Squissy brakes, only sometimes???

[hp383]

Ok this has been an ongoing issue on my 93 4x4 CTD. The brakes are sometimes OK, sometimes spongey, and sometimes the pedal will go to the floor.

In my daily driving routine, I am used to pumping the brakes a good two or three times about half pedal before I plan to try and stop. But on the occasion that I need to stop in a hurry its more like a gradual slow down, with the pedal going nearly to the floor. Once in a while the pedal just goes right to the floor with almost no resistance.

Early on it was thought this was due to a power steering leak, when the fluid got low, the brakes got funny.

Well, now the leak is fixed, has a rebuilt vacuum pump, and a new master cylinder. The mechanic who did the work said he had a hell of a time bleeding the brakes, said he bench bled the master, gravity bled the system, had great hard pedal when off. started the truck and had almost no pedal. did a two man pump bleed, and truck seemed good, took it for a drive and it was OK, but not great. then later had the low pedal issue again.

If the truck is off, I can pump the pedal a couple times, get a good hard pedal that does not sink.

I'm not sure where to go from here, but can tell you that as is there is no such thing as panic stop, and stopping with a load in the box should be planned in advance.

Truck has new brakes, and turned rotors/drums all the way round.

Is there a proportion valve that could fail, would that even cause these symptoms?

Oh more info: The dash brake light comes on and stays on, as does the ABS light. They always have since I had the truck, thought it was a dirty tone ring issue. But truck now has a new locker in the diff, and everything was cleaned and spit shined in the diff case, so should not the ABS light now go out?

[Richie O]

The power steering has nothing to do with the brakes. It is 2 seperate systems that share a drive gear for the vacuum pump and the power steering pump.. Being low on steering fluid will not effect brakes.

[hp383]

I was told that the power steering reservoir was shared between the hyd assist brakes, and the steering. Thus a low power steering reservoir would cause the brakes to not perform correctly.

But regardless of that, now that it isn't leaking anymore, I know that is not the issue, would like to find out what is.

[PToombs]

The newer trucks have hydra-boost, or older trucks like ours that have been converted.

The problem is most likely the ABS valve on the drivers frame above the rear axle. Sometimes they stick internally and do what you describe. Best thing is to remove it and throw it away. If you search on here you can find part numbers for the adapter fittings to hook the lines together, or someone will post them up for you. I removed mine when I replaced the rear brake line, I just went ran the new line right to the hose connection, no adapters needed that way. Make sure you unplug the ABS box behind the glove box to keep the lights off.
This is one of the best mods you can do to your truck, it will stop as good as a new one. (well, almost! )

[hp383]

Hey thanks for that bit of info.

Hopefully someone will post that ABS delete info.

[PToombs]

Boy are you lazy! I don't have good luck with the search and I found it in 2 minutes.

weatherhead; wea7917 + wea7828

napa; wh202x5 + wh252x3

These will connect the line in to and the line out of the valve.

[cougar]

I had the same issue. Mine was the master cylinder. After the third Napa replacement I got one from Car Quest. That one worked. I thought my RWAL was bad too because it can cause similar symptoms. I disconnected the RWAL box and went for a drive. When I clamped on the brakes the rear wheels locked up but the peddle was still funky. Plugged the box back in, no lockup still funky peddle. ABS working as advertised, master cylinder not.

[hp383]

Ok, i must be doing something wrong then, im searching foe ABS valve and come up with three posts. Mine and two others that say to delete it, but none of them show the part numbers, pictures, or other info.

I just tried searching with the part numbers you listed, came up with only one thread... this one.

[PToombs]

I searched with "abs, delete, napa" and came up with 1 post. On the bottom right of that page it says "view whole thread" I clicked on that and came up with this,
viewtopic.php?f=24&t=6199&p=60078&hilit=ABS%2C+delete%2C+napa#p60078

I usually have an awful time using the searchs, I musta got lucky this time. There are several threads on the valve and bad brakes, just have to figure out how to find them.