#@&%~Brakes!!!!!!!

[poolguy]

$580.oo later, with new brake pads on the front, new brake shoes on the rear, a new master cyl, new brake lines to the rear and all new dot 4 fluid, the brakes are exactly like they were before any thing was done!
The mechanic says he tested the rabs valve.
I suppose I'll just go get me a good boat anchor and a chain to stop it with!
Actually it hasn't failed to stop, but the pedal sinks almost to the floor, and is spongey. You can't get any tire to slide (and it rained today) if you slam on brakes. It will stop, but I wouldn't want any load on it or behind it. Any suggestions?
Thanks,
Chuck

 

[icanfixall]

Yes... Look back at my posting. Do that and post back what you find out.

 

[poolguy]

Ok, tried the ebrake set and check. The ebrake pedal goes to the floor. Made no difference in the pedal. Checked the rabs valve while I watched, no movement inside (as checked with a paper clip) and no fluid behind the plug. Everything else is new so we bypassed the rabs valve (ran a new line around it). Pedal is some better, but STILL sinks almost to the floor with moderate pressure!
I will try to get a master cylinder with a larger diameter tomorrow. Don't know what else to do!
Anybody got a suggestion?

 

[icanfixall]

Your rear brakes are not adjusted up properly. When they are the parking brake will set high and hold the truck.

 

[poolguy]

OK, but will this effect the otherwise sinking brake pedal?

 

[tonkadoctor]

OK, but will this effect the otherwise sinking brake pedal?

It will if they are out of adjustment.

Brakes are hydraulic and you can't compress a liquid. If there is nothing to stop the flow of the fluid, like the brake shoes and pads making contact with the drums and rotors the pedal will just keep moving until it physically can't move any more, ie hits the floor. Get them adjusted properly and go from there, not hard to do and costs nothing but time.

 

[icanfixall]

What you are feeling on the peddle is the fluid is filling the front and doing all the stopping work. Then it trys to fill the OUT OF ADJUSTMENT REARS. Thats the sinking brake peddle feeling you have. Plus you have stated the parking brake goes to the floor. It does not hold. That is one of the signs the rears are WAY out of adjustment. Do you front pads wear out lots sooner than the rear shoes???

 

[poolguy]

Thanks, I actually understand the basic physics of it all. I just couldn't crawl around under the truck yet. I fell in an empty pool last fall and tore all the tendons of my left knee (patella, acl etc.) and it's not 100% yet. So I'm using a mechanic shop where I know the owner and they'll let me watch & comment with out throwing things at me.
Replaced the master cyl with a rebuilt, put new pads on the front. Pedal still slowly sank to the floor. (stops, but the pedal slowly sank)
Put new shoes on the rear. Pedal still slowly sank
Checked out the rabs valve by pulling the rubber plug and slipping a straightened paper clip in and checking for movement with engine running. No movement, pulled the cap plug and no fluid behind it. Pedal still slowly sank.
Bypassed the rabs valve with new brakeline to rear. Pedal slowly sinks. Stops better than it used to. but pedal still sinks with moderate pressure like you would apply at a stop light. You can release and reapply pedal, brakes grab just fine but pedal still sinks.
Pushed ebrake and pedal went all the way to floor. No diff in brake pedal.
Adjusted the rear brakes this morning. ebrake sets at less than 1/2 pedal travel. Brakes are more sensitve than they were, stops on a dime! Pedal still sinks slowly.
Replaced the rebuilt master cyl this afternoon with a new one still the 1 1/8
bore. I couldn't find a 1 1/4 or 1 5/16 bore in town. I felt like with everything new, brakes adjusted, rabs valve bypassed it had to be the rebuilt master cyl bypassing internally. Pedal still sinks slowly. Truck stops great! But the pedal sinks as you sit at a stop light!
This one's got me confused.

 

[Camarogenius]

Any fluid leakage?
"New" or "Rebuilt" does not mean it's right. Could be the master cylinder is bad, and the rear brakes were just one of the symptoms.
Did you replace the rubber lines as well?

 

[poolguy]

No, didn't replace the rubber lines but did observe them (all three) as the brakes are applied, and there is no swelling. They look normal.
Also, no there is no fluid leaking that I can find. And the resevoir on the master cylinder stays full.
Honestly, I thought it had to be the rabs valve until we bypassed it. Then I was sure the rebuilt master cyl was the culprit, so we replaced it with a NEW one! I know that new doesn't mean good, but the original, the rebuilt, and now the new one! I can't believe this.
This sinking pedal is the symtom that I had to begin with!!!!!!!!!!!!

 

[Camarogenius]

Two new master cylinders. Hmmm.
I think there's another problem somewhere. I'm going over a complete brake system in my head, and without fluid leakage, I can't come up with anything other than the master cylinder.
What process did you follow for bleeding the master cylinder? How about the entire brake system?
C'mon everybody! What are we not thinking of?

 

[sassyrel]

find a diff brake booster--or check it to see if it leaks---

 

[dave186]

Start at the top. get some plugs for the ports on the master cylinder. not the little plastic ones you use to bench bleed it but brass ones. the ones i have are in an ABS pressure test kit. take the lines off the master and plug the ports, the pedal should be high and hard. if its not, you know something is wrong between the brake pedal and the m/c. if it is, hook up the front line to the master with the rear still plugged and see if you have a sinking pedal. if you do, check the lines and hoses then the calipers. if you dont, start looking towards the rear. you already bypassed the rabs valve so we can eliminate that. are you sure the wheel cylinders arent leaking? sometimes fluid can build up in the rubber cap and you wont see it.

I work in a brake shop and deal with this sort of stuff everyday. we put on lots of the 1 1/4 masters, it makes the pedal feel soooooo much better on these fords.

 

[poolguy]

find a diff brake booster--or check it to see if it leaks---

Could the booster cause this?
M/C was bled in a vice as per provided instructions. Wheels were bled at each wheel except on one where the bleeder broke off, and we had to bleed that one with the line nut. I know thats not ideal, but its all I had.
The strange thing is that it's not losing fluid. As many times as the pedal has sunk after the brakes were depressed, there should be a gallon of brake fluid on the shop floor. Everything is dry. Resevoir is full.
Just so you understand me a little better, I've built several hot rods. Full bodied and a couple of T-buckets. I'm playing with a 91 Mustang conv right now, supercharger, and nitrous. I campaigned a pro-comp drag bike in the late 70's. I've worked on my vehicles since I could drive. I've never had brakes kick my butt before!
I'm new to the diesel arena, but I have 3 Ford diesel trucks currently. 2 are later model powerstrokes, but I drive the 94 IDI. I love this old truck, I bought it from a a member here back in Oct. I think. It's a conversion truck and is quite nice for an older truck. But I also use it in my business and we pull a JD 310E Backhoe (15k lbs) and a track hoe (17k lbs) with it all over the state. Brakes anything less than perfect are unacceptable! I don't want to hurt anyone or get hurt.
If you guys can think of anything that might help, I sure would apreciate it!
Thanks,
Chuck

 

[Compu Doc]

http://www.asashop.org/autoinc/dec99/techtips.htm

First click on the above link and try what it says to make sure that the RABS valve is not the culprit.

Another thing to do is see if your parking brake cables are moving as they should be. You could pull on each on individually from under the truck. Pull each one after the T connector that connects the pedal cable to the rear cables and observe towrds the drum where the cable enters the backing plate. If you do not see them both working then replace them. If you do see them moving then adjust the parking brake first afterwards adjust the brake shoes.

There are 2 ways to adjust brakes. One way is to remove the drum and measure the inside of the drum. Adjust the shoes for the same diameter then reinstall the drums. They would go on kind of tight. Another way is to jack the wheel up and adjust them using an adjusting brake tool also known as a brake spoon. In that method you may also need a flat head screw driver to push the self adjuster out of the way. When you adjust the back brakes using this method adjust them to where you cannot spin the tire by hand and then back the adjustment off where they spin but with a slight drag. In no way should they spin freely. They should stop spinning immediately after you stop spinning them. If they spin after you stop spinning them even one inch then tighten the adjustment more.

If your parking brake is not functioning no matter what you do your back brakes will not function properly. So make sure that is functioning correctly first.