D1 Brakes binding

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Rover Morgan Man

Member
Jun 22, 2015
9
0
Roanoke VA
Hi folks, this is my first posting here. I have a 1998 D1 and two series trucks. I have had series trucks since 1977 and know them pretty well, but I am still trying to figure out the D1. I have had a weird problem twice now. Without any warning the brakes will slowly apply themselves to the point that the vehicle is difficult to overpower the brakes. After sitting a few minutes, you can hear popping where the calipers are releasing and the pressure goes off. After the second time (last Sunday) I replaced the master cylinder hoping that the return in the cylinder of the original was the problem. I haven't had a reoccurrence yet but I am not convinced. The new cylinder seems to leak down while sitting at a light, but it may still be air in the system. I will bleed it some more soon. Has anything like this happened to any of you? What did you find? I know of another D1 that had this problem, and the woman driving is scared to death. I would really like to find out what is going on. Thanks for your input.
Elton
 
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Rover Morgan Man

Member
Jun 22, 2015
9
0
Roanoke VA
Thanks for the replies. PDX, it is definitely the main hydraulic brake system. Fish, it pulls up evenly like all brakes are being applied. The M/C I replaced was a Lucas, I have since replaced it with a new TRW/Lucas. It seems to work ok except it seems to have an internal bypass!! Step on the brakes and it stops well, but if you continue to hold pressure the pedal creeps down requiring a pump up to maintain position down hill. So unless there is another thing or two to try, I think my new cylinder is a bum. Any thoughts?
Elton
 
The Fourth Amigo

The Fourth Amigo

Well-known member
Apr 20, 2009
641
2
If the brakes are applying themselves It would have to be the ABS pump or something with the vacuum servo. Maybe there is a faulty spring in the servo or its not venting to atmosphere properly. You could pull the fuse to the ABS pump and rule that out.
 
fishEH

fishEH

Well-known member
Jan 26, 2009
6,930
203
Lake Villa, IL
ptschram said:
Brett-let's be honest here. IIRC the master cylinders in question were Cardone remans weren't they?

The pedal moving down is most likely the brake booster, but we don't know if it's from vacuum lowering, the booster diaphragm, or what.

Elton-what brand master cylinder did you install?
Click to expand...
IDK, I've not experienced the problem myself and therefore not put much(any) effort into trying to figure it out. Just trying to point OP towards some possible relevant info. :victory:
 
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Rover Morgan Man

Member
Jun 22, 2015
9
0
Roanoke VA
The original to my ownership master cylinder is a TRW/Lucas, and I have just replaced it with another TRW/Lucas. I am pretty sure the M/C is bypassing now because there is no fluid loss anywhere but the pedal slowly goes down. I have ordered a replacement. I believe the original problem binding was the master cylinder not releasing the fluid back to the reservoir. The ABS is not functioning, fuse pulled and unplugged, so I don't think that is an issue. If the problem persists, I will totally remove the ABS system and go back to conventional brakes. Going back to the first issue, is there any way that the booster could be (on rare occasions) keeping pressure on the master causing the brakes to bind up?
 
p m

p m

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Staff member
Apr 19, 2004
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I had brakes that progressively locked up in the manner you described, although on a different (yet British) vehicle restored after a serious head-on accident. The cause was the piston in the master cylinder not returning fully to the position allowing to release the fluid pressure after a brake application - I drove for a while learning not to use brakes as much as I could (the brakes would lock up after 4-5 applications!), and then just made a 2-mm spacer between the MC and the booster.

I don't think ABS is your problem - not on a D1, at least.
 
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Rover Morgan Man

Member
Jun 22, 2015
9
0
Roanoke VA
I found (locally) a TRW/Lucas master cylinder for a good price and bought it. It stopped the vehicle well but would leak down. So I requested and received a warranty replacement for the first cylinder and installed it. When being bench bled it seemed weak on the rear outlet but I put it on. It would not make enough pressure to blow my finger off the hole. So I called the local O'Reiley's and got one of their super doper no name cylinders. It went on and worked like a charm the first time! The only thing wrong is it tilts toward the right a few degrees, just like the first one I took off! It seems the TRW/Lucas one fits better and sits level, but if it does not work correctly what good is it? Has anyone else had problems with these cylinders? Elton
 
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