Brake question

[transalpian]

I'm learning more each day. Today's lession will be brakes!

When I picked up my truck, the brakes were pretty good. Occasionally, they would need "pumped" to stop easily however. It was as if the vacuum servo didn't "work" on the first try.

Yesterday, it seems to have stopped working completely. After I noticed this, I adjusted all four brakes so we're good there. Fluid level is good (and hasn't changed). Vacuum line to the servo looks good.

I could live with a firmer pedal, I just don't have the stopping power I had, even with a really hard push on the brake pedal. If I pump the pedal a lot (5-10 times), the braking power improves, but I really notice the stumble in the engine from all the vacuum being drawn off.

I've been reading about the brake failure valve, but don't think my '74 series 3 88" would have that. It's been dark, so I haven't looked (not really sure where to look, however).

The truck almost feels like the front brakes aren't working, but I've had no fluid loss. Is that possible?

Could it be the vacuum servo (diaphram)? Is the ProLine servo a decent unit?

Thanks for all the help!

Jeremy

[TeriAnn]

There is a master cylinder failure mode where the fluid does not leak out. Chances are good that the rubber seal on the piston inside is not sealing and is getting worse.

A vacuum tester like the Mity-Vac is always a good thing to have in your toolbox. Allows you to test the booster as well as your distributor's vacuum advance as well as do a vacuum bleed of brakes. Any shop should have a vacuum tester can can quickly check your booster in a couple minutes. Cheaper than replacing a good booster. It could be your booster, but the master cylinder is the more likely candidate.

It is anyone's guess as to what brand the Proline booster is, but I would trust Rovers North to try and stock high quality after market parts. They loose money on every return and they may loose you as a customer. They try to source parts fit for use that you as the customer will be happy with.

[transalpian]

Interesting, hadn't considered internal bleed through of the master cylinder.

I have a mitivac. How would I go about testing the booster?

If the booster tests good, and I have no fluid loss, does that point pretty strongly to the master cylinder? Is this a replace or rebuild type of thing?

[transalpian]

One more question (showing my ignorance).

Does the brake booster amplify the force, the stroke, or both?

Thanks!

[amcordo]

I had the same thing happen. It was the MC; but nothing looked awry on it. It just died on the inside. I replaced it.

[transalpian]

MC ordered from our hosts, will post update upon completion!

[cedryck]

I for one share your and others sympathies when it comes to reparing brakes on a series rover, the parts are garbage. One should NOT have to replace a new part, slave, master, or wheel cylinder after only 4 months. Poor, poor quality parts man.

[transalpian]

Update

New master cylinder (proline) received, bench bled, and installed.

Brakes (f and r) adjusted nice and tight

Bleed, starting in the rear, moving to the front. Initially, the pump and turn method, following up with vacuum bleeding.

Results?

Not fantastic.

I've got brakes, so thats an improvement, but the pedal doesn't have any lock-up. I've got brake effect, but the pedal slowly creeps to the floor. It takes less time than a stop light to go to the floor.

Next plan is to take to my mechanic to have them bleed again just to ensure no air in the system.

Any other suggestions?

(I have verified no brake failure valve on my truck, fyi)

Thanks!

[o2batsea]

you have to have both wheels up in the air, that is, both rear and then both front.
Rear first because that's where you bleed first, furthest away from the MC.
Once you get the air out of the lines, then you adjust the snail cams. Adjust them so that there is some appreciable amount of drag. You should be able to turn the wheel by hand, but with some difficulty. You can only do that with both wheels not touching the ground. Repeat for the front.
I guarantee you'll notice the pedal quite firm if you follow this advice.

[transalpian]

Understood about adjusting them firm. Thats where I am now. But why both wheels off the ground at the same time? What would be the difference between that and adjusting one wheel at a time?

[TeriAnn]

Update

I've got brakes, so thats an improvement, but the pedal doesn't have any lock-up. I've got brake effect, but the pedal slowly creeps to the floor. It takes less time than a stop light to go to the floor.


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.

[SafeAirOne]

That's exactly what I was thinking--If you get solid pedal and you keep your foot there and it slowly sinks to the floor, there must be some leakage somewhere, either past the MC piston or back up into the reservoir or out to the world through the plumbing or wheel cylinders.

Even if you had air in the lines, you'd have a spongy pedal, but with constant foot pressure on the pedal, I doubt it would slowly sink to the floor because you're not increasing the compression of the air with a constant pressure on the pedal.

[o2batsea]

Understood about adjusting them firm. Thats where I am now. But why both wheels off the ground at the same time? What would be the difference between that and adjusting one wheel at a time?

Ill let you think about that for a second. OK still stumped? You can't spin the wheel if one is on the ground. If you can't turn the wheel you cannot tell if you have it adjusted tight enough.

[transalpian]

Ill let you think about that for a second. OK still stumped? You can't spin the wheel if one is on the ground. If you can't turn the wheel you cannot tell if you have it adjusted tight enough.


Oh. I've got freewheel front hubs. I can see how it might not work in the front without those.

The rear? I'd think one at a time would work
(did work, for me).

[bkreutz]

Ill let you think about that for a second. OK still stumped? You can't spin the wheel if one is on the ground. If you can't turn the wheel you cannot tell if you have it adjusted tight enough.

Only if you have a locked differential.

[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.

[albersj51]

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?

I am upgrading to a dual "power" system while mine is apart, and I have been told that the early 90's dodge dakota MC is a bolt in fit and pretty cheap, too. I won't be able to give details on whether or not it works for a while though.

[transalpian]

Agree with all of this, but my new master cylinder was bad. With the ports blocked with hydraulic plugs (no leaks), I still had pedal travel.

Its going back to RN, a ford unit is going in its place, but I am replacing the booster servo (while I'm in there).

Will update later this week.



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.

[transalpian]

It works!!!!

Great pedal, rock hard!!

Of course, the new servo helps too, and I think I've got a smidge more power since I'm not bleeding vacuum thru the old faulty booster.

Confirming the info on irfaq.org, I used a master cylinder from a 1996 Ford Explorer (without speed control). I fabricated a 7/16" diameter x 1" long spacer to fill the "hole" in the end of the ford master cylinder. I turned the booster upside down to avoid the vacuum fitting on the booster.

The only tricky part was the lines. I purchased m10 and m12 pieces of brake line, cut the rover lines, and coupled the new and old lines with compression fittings.

Great brakes!!

And, a replacement master cylinder will be $35, if I ever need it!

Thanks for all your help!

[jac04]

The only tricky part was the lines. I purchased m10 and m20 pieces of brake line, cut the rover lines, and coupled the new and old lines with compression fittings.
Did you really use compression fittings on brake lines? You may want to go back and do it right with double flares. Plus, I'm fairly certain that compression fittings on brake lines are illegal in most states.