We have Brakes
The postman kindly brought the replacement brake bleeding tube this morning, and as it hadn't started raining (forecast though) I set too.First job was to find a way, in the absence of a helper, to keep the brake pedal pressed and definitely not released, until I had re-tightened the bleed nipple on the axle. I found that I could rig up a large 'Carver' welding clamp between the chassis and the pedal, so then I could go ahead.
Probably worth pointing out that this brake system is not like the sort that you get on a car - it has two sets of oil immersed brake disks inside the axle, one either side of the differential. They are actuated by concentric cylinders and pistons, each with an 'in' and an 'out' port on top of the axle casing. Fluid from the Master Cylinder is routed to one 'in' port, the 'out' port of that cylinder is piped to the 'in' port of the second cylinder in rigid pipe, and that cylinder's 'out ' port has a bleed nipple in it.
The process its, slacken bleed nipple with tube attached, depress brake pedal and fix it down, tighten bleed nipple, release pedal slowly so master cylinder re-fills, then repeat the cycle.
As I was far from sure that this system had been filled with the correct mineral oil fluid that is compatible with the seals (Not one of the standard 'DOT' fluids), I wanted to flush out all the old, so it's good that the cylinders are in series rather than parallel.
Got it all set up, rubber tube on nipple, catch flask in place, then the rain started. Hang it carry on, just get wet
The old fluid was a very different colour from the new, so it was quite easy to see when we went from old, to mixture, to new just from the colour. Interestingly there must also be a marked difference in the viscosity, as, as soon as the new fluid started coming through, depressing the pedal became much easier forcing the fluid through the bleed nipple. Got through two complete reservoirs of fluid in the end.
As you can see from the picture, the old stuff was in a right mucky state. Smelling it I think it was a mineral oil, but not the right stuff. (I've been sniffing bottles of DOT3 DOT4 and DOT5 brake fluid, I hope nobody notices and gets me taken away
Pedal seems pretty solid (air in system gives a spongy pedal) and driving it back and forwards the length of my loading dock it works OK, but by this time it was pouring down and time to clean up.