Intermittent brake failure

[outono]

Had a close call today going through an intersection. Went to hit the brakes and the pedal hit the ground. There was a grinding / groaning sort of noise that came with it and after a pump or two, the brakes went back to normal.

I have brand new lines, pads, calipers, and rotors on the truck - all the way around. Despite tons of bleeding, the brake pedal still depresses deeper than it should. Yet, when the brakes are working, they worst amazingly.

I've been told its a possible Master Cylinder issue, even though there are no leaks and it looks relatively new.

Any ideas? Why would my brakes suddenly stop working but come back with a single pump? This only appears to happen once a day and usually in the morning.

 

[WaltNYC]

That sounds very similar to ABS sensor issue. Is there an ABS light on the dash (not entirely necessary)? I would try to see if there are any codes. Here is a primer on how to do that...

Discovery I - ABS Blink Code Procedure

RSW Solutions - Land Rover vehicle diagnostic tools

www.rswsolutions.com

 

[mearstrae]

There may be an internal problem with the master cylinder (or the brake booster). I had a similar problem on my wife's '99 Disco 2 and changing out two master cylinders solved the problem (the first master was brand new junk). On my '03 Disco 2 I had the opposite problem, it wouldn't release the rear brakes. Again, the master cylinder was the problem. On the Disco 2's I have to use a scan tool to properly bleed the brakes.

 

[terryjm1]

I am having a similar problem. The advice I received was to check preload on the wheel bearings. I did that and found I didn’t have enough preload on the front bearings. I snugged up both sides and that solved the problem for about 9 months. I have rechecked and it seems the preload is good.

If you don’t have enough preload, when sideways pressure is applied to the tire/wheel and as such the bearings, the brake rotor pushes the calipers pistons back into the caliper cylinders. This makes it so you have to push the piston back out with at least one pump before the brake pad contacts the rotor.

Mine now does what yours does but not unless I have driven at least 20ish miles. I thought I had the problem fixed and started another project on another D1. So, digging back into is going to have to wait until the other D1 is completely roadworthy.

Until then, I will be checking back to see what you come up with.

 

[outono]

That sounds very similar to ABS sensor issue. Is there an ABS light on the dash (not entirely necessary)? I would try to see if there are any codes. Here is a primer on how to do that...

Discovery I - ABS Blink Code Procedure

RSW Solutions - Land Rover vehicle diagnostic tools

www.rswsolutions.com

That could be. My ABS light comes and goes. I know its a seating issue on the sensor because I can push it down and the light goes out. The braking was very light when this happened so i'd be surprised if that is all it took. Also, you'd think i'd experience this more as I drive the truck but it usually happens just once a day and always in the morning, first thing. Perhaps I should just pull the fuse and get rid of the damn thing.

There may be an internal problem with the master cylinder (or the brake booster). I had a similar problem on my wife's '99 Disco 2 and changing out two master cylinders solved the problem (the first master was brand new junk). On my '03 Disco 2 I had the opposite problem, it wouldn't release the rear brakes. Again, the master cylinder was the problem. On the Disco 2's I have to use a scan tool to properly bleed the brakes.

This is what I think the problem is and my shop mentioned it being a likely culprit. They thought maybe the rod was bent? It would explain why the brake pedal still depresses too deeply despite all new brakes and tons of bleeding. The booster is newish and appears to work fine (plus, if it failed it would likely make braking during normal driving very difficult, which isn't the case).

I am having a similar problem. The advice I received was to check preload on the wheel bearings. I did that and found I didn’t have enough preload on the front bearings. I snugged up both sides and that solved the problem for about 9 months. I have rechecked and it seems the preload is good.

If you don’t have enough preload, when sideways pressure is applied to the tire/wheel and as such the bearings, the brake rotor pushes the calipers pistons back into the caliper cylinders. This makes it so you have to push the piston back out with at least one pump before the brake pad contacts the rotor.

Mine now does what yours does but not unless I have driven at least 20ish miles. I thought I had the problem fixed and started another project on another D1. So, digging back into is going to have to wait until the other D1 is completely roadworthy.

Until then, I will be checking back to see what you come up with.

I have all new bearings across the 4 wheels and these were done by a reputable shop so I trust they were done correctly. This is one of those things I didn't have the time or patience to do right by myself

 

[WaltNYC]

"My ABS light comes and goes. "

I'd bet good money it is a sensor issue. They get old and build up too much resistance. Sometimes they don't sit properly in the hub. Sometimes there is simply too much crud in the cylinder where the sensor lives. Read the codes.

 

[Tugela]

"My ABS light comes and goes. "

I'd bet good money it is a sensor issue. They get old and build up too much resistance. Sometimes they don't sit properly in the hub. Sometimes there is simply too much crud in the cylinder where the sensor lives. Read the codes.

Sounds reasonable. I had a similar brake pedal issue on my D1, only it was more pronounced at low speed and with the wheel turned slightly to the right - like coming to a stop at an intersection when setting up for a right turn. The ABS sensor was an inexpensive part that took a few minutes to replace. That solved my problem but absent a certain diagnosis I can't say if your results will be the same.

EDIT: I'll add that an ABS fault code pointed me to the cause.

 

[discostew]

Your describing an unwanted ABS activation. It’s kind of hard to diagnose cause it’s possible that it’s not storing a fault code.
These guys are giving you very good advise. Make sure the wheel speed sensors are pushed down into the holes up front. If they move when you push them down then they are getting pushed up by a loose wheel bearing.
Sounds like your mechanic might have fucked this up. I wish my customers would forgive me like you seem to have done. If you keep driving it you might die

 

[outono]

I'll take it back to the shop and have them look at it. The groaning I heard does indeed sound like the ABS activating. However, the light was off when this happened so who knows.

For the record, I have no known or pending codes outside of a P0461 which is unrelated.

Will follow up as soon as I hear more.

 

[terryjm1]

I will add, my issue first appeared after disassembling the front hub for new rotors. I repacked the bearings and put new seals in. I assume I didn’t get the preload right when I reassembled.

 

[robbyb20]

I'll take it back to the shop and have them look at it. The groaning I heard does indeed sound like the ABS activating. However, the light was off when this happened so who knows.

For the record, I have no known or pending codes outside of a P0461 which is unrelated.

Will follow up as soon as I hear more.

You wont get a code for ABS faults thru OBD. Youll need to use the blink method WaltNYC posted above to get those codes.

Ive had my ABS come and go will activate at low speeds but never had barkes complete go out.

 

[outono]

Found another thread that describes my experience. Thanks for all the advice.

In the meantime, what is the recommended course of action until I can get it to the shop? Can I just pull the ABS fuse and be assured I won't run into this problem again for the time being? If so, which one? The 30A or the 10A? Or both?

 

[discostew]

You wont get a code for ABS faults thru OBD. Youll need to use the blink method WaltNYC posted above to get those codes.

Ive had my ABS come and go will activate at low speeds but never had barkes complete go out.

They don’t really go out when this happens. Chevy trucks used to do it too. When you do an ABS stop cause you need to your standing on the brake pedal. Pressure is high and the ABS is kind of violent and grinding. The pedal is falling on these trucks when that happens. But when it’s light brake apply and the sensor signal falls out the ABS activation just causes the truck to glide thru a stop. There’s not much pressure to begin with so the brakes releasing and the pedal dropping is all you get. Your asshole puckers up.

 

[outono]

UPDATE: pulled the ABS valve fuse under the hood. Brakes feel even better than before, but maybe its in my head. Shop won't look at the truck until Friday so let's see how the rest of the week goes...

 

[jastutte]

when i had my '96 Discovery had the same thing happen to me with the ABS kicking in and sending me through a red light intersection. good times.

i just pulled the fuse for the ABS and lived with the old school brakes. but i also grew up knowing to pump the brakes if they started to lockup on hard or slippery stops since none of the vehicles i had back then even had ABS.

 

[discostew]

I like the Wabco ABS. I think these trucks are great for winter bad weather driving. On systems like this where the pedal drops during ABS stops it takes some getting used to. Bosch made a system for GM that they used in the big body RWD cars. That system did the same shit. Pretty sure if you read the owners manual it will tell you to pump the brakes during ABS braking. That’s kind of messed up because you kind of think ABS does the work and you just keep steady pressure on the pedal. I’m pretty sure they just mean pump it to get pedal again, but you don’t pump it so much as just letting the pedal come back up so you can go again.
It takes some getting used to. But when the system works right it’s great. In a blizzard all stops are ABS stops