Help.. I think i have air in the master cylinder.

projectandinfo · Post by **projectandinfo** » Fri Sep 15, 2017 9:54 am

Break/clutch problems after removing left caliper.

Car:
Mitsubishi Delica L300 4x4 LHD 1993

Symptoms:
I basically have no pedals just footrests, since they went to the ground with me barely using pressure (keep in mind brake and clutch is using the same fluid system/reservoir). This happens with the engine on and off, tried to bleed it with the engine on and off, nothing seem to bleed. In the rep manual it says the car should be on. (clutch now fixed (?) )

What happened:
I think I got some air into the system when the caliper was changed, but it was first under minimum the day after do to the clutch slave cylinder had popped out of places and leaked over night. I don't know why that happened, but the clutch went to the floor faster than earlier and didn't come up again when I was supposed to park it for the night.

What I did after:
I fixed (?) the clutch by loosen the bleeder valve and press the cylinder together with a clamp and then gravity bleed the clutch. Almost no air seen to be in the clutch tubes after ca 5min.
I tried to bleed the brakes again, (this time alone) but no success. A little fluid came out from the rear right, no air. And almost nothing came out the right front caliper, just slow stream of fluid. Left front, seem to be noting at all, first some air bubbles in the bottle, but then nothing(!?). I have never experienced this. I was doing the bottle trick for bleeding it alone, it normally works great to bleed this way. https://www.youtube.com/watch?v=n1NvtUwfRJc

Questions: clutch slave cylinder leak = air in master cylinder? (would that effect the brakes, or was it just a failed caliper removal?)

How can I bleed the master cylinder, without bench bleeding it? I don't look forward to taking it from the car.
Can I gravity bleed the system with the pedal/pedals to the ground over night? I have heard this technic been used on L300 for letting the air flow to the top and let the fluid sink down, but I haven't tried it myself.

Do anyone have any experience with similar problems?

If it's not the master cylinder, what can it be?

Unrelated to the problem, whats the best way of uploading pictures here? I could upload pictures next time.

Post by **Growlerbearnz** » Fri Sep 15, 2017 6:13 pm

Gravity bleed doesn't work very well on our hydraulic systems, the master cylinders are too high. Also, when the pedal is pushed down even a little the reservoir is isolated from the cylinder, so gravity bleeding with the pedal pushed down won't work.

Do a regular bleed- put a clear tube on the nipple and into a jar, open the nipple just a little- about 1/3rd of a turn- then pump the pedal slowly from all the way up to all the way down (about 2 seconds to push down, 2 seconds to come up) while watching the fluid in the tube for bubbles and topping up the reservoir as needed. There's no need to open and close the bleed nipple, if you open it just a little it will act as a one-way valve and the fluid will flow mostly in one direction. Once it's stopped producing bubbles, close the bleeder and remove the tube.

The engine can be off during this, it doesn't make a difference.

Repeat on the left and right front brake callipers, and the rear brake cylinder.

It helps to have a long clear tube so you can put the jar somewhere you can see it. Luckily the fluid reservoir is easy to top up while you're pumping the pedal.

I have no idea why your clutch cylinder fell out- that's very odd.