Sticking brakes

[Skylink]

Hi, my series 2 E Type brakes will not release for about 5 seconds after I take my foot off the brake pedal. I have cleaned the air control valve and the plunger which operates it from the master cylinder, but still the probelem is there.
Any help would be appreciated.

[Heuer]

Are the servo hoses the correct ones otherwise they can collapse under vacuum?

[Skylink]

Hi Heuer,

I will check the servo hoses, and revert, thanks.

The calipers are not sticking. I have read that the valve inside the servo unit can stick also. Have you come across that?

[Heuer]

Yes, and the fix is to use a stronger spring.

[christopher storey]

This is a perennial problem with modern brake fluids. I have had to rebuild one of mine three times as a result. I cured it eventually by buying a lifetime's supply ( a 1lb jamjar ) of red rubber grease and liberally smearing the seals in the servo " master cylinder" with it before reassembly. The old brake fluids such as Girling crimson which were widely used up to the late 60s had much more lubricity probably because they had red grease dissolved in them . Incidentally I try to use dot 3 fluid rather than dot 4 or silicone .

[Skylink]

I have checked the vacum hoses and they are all ok. The brakes seem to stick more as the car is driven more. Should I change the reaction valve before I open the servo ? Are there two springs in the servo, and which one needs to be stronger ?

[christopher storey]

Unless the spring is cracked it will be amply strong enough . The real problem is the shuttle which tends to stick for the reasons I have already set out. As David said, you can in theory overcome this by fitting a stronger spring in the vacuum chamber, ( the large chamber ) but then you upset the calibration of the whole system with unpredictable results because the vacuum may now not be sufficiently strong ( relative to the spring ) to give the requisite assistance. The reaction valve is much less likely to be the culprit. Incidentally, the fact that it gets worse as it gets driven further suggests that heat is playing its part. All 4.2 cars need a heat shield between the exhaust and the servo unit

[Skylink]

Thanks Christopher,

If I open the servo, what should I look out for and is it a matter of greasing the shuttle? Have you a previous post on this issue I should see?

[PeterCrespin]

Before you start tearing things apart, have you definitively established whether it is an hydraulic problem or a vacuum-related problem?

If you disconnect the vacuum at the manifold and plug the manifold you should have brakes that require harder pedal pressure but otherwise behave normally with no sticking after use or general dragging. If you have not performed this test under circumstances where the problem currently occurs then you could easily throw time, money and effort at the problem to no avail.

Pete

[Skylink]

Thanks Pete,

I plugged up the manifold as you said, drove the car and all is fine, no sticking, all wheels free.

[Skylink]

Hi all,

Well, after taking your advice Pete, I realised my problem was with the air system in my brakes.
I decided to start with the reaction valve.
On taking off the white cover of the reaction valve, I noticed that there was outward pressure on the cover retaining screws, which suggested that the little plunger at the end of the master cylinder was stuck in the outward position. After removing the plunger I cleaned the chamber with rolled up 400 grade fine sandpaper. I cleaned the plunger itself, and after replacing it, I checked that it moved freely before assembling the reaction valve and bleeding the front left brake.
To my horror on initial test, on car start up, all brakes locked on. I checked the reaction valve again, and noticed that the diaphram had not seated properly. Having secured the diaphram properly, the brakes are now working perfectly.

Many thanks to you Pete, and also to David and Christopher for your very valuable help and advice.
If you are ever in Southern Ireland, look me up, drinks are on me !

[Skylink]

Forgot to mention in my last post, that my initial cleaning of the plunger and master cylinder bore some time ago must not have been good enough, but following your advice Pete, I decided to check it again, before tackling the bigger job of the servo.