Replaced Timing Belt but . . .

Am now wondering what all the fuss was about.

To backtrack, I have been reading this newsgroup off and on for the last few
years. I've seen many posts here warning of the importance of changing your
Honda Accord's timing belt at 75,000 miles or 7 years (or whatever the
interval is) or dire consequences will occur.

Long story short, I delayed replacing it for well beyond this replacement
interval but finally replaced both the timing belt and water pump on my 1994
Honda Accord with 98,000 miles on it. I am the original owner and the
timing belt had never been replaced before.

I told the shop to keep the old parts so I could see what they looked like,
expecting their condition to be terrible based on posts I have read here.

When I picked up the vehicle, they had placed the old timing belt and water
pump in a plastic bag for me. The timing belt was a small all-rubber belt
with teeth on it which went all the way around. I carefully inspected this
13 year old timing belt and it looked almost brand new! No cuts, nicks,
gouges, discoloration or any other noticeable wear! It looked fine, like it
didn't really need to be replaced. Not at all what I expected it to look
like.

I'm not saying I wish I didn't have it replaced. It gives me peace of mind
to have done so and if you guys say it's important, well you know alot more
about this stuff than I do. Just saying it didn't look at all like it
needed to be replaced.

Is stretching of the belt over time, which I probably would not be able to
notice, the issue affecting an old timing belt?

Anyway, just not what I expected to see.

 

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

 

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.

 

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).

 

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

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