trapped air?

Hey guys & gals, after recently changing my master cylinder and servo I seem to have air trapped ant I can't get it to shift!

I have tried the two man method, pressure bled @ 20 psi with the mc uphill, pumped pedal with pressure bleeder and still the same problem. If I pump the pedal once the breaks are fine until I release the pedal then I need to pump again to get proper breaks again.

Any ideas as I'm all out!

Oh and I've tried bleeding straight from the mc too

is it splashing in m/c when pedals pumped,try isolating by clamping flexis

Not noticed any splashing, will try clamping, do you clamp one and bleed the others or clamp 3 and bleed one?

clamp them to see which are has air ie rear or either front, try looking at m/c for splashing as means seals are poor

If I clamp either side on the front it gets a pedal back, so tried to bleed it out with the pressure bleeder but still no luck. I must have used 2l of fluid by now trying to get this air out. Pads are fine, no bulging in flexi pipes. Any ideas?

I had a right bitch of a time doing mine too. Turns out the aftermarket master cylinder i got didnt open enough to allow the valve / piston to allow fluid though. After eventually sorting it, 60 miles up the road on a trip to the peaks, the clutch pedal went very stiff and the clutch started slipping, had to do about 30 mph from nottingham to the peaks and when you have almost no drive, going up hills isnt fun. Got to the campsite and bled the system from the slave cylinder. That helped a little bit and allowed me to get to the nearby landy indy and they found the problem to be that the pedal had no free play in it and was not allowing the clutch to engage properly. Soon sorted and all has been fine since. Was a bit of a nightmare few days that :|

Interesting, did you end up changing the master cylinder for a new one? It's either that or I've got a week vac pump I guess as there can't be air let in the system... Got to love landys they keep you busy if nothing else!

Did you bleed with your engine running, which also, by chance operates the servo?

Do you have to pump when the engine, and therefore the servo is operating?

You will find that without the engine, your pedal will feel as though there is air in the system and you will have to pump.

That's normal!!

Lyndon said:

Hey guys & gals, after recently changing my master cylinder and servo I seem to have air trapped ant I can't get it to shift!

I have tried the two man method, pressure bled @ 20 psi with the mc uphill, pumped pedal with pressure bleeder and still the same problem. If I pump the pedal once the breaks are fine until I release the pedal then I need to pump again to get proper breaks again.

Any ideas as I'm all out!

Click to expand...

nm, having a moment

Yeah osd, all done with engine running. When driving one full stroke of the pedal and the breaks are much sharper which suggests air but after having tried ever trick in the book I'm starting to think it's either a faulty mc, weak vac pump or a blockage in the lines trapping air wherever it's stuck!

Lyndon said:

Yeah osd, all done with engine running. When driving one full stroke of the pedal and the breaks are much sharper which suggests air but after having tried ever trick in the book I'm starting to think it's either a faulty mc, weak vac pump or a blockage in the lines trapping air wherever it's stuck!

Click to expand...

nothing daft is it, like you fitting the calipers with the nipples on the bottom, or a sticking piston?

trax said:

nothing daft is it, like you fitting the calipers with the nipples on the bottom, or a sticking piston?

Click to expand...

Double checked both of those as that is exactly the type of thing is do! Been over the entire system and everything is as should be. It's starting to do my head in now!

Lyndon said:

Double checked both of those as that is exactly the type of thing is do! Been over the entire system and everything is as should be. It's starting to do my head in now!

Click to expand...

and it's deffo not the rear, if the cams aren't adjusted right or if the shoes are fitted back to front it can muck it up.

else i'm all out of ideas

I think it may be my vac pump as there is no real dip from the pedal when started with my foot on the brake. Think I may try bleeding with the revs up to see if that makes a difference. Any one know how much vacuum a good pump should be creating when in good working order?

With the rears clamped brakes are poor, with the fronts clamped they are better, so rear are fine and it would suggest that air is stuck in the fronts but they have been bled extensively with the engine running, facing uphill, jacked up on each side with a pressure bleeder and I have pumped the pedal. If it's air it's down right stubborn!

Lyndon said:

I think it may be my vac pump as there is no real dip from the pedal when started with my foot on the brake. Think I may try bleeding with the revs up to see if that makes a difference. Any one know how much vacuum a good pump should be creating when in good working order?

Click to expand...

24-30 hg iirc

without a pump the pedals will still work, just be bloody hard to press.. but you can lock em all up.

i also used an oil extractor shoved into the hose to test if that's any use.

i've just stuck on an eleccy pump to mine, so it's still fresh

btw if anyone can get a pug 205 vacuum pump for some pennies, then let me know! (random i know)

Lyndon said:

With the rears clamped brakes are poor, with the fronts clamped they are better, so rear are fine and it would suggest that air is stuck in the fronts but they have been bled extensively with the engine running, facing uphill, jacked up on each side with a pressure bleeder and I have pumped the pedal. If it's air it's down right stubborn!

Click to expand...

no leaks or anything by the callipers? pistons or nipples.. you did close the nipples didn't you :lol:

You know what i might change the bleed nipples, on my t4 couldn't get clutch to get a pedal and after lots of trial and error it turned out to be letting in air through the thred! Got to be worth a go for less than a skin diver

OK< if clamping either of the fronts produces pedal - does clamping the back do the same?

Reason i ask is that my 109 did the same thing at one time - and it turned out the backs were simply badly adjusted - but the back was soaking up all the travel in the pedal so couldn;t get a pedal at all.

I set the shoes tight at the back (2 clicks off locked) and lo and behold pedal was much better with no change in the fronts.

Rear drums are oftem problematic even on trucks with dual master/servo systems.

ajr