Hi, I have fitted a new brake booster and brake master cylinder on my Mercury Montclair from 1957. The vacuum booster is 7 inches and the main brake cylinder having a two circuit which is a corvette cylinder. I have all the drums left when I was only looking to get a two circuit system. I have kept my old vacuum tank left in the system to provide a stable vacuum. I have made a separate intermediate plate and kept the old bracket in the torpedo wall from the original Bendix brake booster. All push rod from the pedal is original to the torpedo wall. On the new vacuum booster, I have measured a new push rod that fits the old bracket from the pedal. I already have a vacuum gauge mounted in the car. I have also checked that all the rods and settings on the rods are okay. So as to avoid that the brakes can be on. Now that I have bled the system and tested the car so I have no function of the brake servo. It's just like having brakes, with out no brake servo. You have to press the pedal hard. I do not see any change in the vacuum, It is stable on the meter. Could it be the valve on brake booster that do not work? Does anyone have any tips what could be the problem. I have no vacuum leaks.

Drives: Mercury Montclair 1957th

www.mercury1957.com

Swedkarla,

Your post is a little hard to read but I'll try to answer anyway. You mention that an original tank was left and that you have run the new booster from that? I'd try direct hose from the booster to the manifold that way you can see if there are other issues with remaining valves etc.

Also with the booster, many of us are using dual diaphram 7" booster with a corvette master. If it's a single it may not be enough.

just some ideas.

Warren

Grizzly (Aussie Mainline)

Thank you for taking the time! I hope you can read a little bit of my bad english. I have already tried what you said and there was no difference. It may be that I need a double as you say. I will try to replace it. Thanks again.

Drives: Mercury Montclair 1957th

www.mercury1957.com

Are you certain that booster is not already a dual diaphragm type?If you purchased those together from one of the USA suppliers you likely have a dual.Thats how they can make them smaller and still work like a bigger one.It is possble you have a defective one.I would contact the supplier and expain the problem.I have a similar setup on mine and it works great.

  

Before you blame the booster, just make sure you have everything adjusted correctly. There should be a little free play on the master cylinder pushrod. Also make sure you have the brakes fully adjusted.

You will then have taken a couple of variables out of the problem. If you are using the setups that are sold on eBay, they are very simple and extremely reliable.

Regards

Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

I forgot to mention that there is a simple way to check the booster. With the engine off, drain the booster of vacuum by pushing the brakes on and off several times. Then when you have no vacuum push the brake pedal in fully - it should feel hard. Start the engine and the pedal should sink a bit as the engine fires up. This may not work that well with your setup with an extra vacuum tank though. I would bypass it for the purpose of the test.

If the pedal does not sink the booster is not working.

Regards

Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

As you are using a separate vacuum tank, likely the vacuum tank has a check valve on the supply line. The booster also has a check valve on the supply line. If the vacuum hoses are reversed on the auxiliary tank the engine will be trying to pull a vacuum against the closed check valve. Your pedal will be very heavy as the booster will not getting the vacuum assist.



Check to see if the hook up is correct. I will try to explain the way to do the hook up.



From the engine run a hose (should always use proper vacuum hose as it is much heavier than fuel line hose so will not collapse and close off the supply) to the inlet of the vacuum tank check valve fitting (it is usually that plastic looking thing or on the older tank check valves it will look like a brass bullet or be a pot medal piece on the supply side of the tank) then run another hose from the outlet side of the vacuum tank to the booster. The spare vacuum tank will act as an additional source of vacuum.



The check valves are inline to prevent a backfire from rupturing the diaphragm in your booster as well will hold a vacuum for a couple of brake applications if your engine should stall, acts as a safety feature, a vacuum reserve pot.

marv

Hi,

Thanks for all the tips!

The booster I get was a Single 7 inch (It was too small). I contacted the guy I bought it from and he had a dual booster left. I also change the brake cylinder when the dual booster had a longer push rod at the front (The old one had a shorter plug pressing against it). Now everything works as it should. Thanks again for all the advice you have given me. I've posted some pictures on my website if you want to see the results.



http://mercury1957.com/mercury1957_photo.php

Drives: Mercury Montclair 1957th

www.mercury1957.com

Glad to hear you got it straightened out.Thats a very nice Mercury you have.I noticed the mounting bracket for the booster.Did you fab that or was that supplied with the booster?Thanks for posting the pics.

  

I work in a CNC milling machine so I have access to the minor things. So this spacer plate, I milled for myself in aluminum. I have also drilled and refurbished engine itself two years ago. I have thought that in the future to order a Y block engine from Tim McMaster with a little more powder in. For the 368 cc engine, there is not so much parts to get hold of if you want to trim. Then it is better with a block of 292 or 312 engines.

Drives: Mercury Montclair 1957th

www.mercury1957.com