Spongy brakes - advice needed please

[tyasman]

I have a '70 S4. Standard throughout. Ever since I bought it (approx 3 years ago) the brakes have needed a second push to get good pressure, and the pedal was a long way down its travel on the first push. I lived with it. It would stop the car on the first push if necessary, so no danger involved.
Thinking the brakes needed bleeding, we stripped them down and serviced the calipers. All brakes were bled, and there is definitely no air in the system. The reservoir is full. I still have the same problem with pumping twice to get good pressure.
Has anyone got any experience of this with advice to offer?
Thanks for answers.

[billwill]

Has a previous owner taken out the brake servo and not fitted a suitable replacement master cylinder?

It may be that your brake servo needs re-furbishing.

[neilsjuke]

?are the rubber hoses ok . Bypass the servo and give it a try. Then look at the master cylinder dont mess about with a kit get a new one .
Neil

[Robbie693]

My Plus 2 is similar, I have new master cylinder, braided hoses and new calipers on the front. All pistons move easily in the calipers. I put it down to the Lockheed servo (which is also new). Do you happen to have one fitted also?

Robbie

[AussieJohn]

I have suffered with this problem for years as well; finally traced to front caliper pistons having too much pullback. A friend has also just gone through the same thing. He found that there were variations in seal sizes; some of the replacements were too big a diameter and caused this problem. Measure the piston pullback!

[europatek]

I've experienced this in my Elan and a couple of Mk1 Cortinas. Each time it's been the master cylinder.
A service kit sorts the problem if the cylinder bore is ok. Otherwise a new cylinder or a sleeve will be required.

[europatek]

I've experienced this in my Elan and a couple of Mk1 Cortinas. Each time it's been the master cylinder.
A service kit sorts the problem if the cylinder bore is ok. Otherwise a new cylinder or a sleeve will be required.

[Allison]

This is a problem we have on one of our two Elans. I cured it by fitting a longer shaft between pedal and master cylinder - but as with all these things that gave excellent brakes except that the clutch had very little movement when fully depressed before engaging. To try to solve that I jiggled the pedal box mounting on the outer mounting plate to bring it as far forward as possible. That improved the clutch but my longer brake shaft was now fouling the steering joint!
So I removed that and put the original shaft back in - so both clutch and brake are now lower than they should be but are almost acceptable! Plan C is yet to be devised but I think a mark 2 shaft is in there somewhere!
I have no doubt there's a simple answer and whilst slave cylinder pull back is a factor when putting new pads on I don't think its the solution here.
Peter

[CBUEB1771]

the brakes have needed a second push to get good pressure, and the pedal was a long way down its travel on the first push.

Also check the front wheel bearing end float. The first time I replaced the front wheel bearings in my +2 I had exactly the same brake behavior. I had incorrectly adjusted the castellated nut to give two much end float. This allows the brake discs to knock the pads back into the calipers too far causing long pedal movement on the first stroke and normal behavior on the second. I recall that the shop manual can be misinterpreted resulting in excessive end float.

[Tonyw]

I would check to see if the brake master cylinder piston is of the correct diameter, then temporarily by-pass the booster to see if that helps.

Tony W

[Leo Leentvaar]

Just out of curiousity. To my recollection the Lockheed servo (the big thingy in the front of the engine bay) is supposed to be actuated on the second time you press the brake pedal, right???
I have to prod the pedal twice to increase stopping power. When I let the car roll out towards a traffic light I only depress the pedal slightly. When I need to come to full stop/decellerate I prod it twice and then it really bites. Took me a wee while to get used to but I always assumed this was normal.( pedal travel is minimal on my car)
Anyhow hope yours gets sorted mate

[oldelanman]

To my recollection the Lockheed servo (the big thingy in the front of the engine bay) is supposed to be actuated on the second time you press the brake pedal, right???

Absolutely not !!! You should not have to pump the pedal to get the brakes to work fully - supposing you have to do an emergency stop, you would want them to operate immediately ! Check for the possible problems suggested above including air trapped in the servo itself - they can be difficult to bleed properly. Try bleeding with the engine running to get the servo secondary piston moving that may help.

Best regards,

[kstrutt11]

I replaced everything and fitted braided hoses, still had a spongy pedal, then I removed the servo fitted a smaller bore master cylinder (should make pedal feel worse) and green stuff pads, it now has a rock hard and nicely progressive pedal.

[simonknee]

This is not correct operation. In my case the cause was rear bearing seized (wore a deep groove in the axle). The resultant wobbly disc would push the pads out.

Whilst I did the recent major overhaul I used a seals kit on the master cylinder. The unit promptly failed after a few hundred miles. Next time I will just buy a new one straight away as you can't always guarantee you'll be doing 10mph in Peckham rather than 70mph on the M1 when it gives up.

Also added braided lines.

One push brakes every time. Lovely.