Brakes slow in releasing

[eddiecross]

Hi,
Just picked up the 67 FHC from long term storage yesterday (rare break in the weather). Car going really well.
However, when I braked and then released the pedal there was a 1-2 second delay in feeling the pads retracting. No veering so I presume not a single caliper sticking.

Front brakes- new caliper seals, hoses, both cylinders rebuilt with new seals plus servo rebuilt.
Rear calipers- I just bled them and replaced rear flexible hose. So would be a possible suspect

Obvious 1st check for me would be to set at idle and lift front and rear wheels and apply brakes to see if the front and rear caliper pistons are retracting and wheels spinning freely.

After that I struggle with the complexity of the system. Are there any standard health check items you can point me to so I can run through to check that all is well with the system?

All the best
Eddie Cross

[christopher storey]

This is usually a servo fault,in which the shuttle on the servo hydraulic cylinder is sticking , but the first thing I would check is that the air valve at the front of the servo control unit ( on the front of the master cylinder ) has a. a clean filter and b. is not itself sticking . If you do the advanced search "+air +reaction +valve" on this board you should find plenty of discussion about this

here is a link to one such discussion

viewtopic.php?f=3&t=14133&p=114864&hili ... te#p114864

[eddiecross]

Many thanks Chris. Will do.
Air valve filter is new so one less item

Regards
Eddie

[Series1 Stu]

Hi Eddie

Just because your reaction valve is new doesn't necessarily mean that it isn't sticking or the vent blocked. I've had some of these where the shuttle/piston has a line of moulding flash on it and it sticks and locks the brakes on.

Carefully remove the flash with a scalpel and sand it back using very fine wet and dry.

Regards

[christopher storey]

I should also have said that with a newly rebuilt system a lack of lubrication of the rubbers can be the problem. A counter to this is to dissolve an ounce or two of red rubber grease in brake fluid and thoroughly flush the system i.e. re-bleed it using the by now reddened fluid

[eddiecross]

Thanks Chris and Stuart for the additional tips.
I was very liberal with the red rubber grease when I replaced the seals in both cylinders and servo diaphram.
I'll go on to check the reaction valve for sticking.
On the plus side both cylinders had been previously re-lined, along with the front calipers so cost was just seals and therefore minimal.
Brakes were fine before I dropped the car into storage so hopefully everything in the correct order.
As usual I wish I had taken plenty of images during the rebuilding....

Regards
Eddie Cross

[eddiecross]

Stripped out air valve. Reaction valve piston was a bit stiff.
Moved back and forth by pressing the brake pedal to move it out and pushing in with a rod.
Plate in front when I pressed brake pedal to stop it flying out.
Added as much rubber grease as possible without completely removing the piston.
It's a firmish push inwards but does move.

Refitted and tested with vacuum gauge on the air valve output connection to the rear of the servo.
Engine idling. Holds a good vacuum and drops to zero and returns to vacuum immediately when brake pressed and released. Should have done this 1st to save on dismantling.

Not road tested but I think I have eliminated this item.

Chris, if still a problem would I be looking at a sticking servo cylinder next?

Regards
Eddie

[christopher storey]

Eddie : it sounds as though you have cured it, but if there is still a problem the servo shuttle is definitely a candidate

[eddiecross]

Just back from a run. Seems to have cured it thx all.
No chance to do emergency stops but can't feel any lag or dragging when I take my foot off the brake for normal driving.

Regards
Eddie

[malcolm]

Just had exactly the same thing. New master cylinder, but the reaction valve was a bit corroded and sticking. Fixed now.

[P B-B]

Another reaction valve issue fixed.
Rear brakes now not staying on.
Thanks to the forum and all the info here

[P B-B]

Thought the image would say it all.
Brand new item. mmmmm