hi all, please be gentle im a newbee,
please help iv no brakes...
i have a doblo 04 1.9jtd with no ABS i bought 4 weeks ago and i have replaced the front discs and pads ( cracked discs and 1 mm on pads ) and removed the fluid cap and pushed back the piston, all went well, i pressed the brake paddle :bang: without the engine running and had preasure untill i started the engine and then lost the presure. iv replaced the master cylinder with a new cylinder and full brake bleed but just the same, no leeks, pistons are gripping all brakes when wheels are off the ground and with no engine running.can it be the servo or a faulty new master cylinder. please help......

Hi it seems as if you have lost a vacuum conection to the servo,or loose bleed nipple.
Welcome to the forum

hi,thanks for reply, the vecuum pipe is the black pipe from the engine to the servo ?,seems ok i never went nere the pipe when changing the disc/pads,would the presure of pushing the piston back force a leek somewhere? if it was the bleed nipple wouldent i have a leek?.im thinking of getting a scrappy master clyinder and trying that.thanks

hi,would a punto mk2 master cylinder and servo fit my doblo 04 1.9jdt.the servo looks the same.

hi,have fitted second hand master cylinder tonight from a punto mk2 but no joy, thats the 3rd one so carnt be that,can the caliper/piston be letting in air?,broken a seal when pused back?

Before you pushed the caliper back to accept the new pads, did you take the top off the brake fluid reservoir?
If not, you may have popped one of the rubber flanges in the master cyl. so when you press the brake, the fluid isn't being compressed in one of the chambers.
I don't know about dobbin but you can buy repair/service kits for most vehicles.

hi thanks for reply,
yes took the top of filler before pushing back the piston,have replaced the master cylinder with an after market then i replaced that one with a used lucas of a punto,one of them must be a gooden.blead the breaks after every fitting of cylinder.carnt see any leeks.have taken the vecume pipe of the servo and there was suction,the break paddle was hard when the vecume pipe was removed,so the servo must be working?

any more ideas out there please...

go back to the beginning......are the discs/pads right parts and fitted correctly?

hi, the discs/pads arnt genuin fiat,but do seem to fit ,wheel spins and caliper grabs and release the discs when engine is not running.
taken offside caliper off last night and no leeks, open the nipple and pushed back the piston,closed nipple pressed brake/piston whent out...took cap off tanks and slowly pushed back piston,fluid rised in tank,presed brack piston whent back out...seems tobe ok..seems tobe air or servo but carnt see how?.... just had a thourt can it be when i pushed back piston has air got into the clutch and know affecting the brakes...the clutch seems ok..the tank was neever drained down always toped up..on bleed...i can see a nipple on a black tube on the clutch line on the gearbox, but carnt see a nut to drain clutch...

thanks for the reply,, sorry for going on trying to be as accuract as possible ..

have you bleed the brakes correctly, from rear to front?

When the engine is running, and press the brake pedal, what happens, does it gradually sink, do you have to pump it a few times, or does it just go flat to the floor of its own accord.
If you do a google search like 'no brakes when engine running' there are lots of other people who have had this problem. Lots of talk of bench priming the master cylinder, adjusting the lever, seized calipers, proper bleeding etc. Are you sure your system is fully bled including the rear wheels? Hope you find the problem and let us know the answer.

hi,
i blead the brakes from back to front using a gunson tyre bleeder (i think thats what its called) when the engine is off the pedal is normal but as you switch engine on and start to press the pedal it becomes spongee and moves slowly down only with your foot presure not on its own, you can pump it a few times and its gets harder but not normal then it becomes soft again. all the pistons act normal without engine on,...cauld there be an leak in an flexable hose letting in air but not leeking fluid,but the fluid would leek out under pressure?
thanks for you help

I'm no brake expert but the fact the pedal goes down presumably continously, suggests a leak or faulty servo. Have you checked the rear drums, even though youve tried a few different servos could they all be bad. You could probably save time taking it to an expert or getting a mobile mechanic in to help. Have you bled the servo?

hi , no i havent looked at the rear drums,what would i be looking for? leeks? sorry if i sound thick.. but you say bleed the servo..what do you mean didnt know you cauld bleed the servo..the vecume sucks air out of the servo to the engine..thats right isnt it?.. mybe get a used servo and master cylinder again and give that a go...thanks for your time.

Yes look leaks on the rear hydraulic cylinders / lines. I worry that you don't know what you are doing and brakes are so important. Please get some expertise in.

hi,all just to keep you all upto date...
took advice and taken the dobee to fiat,they bleed the brakes ( £54 ) and check but nothing was found,recomended changing the master again( i think not) the brakes were better after the bleed,but not as thay should be..when i got back home i noticed that the offside disc was only being marked by the pads on the outer edge of the disc. i removed wheel and noticed that there was play on the caliper, the spring holding the pad had moved and was not sitting on the outer egde of the pad but was pushing the calliper apart,every time the brake was pressed,the calliper would moveapart giving a spongee feel with very litttle brakinging force.... the nere side spring was ok,still siting as it should be... just a little spring cauld cause all this trouble and lose your brakes..hope it dosnt disloge again.

thanks for all the help...