I noticed my brakes weren't working properly so I had them checked and found I had blown a rear end seal on the right side. I had the seal replaced along with new wheel cylinders (left and right side) and new brake shoes. The fronts were fine so nothing was done there. The old brake fluid was sucked out and new fluid was installed. Right after the above work was performed I noticed the brake peddle would slowly go to the floor if constant pressure was applied. (I’ve had the truck for over 2 years and never had the brakes do this before.) I was told that the master cylinder must be bad so a rebuilt one was installed. The peddle still went to the floor so they replaced the master again and it still went to the floor so they installed a "new" master cylinder and low and behold, it still goes to the floor! They have now told me that it is "normal" and I should not be holding downward pressure on the brake peddle thereby allowing it to go to the floor. The brakes do stop the truck but I tow a 10,000 # 5th wheel and I am concerned that I may not be able to stop if I have to hold the brake down in an emergency. I am able to pump the brake peddle back up but it goes back down in about 10 to 15 seconds if constant pressure is applied. The brakes do appear to hold even with the peddle on the floor. Oh yes, they also told me that the brake lines may be expanding and/or the new shoes (Bendix) may be flexing. I have now driven it over 800 miles and the problem still exists. Can anyone tell me if it is me, the truck or the brake specialty shop (Brake Masters) that is the problem?

 

cantbeatus

My son just this weekend, changed the master cylinder on his 97 F-250 4x4 with the powerstroke enigne. He had the exact same problem you describe, which is from my experience, always been a text book symptom of a failed m/c.

But the new master cylinder fixed his.

Was the new M/C bench bled before it was installed? It takes a "while" to bench bleed this style of M/C. Or thats what I found any way.

And thats pure B/S for them telling you this is normal and you should not hold downward pressure on the brake pedal. I think thats short for, they don't know what is wrong with it.

Did they also bleed all four wheels after the M/C install?

Make sure the rear shoes are adjusted out properly, then if its the same, I'd say there is some air in the sytem still.

Whoever "them" are, I would not go back there.

 

I agree. It's a crock of crapola.

If it was expected behavior, they wouldn't have tried to fix the problem three times. In short, they haven't a clue what they're doing, and you need to find another brake shop ASAP.

 

Thanks much for your inputs. I thought they were feeding me a bunch of B/S but it is very reassuring to know I am not alone!! Thanks again, Nick (cantbeatus)

 

Check everywhere for a fluid leak.

 

Yes, this is correct also.

 

I went back to Brake Masters (garage name, stores all over AZ) and had them bleed the lines and adjust the brakes before I posted here. I told them to bleed the heck out of them as I was sure there must be air in the lines. They bled the lines again (3rd time) and insisted that all the air is out and there is no way any air is left. I did see them bleed at the m/c and all four wheels but the problem still exist. I told them I was going to post a message here and maybe even go to a Ford dealer in order to get to the bottom of this. The garage agreed that posting was a good idea but told me if I went to Ford I shouldn't tell them that Brake Masters did the job because they will only bad mouth them and insist that they (Brake Masters) did something wrong.

I did notice something different today which may shed some light on this. I applied constant pressure to the brake peddle this morning when I first got in the truck and the peddle DID NOT go to the floor. As soon as I stared the engine however the peddle went to the floor and did so everytime I applied the brake the rest of the day. Is it possible that this has something to do with a booster pump?? (or) Is it possible I got 3 bad m/c's (2 rebuilt and 1 new)?? (or) Could there still be air traped in the lines??

Again, thanks for all the input,
Nick

 

Forgot to mention that there are no fluid leaks. They did find a small (bubble) leak on the l/f line when installing the m/c for the third time, I guess they missed it the first two times. Anyway, I had them replace the line. No leaks now!
Thanks again,
Nick

 

I was in a garage the other day and overheard a man with the same problem...they replaced the proportioning valve and presto.....it was cured.. hope yours is too

 

cantbeatus


>>>>I did notice something different today which may shed some light on this. I applied constant pressure to the brake peddle this morning when I first got in the truck and the peddle DID NOT go to the floor. As soon as I stared the engine however the peddle went to the floor and did so everytime I applied the brake the rest of the day. Is it possible that this has something to do with a booster pump?? (or) Is it possible I got 3 bad m/c's (2 rebuilt and 1 new)?? (or) Could there still be air traped in the lines??<<<<


When you start the engine and have the vacuum assist to push the brakes harder is why the pedal goes away easier when the engine is running.

What manner did they use to bench bleed the M/C?

 

I was not able to see what manner, if any, was used to "bench bleed" the m/c. I did see them bleeding at the m/c "after" it was installed on the truck. Does it make a difference if it was only bled after being installed?
Thanks

 

cantbeatus

The M/C comes with direct instructions to bench bleed the unit first before mounting on the vehicle.

You say bleeding at the M/C, describe?

I assume you have the round aluminum bodied M/C with the removable reservoir?

 

The body is rounded with an attached reservoir. The rebuilt ones did not have the reservoir but the new one came with it so they didn't reuse the old one. I saw them loosen the brake line fittings at the m/c after attaching it to the truck and another person pressed and pumped the brake peddle. I assumed that would be the same as bench bleeding. Do you think they did it properly and if not, what should I tell them to try??
Thanks, Nick

 

I have heard that abs problems will let the peddel slowly fall also

 

cantbeatus

I can't say with 100 % certainty, but I don't think it can properly be done on this M/C that way.

Because the intructions with my sons say to plug off the brake line fittings , (which it came with these plugs) and bleed slowy so the air bubbles can rise to the top of the reservoir, along with other instructions as well. And it is to be bled by pushing the piston no more than 1" into the bore, until the piston in the back of the M/C will only move less than an 1/8" without resistance. And it took much longer to accomplish that spec than I thought it would. I 'll bet it took 10 - 15 minutes to get that. It seemd like we had to let it set a bit between plunges also to make headway.