Help...drum brakes: pedal is rock solid but front wheels are braked

[Michele]

Please,

anybody with some pill of wisdom...

I've been through all the threads through all the forum...read all sort of stuff.

Vehicle: my ex-MoD 109" IIA.

New master cylinder adjusted and fitted.

Cylinders cleaned and reassembled.

Cylinders clamped all way in, vehicle on stands with nose pointing up.

Brakes bled 2 or three times until my father said pedal was firm.

Back from the Allrad the other day, I went back to the old girl to adjust snail cams properly.

Tried the pedal, and it was as weak as p***!!

My mechanic suggested to clamp the hoses to check if the new mc was faulty or not.

All hoses clamped; brake pedal was rock solid.

Rear hose unclamped: brake pedal still rock solid.

Front hoses unclamped: brake pedal still rock solid!

Now I adjusted the snail cams, rear wheels first, from locked back to when the wheels spin freely (well something grinds once at every turn but to hell with it).

Then I moved to the front...and both wheels are braked.

I winded/unwinded the snail cams both ways but it makes no difference, both wheels stay braked.

Brake pedal is still rock solid...

WTH is going on?

I'm sick of these stupid drum brakes, I could've never imagined a vehicle could've been fitted with such a cr@pp* system.
I must hurry up and move on so I can get the 109" out of the garage and to the MoT check to have it road legal again, but I need the brakes to be functional...I'd convert to discs or even different axles in an heartbeat if I had the €€€ now, but I don't

[steve b]

Hey Michele

It sounds like the front flexi pipes may have broken down internally and are acting as

a one way valve?

hth - 'tis frustrating when a load of new stuff goes on and there are still

problems

cheers

steveb

[tacr2man]

sounds like the m/cyl is adj wrong not allowing fluid to be released when back at start position HTSH

The brakes are perfectly adequate for the vehicle if everything is set right

[Gremlin]

Change your flexible hoses, they are acting like one way valves.

G

[Gremlin]

Damn, i was beatin to it!

G

[Michele]

Flexy hoses reached the top of the list it seems,

just found a mail from a Series-mate who suggested the same thing...

Annoying...very annoying...

Could you guys please try and explain me what "technically" happened inside the hoses then?

I can't make a picture in my mind...

[Michele]

The brakes are perfectly adequate for the vehicle if everything is set right

Fair enough.

But, personally I can't stand the idea of wasting a week to setting everything right every time

[Retroanaconda]

Imagine a piece of rubber becomes partially detached from the inside wall of the hose, the flow can get past it one way but causes it to "close" against the other side in the reverse flow. Acting as a one-way valve. Same principle in your heart!

Not saying this is 100% the issue, but it's a likely candidate. And if the hoses are getting on a bit it will do no harm to change them.

[Michele]

Like cholesterol?

Ouff...parts shop is closed on Saturday, so all postponed to Monday...

I'll do some tests.

I hate the idea I'll have to bleed again after changing the hoses!

Sigh.

Thanks for the advices so far...

[Briarston]

Would agree with the faulty hoses.

Have experienced this twice, not on LR's though.

(Dumper truck and VW camper.) Exactly the syptoms

you describe. Out of curiosity I tried poking a 1/16"welding

rod down one, wouldn't go through without a good push.

[Snagger]

Your description of working on the adjusters sounds as if you may have the shoes on the wrong way around, so that one of the shoes is jammed on and the other adjuster spins without achieving anything. The pegs on the shoes are in different positions, so if the shoes are back to front, the adjusters malfunction in this way. Just an additional thing to look at, but hoses and MC adjustment (there should be a small amount of play on the pedal before it actuates the MC) sound most likely as culprits.

[David Sparkes]

While the failed flexible pipes have been reported before; some people claim clamping the hoses causes an aged hose to break in this manner, it's not the only cause of a 'solid pedal'.

TACR2Man has hit another frequent cause.

sounds like the m/cyl is adj(usted) wrong, not allowing fluid to be released when back at start position.

Have you set the pedal height correctly, then the free play? Both settings are in the Manual, and failure to set them correctly causes one way flow of fluid into the pressurised system, but not out into the unpressurised reservoir.

HTH

[Michele]

Well the MC was bench set by a mechanic who's been into Series for his whole life, and I can say I trust him.

Pedal height...I didn't do anything, I pulled the whole thing and brang it to the guy (200 Km far) to have the new MC installed and adjusted, then came home and fitted it in place...

I'm also quite sure I placed the shoes in correct position, but being my first drum brakes experience as I said, I cannot guarantee it 100%.

I sent pics at time to a mate and he confirmed I did it right, and as far as I understand the front ones can't be mounted the wrong way, as they won't simply fit...right?

I can pull the drums again and check another time if needed?

[Edit: just got a mail from my friend and he points out I can't remove front drums anymore if they're locked solid...oh, great!!! ]

I can't get hoses until Monday when the shop opens, anyway...

[=jon=]

I had a similar problem with brakes locking on randomly with blue box wheel cylinders - they failed internally so would lock on - you'd fiddle with the snail cam and they'd free up, until the next time you hit the brake pedal with reasonable force... Might be worth adding to the list of things to check..

[Michele]

In the meanwhile I found a photo of the re-fitted shoes (DS)...anything wrong with this?

Also my friend suggested me to try and unscrew the hoses a little at the connection, this may relieve pressure maybe?

P.S.
I adjusted the shoes in height/centering after the pic...

[David Sparkes]

In the meanwhile I found a photo of the re-fitted shoes (DS)...anything wrong with this?

It was Snagger who queried shoe position in post 11, so I'll leave further comment to him :-)

[Gremlin]

Put the rubbers on the wheel cylinders.

To relese the shoes just open the bleed nipples and back off the adjusters.

What nick said usually applies to rears, if you switch them you get into all sorts of problems getting the shoes to adjust correctly.

Do not give up, when set up correctly series brakes are as good as any other brake system and will stop a fully laden 109 just fine.

G

[steve b]

loosening a pipe will relieve the pressure Michele as your mechanic says

If you do it at the m/c on the front circuit and it releases the front brakes then it will prove the

flexy's are ok and would also suggest the pedal adj is not quite right . If they are still locked when

you do this then try releasing a pipe nut between the flexy and the wheel cyl and if that works then

the flexy is your problem

As others have said once the system is working and set you should find it quite reliable

cheers

Steveb

[Michele]

Put the rubbers on the wheel cylinders.

To relese the shoes just open the bleed nipples and back off the adjusters.

Oh yeah I forgot to say dust caps went on after I took the pic also

I lost the plot...just got back from the garage, I pulled the front wheels again, I can turn one drum backwards by hand with some effort,

I backed the adjusters off (uhm, clockwise or anti-clockwise? Can't remember! Anyway none of them made any difference),

slightly undone the DS hose at the upper connection until it leaked fluid (and heard a slight noise somewhere), but nothing changed.

I tried to tap the drums off but no way of course...

[Michele]

If you do it at the m/c on the front circuit and it releases the front brakes then it will prove the

flexy's are ok and would also suggest the pedal adj is not quite right .

I haven't tried this yet...will do.

then try releasing a pipe nut between the flexy and the wheel cyl and if that works then

the flexy is your problem

Dang, I did it wrong, I released it at the chassis mount!

[Michele]

Back with news...

I did this:

loosening a pipe will relieve the pressure Michele as your mechanic says

If you do it at the m/c on the front circuit and it releases the front brakes then it will prove the

flexy's are ok and would also suggest the pedal adj is not quite right .

and the result is that front drums spin again now, although for every turn they encounter some resistence at a point.

I got completely lost with adjusters, one clearly locks and unlocks the drum, the other confuses me, there's no ON/OFF position but something in the middle until I get the least resistance at the drum...

I then texted the mechanic for help, and he suggested the flexis may be faulty.

But wasn't the point of the test above to prove they work instead?!?

[CUSSING MODE is now: ON]

P.S.
Edited to say I got another text from the mechanic with instructions for adjusting the MC rod.

I'll try this too...

[Daan]

one thing I will say (sorry if someone already mentioned this) is that you have the 11" drums with the twin leading shoes, right? In that case, bleeding is imposible with the standard setup (bleeding nipple at the bottom cylinder?) air gets trapped in the top cylinder. I am not sure about the locking up problem, or the flexis but the bleeding I used to do by removing the backplate, rotate it untill the bleed nipple is at the highest point, bleed, then refit. You can also re route the pipe to the bottom cylinder first,then to the top.

Daan

[Michele]

you have the 11" drums with the twin leading shoes, right?

Erm, right

In that case, bleeding is imposible with the standard setup

Oh, great to hear! Thanks Land Rover!!!

New update...I hope it's a step forward;

just got back from the box, following the last text from the mechanic I popped the cover of the MC and un-tightened the the nut towards the dash (one turn) and the nut towards the engine accordingly.

Pressed the pedal, now it gets gradually firm(er), unlike before when it simply was rock hard all the travel.

I winded in (clockwise, right? I hope so?) the adjusters so the drum are now tight and don't spin, and pressed the pedal a few times.

This should've adjusted the shoes in position...correct?

Now what?

Should I bleed again?

Or fine tune the adjusters until the drums spin freely?

I can't tell if the pedal is okay, I never had the pleasure to drive a Series, both of mine need a rebuild, so it could even be alright,

but who knows?

[steve b]

It sounds like you are making progress

1. the pushrod on the m/cyl must be loose against the piston when the pedal is at rest against the stop ie

held by the return springs. In this position with the cover plate off you should be able to hold the pushrod

with some wire nose pliers and feel free play side to side . The nuts either side of the pedal trunnion should

be tight

2. adjust the snailcams until they drag then back off one or two clicks. The ones that feel vague may be worn or the pin

in the shoe may not be in the right position - rare but I have seen it

you should have about a fifth of the pedal travel as free movement then another 20-40mm of travel to fully hard pedal

keep at it Michele , nearly there

cheers

Steveb

[Michele]

In this position with the cover plate off you should be able to hold the pushrod

with some wire nose pliers and feel free play side to side . The nuts either side of the pedal trunnion should

be tight

2. adjust the snailcams until they drag then back off one or two clicks.

Well it would be about time!

Cover plate is still off so tomorrow I can check the freeplay (and maybe take another video, I'm having fun ).

As to 2. uhm, I wouldn't say my cams click actually, it's more a ratcheting sound, I had the impression I could count "clicks" but I may be wrong then

Now they're turned all the way clockwise, is that full grad mode? Drums don't turn.

Thanks all for the helps so far