Discovery 1 Master Cylinder Differences

[antichrist]

Anyone know the difference between the ABS (STC1284) master cylinder and the non-ABS (STC1285) MC?

My '95 Disco has ABS, but the modulators seem to fail in what I like to call "death mode", kicking in even on dry tarmac allowing you to go right through intersections. Needless to say, it can be quite exciting.

So I'm thinking of just removing the modulator and am wondering if I need to switch out the master cylinder. The pressure reducing valve is the same, so I'm good there.

I do find this much about them:

ABS STC1284 = 25.4mm CV/CV

Non-ABS STC1285 = 25.4mm AS/AS

I don't know the difference.

Thanks in advance.

[cipx2]

Try disconnecting the ABS pump or ABS ecu first and see what happens.

The symptoms you describe are usually caused by one or two brakes binding, so I suggest investigate that.

[antichrist]

Already done that. I don't want to fix it, I want to get rid of it.

[nicedayforit]

Anyone know the difference between the ABS (STC1284) master cylinder and the non-ABS (STC1285) MC?

My '95 Disco has ABS, but the modulators seem to fail in what I like to call "death mode", kicking in even on dry tarmac allowing you to go right through intersections. Needless to say, it can be quite exciting.

So I'm thinking of just removing the modulator and am wondering if I need to switch out the master cylinder. The pressure reducing valve is the same, so I'm good there.

I do find this much about them:

ABS STC1284 = 25.4mm CV/CV

Non-ABS STC1285 = 25.4mm AS/AS

I don't know the difference.

Thanks in advance.

The problem you have is normally caused by faulty sensors.

The pressure reducing valve on an ABS system has 4 connections on a non ABS system there are 5 connections.

[antichrist]

The pressure reducing valve on an ABS system has 4 connections on a non ABS system there are 5 connections.

Interesting, both the ABS and non-ABS systems have the same part number for the pressure reducing valve, ANR3194.

[cipx2]

The pressure reducing valve is the same for both ABS and non-ABS systems, same part#.

On the ABS systems one of the holes is plugged as you can see in this pic:

To convert it to non-ABS you simply remove the plug and put the brake line going to the front left wheel. The two holes (the one that it's plugged and the one next to it) are simply a like a "T" ramification.

As for the initial question, there are some differences inside the cylinders, I think they're same on the outside.

These are the two repair sets used on the two versions so you can get an idea on differences inside:

- non-ABS:

- ABS:

[antichrist]

Cool, thanks mate! Yeah, I looked at my pressure reducing valve and saw the threaded plug in it, so knew how to handle that, but thanks for the confirmation.

Sorta hard to tell from the photos the difference, but one bloke on another forum told me he used the ABS MC on his Disco after removing the modulator and saw no difference in performance, so I'm guessing it's ok to use.