Hello everyone - thanks for the replies to my earlier thread about a parkbrake fault on my 2002 S Type 3.0. I have thankfully now resolved that problem, but now I find that I have a very soft brake pedal...

I have changed the pads all round and I have bled the system through with new fluid. I've stuck over a litre through the system, making sure I kept going until there was no air bubbles and clean fluid was coming through all round. I haven't got the wheels back on or the car on the ground yet, but up in the air, the brake pedal just doesn't feel right. If I sit in with the engine running and pump it a few times, it starts to feel firm, but then I let it go and give it a press and it feels spongy. I'm at a bit of a loss, because as I say I was confident I'd done a thorough job of bleeding the system.

Are there any peculiarities or common gremlins I could investigate?

The reason I had to bleed the brakes in the first place is because I suffered a hose failure, so replaced the hose but an absolute load of fluid had leaked out. Could it be that I just need to keep going and flush a load more fluid through?

 

I've done all the usual tests to check that the servo is working and the master cylinder has good seal - all seems fine in that regard.

 

OP: Did ypu use a power bleeder or the right leg method of bleeding the brakes? If you used the right leg method, did you push the brake pedal all the way to the end of its travel at the lower end of the stroke?

 

I used the old school method to start with, because I couldn't find my pressurised bleeding thingy, pretty sure I didn't press too far - I did worry about whether I'd done a seal in the master cylinder, but as I say I've done all the usual tests and the master cylinder is definitely holding pressure so don't think I can have rolled a seal or anything as nasty as that.

i've subsequently found the pressure bleeding tool and used that, but still same spongy feel to pedal.

 

I have never used the pressure thingy.
Full brake reservoir, of clean fresh brake fluid and one brake calliper at a time, bleed screw, 1 turn open, with the engine running, and venting to each corner, diagonally one at a time.
Call me old fashioned.

 

Dear Old Fashioned,

Does the engine have to be running? Would it be sufficient to have the ignition on but engine off? I had been wondering if it would help having the ignition on to power the ABS, and then I saw your message.

 

Mr. Old Fashioned: IIRC, your method, while certainly traditional, does not open all the valves in the ABS unit so that old, moisture laden, brake fluid can be replaced with fresh. This is kind of the reasoning behind Jaguar's bi-annual brake fluid replacement regimen.

 

Well I seem to have made progress. I bled the system again with pressure bleeder, but pedal still felt soft. So I bled it with pressure bleeder but at a higher psi and with the engine running - afterwards, the pedal felt better but still felt a touch softer than I'd expect. Took the car for a short drive in a deserted area, lots of brake testing, and the pedal firmed up somewhat. Bled again with higher pressure and engine running, pedal is now firm and brakes operating perfectly.