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Question No Brakes on my Bongo !!

1 year 5 months ago #2613 by Gleavehulme
Gleavehulme created the topic: No Brakes on my Bongo !!
I have a 1997 Mazda Bongo 2.5 turbo diesel that has a good brake pedal that does not pump up when the engine is not running. However, if you keep your foot on the brake and start up the engine the pedal sinks to halfway and then with continued pressure on it the pedal goes down to the floor. You can pump it back up to the halfway level but it still sinks to the floor. I have bled the system numerous times and there is no air in it and the fluid is clean.There are no fluid leaks and I have removed both the pipes from the master cylinder and blanked it off with two unions with liquid metal in the end of them. I have a rock solid pedal that does not pump up. I have removed the servo hose after the engine has been running a couple of minutes and the vacuum is really good. Has anybody got an idea what is causing this phenomena as apart from putting a hammer through the ABS Module theres not much else to eliminate. Is there a special way to bleed the brakes maybe??
Keith T.

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1 year 4 months ago #2629 by Gleavehulme
Gleavehulme replied the topic: No Brakes on my Bongo !!
Hello There,
There MUST be someone out there who knows the answer to this little puzzler as my Bongo has been off the road for two months with no brakes and I have run out of ideas and am in the situation of changing every part on the braking system until it is driveable. I changed the front pads in February, took the top off the master cylinder, pushed the caliper pistons back with the rewind tool (they were not remotely seized) fitted the pads and reassembled it. I pressed the brake pedal and it was solid and high up as normal. I started up the engine with my foot on the brake as it's an automatic and the pedal dropped to about halfway and with continued hard pressure on the pedal it sinks SLOWLY to the floor. It will slightly pump up but still slowly sinks back down. I thought I must have air in the system so I bled it and no air was present. I have now bled it six times and can't find any air in it. I disconnected the two pipes from the master cylinder and blanked it off with two plugs and the pedal is solid with or without the engine running. I pulled the vacuum hose off the servo when running and there is good vacuum and with someone pressing on the pedal it slams back up to the height it should be when running. I removed the master cylinder to see if it was passing into the servo and it is as dry as a bone. The reservoir does not go down and there are no leaks. I removed the next item along the lines which was the A.B.S, module to try and find any blockages and it looked alright to me. The A.B.S. light comes on with ignition and goes off when started up. I clamped shut both front flexible hoses and the flexible hose to the back lines and YES a solid pedal with the engine running. I removed the back clamp(pedal still Solid) then the N/S/F. clamp(still Solid) but when the O/S/F. clamp came off the pedal sinks down slowly to the floor again. Does this indicate that there's something going on inside the caliper for this wheel that's releasing the pressure ?? I recently had an email from a mechanic after I had posted him all I had done and he simply said " It's your vacuum pump) However haven't I already checked this by pulling the pipe off the servo and if it's the pump wouldn't I have a hard pedal with no servo assistance. Help me out guys this is driving me nuts!!

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