2nd Gen Non-Engine/Transmission another brake problem

[FHerault]

Hi,



When I start the truck in the morning and drive it, the 3 or 4 first times I push the pedal are violent, the wheels seem to lock easily, like if I would have old air brakes, but after that, the pedal is quite spongy and the brakes are not very strong.



Front calipers and pads have about 3000 miles only, I've had to stop at a shop because of a major fluid leak and a caliper had seized... The mechanic said that he had trouble with the bleed, because of the combination valve that seemed to not operate properly. Any idea ? Can I test the combination valve and can I repair it or have to change this part ?

The truck was braking better before the caliper change...

 

[B.G. Smith]

A little brake fluid on the rear linings can cause wheel lock up when brakes are first applied on start up. Possible for air to enter if the fluid can get out. The combination valve should switch over and shut off the fluid to front or rear brakes in case of bad leak. It can usually be reset by bleeding the brakes on the end that still has pressure. I don't think the valve is servicable, will have to replace if defective. bg

 

[FHerault]

When I've had the leak few months ago, it was a front brake line that has failed because of rust. The pedal went to the floor and the truck didn't stop. I pushed the parking brake and continue to pump the brake, then drive the truck on the right in a small parking lot. Ouffff ! My daughters were in the truck and they were afraid, so do I... It happens at a big crossroad with a lot of traffic...

In that case, the combination valve should have switch power on the rear brakes, but it seems not.

Has someone ever change this valve ? What about the cost and the skill level ?



Thanks BG for your advices.

 

[B.G. Smith]

For that to happen, either the comb. valve didn't function or your rear brakes were already empty or low of fluid. The master cylinder has two piston, one a little distance behind the other, there are two lines coming off the master cylinder, one to the front brakes , the other to the rear. The lines go to the comb. , one to either end, if pressure is lost in front or rear the pressure in the other end is supposed to force the comb. valve over and block off the leaking side. The valve should not be hard to change, it has two lines in and two lines out and a wire plugged into one end. I would look at the rear brakes to see if you have a leak there before condeming the comb. valve. bg

 

[KRStone]

Mine does it too.

 

[FHerault]

If I had a fluid leak at the rear, the level should drop and I don't see anything wrong behind the drums (fluid leaks). But perhaps I have to verify that the rear brakes are working correctly...



I could accomodate with poor engine power but not with poor brakes... .

 

[WilsonF]

The rear drum brakes on our trucks do not "self adjust" very good, most have to adjust by hand. Could be that they are so far off that they could not stop you.

Floyd

 

[LandShark]

You don't mention where you live, but if it's in a high humidity area, the grab problem may just be a slight bit of rust that can form overnight and cause the first couple of brake applications to grab more than normal.
The spongy feel indicates that you need to find someone that knows how to bleed brakes.

 

[Gene Heck]

Is it the front or the rear that is locking? Pull the rear drums off to just make sure that you don't have a leaking axle seal or wheel cylinder leak. If it's an axle seal and axle oil gets on the linings it will cause the rear brakes (or brake if only on one side) to grab and lock, just the opposite of what you might think would happen. If it's wet or damp out the grabbing problem is worse for the first few applications. It's not that hard to check. The drums on yours come off without removing the axle shaft and hub. You might have to back off the adjustment a little if the drum has a lot of miles and is grooved. Then the drum will slide off over the hub.



Gene

 

[FHerault]

Thanks for all the advices,



This week-end I'll have a look at the rear drums and bleed the brakes. It's time to change the drag link tie-rod so I'll lift the rear too



My feeling is that the problem is more near the master cylinder, instead of at the rear end. But remove the drums, clean and check is a good thing to do before winter...

I think it's the front that is locking easily.

I live in Quebec province, Canada.



Thanks again, have a nice day...

 

[FHerault]

Hi.



Just my feed back :



I've adjusted the rear brakes and wanted to bleed the system.

The brake oil was very dark in the tank so I removed and changed the fluid.

When the tank was nearly empty I saw something in it, It was the little aluminium paper you find on the brake fluid bottle ! The mechanics that had make the repair of the brake line few months ago must have dropped it... and the hole at the bottom of the tank was clogged by this little thing...

After the fluid change and the bleed (and the aluminium cap removal !!!), the pedal is far less spongy and the brakes are more responsive.



I know why I want to do all the maintenance and repair by myself on my vehicles, but sometimes you don't have the choice...

If you have a good and honest mechanic, be smart with him

 

[WilsonF]

Good find!

Floyd