Broken Timing Belt Confirmed

[re_guderian]

You know what? I love the fact that our trucks are 6 - 15 years old, and we're still trying to figure that out for sure... sure beats the alternative of hundreds if us learning the hard way that it's an interference engine. And I'm not saying it isn't, just celebrating the fact that we don't have a lot of data either way...

 

[jgray]

Not likely. If that were the case then every gasser middle east and OZ LC would have broken belts. Heck, Nick would have gone through three broken belts by now! Engine load shouldn't affect the belt life. Or do you mean prolonged water exposure? Any chance your cover plate was left off on a previous t-belt job?

I was referring to mud and water exposure in engine bay. I really do hate mud now; at least the mud we deal with in the southeast United States... Pictures show the red dirty clay mud on top of the engine. The only reason the rest of the engine bay looks good is because I wash, clean and degrease the engine bay nowadays. The tensioner bearing was shot and tensioner had mud caked around it which I assume contributed to it failing. Cover plate was NOT left off after previous job.

And by 'tensioner failed' do you mean it developed slop or that it over-tightened? Trying to figure out how it could be the latter?

You cannot "overtighten" the timing tensioner. It's a hydraulic tensioner with a pin in it that auto-tensions itself after you pull the pin.

How many miles/years on the tensioner?

The original timing belt changed at 134K looked like new. Tensioner was not replaced during the first timing belt change because it also looked to be in great condition. So the tensioner is the original from 1999 and it would have over 204K miles on it prior to self destruction...

Boyyyy...I've always been told this is an interference engine.
Has anyone ever heard of damage after TB break, under load?

I was going 55+mph when it broke so I would consider that under load? I pretty much floored it to pass someone I need to get by merging into another lane on the interstate. I could almost feel it break and then coasted to a stop. I did try to turn the truck over multiple times immediately after losing power and hours later when I came back with a tow truck. Amazing no bent or broken valves...

^ its been debated with most leaning towards the interference side. However when I did my first t-belt I gently rotated one cam by hand through its cycle and I didn't get any interference...FWTW.

I doubt if the crank, in jgray's t-belt break, stopped instantly...but just a guess.

As I mentioned above I was rolling pretty good on the interstate in bad rainy traffic when it broke. I'm either real lucky or the computer immobilized further damage somehow...

 

[APKhaos]

Since the conventional wisdom is that this is an interference engine, how is it possible that it snaps a TB without valve damage?
Been thinking about this. Am I missing something here?
- TB Breaks
- Crank continues to rotate on momentum alone for a few revolutions
- Cams are no longer driven, so valve spring pressure will force the cam to stop at a point of spring pressure balance. At this point, no valves will be at full travel. Does this explain why valves and piston may not have kissed even though it is an interference engine?

 

[e9999]

on a side issue, that starter there looks awfully easy to work on now and it won't be so for long I assume. When was the last time you changed the contacts on it? Anything else tempting in there?

 

[SWUtah]

Since the conventional wisdom is that this is an interference engine, how is it possible that it snaps a TB without valve damage?
Been thinking about this. Am I missing something here?
- TB Breaks
- Crank continues to rotate on momentum alone for a few revolutions
- Cams are no longer driven, so valve spring pressure will force the cam to stop at a point of spring pressure balance. At this point, no valves will be at full travel. Does this explain why valves and piston may not have kissed even though it is an interference engine?

I think we are all witnessing a miracle

 

[adrenalinefjz80]

on a side issue, that starter there looks awfully easy to work on now and it won't be so for long I assume. When was the last time you changed the contacts on it? Anything else tempting in there?

x2. I'd replace the starter, engine mounts, heater Ts, etc. since you likely won't have it this broken down again.

 

[OregonLC]

You cannot "overtighten" the timing tensioner. It's a hydraulic tensioner with a pin in it that auto-tensions itself after you pull the pin.

I'm all caught up with you on that. Just trying to figure out how the tensioner can fail? Did it loosen ad develop slop or did it produce too much pressure on the belt? In what mode did it fail?

Since it was re-used at 134k, any chance it was damaged when it was re-compressed? This actually concerns me a little; I had to re-compress mine when I did my 90k (although it was new)). I had a bolt shear on the water pump and had to pull everything back apart. Tried to do it slowly per the FSM...

I guess the other question I have is why did the shop immediately pull the heads? Were they too convinced that there was damage based upon the 'interference engine' assumption? Did they first run a compression check or borescope it?

 

[OregonLC]

However when I did my first t-belt I gently rotated one cam by hand through its cycle and I didn't get any interference...FWTW.

Brave! I had mine kick over a lobe unintentionally after replacing the cam seals while tightening the cam gear bolt. 'Bout s*** a brick. Glad to hear you've turn them a full 360 sans damage.
https://forum.ih8mud.com/100-series...0-timing-belt-service-info-archives-read.html

There's a lot of arrows here in this thread pointing to non-interference.

This is the 2nd recent post of a broken belt. Lange had one back in Sept, also with no damage. Start on post #11: https://forum.ih8mud.com/100-series...0-timing-belt-service-info-archives-read.html

 

[2001LC]

IMHO
Bearing of timing belt tensioner failed, this is clearly stated by jgray. Probable reason; old bearing allowed silt from muddy water to enter seal of bearing.

What I gain form this thread is to replace; idler & tensioner pulleys if:
1) Vehicle used in deep water/mud, do TB earlier rather than later.
2) Pulley bearings sounds the slightest off compared to new during TB jobs' inspection of components.
3) Third be aware of engine sound while driving. I've never had a bearing fail without the oscillating sound first alerting me.

But hey, if this is not interference engine, I'll only have the additional expense of a tow.

 

[OregonLC]

IMHO
Bearing of timing belt tensioner failed, this is clearly stated by jgray. Probable reason; old bearing allowed silt from muddy water to enter seal of bearing.

Gotcha. I missed reading that in his reply.

This just underscores the imperative to replace everything serviceable while you're in there. Not an area to go cheap. While it appears that the risk of mechanical damage is not present, there's still the cost of a tow, early replacement, down time, etc. Not to mention the R&R of the heads in this case. The tensioner is around $45 and the bearings are $70 and $55. Water pump is $110. Not trying to pick on jgray at all, I just seems that over time there are debates over what to replace. Smart money is on 'all' items.

 

[jgray]

Here's a couple more pictures with heads back on. I think I forgot to mention the head gaskets did blow on both sides after belt broke but they would've been replaced anyway.

I normally replace as much as possible when tearing this deep into a project. I really thought the tensioner was done at the time the first timing belt was done but it was not after further investigation.

I will answer more questions when I'm back on my PC.

Couple more pics... Note the waterline in my intake filter box... This is what a snorkel prevents; not just a cool looking accessory...

 

[APKhaos]

The TB tensioner is a spring device, not hydraulic, or at least it was for the '99 model year.

Interesting that the two cases of TB failure resulted in no collateral damage consistent with interference valve geometry.

Jgray: Notice that the cams and valve trains were removed from the heads. Did you have the heads skimmed, or other head work done?

 

[OregonLC]

The TB tensioner is a spring device, not hydraulic, or at least it was for the '99 model year.

It's hydraulically dampened internally. Prevents the spring from picking up harmonics and creating a wave in the belt. This is why you have to slowly compress the plunger, avoids blowing the seals.

 

[APKhaos]

It's hydraulically dampened internally. Prevents the spring from picking up harmonics and creating a wave in the belt. This is why you have to slowly compress the plunger, avoids blowing the seals.

Good point. Had the thing in my hands and didn't realize that. Thanks.

 

[OregonLC]

For those who don't do their own work, this is what they look like and where they're installed.

 

[2001LC]

Gotcha. I missed reading that in his reply.

This just underscores the imperative to replace everything serviceable while you're in there. Not an area to go cheap. While it appears that the risk of mechanical damage is not present, there's still the cost of a tow, early replacement, down time, etc. Not to mention the R&R of the heads in this case. The tensioner is around $45 and the bearings are $70 and $55. Water pump is $110. Not trying to pick on jgray at all, I just seems that over time there are debates over what to replace. Smart money is on 'all' items.

I'm Sorry if It sounded like I was pointing at you Oregon, I was not. I respect and enjoy your post in all thread I've read where you contributed.

I was only reflecting on what I gained from this TB break Thread. I agree preventive (no reflecting on jgray) is best and did change bearings (pulleys) at my last TB RR. I did not do tensioner, cam or crank seals or water pump as they all check out to FSM spec. Pulley's were changed because I heard the slightest difference in sound while holding in hand and spinning, comparing with new at same time. I did change serpentine belt idler pulley, do to sound. I also keep power steering fluid fresh with M1 syn AFT for schedule maintenance and to keep sound down along with all lubs.

I over-maintain if anything and would have done water pump but I was missing one gasket on a Sunday when buttoning up my TB job. But, I do flush coolant with Toyota red and distilled water 20k or 2 yr and keep eye on level. I'm so an***l I keep logs, just like aircraft maintenance logs on my TLC, and won't even removed little things like skid plate foam piece (coolant packing) do to concerns.https://forum.ih8mud.com/100-series-cruisers/773771-necessary-skid-plate-foam-pad.html

 

[OregonLC]

I'm Sorry if It sounded like I was pointing at you Oregon, I was not. I respect and enjoy your post in all thread I've read where you contributed.

Not at all, it was completely my mistake, I misread his reply. You were correct.

But, I do flush coolant with Toyota red and distilled water 20k or 2 yr and keep eye on level. https://forum.ih8mud.com/100-series-cruisers/773771-necessary-skid-plate-foam-pad.html

Are you flushing with distilled and then filling with SLLC? The current stuff at the dealer is pre-mixed.

 

[2001LC]

I flush with 3 gal Distilled, then mix 100% red with distilled 50/50. I look for -34f IIRC.

 

[OregonLC]

Are you using this

or this?

My dealer doesn't even carry the LLC any more. And its too expensive to ship. Too bad because it would be more economical to mix in the field as you do. IIRC $25/gal for the SLCC and it takes 4 gals to get a complete drain/refill.

 

[cruiserdan]

Those coolants are NOT interchangeable.