1992 Honda Accord - Brake Problems

Don't know the Accord ABS that well, but most systems don't generate pressure, they release it after your foot generates it.

Don't know that I can tell you how they are getting pressurized, but it may not matter - they should release through the Master cylinder.

So whatever the failure mechanism, the master is not in the proper position to release for some reason - so either something is mechanically interfering with the rod from pedal to master cylinder, or there is a failure in the master cylinder itself.

Unless your father-in-law's cuff is worn from "snagging" the brake pedal, the master would be a good place to start.

If you have 4 disks you shouldn't have a modulator, if you have mixed disk and drum then all the answers change. Drums have their own failure modes.

I thought your car brake system are integrated with brake booster( servo mechanism)

As shown from above figure ,If air intake valve is failed ( permanent open) while vacuum valve closed , this case will create pressure force upon pushing rod to master cylinder resulting from pressure difference between vacuum and pressure chambers,

under this condition brake will activated without pressing pedal.

if I'm right, you need to repair or change servo mechanism for more details look for

Automotive Engineering International Online: Tech Briefs,...

Does the problem happen even if he is sitting idle and having never touched the brake?

In addition to the fine responses previously posted I would check the lines going to the calipers. These lines can collapse internally and not allow pressure to be relieved after the foot has been removed from the brake peddle.

This was the case with another vehicle I owned. the inner casing had de laminated from the rest of the line and although there was no sign of a problem on the outside, when the offending line was removed and inspected it was clear what the problem was.

Basically when the pedal was released and the pressure was trying to return to the master it sufficiently closed the hose just like a valve shutting, and would not allow the pressure to relieve from the caliper.

Now if your problem is occurring with the aid of pedal pressure then I would fall back to previous posts and check the master cylinder and brake booster.

I agree. It sounds like your flexible brake hoses may be old and working as "one-way" valves once the brake fluid heats up. One way to check is to try "collapsing" each of the calipers (or wheel cylinders if there are rear drums? can't remember if you said it was 4-wheel disc or not?) without opening a bleeder screw. If the caliper piston doesn't retract easily into the caliper bore (as it should), then it's probably the hoses. How old are they btw?

Some of the older ABS systems actually did pressurize the brake lines during normal operation. This was done to alleviate the brake pedal pulsation found in first-generation ABS systems (which caused alarm to many drivers unaccustomed to their brake pedal behaving that way.)

Does the ABS system work before the brakes lock up? In other words, does the car stop without skidding the first few minutes of driving?

And NEVER manually bleed your brakes... depressing the brake pedal (and therefore the valves and seals of the master cylinder) further than the "normal" brake pedal travel from regular driving can damage the internal seals of the master cylinder.

Just my $0.02... hope that this helps!!!

if the brakes havent been bleed in a manual bleed sys..might give that a try..

my 2 cents ..

A very small amount of water in the brake fluid can cause this. Make sure to use new still sealed brake fluid if you replace what you already have.

A way to test this would be to let them cool down completely after they turn on(apply themselves) from heat. If the brakes release when given time to cool, water in the brake fluid may be the problem.

Old brake fluid can absorb water from the air.

How does that function? The mixture is still liquid, pressure buildup must bleed back to the master cylinder and then in the reservoir......

I do realise that water build up is normal with brake fluid, it should be replaced every 2 to 3 years, probably in Seaside areas even more often....

Its the effect of forcing the brakes on that I am interested in hearing about, as I have NEVER heard of that happening when the rest of the hardware is in working order.....

Please educate us, thanks in advance......

Hmmmm sounds like hydro, dynamic, catastrophic, thermal, expansion.

As water expands and begins to create a vapor the water dynamically increases the size of the endothermic relationship between the caliper and.........

I give up I guess he is gonna have to explain it to me too.

LOL

Its not the problem either.......!!!

There have been some very good ideas posted as expected. Please allow me to help you to isolate the problem. knowing which wheels are dragging is the first place to start.

Do you feel any free play when pushing the brake pedal by hand? If not, adjust some into it.

Which bleeder do you open to relieve the pressure?

If you can not be sure there is free play in the master cylinder, you can loosen the brake master cylinder to booster mounting bolts one full turn on each one and test the car car in a safe location.

Brake hoses will do exactly what you stated. There is no easy way to test the hose without removing it from the car and pressurizing it from the wheel end. BUT, it is unlikely that more than one hose went bad at the same time.

When the master was changed, if a mechanic left off a gasket, or shim between the master and booster, it would cause this problem. Good luck. Try to isolate some and let us know.

The valve he opens to release pressure is next to the abs modulator. I drove the car, it seized up and the same valve didnt release the pressure so I had to open one of the other valves on the wheels. The Abs light comes on once in a while and shuts off again. It doesnt stay on or flash any specific code. I drove it about 5 miles on residential streets and the freeway and when I came to a stop light about 5 miles into the drive the brakes started to slow the car on their own, so much that it actually stopped the car and I couldnt move it from where it was until I released the pressure. As far as I can see, it is the front brakes that seize up. No brake lines were kinked or pinched in any of the recent parts changes.

I hope we can get this fixed soon. He has had no car for 2 weeks now and is having a hard time getting to the store.

I appreciate all the help from all of you. Thank you so much.

Your line my not show any visible problems, ie. kinks, cracks or leaks, but may still collapse on the inside. Again physical inspection of the lines with them removed is the only way to determine this.

the way I figured it out was to take a piece of stranded electrical wire and push it through from the caliper end.

Follow Andy's advice (as well as the great advice given by others) and check for the hot rotor to determine which side would be the culprit. It's the easiest place to start and the easiest fix if it really is the problem. Depending on the type of connectors you have on the lines, you may find the wire trick won't work. If that is the case you will have to find some way to pressurise or feed oil from the caliper side of the line. If it flows through easily, then great no problem if not then replace the line. They are not terribly expensive.

Does the car have dual circuit brakes???

GA from me for a simple check.....

I change the master cilinder and the pedal is till ni the floor

Did you bleed the air out of the mc?

I just found out this problem didnt start happenning until after the master cylinder was changed. Could it have been installed incorrectly? I will check the brake booster to see if that is the problem.

Its simple then, the new master cylinder is either of the wrong type, or it has been wrongly installed so that the brake pedal cannot return 100% and allow any fluid that is warming up/expanding while driving, to escape back into the reservoir. As it should.

The installer should correct his work for free, that is assuming that he understands car mechanics.....which may or may not be true!!!

The reason that only the front brakes go on is that in most vehicles, when lightly loaded, the power to the rear brakes is reduced so that it does not cause locking up of the rear brakes......also they are probably not disks, but drums and they often need a greater "movement" of fluid before contact is made.....but they are probably measurably nearer than they were when cold......

it sounds like your proportioning valve is not working properly. abs is good if the light is not on.