Club 80-90 Forums

Ok I done this to many times before. I'm using my trusty old easybleed kit. (Having just changed the front brakes,calipers,hoses and hard lines at the front). But Ive flushed though a lot of brake fluid though all 4 wheels, twice! got though a litre of brake fluid and i still have a spongy pedal!!
Well ,its nice a solid without servo assistance,but with my foot on the pedal and I start the engine, the servo pulls the pedal down and then its spongy!
I've taken it for a drive to bed the pads in etc and it just feels horrible.
Does air get trapped anywhere in the system? I've tried pumping the brake pedal hard with the easybleed kit on and pushing the fluid though,but no more bubbles. I've run out of ideas. Thanks Steve

chapperss wrote:Well ,its nice a solid without servo assistance

So no hydraulic problem.

but with my foot on the pedal and I start the engine, the servo pulls the pedal down and then its spongy!

Sounds like the servo might be dead/dying.

Oh Bugger! It was fine last week before I took the brakes apart though, not that, that means anything. Thanks .

chapperss wrote:Oh Bugger! It was fine last week before I took the brakes apart though, not that, that means anything. Thanks .

If it's any consolation, I seem to recall reading over on Samba that a servo from an E30 BMW 3-series makes a good braking system upgrade.

before you start buying stuff readjust your rear brakes manually with the adjuster wheel..as you have changed things

Thanks, will check the adjustment, but only did it about 400miles ago as i had a leaking rear cylinder. I'll look into the BMW servo. cheers Steve.

Would a leak in the vacuum lines cause the same symptoms?

I had a similar problem on mine. I found my easy bleed was not quite functioning correctly and it was letting air back in when the pedal was released. You don't need any of that stuff anyway, just crack open a bleed nipple and let it bleed by gravity, no need to pump pedal or anything . It all bleeds very easy and I got proper pedal feel back straight away.

If this were the case would'nt I just have to push harder on the pedal to get the same braking effect,but they wouldnt be spongy? I'm just confused at the moment as to how a faulty servo could make the brakes spongy. Not questioning the Advice, just like to understand whats going on here(its my nature as a maintenance engineer). Thanks all Steve

Thanks lloydy. I Think its worth trying that, go old school and just bleed the brake by hand like I used too! got to be worth a go before I put in all that work to replace the servo.

But if there was a problem with the bleeding or the rear brake adjustment, the pedal'd be soft and long without the engine running.

I've just read this through and I'm afraid I don't see where Adrian has got that diagnosis. When brake servo's fail the symptom is a permanently hard pedal (no assistance) or the pedal going hard prematurely. A sinking pedal as the engine is started, is a positive sign that the servo is working correctly and not the reverse.
The way the original poster describes the servo action is perfectly normal, although I cannot comment on the 'degree' of sponginess or travel.
There are 'other possibilities' the most obvious being damage to the 'tandem' seals in the master cylinder after 'full pedal' bleeding. But I have to say that I would be incline to power bleed (use a pressure bleed technique) before considering replacing anything.

The OP said QUOTE Having just changed the front brakes,calipers,hoses and hard lines at the front ... did you fit new brake pads to worn disks? because if you did, that could well be the reason and there is nothing wrong with the brakes APART FROM a lengthy bedding in period.
otherwise:
My question would be (given you are saying the pedal is solid without the engine running) is there any pedal creep....slowly going down under sustained pressure.

Martin

Thanks "California Dreamin". No I dont have any pedal creep. and I have fitted new discs and pads. I've taken it for a couple of test drives and brakes are good, just spongy. you can see on the discs that the pads have got good contact. I did a few emergency stops in quick succession,all good and all discs and drums were bloody hot afterwards(I did'nt lock any wheels up though when I thought I would)
THe pedal was just so solid before I did the work. It does seem like the servo is working. I'm putting all the pressure I can on the pedal with no movement(far more than you ever would driving) and when I start the engine the pedal still goes down a good 40mm or so( I would expect a bit of movement). I've aready used a pressure brake bleeder, ie one that puts 20psi from a tyre onto the top of the master cylinder and pushed a whole litre of brake fluid though to each wheel! thats 4 litres! far more than I ever have before. I'm going to try and do a manual bleed tonight with my wife on the brake pedal and me underneath(the car not her!). Thanks all. Steve

OK, try this!
Clamp off 3 of the wheel brake hoses - careful not to danage the hoses.
You can get plastic locking pliers just for this job but they are bit expensive and I have used mole grips and 'G' and 'F' clamps to do the job.
Bleed the longest lines first, rear, one wheel at a time. Probably LHR, RHR, LHF last RHF, changing the clamping so that only the hose of the wheel being bled is not clamped.

I did find that a slight sponginess did improve as pads and shoes reseat properly over the next few miles.
In my opinion rear brake needing adjustment would cause pump up not sponginess - once pumped up.

The good part with what you have already done is that there is now good, clean, new brake fluid throughout the system!

Good luck

Ok did a full manual bleed last night, and loads of little bubbles came out. The brakes are now a bit less spongy but not perfect, I'm just going to drive it for a bit to make sure the brakes are bedded in. Hopefully it'll sort it out. But i'm getting a BMW servo to upgrade anyway so I'll see if thats makes a difference,and I might as well change the master cylinder whilst i'm at it. thanks all. Steve