S2 brake HEADACHE!

[Paul bow]

Stroll on I’m in need of some help here guys..
So a completely new brake system, servo , master all lines the lot.
However the brakes just lock up and won’t bleed..
I’ve cracked the nuts at the slave cylinder bleed that out then tried to bleed the brakes out but after the first initial push the pedal then fills the empty lines and goes rock solid, not at all spongy, only when I slacken off again at the slave cylinder, restart again and the same conclusion!
The front brakes stay locked on, up until something is released.
I’ve taken the MC (new) apart all looks good added a little red grease on the piston.
The valve on the front of the slave cylinder (where the rear pipe attaches too) looks fine spring and shuttle good.
Short of dismantling the new servo/slave cylinder I’m all in!!!
Any ideas ?
Thanks in advance

[Paul bow]

A point to note is this is a full resto and the engine is not in the car so no servo, but should still be able get a reasonable peddle..?

[mgcjag]

Is the servo fitted......you say no servo i the car?........Steve

[Paul bow]

Hi Steve yes the servo is fitted and all the pipes connected etc but no engine ..
Just looking to bleed the system prior to fitting engine

[mgcjag]

Hi Paul.....im confused here........have you bled each corner one at a time by pushing, releasing pedal and opening closing bleed nipple.......so system now full..........then if you press the brake pedal what happens...does it just lock the front......are rears ok.. .....does pedal release? ......Steve

[christopher storey]

When you say slave cylinder, do you mean a wheel cylinder ? It sounds as though you are using some unorthodox bleeding method : the correct method is to bleed the wheel cylinder furthest from the brake pedal first, then progress to the next furthest one etc until you have bled all four wheel cylinders. You should not be bleeding at the servo at all unless you cannot get the air out by the usual method. Check before having another go that you have the servo correctly plumbed - the early 4.2s used a different plumbing from the later ones ( the diagram is all in the workshop manual ) and if you have used a combination of the two rather than one scheme or the other ( so that effectively you have plumber the servo back to the servo instead of out to the wheels , I suppose you might just get the effects you describe

[Paul bow]

Sorry for the confusion..
So… everything is connected up servo master, cylinder etc checked and double checked..
However first I had the front of the brake slave cylinder (servo) connected to the front brakes, however after talking to fosseway they informed me that the front of the servo slave cylinder with the valve on it goes to the rear of the car.. so I changed that around as suggested..
Same problem except instead of the rears being locked and not bleeding it’s now the front!
The system front and rear is full of fluid..
The front brakes at present are locked solid until I release something, then you get a pedal again up until you fill the void and then the pedal becomes solid and so brakes locked up again..
Tbh I’m lost, unless it’s the shuttle in the servo sticking, but that’s a brand new item from Sng at around £400 so I’m a bit loathe to strip it down ..
Thanks for the help

[Paul bow]

Just to add .. it’s impossible to bleed in the conventional way as the pedal becomes solid, bleeding the master cylinder first still solid pedal !! Argghhgg

[mgcjag]

Hi Paul...what do you mean..."it’s impossible to bleed in the conventional way as the pedal becomes solid, .....if you open a bleed nipple can you press the pedal easily down..then holding the pedal down you.close the nipple.......then release the pedal..........the wheel should be free to spin..........so now when you press the pedal what happens.....does the brake operate and lock the wheel.......then when you release the pedal is the wheel still locked.........Steve

[scarr27]

Hi Paul,
I have a Series 1 3.8 which I had the same problem with. I know that the 4.2 system is different but the problem sounds identical. It turned out to be the front Master Cylinder.
I posted the problem I had here:
viewtopic.php?f=3&t=18562

Maybe of no help but the main thing to note is that if the MC is being restricted from returning fully (by however small) it will hydraulically lock. In my case it was a bevelled washer that I had put in the wrong way round. Doh!
It was hard to find the problem as the push-rod had slight play in it with your foot off the brake so I assumed it had fully returned. but internally, it hadn't.

good Luck!
Sean

[Paul bow]

Thanks Sean and Mac jag…
So in answer to Mac jag that’s exactly what happens , the brakes come on (front) and stay locked solid, won’t release..
The master cylinder, servo with brake skave cylinder is all brand new, Lockheed genuine parts must be close to £700 of parts..

[abowie]

It does sound like the shuttle is sticking in your servo.

Try pressure bleeding the brakes to see if you can get fluid to come out the caliper bleed nipples.

http://www.projectetype.com/index.php/t ... ringe.html

Check to see that you do actually have holes in the servo attachments.

http://www.projectetype.com/index.php/t ... -much.html

[Paul bow]

Well this really got me puzzled..
Took the MC apart looked fine but still the same pump the brakes get pressure and it locks up solid, even when you undo the bleed nipples on calliper still solid, it’s not until you crack off the servo slave cylinder pressure is released.
What a day 🫣

[mgcjag]

Hi Paul...you said in a post above......"first I had the front of the brake slave cylinder (servo) connected to the front brakes, however after talking to fosseway they informed me that the front of the servo slave cylinder with the valve on it goes to the rear of the car"..............what is the valve your refering to?.....you also said that you swapped the front/rear connections and the locking changes front/rear......so the problem i would think is the servo/slave or master piston not moveing rearwards enough to let fluid release back to the reservoir....ensure all the internal parts are connected in the correct order and the right way around as mentioned in a post above the beveled washer the wrong way around can prevent the master fully releasing..... Steve

[Paul bow]

Hi Steve
So back at it again on the servo on the output terminals (to callipers) one of these the front junc on my servo has a large removable stubby bolt in which the brake line connects to, remove this and you’ll find a small plastic piston with a tiny hole in it and a spring, the spring sits in the servo mc and then the Liston then the large stubby bolt and the REAR line goes to that..
Upon inspection this am when the pedal is depressed zero fluid comes out of that junction even with everything removed, the pedal is rock solid,
I’ve checked double checked and tbh it’s pretty impossible to run the lines incorrectly.. all seemed well ??

[Paul bow]

I should point out that I have a solid pedal and front brakes are locked on.. the rear brake line to the servo is not attached and zero fluid is coming out…

[Paul bow]

..and so
When I crack the front brake pipe at the servo as expected the front brakes free up and then fluid comes out for the rear brakes (from the servo)

[mgcjag]

Pm sent

[gtjoey]

Paul, Welcome to the world of CRAP PARTS....
Its your master, find an ORIGINAL and resleeve and refit.
If your NEW MASTER is from INDIA or China the little valve is usual crushed when the top middle fitting is put together binding the shaft.
You will see. its plain to see. Been there done that .
On average you will go through 10 masters to get 2 that work.
Find an original and resleeve.
Good luck, its the proportion part which is locking up your brakes......
gtjoey1314

[Paul bow]

Thank you GT joey for that info and my friend you are absolutely correct!!
I ordered another servo bolted it on in 30mins brakes solid all around!!!
That’s a full 2 days down the pan!
Anyhow special thanks to Steve been no end of help, sorted!
Cheers guys