt developed a lot of excess slack which would then lead to it jumping. Of course, in the case of the latter some belt teeth would be damaged if not sheared completely off.

If I remember correctly the back side of the timing belt (the smoooth side) is what runs on the tensioner pulley and the water pump so there is no way that teeth would shear in the event that one of those items seized up completely, which is unlikely at 20k miles. It could be possible if one of those items seized that the belt could burn and snap in two but that is not what is claimed to have happened, and again, with 20k miles is very unlikely.

I’m still a bit dubious about this diagnosis. The fact they’ve opened it up and yet can’t tell yo why the belt allegedly jumped does sound pretty suspect to me, especially since it’s a week and counting with no ideas yet.
It would be interesting to know what error code they got that led them to this conclusion.

Wished I could be of more help but without some detailed info or the car in hand about all I can say is that this sounds very strange.
With no previous problems, no noises, no sputtering, etc. and the smell of fuel present my random guess is that the problem is related to the secondary ignition; no spark in other words.

Random small disaster. Belt could have been bad.

I certainly do appreciate your thoroughness and replies. THANK YOU!

I will post more information as I get it from the dealership to get your opinions. I am certainly concern about what is truly happening at the dealership and it sounds like a lot of trial and error going on. I wonder how my vehicle witll turn out at the end. I am actually considering towing it to another dealership. Thouhgts? Does anyone know of a good way to contact Toyota diretly on this issue?

I invested in this SUV for reliability and planned on keeping it for the long run as a truck I could keep for years and now I am facing this issue.

Here is a TSB from Toyota for a no start condition after a cold soak (below freezing). My guess is the TSB applies to your vehicle. I don’t think it is a timing belt issue at all. OK4450 explained all that in his posts.
Print the TSB and take it to Toyota.
If you get no results I would consider a new dealer.

Unless I read it wrong, that TSB has been obsoleted for the OP’s vehicle. It references a different TSB for the 2004 4Runner (see the red box at the top). Any chance you have access to that TSB?


This all being said who cares why if its under warranty. Be glad it is if its an interference motor and glad repairs are fully covered. Things can happen like a jump but rarely.

Good post Dartman. Since the problem occurred on a below zero night that could very well be it. From the list of parts, etc. it sounds like there is a design flaw and extreme cold is causing some severe shrinkage in the suction tube seal, which is then causing the system to inhale air instead of fuel only.

I believe the TSB is valid. In the comments it only states that previous versions of the TSB should be discarded. Replacing one TSB with another is not that rare a thing to happen.
The problem for the OP is that according to the TSB the maximum warranty term for this problem is 36 months/50k miles (depending on state) from the date of vehicle delivery, which in this case was probably late 2003 or early 2004.

Since this vehicle only has a paltry 20k miles on it one would hope that Toyota would cover this under a good-will warranty if nothing else.
(Just wondering, before the vehicle was torn into, if it would start after sitting in the shop all night. Curious if the shop ever considered trying to start it after 24 hours inside a warm building?)

Twin Turbo:
Yes that was the obsolete TSB. Copied the wrong one by mistake. Here is the current TSB. Hope it helps.

I would be inclined to believe in the TSB, but if the dealer did check and find that the timing belt did in fact jump a tooth, then the next question would be, does this engine have the Toyota VVCT (or what ever their variable valve timing is called). The VVCT is sensitive to oil weight and if the proper weight of oil is not used, it can stick and if it is stuck, the dealer is interpreting it as a jumped tooth, when in fact the belt didn’t actually jump a tooth.

I cannot thank you all enough.

The TSB and description about the shrinkage of the suction tube seal makes a lot of sense to me. I am going to the dealership first thing in the AM and will share with you guys the outcome. By the way, they did try to crank it up after 36 hours inside but it would not start. I assume that once the sucti tube seal shrinked, it did not expand again to re-seal. Who knows?

Again, thanks for the help ad advise to all of you.