Datsun Roadster Forum-311s.org

I think you still need the measurement on a stock push rod length....
Or someone can mail a pushrod to you. I would if I had one.
Is the brake pedal currently level with the clutch pedal?
Otherwise time to shave off a little bit of the pushrod.

Linda

Baja, when I say freeplay I am talking about a slight amount of pedal and rod movement before the rod hits the piston in the M/C. That's why I suggested taking the spring off the pedal so you can feel for that freeplay easier. There should be a tiny gap between the end of the rod and the M/C piston to assure the piston travels all the way back. Any pressure on the piston will cause the problems you are having.

]brake level is currently even with the clutch pedal. Dads, I have taken the spring off the brake pedal and even disconnected the rod from the brake pedal to test for the play you are describing. There doesn't seem to be any freeplay or gap at all before the rod engages with the piston. Anyone have a stock push rod they can measure?

Baja, now I see. I bet if you put the M/C back together, don't worry about the cups at this point, and attach the rod like it should there isn't a small gap between the piston and the rod, it is being held firmly in place, such that it is keeping pressure on the piston? If so you may have to grind a bit off the head of the rod and possibly a thinner washer to hold it in place.

I meant reservoirs not cups, sorry

I also used a 510 MC and the stock rod. My new cyl did not have the option for a straight rod, which is a nice option. It fit exactly the same as the old. The problem I had was that the retaining washer was not allowing the rod to come all the way off the piston, so it was keeping the piston partially engaged and keeping an increasing amount of pressure in the front brakes eventually causing them to lock up before I could get home. That did not impress the wife on her first test ride with me. I ended up having to grind the ball end of the stock rod down enough to engage the piston properly and allow it to travel all the way back releasing all the pressure. I ended up with about 1/16 to 1/8 inch of free space between the rod and the piston. No problems since. This is from April 6 last year. It is what II had to do to fix my problem.

It is possible that someone swapped the push rod with another cylinder. Another possibility is IIRC the washer has a bevel and it on the pushrod with the bevel going into the cylinder and not out. When assembled, there should be a few thousandths clearance between the pushrod and the piston. That's why I suggested cleaning that area. As suggested, you can chuck the rod in a drill press and sand the ball end down.

Stock push rod 3.75 inches
Note: Before adjusting the pedal free play, make sure the wheel brakes are correctly adjusted!

With the hand brake off, check the bolt adjuster wedge (#21) located on the backing plate of the rear brakes to ensure its adjusted correctly.
The adjuster proceeds in clicks or notches. The road wheel will often lock temporarily as the adjuster cam passes over center for each click.
Thus the adjuster is alternately hard and then easy to turn.
When the road wheel is fully locked, back off 1-3 clicks. (I usually back off 2 clicks).
Ensure the upper pedal stop (brake switch) is lock nutted in its position.

The pedal free play should be between .31-.47 inches. After the free play is used up, further pressing of the pedal should produce required pressure buildup.

Hopes this helps you.

Cheers
Ray B.

If I was not installing a engine in my car, I would be temped for a road trip. Are you in San Carlos? I camped on the beach when I was 12, might have grown up a bit in the last 60 years.

Great info Ray, thank you for taking the time to measure and post all that data and those pictures.

FJ20 , I am in Loreto B.C.S. on the baja peninsula, about 300 miles north of Cabo,and about 800 miles south of the U.S. border right on the Sea of Cortes. Thanks Ray for the detailed information. I took the master apart again to see about grinding the ball end of the push rod and discovered that because of the beveled washer curving around the ball end, and the cupped piston end fitting around the ball that there is only about 1/32 of an inch between them. Not gonna gain much by grinding the ball end of the pushrod. Also, the springs behind the pistons pushes them out so far that the piston would still be against the retaining washer even if I removed the rod entirely. It seems the master has the wrong kit in it because the piston is going to butt against the retaining washer no matter what adjustments I make. With the spring clip and retaining washer removed, the piston sticks out of the master a good half inch. It seems the only option left is to chuck this piece of s**t master and order a replacement. Just gotta figure out how to get it here.

I think the push rod is still too long so that when you step on the pedal there is no freeplay like Ray’s picture shows before the brake engages.
The 510 master has to be an early one with the correct part no of course.
If you are thinking of ordering another one then you might as well chop away at the push rod and see what happens
You would do well to invite Phil down to your place in Mexico. He is a genius guy and he can fix everything . I think Phil likes to fish also
Linda

Time to take a measurement of the length of the piston and the location of the "bypass" hole. The piston needs to retract out of the cylinder bore to uncover that return hole. Don't chop the rod up as it need the ball to stay attached to the cylinder. If it falls out, no brakes.
If the cylinder was in the car, you could pump the brakes and then release. There should be a spout of brake fluid in each of the brake reservoirs.

Linda,
Thanks for the kind words, its just that I have made every mistake possible....LOL
These are the ports I am talking about.

Just want to say, the support and knowledge on this forum for our Roadster family is outstanding!

My frustration level has met its match. I will bite the bullet and purchase a new or professionally rebuilt master. Any recommendations for vendors? I see Mike Young at Datsun sports sells a resleeved master for $350.00. Anybody purchase one of these? Datsun parts.com has new ones for big bucks.I also recall one of the vendors was having them manufactured but they were a couple months out. Any others I should check with. And I agree with Greg. This is an incredible group and I appreciate everyones input. It just seems my current bastardized Master is beyond hope.