Brake issue..

[DAYLEY/CHALLENGER]

You have the same setup that I have, except I have front disk brakes with drum rear. The booster is a Midland Ross for 71-74.

Hey there  57.  Are you saying that I don't have a 70 booster either?

And I have noticed that there are 2 port sizes , 9/16 &  1/2".  Mine appears to be the same size as the 9/16 wrench fits both lines.  ..?

[Racer57]

Hey there  57.  Are you saying that I don't have a 70 booster either?

And I have noticed that there are 2 port sizes , 9/16 &  1/2".  Mine appears to be the same size as the 9/16 wrench fits both lines.  ..?

I'm only repeating what I was told about my booster when I needed to replace the plastic vacuum line fitting on it. I have no reason to doubt it.
I have a 1/2" ID vacuum line.

[tman]

Booster looks ok, m/c looks wrong.  But if it works good, just get the same one.  Usually the larger reservoir is for the disc brake side.

[1 Wild R/T]

Booster looks ok, m/c looks wrong.  But if it works good, just get the same one.  Usually the larger reservoir is for the disc brake side.

Get the same bore size but not a Disc M/C, Disc M/C has no residual pressure valve in the port to the front brakes...   Granted newer design wheel cylinders don't absolutely need residual pressure valves but it also can improve the pedal.....

[TonyBolton]

I'm seeing some good information in here but I have an issue on my own I hope the original poster does not mind me derailing this but it's kind of sort of on the same thing.

I have a 1970 CUDA with the front disc and rear drum set up and the motor is using a very large cam so I have to use a vacuum pump.

My problem is that the first vacuum pump burned up because it ran all the time and I thought it was just the pump problem I I've replaced that pump with a better one now and it is running all the time as well.

My initial thought was that I had a leak in the hose somewhere between the booster and the pump which is mounted in the trunk.

I just got done diagnosing that hose front to rear and it seems ok and when you plug the hose at one of the joints the pump actually quit working like its supposed to.

I've also noticed that when you go to use the brakes you can pump them once or twice and then when you hold them the brake pedal will very very slowly go down.....not to the floor....but its noticeable.

So after going through all of this the only thing I'm left with is that there is a leak somehow in the booster or maybe even something in the master cylinder.... does this check out with you guys as well?

The brakes work fine and its not really noticeable of lack of stopping power it's just that the pump is running all the time and I can't figure out how to stop it when hooked up.

The booster and master cylinder are the stock equipment from 1970.

Thanks for any help guys I'm really not wanting to burn up another vacuum pump

[DAYLEY/CHALLENGER]

Hey Tony.  I don't mind at all.  The more info the better.  I found a MC at Napa that I liked and have emailed the techs to get an answer on the port sizes.  In fact,I have emailed twice.  No response!  I dom't want to take mine off until I get a replacement but the port sizes are an issue.  Both of mine appear to be 9/16".  The ones I have seen on line show one is 9/16". And one is 1/2".....?

[Chryco Psycho]

Tony I would look at hydro boost as a better option if you have power steering ,
if the pedal is dropping after being pushed & held the master is leaking internally , the booster may be leaking also internally being 45 years old now
 
 The masters I have seen use the same nut size on the lines but the thread size is different fortnt to rear so the lines cannot be connected backwards

[TonyBolton]

Thanks.....I'm looking to do discs in the rear....so I guess just a complete redo of the master/booster will be my option.

Not really feel in the hydroboost.....maybe fear of lack of knowledge. Do they make a dummy proof kit?

[dfrazz]

Thanks.....I'm looking to do discs in the rear....so I guess just a complete redo of the master/booster will be my option.

Not really feel in the hydroboost.....maybe fear of lack of knowledge. Do they make a dummy proof kit?

Its pricey, but pretty straight forward and these guys give you all the help you need.

http://www.tallonhydraulics.com/store/index.php?main_page=index&cPath=54_60_73&zenid=b697c524aadabd8e01078d7b6d4bc522
 

[TonyBolton]

Whew.....that's a chunka change. I think I'd be satisfied with just a 100% working booster/master.

[1 Wild R/T]

FWIW I've never liked how hydraboost assist feels , & I'm far from the only one who feels that way....   Anyone considering the conversion should drive a car with it before making the investment...   A buddy of mine spent the $1000+ dollars, then hated the feel so much he took it off... 

[TonyBolton]

My 02 mustang has factory hydroboost.....its nothing special to me at least.

[Chryco Psycho]

The hydro boost at least has no dependency on engine vacuum / so low engine vacuum has no affect on brake performance with no need for vacuum pumps which cost $$ also . you can adapt hydro boost from later Astro vans I have hydro boost on my truck & love the feel of it .

[DAYLEY/CHALLENGER]

 
 The masters I have seen use the same nut size on the lines but the thread size is different fortnt to rear so the lines cannot be connected backwards
[/quote]

Thanks Chryco.   That makes sense.   Guess I will try something this weekend. 

[wantone]

The hydro boost at least has no dependency on engine vacuum / so low engine vacuum has no affect on brake performance with no need for vacuum pumps which cost $$ also . you can adapt hydro boost from later Astro vans I have hydro boost on my truck & love the feel of it .

Sounds like a kit that needs to happen.