Hey guys,
Well for the last few weeks I have not been very happy with the performance of the already lousy brakes on my REPU. Today I bought some pads for it thinking that may be the issue. I took off the wheels,and found the pads were almost new looking still,and returned the new pads. I then with some assistance from SWMBO we bled the front brakes with fresh new fluid. While doing this I broke a bleeder on the passengers side caliper. Luckily I had a fresh rebuilt one from a few years back that I installed,and then did the bleeding again.This work seems to have actually made the brakes worse. By that I mean now when pressing the pedal it travels to the floor with little stopping power,but a few quick pumps get the pedal rock solid,and the truck stops great. Any ideas? Air in the system? Master cylinder? Rear brakes causing troubles? I am pretty sure the rears use two wheel cylinders per side,so that could be an issue as well. I don't see any leaks in the system,but this has got me worried about driving the truck as it has semi-lousy brakes as it is,and now with having to pump the pedal to stop I don't want to take it on the freeway. Any help would be greatly appreciated.
Chris
I think you have a bad master cylinder.
I agree, Master Cylinder, bleeding them made the unit become worse.
How could bleeding make things worse?
Flushing fluids moves crud around, the extended pushing on the pedal can tear an already damaged seal further, fresher fluids bypass the seal easier, rust in the bore can be further dislodged.
I guess I could have said flushing could have increased the problem.
This would not be a problem with a healthy master cylinder.
Thanks Steve,
I guess I will have to try to find a M/C for a 37 year old Mazda truck. Shouldn't be hard,right??
Rockauto shows one for $80.
Mazdax605 wrote:
Thanks Steve,
I guess I will have to try to find a M/C for a 37 year old Mazda truck. Shouldn't be hard,right??
if it's cast iron, just hone it and rinse it good and put new umbrella seals in it.
Where would one get these "umbrella seal"?
Chris
Mazdax605 wrote:
Where would one get these "umbrella seal"?
Chris
Master cylinder rebuilt kit.
Mazdax605 wrote:
Where would one get these "umbrella seal"?
Chris
yeah, i called it an umbrella seal to differentiate from an o-ring, but i should've just called it a master cylinder piston seal. if you can't get a REPU MC rebuild kit, you can probably just measure the MC bore and buy a seal kit for that bore from NAPA.
On the subject of replacing brake hydraulics. Is there anyway to do it without making a complete mess,and letting as little air into the system as possible? I always seem to make a real mess when replacing a caliper,or MC,and there doesn't seem any way to avoid it.
Chris
I tried ordering the MC from Rock auto,and it is no longer available. This sucks!!!
Chris
You can try black dragon they arent cheap though
The problem with Black Dragon is they seem to only deal in the RX-7 world.
Amazingly, AutoZone still stocks a remanufatured REPU brake master cylinder and rebuild kits:
http://www.autozone.com/autozone/parts/Fenco-Reman-Master-Cylinder-Brake-System/1974-Mazda-Pickup/_/N-iov5dZ8kn47?counter=1&itemIdentifier=718874_0_0_12960
http://www.autozone.com/autozone/parts/Brakeware-Master-Cylinder-Kit-Brake/1974-Mazda-Pickup/_/N-iov5dZ8knp5?counter=0&itemIdentifier=50922_0_0_3912%2C12972
Of course, these are FLAPS parts so proceed with caution. However, I have not had a problem yet with my reman FC brake master cylinder I installed 30K miles ago. It was also a Fenco reman.
EDIT: I also found a new one from Centric, the parent company of Power Slot and Stop-Tech:
http://www.prostockautoparts.com/products/1974-MAZDA+TRUCK-ROTARY+PICKUP-2RTR--1308+80-Master+Cylinder,+Brake.htm
I ordered one this afternoon from AutoZone,but I am not confident they will be able to get it like they say they can. Maybe I should order two?
Chris
RexSeven wrote:
Of course, these are FLAPS parts so proceed with caution. However, I have not had a problem yet with my reman FC brake master cylinder I installed 30K miles ago. It was also a Fenco reman.
I assume FLAPS is an acronym for misc vendors perceived as dodgy in the quality department? Would you mind decoding?
EDIT: Berkeleying Local Auto Parts Store? Am I close?
ransom wrote:
RexSeven wrote:
Of course, these are FLAPS parts so proceed with caution. However, I have not had a problem yet with my reman FC brake master cylinder I installed 30K miles ago. It was also a Fenco reman.
I assume FLAPS is an acronym for misc vendors perceived as dodgy in the quality department? Would you mind decoding?
EDIT: Berkeleying Local Auto Parts Store? Am I close?
Full Line Auto Parts Store, though your guess would be pretty appropriate for the many times they screw up!
RexSeven wrote:
ransom wrote:
RexSeven wrote:
Of course, these are FLAPS parts so proceed with caution. However, I have not had a problem yet with my reman FC brake master cylinder I installed 30K miles ago. It was also a Fenco reman.
I assume FLAPS is an acronym for misc vendors perceived as dodgy in the quality department? Would you mind decoding?
EDIT: Berkeleying Local Auto Parts Store? Am I close?
Full Line Auto Parts Store, though your guess would be pretty appropriate for the many times they screw up!
Generally I have good luck with a true local parts store. Chain store usually screws up. I was recently told that 1974 F-100's do not have a voltage regulator. When I looked at the screen they were searching for vultage regulator.
What about a master cylinder from a newer Mazda truck?
Just because it's not listed doen't mean you can't find something that fits. If it's a 13/16 bore for instance that's the same as an RX7. The ports may come out of the side, bottom etc but it can still be used. The M/C on the Jensenator is a RX7 piece, it had 3 ports where I only needed 2. Solution? A blockoff plug for the extra port, it was a 10mm to 3/16 inverted flare adaptor with a 3/16 blockoff plug screwed into it. Problem solved. 
So I picked up the master cylinder today. Aside from a problem with the new one having a step in it where it meets the brake booster that was a bit larger,and needed some machining on the triangular plate that it mounted to it went in fairly straight forward. I did however run into a problem with the passengers side rear wheel cylinders(yes two) leaking,or at least one of them is. Should I replace both of them on that side along with the shoes,or should I do all four wheel cylinders? Can I just clean up the drum on that leaky side with brake clean,and reuse it,or do I need to replace it?
Thanks,
Chris
I would install a GSL LSD disc brake rear, but if you do the cylinders, do em all
Not changing the differential,Steve. Why did Mazda use 4 cylinders on the rear axle? Making up for the lack of cylinders under the hood,maybe?
Not up to date on the Repu, and not a drum brake guy, but it sure sounds odd
