What could cause brake-pressure build-up, only when engine is running? When turning off the engine, the brakes seem to be fine, but when starting the engine again, pressure is building up and the brake pedal feels like a brick...

Any kind of help would be greatly appreciated.

If the servo needs to be replaced, what do you think of an aftermarket servo?

 

you do mean the BRAKES and BRAKE SERVO, correct?

 

Yes I do.

 

I would contact someone in the brake booster rebuild business, like this company:

Booster Dewey Power Brake Booster Exchange Inc.

overall, it sounds like a bad booster or vacuum issue, there are ways to check it but I do not want to advise on brake issues, it is a Safety issue and I am no expert in the matter.

 

The original boosters are maintainable, as I remember stripping mine down to replace the hydraulic seals. The push rod setting needs a depth gauge, which is normally part of a vernier caliper. I remember having to buy one to do the job. There were some instructions on the setting too, but it was in the 80s so I can't remember any more.

SNG Barratt have the servo on an exchange basis or you can get kits for the wearing parts and do it yourself, but you need to know what you're doing as your life may depend on it ! I did mine, and I'm still here !!

http://www.sngbarratt.com/ProductDet...d54cd8f560&l=7

 

Thanks for your replies! Much appreciated.
I have replaced all the seals and gaskets and at first the brake pressure remained for several seconds after taking the foot off the brake pedal, even with the engine turned off, so we took it apart again and shortened the long rod 1 mm, shortened the short diagonal rod somewhat since the return valve there was leaking a little, I also grinded a little on the concave washer to make it move better in the cylinder. The lid was tightened/sealed better since it leaked a little after reassembly, which showed it self in bad idle performance and bad accelerate response.
This solved some of the problems, but sadly not all.

Unfortunately I couldn't find any e-mail address in the provided link...

 

For a slightly uprated servo with higher boost you could look at this too.. Works great with a MK2
http://www.sngbarratt.com/PartSearch...partno=LR18230


.

 

SNG:
the link posted takes one to the SELECT YOUR COUNTRY page, not to the part image.

 

Hmm, it works for me.

 

This is the exact one that I ordered for my S-Type. A lot cheaper, higher boost, and no exchange.

 

Got it. Many thanks! Servo ordered. Hoping that solves the problem.

 

for the future...

 

Hi, many thanks for the picture, but that must be a different booster, than the one we've been working on... Could that be S-type booster?