China POS Master Cylinder
 

I purchased a replacement MC for my 65 LeMans bracket car. It's not the factory type it's a light weight aluminum unit and the previously one worked for many years. I have installed three in a row from O'Rileys Auto Parts and all three are bad. The port for the rear brakes won't build pressure but the one for the front brakes does. This is very frustrating how they can peddle this China garbage. I have posted pictures of the one I have so now I am looking for recommendations for a unit from another brand that maybe someone has had good luck with. Thanks.

That is more or less the "Mopar" master cylinder used by just about everyone. Did you pop it apart and see if one of the lip seals may have been put on a piston backwards? It's possible they made a run of hundreds of them with the same defect. If you take the snap ring off and pull it apart, take a look at the seals. At the closed end of the cylinder there should be a piston with 1 seal, the lip toward the closed end. That makes one closed chamber. The second and third lip seals face each other, creating a second sealed chamber when you push them forward. Make sure the 4 little drillings are open from the reservoir into these two chambers when the cylinder is at rest. That's how they refill when you release the brake and vent as the fluid temperature increases. There is nothing else really inside those simple cylinders. I would recommend buying only a new master cylinder for a race car. Not sure if you are buying re-manufactured ones or not. Good luck with it.

I used one Summit sells, looks the same as yours. I don't remember the brand, but I think I still have the box. It's been reliable with regards to braking. The caps were difficult to get to seal correctly though. Seems that's pretty common with this style MC though.

Kinda hit and miss with offshore parts, is that a cast iron body? I've got a new one from autozone for $35 thats an aluminum body and its been ok. Id try a differant vendor and cross your fingers.

I have 4 of that type, 3 that brand different piston diameters all seem to work good.

I did have new Wilwood Dynalites after 15 runs not hold pressure an not leaking(why I have a couple of MCs to rule that out) Swapped new calipers and fine.

Need recommendations for a MC
 

Here are pictures taken of the piston of the last defective unit I removed from the car. I am not so concerned as to why these did not work as what I need to get that will work. Looking for recommendations of one that does work. Thanks.

I use a stock replacement drum brake master cylinder...works great. Strange front disk and rear drum brakes...

Yeah I don't want to use a big heavy cast iron unit looking for the lightweight aluminum with plastic reservoir, one that actually works

Here's the brand Summit has(d). I'm not sure what variety of bore sizes they have, so verify it's available in the bore size you want.

Bill Eveland

What is the part number for the one you got at Autozone?

How are you bleeding them

Its been awhile, but this is the one they list currantly. Im using one for a 85 chrysler 5th ave. Right around a 1" bore. It looks like cast iron in the pic, not sure how accurate that is.

https://www.autozone.com/brakes-and-...1822/49330_0_0

All of the Strange are larger than 1".

Thanks for the pics of the "guts". Is that all that was in there? No secondary piston? I see they used a double lip seal in one location. That's a little money saving idea and you can't put it on backwards with two lips on it. Easier for the 4 year old Chinese kid to assemble. Do the seals seem to have some friction in the bore? Just wondering if the wrong size seals for the bore were used. As far as a good brand, hard to say other than just trying various different ones until you get one that works. I use nearly all NAPA parts unless buying direct from a race vendor. Can't honestly say I have never received a defective MC from NAPA. Needed two try's to get a working one on a Sprinter Van a year or so ago.

mgarblik

You ask how I bled the master cylinder, every way possible. Putting bleeder hoses from the ports and into the reservoir and pumping until clear of bubbles, per the instructions that came with the unit basically pushing in the piston less than one inch and holding for 20 seconds repeated several times until no more bubbles come up and finally I bled it with a MC bleeding tool ( Cardone 10-5000mcb) that forces fluid up through the ports . All worthless as no matter what I do the port for the rear brakes will not build pressure.

I went through several, even Strange gave me fits. Call Lamb and don't look back.

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.

Same for me!

I bleed with the plugs too and store my extra full and plugged.

Today I bought another MC from NAPA it's what NAPA sells for the Dorman M99294 as I can't find an actual Dorman. It pretty much looks like it came out of the same China factory as the ones I have been getting from O'Rileys. Sure enough it's bad too. I tried bleeding just like you (firechicken) said in a vice but no matter what I can still depress the plunger way beyond an 1/8". Tomorrow I will head for pick a parts and get a used one off of a car.