300Tdi - no brake pedal pressure

[travelrover]

I was having trouble getting brake peddle pressure as I had decided to flush the system last year. I had some on the second pump which was sort of ok. I bleed the system three times and no change, but rego is coming up so on advice of a few I replaced the master cylinder. The replacement was the genuine item.

When bleeding got plenty of pressure and fluid through the front brakes, but bleeding the rear brakes very very little fluid came through but there was peddle pressure. But then when I went to test the vehicle there was zero pressure, no resistance at all.

I will re-bleed during the week weather permitting but was wondering what else it may be? No leaks, everything looks fine. Can’t help thinking the new master cylinder..???

Any clues?

Also does anyone know what this is, mounted next to the master cylinder. It has three wires (all cut) red white and black and couple of tubes plugged into it.
134882

[bee utey]

The gizmo looks like a cruise control actuator.

Brake problems may be due to an internally collapsed flexible rubber brake hose at the diff end.

[Tins]

Hi. Is your M/cyl off the car now? One simple test if it is is to clamp it in a vice and put some fluid in it. press a finger over each of the outlet ports and push the piston in with a rod or screwdriver or something. If the fluid pushes your finger off the port it is working. Repeat on the other circuit. In fact, back in the olden days when I was doing this stuff we used to do this to "activate" the m/cyl. Of course, if you meet no resistance when doing nthis it's the m/cyl that is faulty, but that is unlikely. A new cylinder is unlikely to be completely without some seal.

I would try pressure bleeding next. If all seals are OK, then only air can be your problem. Unless you left out the rod from the booster....

[Tins]

Brake problems may be due to an internally collapsed flexible rubber brake hose at the diff end.

Producing "zero pressure, no resistance at all."?

[travelrover]

The gizmo looks like a cruise control actuator.

Brake problems may be due to an internally collapsed flexible rubber brake hose at the diff end.Arrr, yes that will be what it is, cruise control. I have been removing bits of this since i bought the project vehicle.

Thanks for advice bee utey. I shall replace that hose too.

[bee utey]

Producing "zero pressure, no resistance at all."?

Of course. Brake hose is blocked during bleeding due to initial fast fluid movement dislodging the lining:


but bleeding the rear brakes very very little fluid came through but there was peddle pressure.

then rubber moves to allow air in rear circuit to percolate forward resulting in:


But then when I went to test the vehicle there was zero pressure, no resistance at all.

Only a theory, of course. Based on experience with old hoses on various old vehicles that I've had the privilege of fixing up. But yeah, I could be wrong. [biggrin]

[travelrover]

Producing "zero pressure, no resistance at all."?Hi johtins. The cylinder is on the vehicle now and i am reluctant to remove it unless as a last resort. I will replace the rubber hose at the rear as bee utey suggested and get it pressure bleed and see it that sorts it.

[Tins]

Of course.



Only a theory, of course. Based on experience with old hoses on various old vehicles that I've had the privilege of fixing up. But yeah, I could be wrong. [biggrin]

It was merely a question, and an appropriate one given the car has a dual braking circuit.

[travelrover]

Before I replaced the master cylinder I at least had some pressure and the second pump there was plenty. Even when bleeding (before replacing the cylinder) I would get pressure and good flow at each wheel.

[Tins]

Hi johtins. The cylinder is on the vehicle now and i am reluctant to remove it unless as a last resort.

Don't blame you. I was merely trying to point out a way to eliminate the m/cyl from your fault finding process. Those tests can be carried out in the car, bearing in mind the effect brake fluid can have on paint....

[Sivvy130]

I would try clamping each flexible rubber hose individually (both fronts and rear) and see when clamping one if the pressure comes back. That would isolate a problem.

You could also remove the master cylinder and look inside you’re booster to see if it’s full of oil.(leaking vac pump). If so you could possibly have a faulty booster. Usually this gives a hard to push pedal but I have had once before a very soft pedal from a failed brake booster on a tdi.

Good luck!

[travelrover]

.

Don't blame you. I was merely trying to point out a way to eliminate the m/cyl from your fault finding process. Those tests can be carried out in the car, bearing in mind the effect brake fluid can have on paint....

Thanks again Johntins. I may we’ll end up having to pull it all out so will bear that in mind. The paint work is not a major concern as this is my project vehicle and is fairly rough on the outside. Painting it may be on the list in the distant future... mechanical is fine, except the brakes :-)

[travelrover]

I would try clamping each flexible rubber hose individually (both fronts and rear) and see when clamping one if the pressure comes back. That would isolate a problem.

You could also remove the master cylinder and look inside you’re booster to see if it’s full of oil.(leaking vac pump). If so you could possibly have a faulty booster. Usually this gives a hard to push pedal but I have had once before a very soft pedal from a failed brake booster on a tdi.

Good luck!

Hi sivvy130, I had a look at the booster when I pulled the m/c out and appeared ok, pedal travel is smooth. Silly thing is it was working fine until I decided to flush the system as part of replacing all the fluids as I had no knowledge of when it was last done. Now I have problems:-)

[Ancient Mariner]

Wilwood supply with a new master cyl 2 plastic barb fittings and 2 short pieces of clear plastic tube .You fit these to the MC fill with fluid and pump by hand till no more bubbles fit the MC,remove tubes .If this procedure is not followed it is very hard to bleed the system

AM

[Tins]

When you release the pedal, does it come back up by itself?

When you try and bleed, does the fluid level change?

When you say "no resistance", is that all the way to the floor?

Have you tried 'drip bleeding'?

Basic stuff, but did you bleed from the longest to the shortest pipe run?

[travelrover]

When you release the pedal, does it come back up by itself?
Yes it does

When you try and bleed, does the fluid level change?
Yes, the front brakes at least (no discernible change with the rears)

When you say "no resistance", is that all the way to the floor?
Correct, but this was after bleeding done, or as much as I could get done. When bleeding each corner there was pressure. It was when I went to move the vehicle (and down a hill) that I discovered there where no brakes at all.

Have you tried 'drip bleeding'?
No, ran out of time yesterday as I had to wait for my peddle pusher to get home from work and then a storm came through and this vehicle is too high to get into the shed (or the shed is too low I guess) so it was beer o'clock.

Basic stuff, but did you bleed from the longest to the shortest pipe run?
Front left first (per Haynes Manual/Land Rover Workshop TV)
Front Right
Rear Left
Rear right



Not going to have much opportunity to do anything until next weekend now and the temps are supposed to be mid 40's so maybe nothing is going to get done. I have ordered a replacement flexible hose for the rear from Mario so should be here soon. Will swap that out and try again. Will also get a break hose clamp from Supercheap and isolate each wheel per the above suggestion from Sivvy130. Oh better get some more brake fluid too :-)

[scanfor]

I was having trouble getting brake peddle pressure as I had decided to flush the system last year. I had some on the second pump which was sort of ok. I bleed the system three times and no change, but rego is coming up so on advice of a few I replaced the master cylinder. The replacement was the genuine item.

When bleeding got plenty of pressure and fluid through the front brakes, but bleeding the rear brakes very very little fluid came through but there was peddle pressure. But then when I went to test the vehicle there was zero pressure, no resistance at all.

I will re-bleed during the week weather permitting but was wondering what else it may be? No leaks, everything looks fine. Can’t help thinking the new master cylinder..???

Any clues?

Also does anyone know what this is, mounted next to the master cylinder. It has three wires (all cut) red white and black and couple of tubes plugged into it.
134882

Do not discount the possibility that the "new" master cylinder is U/S.
I went through two "new" ones before I worked that out.

[Tins]

Do not discount the possibility that the "new" master cylinder is U/S.
I went through two "new" ones before I worked that out.

Pretty much where I'm leaning.

[hydronaut]

Last year I replaced the MC on a disco series 1 (I also run a RRC) and went through all of this, and the new MC was a dudd MC (still waiting for my $400 back). The pedal went straight to the floor with the usual squishing noise. Now a new MC does not bleed easily just by itself. You may need to brake the lines at the MC and make sure all that nasty air is gone. Just break them and have a cup of tea. If you then get a teeny amount of pedal pressure you are in business. I know nothing of defenders, but I have little faith in pressure bleeding as such. for the traditionalists, having the missus pump up the brakes while you bleed is a path to divorce and should be treated accordingly. All I do is hang a reservoir 10 feet higher the the car, join the tube from it to the nipple, open it and break every connector under the bonnet, and leave it for a couple of hours. Seems to work. The theory being that if the fluid can seep everywhere you don't want then surely ..... As to the crook MC I eventually swallowed my pride and took it to a great bunch of guys who run a shop. They confirmed the dudd MC and rang the spare parts shop to add some gravitas. $50 well spent. And to get the second opinion, I went to their shop on handbrake and in LR. Finally (and it is easy to say) Don't let the frustration of it all get you down.

[Tins]

Last year I replaced the MC on a disco series 1 (I also run a RRC) and went through all of this, and the new MC was a dudd MC (still waiting for my $400 back). The pedal went straight to the floor with the usual squishing noise. Now a new MC does not bleed easily just by itself. You may need to brake the lines at the MC and make sure all that nasty air is gone. Just break them and have a cup of tea. If you then get a teeny amount of pedal pressure you are in business. I know nothing of defenders, but I have little faith in pressure bleeding as such. for the traditionalists, having the missus pump up the brakes while you bleed is a path to divorce and should be treated accordingly. All I do is hang a reservoir 10 feet higher the the car, join the tube from it to the nipple, open it and break every connector under the bonnet, and leave it for a couple of hours. Seems to work. The theory being that if the fluid can seep everywhere you don't want then surely ..... As to the crook MC I eventually swallowed my pride and took it to a great bunch of guys who run a shop. They confirmed the dudd MC and rang the spare parts shop to add some gravitas. $50 well spent. And to get the second opinion, I went to their shop on handbrake and in LR. Finally (and it is easy to say) Don't let the frustration of it all get you down.

Funny, ain't it. Back in the dark ages, I was taught to bleed the m/cyl before I fitted it. This was on mil spec IIas. Not sure it helped, but it is a practise I have continued.

[travelrover]

Last year I replaced the MC on a disco series 1 (I also run a RRC) and went through all of this, and the new MC was a dudd MC (still waiting for my $400 back). The pedal went straight to the floor with the usual squishing noise. Now a new MC does not bleed easily just by itself. You may need to brake the lines at the MC and make sure all that nasty air is gone. Just break them and have a cup of tea. If you then get a teeny amount of pedal pressure you are in business. I know nothing of defenders, but I have little faith in pressure bleeding as such. for the traditionalists, having the missus pump up the brakes while you bleed is a path to divorce and should be treated accordingly. All I do is hang a reservoir 10 feet higher the the car, join the tube from it to the nipple, open it and break every connector under the bonnet, and leave it for a couple of hours. Seems to work. The theory being that if the fluid can seep everywhere you don't want then surely ..... As to the crook MC I eventually swallowed my pride and took it to a great bunch of guys who run a shop. They confirmed the dudd MC and rang the spare parts shop to add some gravitas. $50 well spent. And to get the second opinion, I went to their shop on handbrake and in LR. Finally (and it is easy to say) Don't let the frustration of it all get you down.Thanks hydronaut. I called the guy that has serviced my defenders and range rovers for the last 30 years and said to crack the two connections on the side of the mc (there are three altogether on this model, the other underneath) and pump the pedal slowly a couple of times. Much as you suggest.
No assistant for a couple of days and going to be 40+ until Tuesday so i guess she will not be keen to pump the pedal till it cools down a little.

Anyway i will try that first thing tomorrow. Have managed to get some hose clamps and a replacement hose for the rear. Re the no fluid flow at the rear he suggested removing the nipples and poking a small drill bit in the hole to dislodge any foreign matter. Hope i dont run out of fresh brake fluid.

Rego is due tomorrow :-)

[hydronaut]

Thanks hydronaut. I called the guy that has serviced my defenders and range rovers for the last 30 years and said to crack the two connections on the side of the mc (there are three altogether on this model, the other underneath) and pump the pedal slowly a couple of times. Much as you suggest.
No assistant for a couple of days and going to be 40+ until Tuesday so i guess she will not be keen to pump the pedal till it cools down a little.

Anyway i will try that first thing tomorrow. Have managed to get some hose clamps and a replacement hose for the rear. Re the no fluid flow at the rear he suggested removing the nipples and poking a small drill bit in the hole to dislodge any foreign matter. Hope i dont run out of fresh brake fluid.

Rego is due tomorrow :-)


some supercheaps have brake fluid by 4+ litres. much cheaper

[Pcm2048]

You might like to check the brake damper as when it fails you will get no brake pressure.

When they are on the way out, the pedal will act intermittently, sometimes it works, sometimes it does not work, and sometime it half works. There is no way I know of to test it, and it is sealed, so the only option is to replace it. It is the small disk like object between the master cylinder and the slave cylinder, located next to the slave cylinder. It is cheap and easy to get and easy to replace, and may cure your dodgy pedal.




I was having trouble getting brake peddle pressure as I had decided to flush the system last year. I had some on the second pump which was sort of ok. I bleed the system three times and no change, but rego is coming up so on advice of a few I replaced the master cylinder. The replacement was the genuine item.

When bleeding got plenty of pressure and fluid through the front brakes, but bleeding the rear brakes very very little fluid came through but there was peddle pressure. But then when I went to test the vehicle there was zero pressure, no resistance at all.

I will re-bleed during the week weather permitting but was wondering what else it may be? No leaks, everything looks fine. Can’t help thinking the new master cylinder..???

Any clues?

Also does anyone know what this is, mounted next to the master cylinder. It has three wires (all cut) red white and black and couple of tubes plugged into it.
134882

[travelrover]

Yesterday I cracked the two lines off the top of the m/c and slowly pumped the pedal a couple of times and I could see bubbles weeping out of the unions. I left it like this for maybe an hour and then tightened them up and finally had some pedal pressure. I left it overnight and this morning there was much more pressure so I took it for a run and it performed well under some heavy braking :-)
Hopefully problem solved, at least for now.

Thanks to all for your suggestions.

[travelrover]

Passed its rego inspection today with no issues so am a happy Chappy :-)