109" Master Cylinder bleeding

Hi all,

First time back on the forums for a long time. Used to be old Minis, now its Land Rovers.
Same issues, just bigger parts.

I've recently replaced the Brake master cylinder on my new (to me) 109" Series 3.
As far as I can tell, the new Bearmach BR2227 cylinder is the same as the one I removed.
Problem is, I cannot seem to get a pedal, no matter what I do.

After (incorrectly) fitting the new unit dry and trying to bleed on the car, I subsequently removed it and bench bled. Seemed to fully charge it with no air bubbles.
Refit, tighten pipes up, bleed at wheel cylinders ... get a steady stream of fluid with no bubbles, but pedal still soft.
The pedal seems to have the feel of fluid in the cylinder at first press (to the floor), but then doesn't seem to refill / recharge quickly. It takes a few seconds for the master cylinder to refill it from the reservoir.

Tried pressure pot and vacuum bleeding to no avail.
If anyone can shed some light on the topic, I'd really appreciate it.

Many thanks in advance,
Bill

You can try doing the adjusters right up so the brakes are 'on', then bleed, that should give you a very firm pedal. turn the adjusters back to the proper adjustment and you should be good to go.
If there is too much movement in the shoes then you'll end up with long pedal moment to get any brakes, probably less obvious on tiny mini brakes

Also, is the master cylinder returning all the way?

kermit_rr said:

Also, is the master cylinder returning all the way?

Click to expand...

Hi Kermit_rr
Thanks for the reply.

Yes, I believe so. It just takes 5-10 seconds for the pedal to feel 'recharged' with fluid again. full stroke available on the master.

I haven't played with the adjusters at all since fitting the new master, as I hadn't changed any slaves or friction material. Hopefully this may be the issue. I'll have a try and report back.

Sounds like this could be simply a shoe adjustment issue.. you press the pedal then the shoes take time to retract.
The shoes should be 'just touching', ie jack the wheel and it should turn but you should hear the shoes just catching.. if you can't hear that then there's too much movement in the pistons at the wheel

kermit_rr said:

Sounds like this could be simply a shoe adjustment issue.. you press the pedal then the shoes take time to retract.
The shoes should be 'just touching', ie jack the wheel and it should turn but you should hear the shoes just catching.. if you can't hear that then there's too much movement in the pistons at the wheel

Click to expand...

Thanks for the info. Interested as to why they would have moved during the time the master was removed.

I’ll hack it up and see if there is any outward adjustment.

They won't have moved, but the master cylinder push rod may not be the same length, there's adjustment there too which could compensate for issues elsewhere

... I'm sure you know.. disturb one thing and you get the knock on effect

kermit_rr said:

They won't have moved, but the master cylinder push rod may not be the same length, there's adjustment there too which could compensate for issues elsewhere

Click to expand...

Agreed!
Is there a base setting for new pushrods? I’ve read 1.5mm of free play before master cylinder piston take up.

Oh yes. You seem to chase problems to the next weak link too. Especially with brakes.

yes a 16th (1.5mm) is the free play.. if i recall, the push rod length is related to the pedal height from the floor

I did wonder if the pushrod was too long and bottoming out on the pedal tower body. Need to be in front of the car really.

If you are worried about the bleed of it I would leave it overnight with the pedal depressed. They are known for being difficult to bleed and this has helped my several times when replacing brake components. but I would agree it sounds more like and adjustment issue.

dag019 said:

If you are worried about the bleed of it I would leave it overnight with the pedal depressed. They are known for being difficult to bleed and this has helped my several times when replacing brake components. but I would agree it sounds more like and adjustment issue.

Click to expand...

Thanks all. Got home tonight and set the pedal and pushrod as per the book. Drum adjusters all the way out and had a got at bleeding.
Still no ‘full’ pedal. Fluid doesn’t seem to be being drawn out of the reservoir at all.

removed the whole tower assembly as I have a (2nd) new master arriving in the next few days.

I wonder if I’ve damaged or flipped a seal in the current unit by running it dry on first install?

It's unlikely, the masters are easy enough to open and inspect, even just for interest rather than to fix.

Does sound the like push rod isn't fully returning though.

So, an update on the above.
I now have an air free system and a working brake pedal.

A replacement master cylinder has seemed to fix the issue.
Whether the first 'new' master was faulty or I had damaged it by not bleeding it first, I guess we will never know.
Installing the 2nd new master cylinder, already bench bled seemed provide a decent pedal from the outset and a conventional bleeding procedure.

I've attached a photograph of the dismantled cylinder, in case it can help someone else to visualise the innards.

I now have to jack the car up, adjust the brake shoes again (as i'd wound them all the way out to aid with bleeding)

Also had another slight issue with the new master cylinder pushrod being too long for the pedal tower assembly. So a pair of spacers have remedied that.

Will report back once adjusted and road tested.
Thank you all for the help and advice.

Glad to hear you're sorted

The Saga continues.
Shoes adjusted. Until they bite then one click back.
Still can't get a firm pedal (takes two/three pumps to get pressure). Doesn't appear to have any air in the lines any more (could well be wrong though).

Going to double check pedal height, backstop and push rod tonight. It doesn't appear to have 'free' play, but it isn't sticking on any more.

This is going to sound a bit lame but are you sure air isn’t being sucked in through the bleed nipple threads when you lift the pedal. It’s happened to me in the past when using a one man bleed valve/tube gizmo. I even used ptfe tape on my new slaves this time as the threads seemed overly slack.

Agree with Bobsticle above, I've found the nipples are loose especially with cheaper branded parts.

Easy workaround is pressure bleeding or an vacuum type bleeder that drawers fluid out through the bleed nipple.

WoodyO said:

Agree with Bobsticle above, I've found the nipples are loose especially with cheaper branded parts.

Easy workaround is pressure bleeding or an vacuum type bleeder that drawers fluid out through the bleed nipple.

Click to expand...

Thank you guys.

I purchased a pressure bleeder, but haven't had any great success in sealing the cap to the reservoir tight enough not to spray brake fluid all over my bulkhead.
A friend has a vac bleeder, make have to bribe him with Tea and cake.