P38A brake pedal? noise

kermit_rr · Oct 15, 2021

Thought I'd best start a thread to see if we can get to the root of it.
The brakes work fine, accumulator is in good order, but system loses most/all pressure over an hour or 2 Which means the pump runs for a good half minute or so when is been stood for a short while.
When the pressure is up and the pump has stopped, you hear the noise in the video, once you've depressurised completely, the noise goes away and you only hear normal pedal linkage movement
https://m.youtube.com/shorts/CT6n4Yc0ewU

kermit_rr · Oct 19, 2021

I'm guessing nobody elses makes this noise

Are these units diy repairable? wondering if I should buy one off ebay, swap, then rebuild mine and see whats what..i can only assume something will break eventually

Rubberknees · Oct 19, 2021

kermit_rr said:
Thought I'd best start a thread to see if we can get to the root of it.
The brakes work fine, accumulator is in good order, but system loses most/all pressure over an hour or 2 Which means the pump runs for a good half minute or so when is been stood for a short while.
When the pressure is up and the pump has stopped, you hear the noise in the video, once you've depressurised completely, the noise goes away and you only hear normal pedal linkage movement
https://m.youtube.com/shorts/CT6n4Yc0ewU

Wammers helped me when I had brake pump problems and if the pump takes more than 43 secs to pressurise its no good. In fact once it takes more than 25 secs its starting to fail. 4 pumps of the pedal and then pump should kick in. My pump was the pressure switch that failed, it crept up to 30 secs running and then ended up running constantly. I just changed the complete lot, was a lot easier. ABS light started coming on after about 2 to 3 miles as well. Hope some of this helps

kermit_rr · Oct 19, 2021

Rubberknees said:
Wammers helped me when I had brake pump problems and if the pump takes more than 43 secs to pressurise its no good. In fact once it takes more than 25 secs its starting to fail. 4 pumps of the pedal and then pump should kick in. My pump was the pressure switch that failed, it crept up to 30 secs running and then ended up running constantly. I just changed the complete lot, was a lot easier. ABS light started coming on after about 2 to 3 miles as well. Hope some of this helps

the pump kicks in after 4 pumps, so that bit is ok
car hasnt been started for a couple of days, i'll time how long the pump takes to cut off in a short while. I'll leave it 30 mins and see how long the pump runs again
either way sounds like i need a replacement unit

kermit_rr · Oct 19, 2021

1st time, pump runs for 33-34 seconds
will check again in 30 mins or so

Rubberknees · Oct 19, 2021

kermit_rr said:
1st time, pump runs for 33-34 seconds
will check again in 30 mins or so

Has accumulator been replaced at all? Could be first port of call

Marshall8hp · Oct 19, 2021

kermit_rr said:
1st time, pump runs for 33-34 seconds
will check again in 30 mins or so

Spot on.

kermit_rr · Oct 19, 2021

Rubberknees said:
Has accumulator been replaced at all? Could be first port of call

First thing i did when i got it as the pump was coming in every other press

Rubberknees · Oct 19, 2021

kermit_rr said:
First thing i did when i got it as the pump was coming in every other press

33 secs is within limit for the pump but when mine got to that time it wasn't long before it needed changing

kermit_rr · Oct 19, 2021

pump on for 8 seconds after 30mins. didnt touch the brake pedal in that time

kermit_rr · Oct 19, 2021

its not the pump thats making noise though, its the abs/tc unit

Rubberknees · Oct 19, 2021

kermit_rr said:
pump on for 8 seconds after 30mins. didnt touch the brake pedal in that time

Thats good The one I have on now is that on start up first thing then ok unless you leave it an hour or so and then 8secs again on start up. Some one with more knowledge than me should be along later but my thought is the pressure switch in pump

Rubberknees · Oct 19, 2021

kermit_rr said:
its not the pump thats making noise though, its the abs/tc unit

Is that the block with the 3 bleed nipples on?

kermit_rr · Oct 19, 2021

Rubberknees said:
Is that the block with the 3 bleed nipples on?

yep that one, underneath the brake fluid reservoir

Rubberknees · Oct 19, 2021

kermit_rr said:
yep that one, underneath the brake fluid reservoir

Maybe something worn and/or sticking inside or even false signal causing activation

kermit_rr · Oct 19, 2021

Rubberknees said:
Maybe something worn and/or sticking inside or even false signal causing activation

That's what I'm thinking, nothing can activate while the ignition is off though, can it? I dunno

Rubberknees · Oct 19, 2021

kermit_rr said:
That's what I'm thinking, nothing can activate while the ignition is off though, can it? I dunno

Wouldn't have thought so

kermit_rr · Oct 19, 2021

Rubberknees said:
Wouldn't have thought so

if its strippable without specialist tools, its something i'd like to do, if for no other reason than to see how it works

Rubberknees · Oct 19, 2021

kermit_rr said:
if its strippable without specialist tools, its something i'd like to do, if for no other reason than to see how it works

Like me there BUT take lots of photos and make note of where everything goes. Brakes on a vehicle are important

kermit_rr · Oct 19, 2021

Rubberknees said:
Brakes on a vehicle are important

thats why i dont like new noises

I'm reluctant to turn the radio on to drown it out

P38A brake pedal? noise

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