Spongy brake pedal

Sorry to ask the same question but I have a spongy pedal and after pumping several times does NOT go hard. In an emergency stop only one wheel locks up.
I have put on new calipers recently and new pads and bled the brakes with no air in system. I couldn't figure out from the post whether it is the booster or main cylinder?? Thanks in advance

Hopefully going north again to look at it. A few ideas to test. Will let you know.

Tom.

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Originally Posted by Hopton1973

Sorry to ask the same question but I have a spongy pedal and after pumping several times does NOT go hard. In an emergency stop only one wheel locks up.
I have put on new calipers recently and new pads and bled the brakes with no air in system. I couldn't figure out from the post whether it is the booster or main cylinder?? Thanks in advance

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Booster problem will give you a HARD pedal

Sent from my GT-N8020 using AULRO mobile app

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Originally Posted by disco 3 door

Booster problem will give you a HARD pedal

Sent from my GT-N8020 using AULRO mobile app

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Thank you for your advice. You also previously stated that there was air in the system. Please take the time to re-read the topic. You will see that the system has been manually bled, pressure bled and vacuum bled - several times. I consider myself very competent in this area, having been working on brakes for around 38 years, including motorbikes, cars and heavy vehicles (semis). I also consider that all 4 x four in Kotara are capable, they have also gone over this vehicles brakes.

I politely suggest that if you do not have a constructive answer to the problem that you refrain from inferring that people are wrong.

Thanks,
Tom

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Originally Posted by wrinklearthur

The other day I made a comment about starting the wrong end first, at the MC. :p

So now I am instead going to inspect the wheel bearings and change the bearings and seals as required and I bet that fixes the problem of a spongy pedal in 'Fred'.
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Before I started to restore the brakes on 'Fred', I had the computer faults read then reset and the test came up with two faults;

The brake light switch was shown as open ???
The ABS sensor on the Front LHS is too high, this will need exploring carefully.
The weather here isn't too good and the shed is full of stalled project. :thumbsdown:
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Yes, I had the sensor problem. That was a simple fix, just pulling the sensor out, cleaning it and gently tapping it back in until it was seated. I know my problem isn't wheel bearing related, they are ok at least.

I have a few new ideas to try in regards to testing the vacuum pump and the booster. Hopefully will be in Port Stephens this weekend (I so wish it was in my backyard - it would be going by now). :)

I will be going armed with new rear rotors, front brake lines and a complete set of caliper pistons and seals as well as as my pressure bleeder and hand held vacuum pump.

I will let you know how I go.


Cheers,
Tom.

Quote:

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Originally Posted by BathurstTom

Thank you for your advice. You also previously stated that there was air in the system. Please take the time to re-read the topic. You will see that the system has been manually bled, pressure bled and vacuum bled - several times. I consider myself very competent in this area, having been working on brakes for around 38 years, including motorbikes, cars and heavy vehicles (semis). I also consider that all 4 x four in Kotara are capable, they have also gone over this vehicles brakes.

I politely suggest that if you do not have a constructive answer to the problem that you refrain from inferring that people are wrong.

Thanks,
Tom

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And yet you still have a problem.

You start a thread asking for assistance and then deride someone who offers same, based on your interpretation of his posts:censored:.

Good luck with the problem.

Too wet to get much done so I took the calipers off and brought them home. New pistons and seals installed. Will fit them when I go up next time...


Tom.

I have been talking to a couple of Disco owners down here and they have told me, when bleeding the brakes to disconnect the battery to disable the ABS module.

Tapped the LHS front wheel sensor down and now the ABS light goes out and stays off. Good!

Pumped the brake pedal with engine off, the pedal goes hard and doesn't sink at all. Then started the engine with the pedal held on, the pedal goes down with the vacuum to about halfway, but now it feels spongy and wants to slowly keep sinking to the floor. Bad!

The tests were done without moving the vehicle, so I am thinking there are some lines that may still have air in them, by not moving the vehicle should rule out any possible slackness in the wheel bearings .

I was going to pop the bonnets of our two Discovery today and compare the differences of the two types of master cylinders, but I ended up changing tyres and photographing a threesome of Blue tongue lizards. Tomorrow now.

Got a quote from a brake service in Hobart for a ABS brake mastercylinder about $260, that's a lot better price for the same thing off fleabay.

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Hi Arthur, I knew about disconnecting the battery. That's in the manual. One of the things all4xfour said was that the calipers may be sticking. Having pulled them apart today, one back one may have, but the rest looked fine. They're now reconditioned. Will be going back up next week and I have a few days off to sort it out.

I'll let you know how I go.

I am still suspecting the booster - especially the valve in the back of it.

Cheers,
Tom.