[mgarblik]

The part you purchased is a Dorman part. NAPA sells parts under the NAPA Solutions line that is re-boxed Dorman stuff. 100% of Dorman replacement parts are made in China. But that in itself likely is not the issue. It seems there has to be some compatibility issue between the replacement MC, the booster, the rest of the braking system. 4 defective MC's in a row from two vendors, even if the same manufacture source, is very unlikely. Not impossible, but very strange at least. What was wrong with the original one you were using? Soft pedal, leaking? Can it be rebuilt?

[Bill Eveland]

What are you using for a proportioning valve? I had a factory one I fought for a long time, after I swapped to an adjustable Wilwood, I had a great pedal in about 5 minutes.

[chiefbigb]

I was thinking the same thing Mark.

[Bill Eveland]

Just to be clear, your using the front port for the rear brakes i hope? The port closest to the firewall is for the front brakes, or the axle that requires more volume according to Strange. They sell theirs for about $90.

[Tim Corcoran]

The original MC was installed about 25 years ago and I believe it was a unit I got from a wrecking yard. Recently the car sat for a few years and the brake fluid hardened inside the MC and the piston was frozen and couldn't be moved. That unit looks just like the ones I have been installing that don't work, that unit went into the trash. The plumbing is such that the forward port goes to a line lock then through an adjustable proportioning valve then to the front disc brakes. The rear port the one closest to the firewall goes straight to the rear drum brakes. I drove the car like this for a many years and as the car evolved from a low 12 second then to an eleven second street car to a ten second drag car I raced it for many years like that and the brakes worked just fine stopping the car on the street and from hundreds of 130 MPH 1/4 mile runs with no issues. So Bill even if what you say is correct the old MC was plumbed the same way and had a hard pedal and the car stopped just fine. Even if the lines are backwards that would not explain why the pedal goes to the floor with a fully bled MC and full system bled. I have no leaks anywhere in the system the MC was bled with the plugs in as the method stated. Then bleeder lines going from the outlet ports into the reservoir and cycled many many times with no air bubbles. I am about ready to set the car on fire and push it off a cliff I am so frustrated I want to start racing again and don't know what to try next.

[Bill Eveland]

Maybe try the Stange one than ? I would think it would be a better quality coming from them.

https://www.summitracing.com/parts/str-b3360

[johnta1]

How did you bleed the front and rear brakes?

[Tim Corcoran]

[QUOTE=firechickenman;6271819]I have found the best way to bleed a master cylinder is to plug both ports, fill with fluid, and pump the cylinder (about 1/2") until the piston can only be pushed in approx. 1/8". If it doesn't get to that point of only being able to depress the piston 1/8" or so, that tells me there is either air still in it or it's a bad cylinder. This method does take a little extra time and sometimes I feel like I'm never gong to get the air out but once it's bled, you can feel confident that you're putting a good part on the vehicle.

I bled it like that and with both plugs in I can not depress the piston an 1/8"

[johnta1]

This should show the MC is good?

The problem is stream?

[Tim Corcoran]

Originally Posted by Bill Eveland

Just to be clear, your using the front port for the rear brakes i hope? The port closest to the firewall is for the front brakes, or the axle that requires more volume according to Strange. They sell theirs for about $90.

Bill, I called Strange and talked to their tech line. I inquired about their Strange P/N B336TA master cylinder. I was told that the front port is for the front brakes and the rear port is for the rear brakes. He also said to put the adjustable proportioning valve on the front brakes just like I have mine set up. The Strange B336TA MC looks very much like the ones I have been using I believe my plumbing is correct. The components I have installed are a 10 psi residual valve for the rear drum brakes, an adjustable proportioning valve and line lock on the front brakes. These components have been on the car for many years. I just ordered new replacements for these components just in case one of these units might be the problem. If this doesn't solve the problem I will replace or rebuild the rear wheel cylinders as the the front calipers are new. At this point I am assuming the MC is good but if changing these components doesn't work then I will get the Strange B336TA MC.

[rod cole]

I feel that many bad master cylinders is highly unlikely.
i suggest first step back a minute and then do a old fashioned gravity bleed . Fill cylinder open one bleeder and wait until gravity does its thang. Move to the next bleeder and wait. This may take more than a few minutes but it will work. good luck and step back a little

[Bill Eveland]

The one i listed was a smaller bore, but even on their website states the same thing i said about what port goes where...

https://www.strangeengineering.net/p...313-bore.html/

[chiefbigb]

You replaces the front calipers at the same time and have not had brakes since? If so I have seen left and right sides swapped and the bleeders are on the bottom then.

[Tim Corcoran]

Big Chief, calipers installed correctly thanks.

Bill, I see on the Strange website it does say the rear port goes to the system that requires the larger volume thanks for pointing that out but even so that is not my problem it has been plumbed like that for years and brakes were fine. I guess their tech guy is not so savvy about their products and brake systems. I know bleeding was done correctly so after changing out the line lock, proportioning valve and 10 psi residual valve (parts on order from Summit) if I still the same problem after changing out those components then I will change out the rear cylinders and if that doesn't fix it then I will get the strange MC and install that.

John, to answer your question regarding how I bled the front and rear brakes. With an assistant in the car and the car up on the lift I have a 1 quart plastic container wired up in place to catch the fluid. I put a rubber hose on the bleeder valve and submerge the other end into the fluid in the catch container. Going in sequence from RR to LR to RF to LF I have the assistant pump the brake pedal a couple times to build some pressure then hold the pedal firm. I then open the bleeder valve and watch for bubbles to come out of the submerged end of the hose. I close the bleeder valve each time before the assistant lifts his/her foot off the brake pedal. This process is repeated until no more bubbles come out then a few more times bubble free to be sure. This process is repeated at each wheel following the proper sequence checking/adding fluid to the reservoir after each wheel is bled to assure the reservoir does not run low.

[johnta1]

Thanks, Tim.

Wonder if you try plugging one port (front or back) and try bleeding the other side (front or back brakes). Maybe try to narrow it down to one end or the other?
(I don't think the MC is bad)
Flexible hoses on front or rear brakes?

[Tim Corcoran]

Flex hoses all new, after I install the new line lock, proportioning valve and 10 psi residual valve if problem persists I will try that.