Brake problem - Holding on

[D Murton]

Had a grand day out yesterday. 180 miles up through Thetford, Swaffham & Fakenham to Wells, along the coast to Cromer & home via Norwich & the 4a ran perfectly except for a problem on the way home.

In stop/start traffic through Norwich it felt as though the front brakes were hanging on under light braking although they were releasing as soon as I got moving.

Then on a couple of occasions the brake pedal had no movement at all when pressed although another press and it returned to normal..

I am guessing that this must be either sticking pistons in the caliper or pads tight on the pins.

The car has a servo fitted & uses Dot4 fluid.

Its going to be be a couple of weeks before I can have a good look.

Any other suggestions what could cause this?

 

Thanks

 

Dave

[RogerH]

Hi Dave,

not too sure but isn't there a valve in the master cylinder that allows the pressure from the 'on brakes' to be relieved when you take your foot off the pedal -

could be sticking closed!!

[Ade-TR4]

Could be a sticky servo.

I had a similar issue with a Lockheed unit

Cheers

Adey

[shroptr]

hi had a problem on the tr4 last week, had put new caliphers and hoses on so automacticaly thougth it was those, after an 8 hour rush to fix (we were off to normandy that night) it turned out to be the brake restrictor valve see link, took the guts out and drove 950 miles to normandy and back no probs

all the best simon

 

http://www.britishcarforum.com/bcforum/ubbthreads.php/topics/378136/Re_TR3_Restrictor_Valve

[JFerg]

A master cylinder over-adjusted will have the same effect; back it off a smidge to give more play and you may well solve the problem.

 

JFerg

[D Murton]

Thanks for the replies

 

My 4A doesn't have a restrictor fitted & I,m fairly sure that the valve in the master cylinder just stops the fluid returning to the reservoir,

 

Is there any way that a servo can be tested? Would it be OK to disconnect the servo from the manifold & plug the manifold & try it like that?

 

Dave

[pfenlon]

Dave a simple test for a servo to see if its working is to pump the pedal a couple of times without the engine running, and with your foot still on the pedal start the engine and the pedal should go down a little, if it doesnt the servo's goosed.

[Allan Jezzard]

Just had a similar experience on the back brakes of my 6. It proved to be a flexi hose interior breaking down, effectively turning it into a non return valve. Replacing the two hoses with braded versions cured the problem instantly.

[D Murton]

Hi all

 

As an update to my post I disconnected the servo vacuum pipe and the problem with the brakes holding on has disappeared so obviously the servo needs replacing.

Having checked all the usual suspects the price of a replacement varies considerably from about £95 to over £200

While I am a great believer in you get what you pay for this does seem a big difference.

Has anyone bought a servo recently.& where from?

 

Thanks

 

Dave

[Ade-TR4]

The cheap and cheerful servos are based on the lockheed-6. Kits can be had for £65 upwards on fleabay and work fine.

Original Girling/ Bendix Mot-a-vat units are considerably more expensive, especially if they require an overhaul.

Cheers

Ade