P38A Braking System Problem on P38a - Pedal Travel Question and What to do Next?

Hello,

Looking for advice with braking issues on my P38a, Its a 1998 GEMS V8

A couple of weeks ago the brakes went weak, they barely stop the car. Having had a look at the threads I bought a master cylinder & ABS pump that were bundled together on e-bay.

I have swapped over the ABS pump & accumulator, bled using the front bleed valve on the master cylinder but this did not improve the situation. Its back exactly as it was.

I inspected all the brake pipes etc which look fine then thought I would try bleeding the system as it seems like the next easiest thing. I started by depressurising the system and then started on bleeding one of the front calipers. I manged to get a bit of fluid through but have found that it just doesn't seam to be pushing much fluid through when the pedal is pumped. Am doing on my own do wedging down the pedal then opening and closing the bleed valve then back to the pedal...

The outcome of my attempt at "Bleeding" the caliper has ultimately made the situation a little worse so pretty sure I have drawn some air back into the caliper.

One thing to note is that there isn't much travel in the brake pedal. I see a youtuber's pedal going right to the floor but mine only shifts about an inch & 1/2. Its always been the case as long as I have had the car (5 years)

The other thing to note is that there are no warning lights or messages on the car. The 3 brake warning lights operate as normal i.e. light up and go off after a second or two, the ABS light goes off once I get moving.

I am pretty sure the Pump & accumulator are good as when I depreasurise the reservoir fills to the brim with fluid so I am taking this as the nitrogen expanding and squeezing back the fluid.

So I am curious about the travel pedal and what other P38's feel like? When working mine had little travel & weak braking when the engine was off but decent brakes when the engine was running.

I could use some help with thoughts on what the problem might be and what to do next. I have a replacement master cylinder and am starting to think this is where we are heading but it looks a bit messy so thought I would reach out to the forum first

Also, any tips on beading the brakes solo would be appreciated. I can call the wife over if needed but she really isn't enthusiastic about this kind of stuff!

Silly question maybe. Can you actually hear the brake pump running and building pressure? Can you hear it stop pumping? If the accumulator is knackered then the system won't hold any pressure

pwood999 said:

1. Download RAVE from technical archive at top of this forum.
2. Read the section on bleeding brakes
3. Get a helper because you cannot do it on your own.
4. do the actual brake bleed process, repeating until all air is expelled.

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Thanks Pete, Checking out the RAVE and buttering up the wife!

kermit_rr said:

Silly question maybe. Can you actually hear the brake pump running and building pressure? Can you hear it stop pumping? If the accumulator is knackered then the system won't hold any pressure

Click to expand...

Hello, Yes, I can hear the pump running and cutting out once pressure is built up. I also see the fluid level come down a bit in the reservoir as the pump builds up the pressure.
Interestingly the replacement one is much quieter, the old one was much more rattly.

teflongrasshopper said:

buttering up the wife!

Click to expand...

That's for a different thread

If you changed the "master cylinder" did you fit the correct one? Not sure why you would change the master cylinder, they rarely fail.
I suspect your original problem was just the sphere.

Datatek said:

If you changed the "master cylinder" did you fit the correct one? Not sure why you would change the master cylinder, they rarely fail.
I suspect your original problem was just the sphere.

Click to expand...

Hello, I have not changed the master cylinder and hoping this won't be necessary however I have one to hand if needed.

It's the brake pedal travel that is making me wonder if the master cylinder is knackered as there doesn't seem to be much and I am pretty sure that the ABS pump and sphere are sound now.

You have to bleed it correctly exactly as per rave

There's a bleed nipple right at the back, under the bulkhead, easy to miss

Hello, thanks for all your help.

The clear consensus is to bleed the system properly. I have the instructions from the RAVE and will run through the process tomorrow.

Invest in an Eezibleed
Think @Mark Piercy has a pretty fancy one

kermit_rr said:

That's for a different thread

Click to expand...

Tell me more

As said previously you have to follow Rave to the letter when bleeding the brakes

oakey said:

Invest in an Eezibleed
Think @Mark Piercy has a pretty fancy one

Click to expand...

I do matey, there are two bleed screws tucked up under the bulk head and one a little lower down on the side of the distribution block. If you just flushing the system with no air present you can start bleeding from the top nipple down and then go to the furthest wheel and so on but if the system has been emptied and air is present then the procedure in rave has to be done to the T'.
I have this bugger and use it in the garage for clients cars. Spot on every time.

The eezibleed is ok I’ve your attempting to bleed them on your own

Eezibleed is ok for filling the system after changing rear pipes, but not ideal for bleeding properly. Several of the steps require bleed valves opened & closed with specific pedal actions.

When bleeding the master cylinder, it's much easier if you remove the coolant reservoir first, and also cut back some of the firewall foam around the bleed nipples.

Hello All,

Thanks for all the advice, I did look at the eazibleed however I think there is truth in that getting an assistant on the case is the easiest way to do the job.

So on my case I got my assistant to run through the RAVE brake bleeding procedure with me. All looked OK on the first bleed valve at the master cylinder. She noted that when the valve was open the pedal travelled right to the floor and I could see a good amount of fluid being pushed through.

Then, on to the front callipers which were a problem. When the valve was opened there was very little travel in the pedal & no fluid was being pumped through. I tried both front callipers and it was the same for both. Its like the pressure on the pedal isn't making its way down through the system. With the valve closed pedal travel was exactly the same.

From under the car I could hear sounds akin to squeezing and pressure moving about from the master cylinder.

I am thinking its a blockage in the system, maybe something broke lose or has failed closing off a pathway for the fluid to the callipers.

What do you guys think? What next?

teflongrasshopper said:

Hello All,

Thanks for all the advice, I did look at the eazibleed however I think there is truth in that getting an assistant on the case is the easiest way to do the job.

So on my case I got my assistant to run through the RAVE brake bleeding procedure with me. All looked OK on the first bleed valve at the master cylinder. She noted that when the valve was open the pedal travelled right to the floor and I could see a good amount of fluid being pushed through.

Then, on to the front callipers which were a problem. When the valve was opened there was very little travel in the pedal & no fluid was being pumped through. I tried both front callipers and it was the same for both. Its like the pressure on the pedal isn't making its way down through the system. With the valve closed pedal travel was exactly the same.

From under the car I could hear sounds akin to squeezing and pressure moving about from the master cylinder.

I am thinking its a blockage in the system, maybe something broke lose or has failed closing off a pathway for the fluid to the callipers.

What do you guys think? What next?

Click to expand...

Blocked bleed nipples? May be worth taking them out and see they're clear.

Pretty sure RAVE says to do the fronts first? I'm sure i did a few weeks ago