Spongy Brakes

[alfwayliner]

My 2.0 HDI 110 estate has just failed it's MOT due to spongy brake pedal. I've tried bleeding the brakes a number of times but got nowhere. I changed the master cylinder and bled them again, no change. I took it round to a local garage and they bed the thing a few times and faffed around a bit and said they couldn't find the fault but suggested it could be the ABS Pump.

Symptoms are that the brake pedal has a lot of travel but if you release it and press again the pedal behaves as it should, The servo and vacuum appear to be working according to the tests in the haynes manual.

Could the ABS pump be the problem? or does anyone have any suggestions

[mjb]

I wonder if one of your brakes is leaking air back in?

[alfwayliner]

Thanks for the quick response.

If air is being drawn back in then would that not indicate a poor seal and as pressure is applied through the system, result in a leak of fluid at some point?

[mjb]

maybe, but air can fit through gaps a hell of a lot smaller than brake fluid can... anyhow, don't take what I'm saying as gospel, it's just an idea I had

[teamster1975]

The fluid may be knackered; I had the same problem on an ashtray and when I bled the fluid through it was all aerated.
Also check that the diaphragm is making a good seal on the reservoir!

[djheath]

Are the flexible brake lines ok? They could be knackered and ballooning when pressure is applied perhaps?

[alfwayliner]

The fluid may be knackered; I had the same problem on an ashtray and when I bled the fluid through it was all aerated.
Also check that the diaphragm is making a good seal on the reservoir!

Between me and the local garage we've put about three litres of new fluid in and the reservoir is fully sealed.

[alfwayliner]

Are the flexible brake lines ok? They could be knackered and ballooning when pressure is applied perhaps?

They look ok to me and the garage never commented on them.

[alfwayliner]

In the absence of any repsonses I was wondering how exactly do they bleed the ABS unit and would this be a costly job.

Also if I bought either a new or second hand unit wouldn't that need bleeding as well?

[steve_earwig]

According to Haynes they use some sort of test rig, might be worth a call. We did have someone else come on here with impossible to bleed brakes but I think he gave up on us before we figured it out

I can't think of much else to suggest, the estates have a load valve on the rear axle that might be stopping you getting all the fluid through, seized caliper that's flexing the disk, warped disk that's flinging the pads too far back... clutching at straws I know. We do have bods on here that know a heck of a lot more than I do so give us a chance before you put a match to it...

[alfwayliner]

According to Haynes they use some sort of test rig, might be worth a call. We did have someone else come on here with impossible to bleed brakes but I think he gave up on us before we figured it out

Yeah got that bit out the haynes myself, seems it's all something of a black art.

I can't think of much else to suggest, the estates have a load valve on the rear axle that might be stopping you getting all the fluid through, seized caliper that's flexing the disk, warped disk that's flinging the pads too far back... clutching at straws I know. We do have bods on here that know a heck of a lot more than I do so give us a chance before you put a match to it...

Mechanically the brakes are sound and do stop the car and dont bind. I'll give it anotehr 24 hours and then give a local dealer a call and get them to plug it into whatever it is they plug it into. I just hope it's not going to be an expensive job, but it'll get sorted as it's been a bloody good car, I've just had the cambelt and water pump done by Jasper5, i'm getting 50 mpg and it only failed the MOT on the spongy brakes so it's good for at least another 12 months once I've sorted the brakes!

[alfwayliner]

Well I've got caliper rebuild kits and some goodridge hoses, so I'll have a go at this again at the weekend and see what happens if it doesn't clear it then I'll risk a trip to he d£al£r$

[alfwayliner]

Oh well, due to work commitments and the good old British Summer, I've just got round to fitting the caliper kits and hoses and I've still got the same old problem!!!!

I've stripped down and rebuilt all four calipers with the new seals and goodridge hoses, bleeding and testing after each one and still have the same problem.

The brakes have a lot of travel and appear to be creeping down when you keep foot pressure down with the engine switched on.

With the engine off the brake pedal will firm up and creep down when the engine is turned on so I thnk the servo is OK.

I'm going to call the local dealers tomorrow and get them to have a look as I really can't be arsed spending any more time on it.

I'll post an update when I get something to report

P

[alfwayliner]

Bollox, just giving the car a clean out after all the work I did and I knocked the handbrake side ways slightly and now it looks like I've broke the tooth on the ratchet as it won't lock off!!!!

had to take he console off and look at the thing and I cant see any way to get inside the thing to get it sorted, any ideas? or is it a visit to the scrappy!

[Panda]

Hello,

I did something similar to my handbrake when I had the back brakes apart and the handbrake cable was disconnected. This resulted in the cable slipping out of its guide and getting kinked / trapped by the handbrake lever ratchet assembly. The effect was that the handbrake lever wouldn't go down fully as the cable was snagging. I had to replace the main cable assembly as it was damaged. This unfortunately involves removing the middle section of the exhaust to get access to it where it passes through the floor.

Now to your spongey brake problem. This still sounds like air in a caliper to me. Haynes says you must disconnect the battery before going near the brakes to avoid getting air in the ABS pump but I'm not convinced - does anyone know how this could happen. I read somewhere that on the 405 rear calipers when the rear of the vehicle is jacked up, the trailing arms drop and the bleed nipple is no longer at the highest point, thus preventing effective bleeding. Not sure if this is the same on the 406 - when I last bled my 406 rear calipers I did it without jacking up the car and it seemed to work OK. Either way, clamping the flexible brake hoses one by one (or two at a time) might be the best way to troubleshoot where the air is.