Replaced Timing Belt but . . .

A timing belt ready to fail looks very much like a new one, but usually dustier and a little scuffed on the backside where it rolls against the tensioner. The failure typically occurs where the teeth attach to the belt. On a new belt the teeth are firmly attached. By the time it's ready to be replaced the teeth can be picked off with a knife blade. I'd expect yours to be in that condition. By the time I replaced the belt on our old Volvo - a non-interference engine - at about 150K miles the teeth could be picked off with a thumbnail. Although the belt is often referred to as "breaking" I've never personally seen one fail that way. They don't stretch measureably. Timing chains are said to stretch, but as with bicycle chains it is really that the pivots wear and the slack makes the overall chain longer.

That lack of visible change in the timing belt is why they are replaced on schedule rather than on visual inspection. There is no reliable visible warning of impending failure.

Mike

"Trident" wrote in news:0_WdnSy snipped-for-privacy@comcast.com:

It's not "all rubber". It has a fabric carcass that extends even into the teeth. The carcass provides the belt with all its strength.

Wear manifests as deterioration of the fabric carcass. You cannot see that wear with your eyes.

You have no idea when the carcass has weakened to the point of failure until the weave separates and the belt breaks or the teeth strip off.

They never do.

See above.

teeth. The carcass provides the belt with all its strength.

So is the fabric in the core of the timing belt surrounded by the rubber so that it cannot be seen? I still have the old timing belt, and when I inspect it carefully I cannot see fabric anywhere. I can see how the fabric would provide added strength. Maybe I'll disect it and see exactly how the fabric works.

Thanks.

I've seen a few stretch. This was typical of mid to late 80's Accords and Preludes if I remember correctly. The belt would stretch and then the distributor would start making a tapping noise. Retensioning the belt would usually set things straight and quiet down the distributor.

Eric

Interesting. Maybe a reinforcing fabric that has since been updated, I hope.

Mike

that's /highly/ unlikely. much more probable it was never set right in the first place. the tensioning procedure is somewhat involved and in my experience, frequently not done right.

the fibers in the belt start to fatigue. can't see them obviously.

"Trident" wrote in news:2rqdnVdmzZz7uOnbnZ2dnUVZ snipped-for-privacy@comcast.com:

Belt manufacture starts with the fabric. The carcass is then impregnated with rubber under high pressure.

Trust me. Your timing belt has fabric in it.

I believe you. I'm just a curious guy. I like to see exactly how things work in an attempt to educate myself.

Wishful thinking, perhaps.

not at all. possibly the greatest thing you can do if that's your desire is go to a junk yard. there' you'll see all kinds of componentry disassembled so you can see pretty much exactly how it all works. i think they're amazing places.

The fabric helps to minimize elongation of the belt while, as I believe the fabric is actually highly drawn fibers or monofilaments with high tensile and minimal elongation properties.

Embedding these in the belt cross section adds strength and minimizes the elongation while not affecting the "suppleness" (it's ability to bend around a specific radius without buckling or bulging).

L Alpert wrote: > The fabric helps to minimize elongation of the belt while, as I believe the

==========================

It's just like 'strapping tape' that has woven fibreglass in it. Unlike shipping tape you use for packing boxes, which can stretch or break, strapping tape will hold a TON of load before breaking. You can _clearly see_ the fibers in the side view of the timing belt.

The usual area of failure on a TB is when the teeth shear off because the fibreglass threads have finally lost their strength.

'Inspecting' a Timing Belt is usually a waste of time unless the idler has seized and the backside of the belt will show chafing, or there's leakage problems and the belt is soaked with coolant or oil..

'Curly'

Or if you suspect a thief may have taken it and replaced it with a belt made of Band-Aids with cartoon characters on them. Otherwise, I agree - a timing belt about to fail looks like one with a few miles on it.

Mike