Monday 6 May 2019

Bleeding Brakes and Clutch

Series Land Rovers can be difficult to bleed, and with new master, wheel, and slave cylinders, and new brake pipes throughout, there was plenty of places for air to hide..

I bled the clutch first, this was straightforward as they're easy to get to on a 2A and sit upright. I pumped the fluid through at the pedal and operated the bleed nipple while I sat there doing it. The fluid came through aerated to begin with and then came through solid and I nipped it up and had a good clutch pedal. I fit a steel braided hose between the slave and master outlet pipe. The master is an OEM. The slave is a repro part. I packed their boots with red rubber brake grease.

I bled the brakes the same way to begin with, into a one-man bleed kit from Halfrauds (not to be confused with the one-man pressure bleeder I link and talk about further down) with the non-return valve in the bleed hose. I found a couple of leaks very quickly and nipped up the unions which fixed those. I did all four wheels about four times with the one-man bleed kit but still had a spongy pedal. At this point it would go all the way to the floor on the first stroke!

I then tried doing it manually with a helper, as I thought the cylinders might be drawing air back past the bleed threads when the pedal was coming back up. (Despite having some PTFE on all my bleed nipples.) I thought closing the bleed nipples before the helper let the pedal up would sort this. We did it three times round and the pedal was better but still no cigar; it would go down to within an inch of the floor but not touch it any more, but still get firmer with more pumps..

I then got a pressure bleeder from Paddock Spares for about £15. They do fit the shared 'bean can' reservoir like my 2A has. I had trouble getting good seals everywhere until I started using wads of PTFE tape everywhere I could hear air or see fluid escaping. You're aiming for a complete seal when you connect the pressure valve to your front O/S tyre. You don't want your wheel going down, and you don't want to stop and start while you're working as you'll get air in the input tube. Once I'd got good seals I was able to blast all four wheels in turn again, and I went around about 3 times. Again the pedal was better but still no cigar as it would go down past half way on the first press and firm up with two or three more. You're aiming for a firm pedal that does not get firmer with successive pumps - this firming up indicates air somewhere being compressed..

I then bought three bar type flexi hose clamps. With all three flexis clamped off the pedal would not move at all. This was a good sign as it meant no air was trapped between the reservoir and the flexis or in the master cylinder. I removed the rear flexi clamp and the pedal was still incredibly firm so that gave me confidence the rear cylinders were bled. I clamped the back off again, and opened each front one in turn. Each one made the pedal a bit worse and with both fronts unclamped the spongy pedal was back, so now I knew the air was in the front cylinders. I bled each one with the rest clamped off using the pressure bleeder. I didn't get any air out to begin with. When I tightened the brake adjusters up tight to bring the pistons out the wheel cylinders inside the drum, I then got some air out both sides - it must have been stuck somewhere at the end of the piston and so not coming out when bled normally. This was a tip from a neighbour who said he'd had to do this often working on HGVs years ago. The pedal felt good now. I set the adjusters back where they should be and tried once more, got no air, so removed all the clamps and tried the pedal. It's really good now. It goes down about half way on the first press and does not get any firmed with more pumps. I can't see any leaks and I'm not losing fluid from the reservoir overnight.

The pressure bleeder I used:

https://www.paddockspares.com/one-man-brake-bleeder-hose-kit.html


The kind of bar type clamps I used. Put your hose mid-point between the bars at the pivot end, not further down towards the thumb screw end. The pivot end is where the gap is just right to seal off your flexi hose with the minimal amount of pressure, so as not to damage the hose.