Bleedin AP brakes! and a spongey pedal.

[adam quantrill]

I just noticed my Lockheed AP 4-pot calipers have 4 bleed nipples on each!
What do you do with them - is there a sequence for bleeding these things, or flushing out/replacing the fluid?

I also have a spongey brake pedal, it seems fine until the vacuum assist is on there and then there's a few inches of travel before the brakes start to bite. Reading some previous posts this may well be the master cylinder on its way out? I was hoping bleeding the brakes might help but it didn't seem to.

[mrzigazaga]

Hi Adam..Mine have four bleed nipples also..ooo missus...I seem to recall reading that you bleed the highest point first..When my servo was leaking the pedal felt how you have described..I changed the MC but there was no difference..On closer inspection you could hear the air escaping in the footwell when the pedal was depressed..We built the pressure up again and switched the engine off and you could definitely hear it..Ziga

[adam quantrill]

Do you mean a little "whoosh" when you press the pedal, until the vacuum is all used up? I thought that was normal. I'll keep it in mind though. I think I get about three presses until the servo stops working (engine off of course), which seems reasonably normal.

Will replace the (almost used up) pads first though.

[ElvisWedgely]

Switch engine off. Press brake pedal firmly and keep it pressed. Start the engine. If the pedal sinks a little with the pressure under your foot, the servo is working. Suspect either a leak in the system, faulty master cylinder or air in system.

Tony. TCB.

[Campbell]

This also could be cooked fluid in the calipers, if you going to run new fluid through, i pull it through all the nipples, that way i know they are all working, you could do it the old fashond way and get some one to press the pedal or use a pressure bleeder or a vacume bleeder, im all for the vacume system, also what condition are all you flexies in, ive replaced the rear as the fronts were on braded SS and what a difference in feel, i recon the rear was changing shape but DOT4 is prity cheep to so if they havent beed done for a few years start there as im sure the fluid should be replaced every 2 to 3 years...

How big is the mot list?...

[adam quantrill]

20 items - it's a record! But 6 fails 2 easy (washer motor has just packed up). 2 non-existent (UJ play). Spongey brakes are the biggest problem to solve.

[wild rover]

Go for the vacuum bleeder with new fluid, works a treat.

[adam quantrill]

I've heard of a pressure bleeder but how does a vacuum one work - sucking through the bleed nipple? Is there an extra reservoir extending the capacity - the usual problem being that the top runs out if you don't keep topping it up....

[mrzigazaga]

adam quantrill said:

Do you mean a little "whoosh" when you press the pedal. I think I get about three presses until the servo stops working (engine off of course), which seems reasonably normal.

Hi Mate..Mine used all the air in one push of the pedal..Almost like a hissing after the pedal was depressed..By the sound of it yours is working ok...Ziga

[B@man]

I had a right ball ache bleeding mine after fitting rebuilt calipers and new flexi's I bought one of those gunstons pressure bleeding kits that connect to a tyre valve (and have a reservoir for extra fluid) wish I'd bought one years ago turned a nightmare into a quick n simple task.

I think my Master Cyl is on the way out as well, the feel of the pedal is not consistent, sometimes it's great and stops well and other times are brown trouser jobs.... It's on the winter list !!

[Number 7]

I change the fluid in mine every year - I helps avoid problems on trackdays - I use the Gunsons pressure bleeder hooked up to one of the wedge tyres, and I work from the rear to the front, from n/s to o/s and from the lowest of the nipples on each caliper to the highest. Never had any problems and it means you don't need a helper.

[adam quantrill]

Well I tried the "Elvis" method and the pedal went down on starting the engine. I also checked the "Zig" method and actually the reservoir is quite quiet unless you really press the pedal hard. No hissing.

So I think the vacuum assist is fine. More bleeding/fluid replacing for the rear calipers to go, and I'll start fitting fresh pads when they arrive. I have an old but working master that might go on if no other joy.

[wild rover]

Draper do the vacuum kit which attaches to the compressor, they also supply a spare reservoir to ensure a fresh supply of fluid, saves the possibility of damaging seals.

[GV]

I got sick of bleeding copious ammounts of nipples and ended up swapping my APs for a set of Hi Specs. Brakes are much more confident and the steering appears lighter too. Good upgrade IMO.

[dixiebabes]

adam quantrill said:

I just noticed my Lockheed AP 4-pot calipers have 4 bleed nipples on each!
What do you do with them - is there a sequence for bleeding these things, or flushing out/replacing the fluid?

I also have a spongey brake pedal, it seems fine until the vacuum assist is on there and then there's a few inches of travel before the brakes start to bite. Reading some previous posts this may well be the master cylinder on its way out? I was hoping bleeding the brakes might help but it didn't seem to.

Adam I changed my master cylinder after the same symptoms. Not much different I think its just air. I haven't had chance to try and bleed mine again. Away offshore so it will have to wait till I get back but will need to get them done before the rusty.

Dix

[adam quantrill]

Yes in the end I stuck on my spare master cylinder. I have a suspicion that on the original one, the rearmost joint between the reservoir and the cylinder is letting air in occasionally. So you could bleed it, but it would occasionally go floppy again. (Fnarr fnarr)

As the original one has only done 50k miles I'm going to get a seal kit for it. The replacement is off my old white wedge that did 100k+++ and has been on the shelf for 15 years (with all ports sealed up of course) but nevertheless works perfectly. Even so I'd like a fresh replacement.

[rev-erend]

Just bleed the highest points.. ignore the others.