The pedal travel on my P38 seems to have suddenly changed, the top half of the pedal travel does almost nothing. This seems to have happened suddenly after being parked up for a week. The pedal doesn't sink down and if I stamp hard ABS activates as normal.

I've checked and the brake fluid level hasn't changed. I've also checked the hard brake lines and flexis but can't find any leaks. The ABS pump is working normally and cuts in after 3-4 pedal presses. Discs/pads are new all around from a few months ago.

I'm planning to bleed it again per RAVE but I'm concerned that this just appeared out of nowhere with no obvious cause. Anyone got any thoughts on what could cause this?

I bled the system per RAVE today but the pedal hasn't changed at all. I'm guessing it's something internally wrong in the ABS modulator block.

It's interesting that the RAVE bleed procedure wants you to use the lower two thirds of the pedal travel at the end when bleeding the fronts. I'd say my issue feels like it's only the lower two thirds of the pedal travel that is working properly.

I'll find another and strip this one down to see if I can see what the problem was.

Update: I replaced the modulator today and now have a perfect pedal again. So it was something wrong in the old modulator.

Handily someone on a Facebook group posted a guide on installing 4 wheel traction control in the early cars. Since I had to take the modulator out anyway I upgraded it, and the ABS ECU to the WABCO D type with 4 wheel traction control. Everything is working great, no warning lights/errors, diagnostics communicates and the pedal feels great.

Do you now have front TC on a GEMS P38?

There is a plastic part that breaks on the early modulators. Can't remember the full details but do a search on RR.net,
The later ones were redesigned with a metal part. I half remember that it is repairable.
Easier to do what you have done and replace the whole modulator. There are different types.

Harv wrote:

Do you now have front TC on a GEMS P38?

Yes. I fitted the later ABS ECU and modulator.

dave3d wrote:

There is a plastic part that breaks on the early modulators. Can't remember the full details but do a search on RR.net,
The later ones were redesigned with a metal part. I half remember that it is repairable.
Easier to do what you have done and replace the whole modulator. There are different types.

I did have the BMR kit with the metal washers in the broken modulator. I must have installed that about five years ago. I thought about buying another kit and fitting it to another modulator but the later modulator and ECU seemed like a better option. I'll take the old modulator apart at some point and see if I can see what's gone wrong.

Wow, I didn’t know I could get front TC. Lack of 4 wheel TC is really the only thing that I had wished a Bosch P38 for.

@jacckk, it might be a good idea if you can copy and paste the guide on doing the mod on here. Then it won't get lost in the fb mire.

4 wheel TC Install

Thanks for that Marshall. I printed a copy so I have it when the time comes.