Power Brake booster question-54 mercury

[Bob from Northport]

I have a 54 Mercury that the previous owner installed a power brake after market unit on. The brakes are a hard pedal, but the car does stop. I was removing some of the steel lines on the engine to clean before installing a rebuilt carburetor. When I went to remove the rubber line connection to the booster, there was considerable vacuum still on the line. It came from the fitting the hose connects to on the booster. The car had been sitting unstarted for about a week and a half. Shouldn't the vacuum have bleed off by that time?? Does that indicate a problem with the booster unit??

 

[miker98038]

There’s typically a check valve between the vacuum source and the booster to give at least one stop with the engine dead. That it would hold the vacuum for a week kind of surprises me, but that would be it. I’m not used to things working right.

 

[KULTULZ]

Need a photo(s) of the install.

 

[Bob from Northport]

Here are two photos I have of the install. There is another hose from the connection that runs down under the left side of the engine. No idea yet what that hose is connected to for vacuum. It is a three way hose connection to vacuum

 

[miker98038]

Is the vacuum source the intake manifold or carb fitting? Brakes still drums? I’ve seen vehicles with vacuum canisters, might that be where the 3rd hose goes?

Anything that says what the master cylinder is that is on there?

The problem with those aftermarket kits is while they might work and be safe, it’s hard to identify the components.

When you say the pedal is hard, do you mean you have to push really hard to stop, or that it goes down and stops firmly with no sponginess?

I’m trying to help, not be a wise ***.

 

[KULTULZ]

There is a vacuum reservoir under the car. It was used for the TREADLE-VAC BOOSTER. That is where your excess vacuum is coming from.

If you decide to remove, please don't shiat-can.

If the pedal is hard on power assist, either there is no/little vacuum or the wheel cylinder(s) piston(s) may be frozen.

 

[Ford blue blood]

I would check the linkage between the pedal/booster and booster/master cylinder. I agree with KULTULZ there used to be a Treadlevac in there.

 

[KULTULZ]

I would check the linkage between the pedal/booster and booster/master cylinder. I agree with KULTULZ there used to be a Treadlevac in there.

​

You're right!

... cough ... cough ... Let me get these cobwebs out of my lungs ...

There is a tech problem going from TREADLE-VAC POWER to later style booster power and it had to do with the push-rod. It seems one had to used the STD BRAKE push-rod.

There is a complete thread here somewhere (I can never find anything) that describes the conversion.

 

[KULTULZ]

Here 'ya go - https://www.jalopyjournal.com/forum/threads/1954-lincoln-brake-swap-question.1271208/

Same car, same problem.

 

[miker98038]

Nice find K.

It’s hell to get old and not remember things. I went thru the treadlevac linkage problem on a 56 Chev conversion some years ago. Just remembered.

 

[KULTULZ]

It is getting embarrassing. There were a few discussions like this just a short while ago on LINC-MERC.

FORD BLUE BIRD deserves the credit as he rattled my cage .. zzzz

 

[Bob from Northport]

miker98038-
1. The vacuum source is from the manifold, big brass fittings to the hose that runs toward the booster.
2. There is NO ID on this unit. Just gone by photos to see its an aftermarket unit. One source says the bore size on the master cylinder maybe too large in diameter.
3. Pushing the pedal down is like it is a manual brake pedal. I have a close friend who owns a 50 Ford Crestliner, and the power brakes on that car are stellar. Just like a GM.
Put you through the windshield if you really hi them hard. They are drum brakes. I paln to change out all the lines and cylinders this winter.
You and Mr. KULTULZ are a great source of information. I greatly appreciate all you are giving me.
I will have to look under the car tomorrow and see if there is another canister there.
Thanks for the article in the conversion.

 

[KULTULZ]

Attached are ILL of both the MANUAL BRAKE PEDAL and POWER BRAKE PEDAL setup -

 

[miker98038]

Study the link K sent. I went down the wrong rabbit hole, forgetting the Merc was a high line car and kept thinking about the remote unit used by Fords. The treadle vac was found on nicer cars most of the time. Worked good, but expensive to rebuild these days.

A lot of the problem may be in the linkage you’ll just have to look.

I’ve been around a lot of aftermarket brake kits, with varying results. All too often there’s either no documentation with them, or there are mismatched parts. A low volume car like yours is a prime example. You might be able to find out the bore size on a non power brake Merc and then verify the size you have. That would be a start. The linkage (if not done right) will be next.

This is a quick, not very technical read. Run down to the “hard brake pedal” test. Ignore the power steering note, that would be for a hydroboost not a vacuum system.

https://www.wikihow.com/Test-a-Brake-Booster

 

[Bob from Northport]

More good stuff. Thanks!!

 

[KULTULZ]

IF the car came through with MANUAL BRAKE, you are ahead of the game. Check pedal/linkage under instrument panel as to the ILL's. If it has MANUAL linkage, your problem will be with the push-rod adjustment/length.

This 'kit' someone hung has a DISC/DRUM MC. That just right there tells you you are going to have to do a lot of parts replacements. As mentioned, the MC piston sizes are not going to work with the drum brakes correctly.

Are you planning on keeping the car four wheel drum or a disc conversion?