Hot Rods 1" master cylinder with disc/disc. Help needed urgently.

From what I have learned about dual master cylinders there is an volume differential between the two sections in initial take-up, which seems evident now that you have reversed the ports.

I am not a brake expert by any means; but I feel you need to increase your pedal ratio, 5 to 1 would not get you adequate application pressure on a drum/drum system and your un-boosted disc/disc would be even worse.

You may even find your problem will go away if you were able to generate higher line pressure.

 

Well, the Pirate 4x4 specifies that 'properly' is the reason you HAVE to remove the MC from the car to make sure it is dead level, not angled in any way. The very reason they call it 'bench bleeding' is because they want it out of the car and set up level on the bench. That is documented in several web page I have explored.

To be honest, I'd love to know whether Ford or GM have a battalion of people carefully bench bleeding master cylinders before they are carefully installed in the cars, lest there be the slightest air bubble that could cause a massive class action law suit.

Seriously, these type MCs are the basic brake systems of millions of cars, maintained by millions of every day guys, are they really that fragile and sensitive and that each one needs personal and finite treatment, removal from the car, every time a single bubble gets into the system???

 

I weight 220 lbs, and with all my leg pressure on the pedal those back wheels were still moving with my wifes hand on them, while the fronts were locked up solid.

Now they ports are swapped the rear wheels are locked solid with merely a foot laying on the brake pedal.

Were the transmission working as it should I could probably have driven it a few miles, worn the pads and discs in a little, taken some slack out of the system, and improved rear brake performance, but it is definitely right on the ragged edge if I can move the wheels by laying a hand on them at full pedal depression. There is/ was definitely a feeling of mechanical contact at about half pedal stroke, which I feel is the rear half of the MC running out of stroke.

 

The corvette master worked really well for me, once I had the lines in correctly.

 

FUNNY STUFF! No, they are not.

If you switched lines and the problem stayed on the same port of the M/C, that looks like it's the culprit.

 

I did a friends drag car like this took master apart and seen nothing bad.Back together and still no work.Bought another brand new master the same part number worked great. justcan't explain some things

 

On that note. There was a thread some time back where a dual master had issue's, a new one as well. The a hole or holes we're not completely drill thru from the reservoir to the cly bore it's self.

 

I'm just about sick of the sight of brake fluid now, but I might pull out the MC and strip it down, see if anything obvious is amiss. I have to pull the trans anyway,so why not get all greasy and roll around the garage floor a bit more

And I'll order up a 'Vette MC too, or something similar designed for disc/disc.

 

I had a problem with what felt like air in brake system, bleeding did not help. The problem was the rear calipers have a slot in the face of the piston & the pad has pins that must enguage the slot so that when the hand brake is engauged the piston does not turn. Got the pad pins into the slot & have good brakes.

 

Mine are lined up, and the handbrake is not yet connected. Everything back there is brand new. I also pumped the handbrake levers several times to crank the pistons out as far as they can go.

 

i would just get the right master and be done with it. on my yota crawler i have disc all the way around and had a f350 disc/drum master. the rears alway took two pumps to get the to work, after i swapped out the master to a disc/disc they worked as intended.


read up on some brake manufactures sites.


http://www.mpbrakes.com/technical-support/reference-master-cylinders.cfm



DRUM / DRUM
A drum / drum master is designed to deliver fluid pressure and volume to the front and the rear of a braking system in equal proportions. Drum brakes will require less fluid and pressure than disc brakes. Typically a drum brake master will be smaller than a disc master and the fluid reservoir chambers will be equal in size. Since drum brakes require the use of residual pressure valves the original drum master cylinders had residual valves built into the outlets. Later model aftermarket units do not have these valves and they must be installed in the lines externally. Failure to incorporate residual valves will cause spongy brakes.

Generally speaking it's not a good idea to use a drum brake master for disc brakes since the amount of fluid the cylinder pushes will not be sufficient.





DISC / DRUM
A disc / drum master is designed to push more fluid volume to the front disc brakes since disc brakes require more volume than drum brakes. Generally speaking a disc / drum master will have one fluid reservoir larger than the other.This is because the disc brake pads wear faster than the drum shoes and the fluid reservoir will drop faster. Original disc / drum masters had a built in residual pressure valve to the rear drum brakes only.
Never reverse the outlets on a disc / drum master. Doing this will cause the front disc brakes to drag excessively from the residual pressure valve.





DISC / DISC
A four wheel disc brake master cylinder is designed to supply more fluid pressure and volume to the rear disc brakes than the disc / drum master does. This is acheived through an internal piston re design. The piston that feeds the rear brakes on a disc / drum master will run out of stroke, limiting the amount of fluid pressure and volume that may be supplied to the rear isc brakes.
The four wheel disc master redesign delivers the extra needed volume and pressure to the rear allowing your rear disc brakes to function properly. If you attempt to use a disc/drum master on a four wheel disc system you will get poor rear brake function and experience a spongy brake pedal with a long pedal travel.

 

Noticing the adjustable valve going to the rear brakes,....Is it set to give enough operating flow to the rear brakes? Just a thought..... I'm in agreement with the Corvette type m/cyl guys,... Those seem to work best with disc/disc systems.

4TTRUK

 

Sounds like you keep avoiding taking the advise of many and just go and buy another MC. Whats the deal?? You probably have spent half the cost in brake fluid already. Just my 2 cents, and they're period correct.

 

I've actually removed it from the system completely, made no difference.

Take a look at my location Mr Gent. Not too many auto suppliers over here sell 'Vette master cylinders off the shelf.

I could order one, get it shipped air mail, probably triple the cost by the time it arrives here. If it arrives at all after customs take a look at it.

 

Not that it would be easier for you to find, but I've used a 1979 Trans-Am, manual 4 wheel disc brake master on quite a few cars. Slightly smaller and cheaper than a Vette master. I know, good luck finding either over there.

 

if you cant get a disc disc master right now, try disconecting the rears from the master and "T" them into the front line and take it for a spin and see if the cures your problem. if it does, you at least know what you need to do. dont you have parts stores their? if you do what about a master off of something else ( like a jap car). i would imagine that you have something their that has a disc/disc setup that you can get a master from.

 

I don't know if anything Japanese has big enough diameter MC. The breakers yards, 'auto surplus' as they call them, will tell you anything they think you want to hear. I'll do some asking around a few buddies and see what they know.

I have considered just connecting front and back together to 'share' the fluid and pressure. Still battling with the trans so I can't drive it anyway. I seem to have forwards gears but no reverse. The rear brakes work enough to load the trans against, which is better than before.

I did one big stomp on the throttle in the drive (just to see if I could shake anything lose inside the trans, of course) and the body twisted, the tyres screeched, and all our dogs ran for the hills....

 

This looks like what I need:http://www.speedwaymotors.com/Garag...on-Master-Cylinder-1-1-8-Inch-Bore,51919.html

 

Is the brake bleeder at the top of the calipers.If not you can not get the air out of the system

 

Yes, bleeders are all at the top.

 

That looks like the one you need.

Charlie

 

Getting it over to here is the painful part. I fly to the USA next week, so simple, you might think, buy it then.

Unfortunatly I don't get more than a few hours on the ground before we helicopter out to my ship. No time to buy anything, and the hotel we use has stopped people getting stuff sent there while we are offshore.

I usually send stuff to an in-laws place, in New York, and he ships it sea freight to the Philippines, which can take up to two months....

 

If you have and address,buy one on the bay 320923679820 and have it sent to you.

 

As a last ditch attempt to get drivable, I joined the front and back circuits, so they all share their juice. The pedal felt good, but slowly sank to the floor. Then I noticed fluid transferring to the small reservoir chamber until it overflowed and flooded onto the floor.

Fuck it, I've had enough.

No brakes, no reverse in the tranny, and no time to fix anything before I fly out to work next week. So, it'll be next year before I drive it now!

 

You need the one at the bottom of the page with 1" Bore. Not the 2 up top that are 1 1/8" Bore.

 

The one that says:' and is suited for disc/drum combinations'?

I already have a 1" disc/drum MC, but I need disc/disc, like the 1 1/8" ones state.

 

Read the notes on 1 1/8" bore. Also, your going manual, smaller is what's needed. I think that last unit was faulty, did you find anything wrong with it after opening it?

 

With manual brakes you do not need a large bore MC 7/8" or 15/16" is best. Get away from Speedway if you can and get a MC from a part supply store. A Ford Granada and Lincoln Versailles (77-81) had a dual disc combo with there 9" rear. But do order a manual cylinder and check to see that it is a manual MC with a deep plunger hole in the piston! Also the early corvettes had a dual disc combo with manual brakes but I think they had a 1 or 1 1/8" bore whitch will give you a hard pedal when brakes are applied.
If you are coming to the states get someone near your area to pick you one up and drop it off to you when you arrive. Not with the motel. Then you are good to go when you get back.

 

True, I'm not seeing a 1" bore disc/disc at Speedway. 1 1/8" is a lot more flow than 1" so would need a longer lever etc.

I pulled the MC apart, can see nothing wrong. The bore looks good, seals look good, all holes appear to be drilled correctly. Total stroke is exactly 1", whereas someone earlier said it should have been nearer 1 1/2".

I'll do more checking around when I'm offshore, and see if I can get a buddy to bring it over when we crew change.

Might even look at some Jap stuff before I leave here, but it could involve a bunch of fiddling and adapting.

I'm worn out, been working on this every day sorting out the numerous little odd and ends to get it roadworthy. I really hate watching those BS TV programs where they completely build a whole car, ground up, in a couple of weeks.....