Outer Limits 4x4 Board

Gday,
Having issues with getting the brakes to work properly. GU disc brakes front and rear, tried with the navara brake master cyl and we could pump it up but then when we start it, it looses brake pressure and goes to the floor. Tried a GQ master cyl(was working when we pulled it off the gq), bled the system got good pressure when it was off, turned it on and lost all pressure?.
Pulled the booster line off and blocked the booster, the brakes go semi hard but still spongey.

Any idea?

vaccum to booster problem ??

sounds like a lot of air in the brakes try just doing a bleed on your brakes

vacume bleed may do it had to do that a few times on trucks to get it to harden up.

maybe worth having a look at your brake lines and see where air could be getting trapped. also the position of the bleeders on the calipers. just make sure you're giving the air the best chance to get out

The booster seems to be working, and theres good vac off the line.
Checked all the bleed nipples are at the top of the calipers. tried using a vac bleeder.
Weve got it now that if you apply fast pressure to the pedal with the car on or off it goes hard and keeps pressure. But if you apply the brake slowly itll go to the floor?

joshy wrote:
Weve got it now that if you apply fast pressure to the pedal with the car on or off it goes hard and keeps pressure. But if you apply the brake slowly itll go to the floor?

This will normaly point to seals in the brake master cyld bypassing or an external leak sumwhere taking a gess that you would know if there was an extenal leak. id go internal in the brake booster may have over stroked it into an area it dosnt normal run when bleeding it up and damaged the seals i try nt to go to the floor when bleeding in older gear for this reason.

from you last comment i belive its the seals in your master ive been down this path on removal of the master cyl i found the seals had gone
same syptom push pedal fast feels ok push slow it fades away to the floor

Thanks guys, we spent a few more ours at it. ended up plugging up one part of the line at a time to see where the problem was. The front left rubber line to the calliper must have a hole in it as once we plugged it off we got good braking pressure. Just have to get a new rubber hose made up.

it woulnt hurt to get both of them done, if one is stuffed the other one wont be far behind it

rob

Yeah i was thinking i might replace all the rubber lines just in case.

wow. no viagra jokes. im shocked haha