i would like to disable, assuming it's safe to drive it afterwards, the power braking on my mk2. it is sticking in the on position and i often have to tap the pedal several times after application to fully release the brakes. if so, how would one go about that?

is it as simple as denying the servo a vacuum? possibly by pulling the vacuum line off the check valve, assuming there is one, or something similar?

 

Remove vacuum feed & block to inlet manifold.

 

Sounds like you have a sticking reaction valve. There is a small bore with a piston under the vacuum diaphragm that is usually in a white plastic housing. Remove the housing, remove diaphragm and you can see the end of a small piston. That is sticking in the bore due to rust and can't move properly. If you remove that (brake pressure will force it out), polish the bore with fine (1500-2000 grit) sandpaper and reinstall, then the brakes should work as intended.

I made a mechanism so I could do this myself, all it is is some metal to keep the little piston from coming out of the bore and flying across the garage and disappearing when I step on the brake. If you have a helper, have them put a rag over the bore to catch the piston and that's all you need.

Brake fluid will come out when the piston is removed, so either plug it or be prepared to catch some fluid and refill the reservoir.

In the photo, the piston is behind the hex screwdriver bit I have under the metal bar. The bar and bolts are nothing but a catch mechanism so I could do it by myself. You can see the rust in the bore around the screwdriver bit. This is always open to the atmosphere, so can rust easily.

Once you have cleaned the bore with a small cylinder of sandpaper, put some clean brake fluid on the seals of the piston and reinstall. You should have properly functioning brakes again.

 

would that be a hose connected somewhere on the fuel/air intake manifold on the head? the hose that then leads to the booster mechanism?

 

yes, your assumption is correct. that is exactly the problem i'm trying to solve.

had the car on a lift yesterday with a mech and we were looking at the servo. but what confuses me is that the brake master cylinder is on the left side firewall just above the pedal on my LHD car, where one would expect it to be, yet the servo, and it's white (approximately five inch) circular plastic piston apparatus is way down low in the engine bay, halfway into the right front wheel well!

do i have this right??? *headscratch*

and is it possible to do this, not that i think you should necessarily know, without removing the servo from the engine bay?

 

You do have it right. It's a remote servo.

Yes, this can be done with the servo in place. It's not very complicated, once you get to it. The screws on the housing are probably Pozidrive, rather than a phillips, and a stubby screwdriver helps.

 

thanks so very much. i think i have the confidence to take a crack at it now!

...poziIdrive!!! why do they have to keep improving everything?

 

Pozi is very common in Europe. It is designed to grip, while philips is designed to slip out. Phillips was invented to limit torque on assembly before automatic torque limiting machines were invented.

The easy way to tell a pozi is the hash mark at 45 degrees to the main slots.

 

Jagboi’s description of the cause and of the solution is correct . i had exactly the same issue on my Mk2 which became increasingly worse. Removing the piston and cleaning fixed the problem.

 

Yes there is a metal hose from the inlet manifold. This would take the booster out of circuit. I agree with JB's comments as a possible fault. Your booster might require further attention however. i.e. A full rebuild

 

Refresh page for picture.

 

Barratts offer a complete rebuild service. They do a beautiful job but are expensive. An option is a far cheaper Lockheed booster/servo which requires minor pipework rejigging.

This is Barratts rebuild standard & what I did.

 

1965 Season changes: The next changes came in October 1964. They affected the brakes and the manual gearbox from Moss to full synchro. The brakes simply gained a bigger servo (with an 8in diameter instead of the earlier 6.875in diameter) so that lower pedal pressures were needed ~ 8" shown above.

 

ah HA!

if a picture is worth a thousand words...one with a big yellow arrow is even better! many thanks.

 

Only a pleasure Huey! ~ I'm a picture man as I'm sure you have noticed on this forum.

 

good to know, thanks.

the car sat in goodness knows where for over a year recently in somewhere other than central california, where it experienced a real winter for the first time in its life. not surprising that a piece of raw steel exposed to the atmosphere has rusted.

now that i know what's going on, i may even concede and give my lazy side a shot at it, do nothing, and hope that exercising it will work out the rust. maybe not the best choice, i know, and can easily fail... but it has never failed to be easy.

 

Expensive option:




Cheaper option:

 

I fitted a Lockheed LR18230 when my OEM unit failed, and the reconditioned C24707 they sent me also failed when first fitted. My Lockheed unit was also black not cadmium plated. It also needed be modified to fit as the mounting points were slightly different.

 

Going back to Huey's original question, I've never driven a Mk2 without a servo. The servo gives a boost ratio of around 3:1 and some go to 4:1, a lot of assistance. The cylinders at the wheels are not very large diameter and require a lot of pressure to produce a decent force against the disc. So if you try to go without the assistance, it's advisable to do some testing in a safe place before going onto the public road. It might be worth checking the strength of the seat mounting as well as you're going to be pressing mighty hard in an emergency stop.

 

The 8" is 4 to 1