Rebuilt enitre system including new master, resleeved caliper pistons and booster. Experiencing about 1/2 sec delay in full release when I lift off pedal. Notice it most when system is at temp following hard application in combination w/ downshift. Both front and rear seem to remain engaged momentarily.

Tried a new booster but didn't solve problem. Installed vacuum gage between booster and reaction valve. Vacuum initiates instant pedal is released and rises to 15in hg at idle in less than a sec.

Only thing left is the "trap" valve. Seems an odd place for a valve and Bentley manual provides no info on intended function. Shouldn't flow be unrestricted in both directions?

Planning to run at Limerock and am concerned hard throttle application prior to complete release could induce wheel spin. Has anyone else experienced this delay? Is it normal and just something I should compensate for when driving?

Submitted by NC13-48859 on Tue, 06/19/2012 - 13:33

With my freshly restored 67 roadster, IÔÇÖm experiencing a similar problem. IÔÇÖm not using silicone fluid and the servo assembly is new. The severity of the problem is definitely a function of temperature. At startup, no problem. As temperature builds up in the engine compartment the brakes will lockup following braking requiring a pump on the brake pedal for the brakes to release. Any further thoughts as to what may be causing this problem?

Submitted by phil19564@1usa.com on Wed, 05/30/2012 - 17:00

I've seen that problem occasionally with the older (150, MK9, MK2, etc.) boosters, even when rebuilt, that used silicone brake fluid. A change back to the old stuff solved it. The silicone fluid seemed too thick and made the non-pressure movement slower. But, fewer problems with the E-type boosters with silicone, unless they were re-sleeved and honed too tight.

Just my thoughts,
Phil.

Submitted by mr.jwhey@rocke… on Wed, 05/30/2012 - 08:52

Craig- I replaced all the lines with new ss ones, so that's not it. thnx.

George- Reaction valve checks out ok on vacuum test. There's a small spring loaded plastic poppet valve in the fluid outlet of the master leading to the booster, which is refered to as trap valve in my Bentley manual. Not sure what purpose is- anything that restricts return flow would seem to cause problem like what I'm having.

Regards, Jay

Submitted by SW03-47225 on Wed, 05/30/2012 - 00:33

I've had the same symptoms on an old 911, the rubber bake lines to the suspension had swelled internally leaving a very small office for the brake fluid. The pressure would release, but the last 20% of the pressures took 2-3 seconds to bleed down. Remove one of the lines and take a look inside.

Craig Wright

Submitted by SE98-32482CJ on Tue, 05/29/2012 - 21:09

By "trap valve" I assume you mean the reaction valve? Sounds like it is sticking or the filter is dirty.