Brake pedal feels spongy

[anonymous-user]

Hi all

Finally got my '5 on the road over the weekend after refusbishing all 4 calipers with new seals and boots, and flushing through the brake fluid also - bled all 4 corners in the right order, took the car for a drive, then did the same again.

So, there should be no air in the systems at all but my pedal still feels spongy, the car stops but the pedal doesn't feel as firm as it used to (I've not driven it in 6 months!).

Any ideas guys? The pedal felt better previous to renewing and refurbishing the calipers and fluid so I'd have thought it would've felt firmer if anything.

[Petrolhead]

does it pump up?

[sunbeam alpine]

Sometimes you need to keep the system under pressure to bed in the seals - try pushing the brake pedal down and putting some weight on it, and leave it overnight.

[anonymous-user]

Thanks guys.

The pedal pumps up - well, it goes solid after being depressed a few times, I think this is what you mean?

Have done the obvious and checked for leaks around caliper piston dust boots, bleed nipples, where flexible lines join calipers - I used new crush washers all round when putting the lines back on so they should've sealed up nicely.

I'll try putting some weight on the pedal overnight tonight, my trusty concrete block wheel chocks will come in handy for that.

I wondered if it could be anything to do with the rear caliper adjusters as it's the 1st time I've worked on them, but did as prescribed and tightened up pads to disc then wound back half a turn?

[Mazdamender]

You still have air in the system,if she has ABS? best bleeding with her running, but make sure you do not get air in the ABS pump,it is a bh to get back out.
M-m

[anonymous-user]

Mazdamender said:

You still have air in the system

Hmmm, I've already bled all four corners twice and put a full litre bottle of brake fluid through, is it possible for air to get stuck anywhere? Its a mk.1 so doesn't have ABS.

I did them in the order NSR, OSR, NSF, OSF,

Would buying an 'easy bleed' do a better job of bleeding them than my assistant and I?! Did a thorough job as far as I could tell, made sure lots of clean fluid was coming through, only thing I can think of is that the tube wasn't fitting 100% and was letting air get sucked back up into the system.

[skinny]

how far did you crack the bleed nipples open - if you open too much then i've heard that air can get in to the caliper through the threads. when i bleed mine i like to have a fair amount of resistance behind the pedal so that it's stiff rather than flopping to the floor when i'm pumping the fluid out and never had a problem doing it that way.

also, if you are doing it by yourself, make sure the pipe rises initially out of the nipple and also that the other end is submerged in your fluid in the pot.

[anonymous-user]

skinny said:

how far did you crack the bleed nipples open

Don't know is the honest answer, my old man did that part as he's bled brakes many times over the years, never had any problems, I was the pedal pusher on this occasion.

skinny said:

make sure the pipe rises initially out of the nipple and also that the other end is submerged in your fluid in the pot.

Yeah, he actually brought up a jar of old fluid with him to submerge his tried and trusted bleed tube in, knows what he's doing!

It was him that suggested that perhaps the tube was a fraction too loose, so air may have been getting drawn back up between nipple and tube, but it seemed a pretty good fit to me.

As asked above is there anywhere that air can get trapped or should it all get forced up through the bleed nipples?

[skinny]

should all go up through the bleed points - you seem to know what you're doing so i'm guessing you never let the master cylinder level drop below minimum whilst bleeding the brakes?

also have someone watch the master cylinder whilst pressing the pedal hard to make sure it's not moving - and also make sure the flexible pipes aren't bulging or expanding under pressure... tho neither of those are something that will have changed over the bleed procedure...

lastly, aside from doing the pistons and seals, did you clean and re-grease the slider pins, and also perform a full handbrake adjustment on the rears? if you haven't got the handbrake done properly then the first bit of brake pedal travel is just going to take up the slack there.

[anonymous-user]

Cheers skinny

skinny said:

so i'm guessing you never let the master cylinder level drop below minimum whilst bleeding the brakes?

No, it was well topped up throughout with fresh Dot 4 from a brand new bottle.

skinny said:

also have someone watch the master cylinder whilst pressing the pedal hard to make sure it's not moving

Do you mean the fluid level or the actual master cylinder itself (sorry if that's a stupid question)

skinny said:

lastly, aside from doing the pistons and seals, did you clean and re-grease the slider pins, and also perform a full handbrake adjustment on the rears?

Yeah, greased the slider pins with red rubber grease, again fresh stuff, the calipers moved freely on the sliders by hand.

With regards to the handbrake all I did when I put the calipers back on was wind the piston in until the pads gripped the discs, then wound back half a turn - is that all that's required or should I have adjusted in the cabin at the actual lever too to make a difference? The handbrake does work but needs about 8 clicks to hold, that was my next job to do that but didn't think that would affect the footbraking?

Thanks again.

[anonymous-user]

as I found out when adjusting my handbrake, you need to loosen the lever linkage itself before setting the calipers. Take off the plastic cover (1 screw on the passenger side) then loosen the large vertical screw right back until its pretty loose. Then you can set the rear calipers as you have done (tighten the adjuster hex-head screw until they grip the disc, then back off 1/2 turn), then tighten the handbrake lever screw until you get a nice handbrake action with about 6 or so clicks I think it is.

Leaving the handbrake lever adjuster tight when you alter the calipers doesn't work at all, as I recently found out when I had to take it all apart about 5 times before I got it working.

Edited by anonymous-user on Monday 4th July 19:08

[skinny]

as above, ideally you want to slacken the cable off at the handle end too whilst you're adjusting, then do the caliper ends with the hex key and then tighten up the cable at the handle - you should be looking for more like 4 clicks.

as for the movement, the actual master cylinder - with high pedal force, the m/c unit can push into the engine bay slightly. if you have the standard engine bay strut brace you can make an simple and effective brace to stop the m/c moving.

Edited by skinny on Monday 4th July 19:23

[anonymous-user]

Thanks again guys. Looks like rain here today so won't get an opportunity to try the above but will report back with the results when I do!

[ronime]

Tap the calipers lightly with a hammer to dislodge any air bubbles just before bleeding. Sometimes air bubbles get stuck behind the pistons due to surface tension.