Timing belt question, 99 Honda Accord DX

The torque needed to free the pulley bolt on Hondas is so
large that a special crankshaft pulley holding tool is
recommended for the bolt's removal. People talk about
pushing on the brakes (and so immobilizing the drive train
and so presumably the crank pulley, in the vein of what you
are saying) while trying to free the bolt and say the pulley
still is not immobilized when torque is applied to the bolt.
I suppose a risktaker could try taking both front wheels off
and immobilizing the axles with long crowbars or similar
between the lugnut studs. From awareness of the torque
needed to free the pulley bolt on my manual drive Civics, I
personally would be mighty afraid of toppling the car off
the jackstands.

Crude calculation: Typically 400 lbs. or more of torque is
needed to free the pulley bolt. Some 400 ft-lbs applied at
the pulley bolt means something like 100 ft-lbs applied by
each of the four wheel studs involved on the two wheels. The
moment arm from wheel stud to wheel center is about 2
inches. So around (100 ft-lbs/2 in*12 in/foot =) 600 lbs. of
force is being applied to each wheel stud. This is around
1/4 of the weight of the car that is being messed with.

 

I did some Googling around about Broken TBs on Hondas and the interference
vs non-interference question and found this thread. I have to agree about
the A20A engines being non-interference and that anything that is truly
interference is bound to get trashed, regardless of the speed that the belt
breaks. http://www.3geez.com/forum/showthread.php?t=35768

 

I did say theoretically & recommended is not the same as required. I'm
pretty sure the shops just put an impact wrench on it and spin it off.

When we changed the belt on the '91 Mazda pickup, the solution was to simply
put a real person in the car with her foot planted firmly on the main brake
pedal. Of course, it won't work if the clutch slips.

I tried it once on the '81 Accord, but the clutch was so far gone at the
time, it just slipped. At the time, I didn't have an immobilizer & ended up
paying a shop to change it.

I am familiar with the amount of force needed to break the bolt loose. I
have the immobilizer and have done the job myself with manual tools on a '96
Odyssey and a '95 Integra (both automatic trans.). You haven't really lived
until you try the Odyssey. It's torqued about 50 lb-ft more than an Integra
or Civic. I certainly would not consider anything involving jack stands. It
would have to be either all wheels on the ground or, preferably, good sturdy
ramps to get some space under the engine.

By your calculation, I would think the drive train should be able to handle
the force. It spends its life accelerating and stopping a ton an a half of
car after all.

These days, I just sit back & bask in the glow knowing that both of my
current cars ('06 CR-V & '08 Altima) use timing chains, so with a little
luck my days of changing belts are over.

 

Sounds like you're in luck then. At least you don't have to fear
instantaneous catastrophic destruction.

I was only responding to what read to me like confusion about what an
interference engine is.

 

Yes, pardon. I know you are one of the experienced, well
seasoned regulars here. I did not give enough credit to your
qualification "theoretically... "

I too thought about the drive train (relative to my numbers
and also normal operating conditions) and also think the
gears yada would not be limiting. That is, they would hold
just fine while freeing the pulley bolt.

It is a lot of work for me, but learning how to do it was a
great education, meaning wealth itself.

 

A person at Honda-tech.com a few years back tossed out that,
when a TB breaks, it is possible for the cam to be in a
position such that all the valves are shut.

 

I'm no expert on any of this stuff but that doesn't sound possible. I would
think that at any one time, the only cylinder with the valves closed would
be the cylinder on the compression stroke. While it's doing that, the
opposite cylinder, on a 4 cyl engine, is on the exhaust stroke with the
exhaust valves open. Check out this video.
http://www.youtube.com/watch?v=Hhc6xM0wjKQ&feature=related

 

This video shows the operation of the four cylinder better. Easier to see
what's doing what, when.
http://www.youtube.com/watch?v=4vWoSXYnTa0&feature=related

 

My boss's old '94 CR-V had its belt break (he was WAAAY overdue!!!). No
damage. And he was going highway speed at the time.

Still, the downside of an unlucky break is /extremely/ expensive, so it's
very, very unwise to try and save a few bucks stretching the belt's life.

 

I agree.

Since my '88 Accord had it's water pump explode at an early age, I tend
to think that replacing the TB, Water Pump and Tensioners, as well as
any rubber belts you have to remove to access said parts is the most
economical way to deal with the Honda engine.

dan

 

Impressive video, thanks.

And thanks to all those who contributed in this thread. I will have
the TB changed soon. My thinking: I'm hoping to have this car for
another 10 years. Obviously for safety's sake I need to have the
TB done sometime in that period, and right now makes the most sense
given that.

 

Right, I follow. Perhaps the valves could all land in an
intermediate position when the cam stops. I would have to
think about it more.

I did notice recently at the yard that the "valve reliefs"
(those indentations on top of the pistons that I am not sure
all or any Hondas have) may certainly be assisting the
valves' protection when timing is lost. For all I know
whether damage occurs may depend on so much: the engine
temperature (higher temp = less clearance?); carbon buildup;
which Honda engine we're talking about; manual vs. auto
tranny.

I wonder if the valves can even be pushed shut (without
damaging them) for a number of cycles as the engine comes to
a stop. But this may be naive on my part.