Recently changed front to rear brake pipes after mot failure, bled all four bleed nipples on calipers but only rear brakes seem to be working , didnt bleed the valve on rear axle because of severe rust etc, I've cleaned and soaked it in penetrating oil ready for another attempt, could this be the cause of my problem? I've read several posts on the various sites saying cruiser brakes are a mare to bleed, any suggestions would be appreciated .
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Brake bleeding nightmare
- Thread starter trev.w
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When you say the valve on the rear axle do you mean the one on the load sensing valve? If so I've never bled my valve and I've never had a problem bleeding the brakes. People have had master cylinder seal damage whilst attempting brake bleeding so perhaps you have this. Probably best to put a new master cylinder in.
Yeh the load sensing valve, from what I've read you are supposed to bleed that last, thought about master cylinder but everything was fine before renewing the brake pipes, if it was leaking wouldn't I be losing fluid tho? which I'm not,when I took old pipes off it was left overnight before I put the new ones on and the master cylinder had drained right down, just wondering if I have a air lock in load sensing valve
Chris J always warns of bleeding using the pedal, whereby putting the pedal to the floor takes the MC piston way past its normal travel and it damages the piston seal.
He uses a pressure/or vacuum (not sure which) bleed kit that draws (or pushes) the fluid and air through the system instead of using the pedal.
When damaged, the MC piston seal doesn't let fluid escape as in a leak, it just doesn't push the fluid through like it should, it leaks past the seal instead.
He uses a pressure/or vacuum (not sure which) bleed kit that draws (or pushes) the fluid and air through the system instead of using the pedal.
When damaged, the MC piston seal doesn't let fluid escape as in a leak, it just doesn't push the fluid through like it should, it leaks past the seal instead.
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Trev you've most likely damaged the master cylinder seal which does not leak and only manifests itself in the fact you can't bleed the brakes. I don't think there will be a bubble in the Load Sensing Valve as the brakes bleed OK without opening this particular nipple. People on here have driven themselves nuts before taking advice and changing the cylinder. Not saying 100% that it is the M/C but you have nowhere else to go.
I used the peddle to the floor method, did it before after changing rear brake pipes,and everything was fine, maybe this time I didn't get away with it, was thinking of taking to a garage to get it bled by vacuum , but if I've damaged any seals could be a waste of time, any way of testing to see if seals are damaged before changing m/c?
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I've never had a problem with any car using the pedal method. You need an assistant though to press the pedal down and when there say "down" whilst you, on the nipple tighten it up. Then you say "OK" and the assistant raises the pedal slowly and says "up". Then you open the nipple and say "OK" and the assistant presses the pedal down and says "down". The nipple should be fed into a rubber hose the other end of which is held under brake fluid in a jar so you can see when bubbles stop coming out.
I should have been clearer. There are 2 seals in the M/C. Sounds like you damaged the front M/C seal as this only travels its normal distance when you bleed the rear brakes. When you bleed the front you can then stress I the front seal so that would make one suspect it is in fact a seal.
Hope it turns out OK. Feedback would be good to add to over all knowledge on the forum.
I should have been clearer. There are 2 seals in the M/C. Sounds like you damaged the front M/C seal as this only travels its normal distance when you bleed the rear brakes. When you bleed the front you can then stress I the front seal so that would make one suspect it is in fact a seal.
Hope it turns out OK. Feedback would be good to add to over all knowledge on the forum.
Used both bleed methods, one with assistant (wife who was pressing accelerator at first, tell she doesn't drive the truck much lol)and with an easibleed single person pipe, read on i8mud one guy made a vacuum/pressure pump out of a garden spray pump,might give that a go when I bleed them next,
Every 80 I have bled with peddle has screwed the mc seals it's very common
You can see the marks inside the cylinder
I vacuum bleed and it is faster and uses way less fluid plus doesn't need that up down shouting match
You can see the marks inside the cylinder
I vacuum bleed and it is faster and uses way less fluid plus doesn't need that up down shouting match
I think you might need the pressure to force the fluid out quicker than the bubbles can float upwards. I maybe wrong but it seems reasonable. [emoji6]
Nice one Sag!
Latest news on brake bleed, Everthing back to normal, freed bleed nipple on load compensating valve, big spurt of air then fluid brake pedal hard, went round al five nipples again and brakes are spot on, thankfully not the m/seals, thanks for all the input guys
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Crikey I've never opened that nipple!! Glad you got it sorted.
