Brake question

[transalpian]

I'm confused from that statement. The pedal goes to the floor with you foot applying pressure or all by itself with no foot on it?

If it goes down all by itself: I can see that is you have air in the system and if the pedal spring(s) is/are missing. Depending upon the version there should be one or two springs on the pedal that keep the pedal up top.

If it goes down after reaching a firm brake and maintaining foot pressure on pedal:
This is a classic diagnostic of a bad master cylinder. Once you have pumped enough fluid into the cylinders to set the brakes they should hold solidly as long as your foot keeps pressure on the brakes.

Silly question. How are the rubber hoses on your brake system? Old hoses that balloon out under pressure can act like air in the system.

The brake pedal does not go down by itself. All the springs are in place and springy.

The pedal goes (slowly) to the floor under foot pressure. The brakes work (slow the truck) while this happens.


Starting from the end, hoses are new. I also held onto them while the brakes were being pumped to try to feel any ballooning. Nada.

[transalpian]

My last reply was chopped up and my iphone won't let me edit.

Anyway, the hoses are new, and checked by me yesterday. The brakes work, but the pedal goes to the floor under foot pressure. They don't feel spongy, but I'm only adequate at bleeding.

There are no leaks I can see, and the fluid level stays constant so even if brake fluid were getting sucked thru the servo intobthe intake manifold, I'd see it eventually!

I didn't check the new rn master before install. I supose I need to take it apart and check it?

Not really what I wanted to do...

[LaneRover]

My last reply was chopped up and my iphone won't let me edit.

Anyway, the hoses are new, and checked by me yesterday. The brakes work, but the pedal goes to the floor under foot pressure. They don't feel spongy, but I'm only adequate at bleeding.

There are no leaks I can see, and the fluid level stays constant so even if brake fluid were getting sucked thru the servo intobthe intake manifold, I'd see it eventually!

I didn't check the new rn master before install. I supose I need to take it apart and check it?

Not really what I wanted to do...

Did you get genuine or aftermarket? I had (or have) the same problem. Put a new master in and pedal goes to the floor under pressure - though the brakes do work. Send it back, get another and the same thing. Unfortunately I have not been back to Maine to deal with the truck or I would have figured it out by now.

[transalpian]

Did you get genuine or aftermarket? I had (or have) the same problem. Put a new master in and pedal goes to the floor under pressure - though the brakes do work. Send it back, get another and the same thing. Unfortunately I have not been back to Maine to deal with the truck or I would have figured it out by now.

Proline, from rn

[SafeAirOne]

If you don't have any external leakage and the flex hoses are all good, I still maintain that fluid is leaking past the MC piston or the resivoir isolation valve inside the MC.

I've had brand new cylinders go bad in a few weeks due to quality/manufacturing issues, though not from RN.

[LaneRover]

Proline, from rn

Me too

[wrighthm]

I just installed a new master cylinder from RN (ril brand proline). I've gone through 60 bucs in fluid trying to bleed my brakes when tonight my pedal started getting worse and I noticed very tiny bubbles in the line ( even smaller than soda). Pedal felt as if I had erased every bit of work I had done today but didn't get any worse after that. I can't build pressure by pumping and in my fluid container I could see the tiny bubbles coming in from my brake line after I would pump the pedal. Sorry for the hijack, but maybe you can check if your master is producing bubbles like mine and maybe someone will have an idea if my master has failed (1 week old with only a half done bleeding procedure under it's belt)?

[TeriAnn]

I just installed a new master cylinder from RN (ril brand proline). I've gone through 60 bucs in fluid trying to bleed my brakes when tonight my pedal started getting worse and I noticed very tiny bubbles in the line ( even smaller than soda). Pedal felt as if I had erased every bit of work I had done today but didn't get any worse after that. I can't build pressure by pumping and in my fluid container I could see the tiny bubbles coming in from my brake line after I would pump the pedal.

Any chance your connections might not be completely tight? Any moisture there?

[amcordo]

How about the slave cylinder? Maybe that's part of the problem... I'm a big fan of systematically replacing parts and hoping for the best. So maybe try replacing that...

[transalpian]

What if I remove both brake lines from the master cylinder and plug the ports in the master cylinder with appropriate plugs.

Once the master cylinder is bled, can I then test it in place?

In other words, if the master cylinder is isolated from the piping and wheel cylinders and still bleeds through when the brake pedal is pressed, can I be sure the problem is in the master cylinder? Is there anything else that could be a failure mode in that test scenerio?

I don't think there is, but I'm to the point of asking (appearingly) stupid questions in an attempt to isolate the problem I'm having.

I'm almost 99% certain I got a bad replacement master cylinder last week.

[TeriAnn]

What if I remove both brake lines from the master cylinder and plug the ports in the master cylinder with appropriate plugs.

Nope. You get brake flex line clamps then clamp all three flex lines. Lets you test the master cylinder and the brake lines to the rubber hoses.

Moss motors sells brake clamps that do not crush the inside of hoses. Personally I use lab tubing clamps from a chem supply company.

[Sputnicker]

Another method is to undo the female fitting from the master-cylinder-side of the flex hose and install a bleed screw in lieu of the hose(s). This isolates the master cylinder and hard lines. It's also a good way to limp home if you have a leaky wheel cylinder - stops the leak and you still have brakes on 3 wheels.

My guess is that it's your new master cylinder. It's the only part of the system where fluid can bypass a seal and not leak (it gets pushed back into the reservoir).

[wrighthm]

I received my new replacement mc for my other new mc and just completed installation. The one week old mc was tested outside the car with brake fluid and I got some rubber smoke, dark fluid coming from it. The rubber failed in about three days... The new one is working for now although I cannot get a pedal that is less than four pump braking. I borrowed a "motive" pressure bleeder from a fellow rover owner here in Lexington KY who has a 109. I have only gone through one cycle of bleeding with it. I finally got a solid stream of fluid on all four wheels although the pedal still takes four pumps to be solid braking. I have heard from some of the rovers north family that I may not get a good pedal until I go through the bleeding procedure 3 times while getting a solid stream of fluid with no air. I'll try more tomorrow but I am seriously at the end of my rope ( today I bought the bottle of dot4 that tipped me over $100 worth and finished my millionth hour of bleeding in the past three weeks). To top things off I can't even be certain I won't be right back here in another three days trying to get yet another master cylinder. It will be the last one I buy if this one in the truck now does not hold up.

Once again with a hijack, sorry.

Appreciate all of you here.

[transalpian]

I'm talking to the folks at RN about a potential recall issue, will post here any outcome.

I'm strongly considering the Ford MC swap, if for no other reason than to be able to find the parts.

Anyone have luck with this approach? From what I understand, need tubing adapters and an actuator rod spacer.

Any thoughts?

[Sputnicker]

There is great availability on Land Rover brake parts from multiple manufacturers. I would suggest you try a different manufacturer for the master cylinder, in case there is a batch problem. Generally, they are quite reliable. Other master cylinders can be adapted, but it's easy to lose track of what you used and what modifications you made.

Not getting a firm pedal without pumping can have many causes - not all of them hydraulic/bleeding-related. Series Land Rover master cylinders have barely enough volume when the rest of the system is perfect, so any mechanical slop can result in low/no pedal. Try adjusting them, look for worn adjusters; check for loose pivot pins (where the bottom of the shoes attach to the backing plate). There are many discussions in the archives on this topic.

I recently replaced every cylinder, every line (hard and flex) and the adjusters and still had almost no pedal on the first pump. I finally had the front drums turned and went from almost no pedal to full pedal (best $20 I ever spent). The drums had showed no signs of unusual wear, but they were out of round. Accordingly, the adjusters had to be backed off far enough to clear the eccentric drum, which increased the volume of fluid required to push the shoes into the drum.