A basic question about hydraulics

[dave21478]

I have been messing with this all day today and its wrecking my head now and I am not able to think straight.

 

So, I changed the clutch on the freelander a while back and fitted a new slave and master cylinder at the same time as is advised to do. The slave is on of these silly concentric things inside the bellhousing. The parts are separated by a quick-release coupling in the pipe. The slave side of the pipework is metal, and from the master cylinder to the coupling is plastic.

 

All was well until the new master cylinder fell to bits. I still had the old one, and an old,old one from years ago in my spares pile, so with a bit of faff, I soon had one good one and one pretty good one out of the three.

 

This morning I fitted the good one and the pedal was floppy as granny tits. No amount of bleeding did anything. I swapped it for the other one and quickly the pedal got stiff and it felt fine. Happy days. Well until I did about 20 miles and it started getting harder and harder to select gears until I had to switch off the engine each time I wanted first.

 

So more bleeding and it got better, but didnt last again.

 

Looking on the landy forums, some other people have had problems with the quick release coupling, especially on a Borg and Beck branded slave cylinder, which mine is. Sure enough the coupling was wet with fluid. A few hours pissing about with o-rings made no difference.

 

So, i sacked it off and binned the plastic tube altogether. I braised a brake pipe union onto the barb on the master cylinder and ran a bit of brake pipe down and fitted male and female brake pipe fittings in place of the quick release thing. This seems to be not leaking, although its hard to tell as the whole place is swimming in fluid.

After much stress bleeding it, the pedal now feels ok, but the clutch is not disengaging fully. When I try for a gear it wont go in and the car starts to creep forwards.

 

so, some questions...

 

1 - what the fuck am I doing wrong?

2 - how can I fix this?

3 - the brake pipe is smaller internal diameter than the original plastic pipe. Its 3mm i/d as opposed to the original which was 4mm. Does this matter? my tired brain says no, for a full stroke of the master cylinder piston, it will push out its volume of fluid no matter what. However, it seems to only be transferring half of what is needed to disengage the clutch.

 

*sobs*

 

 

[Asimo]

That change in Pipe dia. shouldn't matter much.

 

If there was still a small amount of air in the system, squashing that air up before anything useful can happen at the slave would steal some of the master cylinder travel.

 

Blead again

[red5]

Buy new m/cyl unless you're sure that the seals aren't rolling and the piston is retracting fully.

 

Tried the 'pump 4/5 times and then release bleed nipple whilst keeping pedal down' routine?

[dave21478]

yeah, i thought that might be the answer.

I have already put 1.5 litres through it. Due to it being LHD there is no room to get a pressure bleeder on the cap, so it as to be done the old fashioned way. I will try again tomorrow when I can get someone to pump the pedal for me - doing it on my own is a nightmare.

[scruff]

I've no idea of the setup on these but is the pedal getting full travel? 

[dave21478]

Yeah, i have been pumping it 5 times and holding down, but it makes no difference.

 

The seals are ok and if I take the master cylinder off, which I have done several times, and hold it in the vice, it seems to work as it should, and if I plug the end of the pipe it build up pressure. Its just when its connected to the slave cylinder that things go south.

 

I have left it with the pedal wedged down for tonight - this can occasionally help tricky brake bleeding for some reason. No harm in trying.

[dave21478]

yeah, pedal travel is fine. Its giving the full stroke length available.

[jonathan_dyane]

Pipe diameter won't make any difference.

[spike60]

It may be worth trying to reverse bleed it. Get a large syringe full of brake fluid with some piping pushed onto the bleed nipple and push the fluid and bubbles back up into the master cylinder. This can sometimes sort troublesome soft pedals.

[Albert Ross]

IIRC the Freeloader clutch hydraulics are available, SEALED, in a two piece kit. Mismatch them or remove covers that say DO NOT REMOVE COVER at your own peril/expense. Bite the bullet. Buy new, buy sealed, buy guaranteed, fit, forget.

[dave21478]

It cant be reverse bled or suction bled as the bleed nipple is almost tight up against the engine mount - no room to get a tube on. Genius design.

[dave21478]

And yes, it was two brand new, sealed units that just straight up didnt work. I am not going to buy another master cylinder as it would be wasted money, and if the fault is with the slave cylinder then that means doing this....

...again and frankly - fuck that.

 

 

[dave21478]

The old "wedge it down overnight" trick works its magic again.

 

I let the pedal up this morning and there was a gurgle from the master cylinder as air was released and it is working fine.

 

Just need to keep an eye on it for leaks now.

[Skizzer]

Well done.  Beelzebub lives in hydraulics as far as I'm concerned: watch me take a year of head-scratching to get some brakes bled.