Timing belt issue on 80 series

jimmynut123

New Member
I am in uk
Apr 22, 2018
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Looking for a second opinion on a timing belt issue we’re having. Long story short, the truck had a brand new genuine timing belt kit 12 months ago and 25,000 miles later the old water pump started to leak.
After the new water pump was fitted, we put the timing belt back on in the correct way, the belt seems to snap or bounce loose on the long side when revving hard, now we don’t know if this is normal for the 80 series so could do with a second opinion?

I have a video but can’t seem to upload it!
 

Towpack

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Oct 4, 2011
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I would say not. Ive only watched mine for 30 secs or so after fitting a new belt and tensioner and revving it a few times but could see no bounce as you describe it. The tension on the long side of the belt will vary with cam/valve load as the engine spins but the tensioner should take up any slack which could cause the problem you've described. Is the tensioner in good working order?
 

jimmynut123

New Member
I am in uk
Apr 22, 2018
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Yes the tensioner was new same as the belt only done 25,000 miles. Possibly faulty tensioner? Maybe just put a brand new kit on again to see if that solves it. Never the best to re use a belt I suppose.
 

Chris

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I have actually seen 'whip' in the timing belt before. I'm not saying it's right, wrong or common, but I have seen it myself. Whilst it will have some people screaming for the hills, there's no reason at all that a timing belt shouldn't be reused. If it was installed correctly and removed carefully and stored safely, what possible reason would there be to not use it given that in use it's stretched tight, locked under a hot bonnet and spun up at 70 mph down the motorway. They're only damaged really if kinked. But they are so cheap that if they've done 25k then you could just swap it out and it gives you another 60k grace.

It depends on what revs you took it to I think. What I saw was whip when it was revved hard and quickly. If the speed was built slowly then it didn't do it.
 
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frank rabbets

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Mar 1, 2010
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You have to be very careful reusing the old tensioner. A new one comes preset fully compressed and pulling the pin causes it to fly out. When compressing it for reuse it does not"fly back". If you compress it quickly it will rupture the internals or split the case rendering its damping effect useless. I took mine apart years ago to see how it worked and lost all the oil so I reassembled it with engine oil and it's still Ok after 160k miles.
 
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Towpack

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The 24v tensioner is partially hydraulic, the oil is for damping and the piston is forced out by strong springs. If the oil was lost I doubt the tensioner would fail completely but it would oscillate in and out as the belt tension changes with the engine running.
 

iwan_t24

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I am in wales
Mar 28, 2011
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The thing with the tensioner is that when you check it there's 2 things.. on the top if there's oil present on the seal then they state to change it. Secondly if you turn it upside down and press it down on a solid surface it may have free movement and it doesn't give confidence to refit it.

Also in the fsm it states there should be a minimum measured amount of protrusion on the plunger. Which after reading this it sounds like the strength of the spring.

@frank rabbets very interested in reading the fact that you stripped it down and refilled with engine oil. In my 24v I'm running a tensioner from a mk5 d4d hilux. Same part and it fits by turning it over 180 degrees same on the 1kzt too! You've inspired me to take a look inside the one with free play... curious!

These gear driven bottom end motors are great because the cambelt does half the work or revolutions compared to a cambelt that is run from the crankshaft..
 

jimmynut123

New Member
I am in uk
Apr 22, 2018
10
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3
All very helpful comments thanks for the advice. The truck is a 12 valve 1991 one of the early 80 series. Fitting a full new kit tomorrow morning so will see if it fixes the ‘whipping’ issue fingers crossed!
 
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