Timing belt tensioners - importance of replacement

[Mos]

Hi,

The (very fluffy) timing belt on the 1G-FE:



The reason why:



Moral of the story - change your tensioners and bearings when you change timing belts

This engine has under 140,000kms - the scheduled timing belt replacement.
Chances are the belt would have been replaced prior to popping through normal servicing (the noise was not ignorable), but I'm curious what could have caused this as I'd expect most toyota parts to last well beyond the scheduled kms. Thoughts?

Mos.

[ViPeR_NiPPleX]

How did so much dirt get behind your timing cover!?

So was the bearing just seized and squeeling like mad?

[Herus]

I think thats actually timing belt...

Andrew

[Mos]

Yes, the fluff is all of the timing belt that isn't there
You can see in the first photo how much belt should be there - there's at least 1/3rd missing.

The bearing itself on the tensioner was fine - it was the pivot that got damaged, allowing the whole assembly to skew. As the tensioner piston assembly ate further into the centre of the bearing, the skew got worse.

Mos.

[Dale]

If it's gone off skew like that maybe something was overtightened or not installed correctly

How is the piston held in place? A bolt and a locater dowel or something along those lines?

I thought these would have had a spring loaded tensioner, the EPC says they're meant to!

[Draven]

that actually seems to be a fairly common problem with toyotas - timing belts being skewed. on general principle I've always changed tensioners when I change timing belts.. but 1 of my timing belt changes was due to a tensioner failure, the other one a failing of the timing pulley on the crank!

[TA-022]

same on the 5sfe in me Mrs 204 Celica.

Belt ticked of as done at 100k ... at 140k major flapping sounds.

Idler had shat the bearing and between every single tooth the rubber was cracked ... just beggin to snap.

And this drove to Dubbo!

[Mos]

This was a from-factory, under 7 year old assembly, so nothing to suggest anything would've been overtightened or incorrectly assembled.
This looks like a failure of the bush or the pivot that the tensioner pivots on. I don't know what material the bush is made from but you can see how deformed it is, and you can see corresponding deformation in the pivot surface of the bolt. Maybe it is poor choice of material, or poor design of pivot area - the pivot height is maybe two thirds of the width of the tensioner, whereas on the 1UZ the pivot height is larger than the width of the tensioner. If this is premature failure, then I'm curious what caused it.

This is how much movement it allowed (as hard as it is to see..):


EPC for what vehicle? This isn't a 1G-GTE... It's a much more modern 1G-FE of 2000 vintage (with, so it seems, "improvements" ).

Mos.

[lexsmaz]

I have never worked on one of these set up's but i would think from what you are saying that the if the tensioner bearing is ok, but the wear is only on the pivot bush ( ie eccentric )that the pivot bolt was not clamping the internal section of the bearing tight enough or even a bit loose, allowing it to move with the movement of the belt .. because when the pivot bolt is tightened after adjusting the cam belt it should lock up & hold tight the inner section of the tensioner bearing .. if it was designed to swing with the belt movement it would have had an internal sleeve bearing fitted ...... Or the other thought is that the bracket arrangement that it bolts to is an actual dampner / tensioner arrangement which has failed, something that was designed to have restricted movement has now allowed the tensioner to go crazy with the belt, so hard to tell from the photo but the second scenario is looking more plausible ....
Anyway thats my 2 cents worth ........ Rob .

[lexsmaz]

Just Re read this thread if the pivot height you are refering is the actual bolt collar length being 2/3 of the width of the tensioner, that means that the bearing is meant to be clamped tight between the bolt head & the tensioner base no movement allowed .... Otherwise it was meant to move the collar length on the bolt would have been slightly longer than tensioner width, so when the bolt is tightened the bolt is bottoming on the end of the collar of the bolt & not the item its going through in this case being the tensioner .. The only time the tensioner works is when setting up the cam timing initially .... for it to chop out, the bolt must not have been tightened properly or some shit in the thread stopping the bolt short from it tightening up on the tensioner .............

[Mos]

Rob,
I agree about locking up the tensioner in the older designs with a spring only.
However, every newer set up that has a hydraulic damper/tensioner allows movement of the tensioner assembly - this is one such assembly.

The collar on the bolt sits inside the flogged out bush on the bearing, and the collar bolts down on the actual hydraulic damper portion and holds that tight. The large allen key in the front of the bearing allows the assembly to be moved out to install the belt.
Trust me when I say the bolt was *very* tight.

I take your point about collar/pivot length being too short - that's what I'm thinking as well, but this tensioner arrangement is definitely allowed to move by design.

So I guess extrapolating from what you're saying, it was possible the damper stopped damping, which allowed vibration from the belt to vibrate the bearing, flogging out the bush and pivot...?

Mos.

[Vios-GT_07]

i've experienced this on 4A-FC and 4A-C engines.. funnily enough, they both didn't squeal or anything.. i just randomly decided to open the timing cover when doing the service, noticed strange markings on the timing belt and then ripped everything apart to see what was cutting up the belt.. yeap was the tensioner.. both cases, tensioner had seized, and in both cases was 20 to 40,000 kms after changing the timing belt but not the tensioner bit...

[cambelt]

I,ll make it aware that timing belt tensioners (and fan belt tensioners ) are generally not made by toyota or nissan whoever it may be . Lots are USA /canadian made etc (quality not there maybe)
Dave