No brakes with engine running

[RobParkerMB]

I've recently replaced all of my brake components. I have bled them, and with the engine off I have a pedal, as soon as I start it, there is nothing, literally nothing at all, it's like the pedal isn't even connected. Have I still got air in there somewhere? I don't get alot of fluid out of the rear bleed nipples.

[rogerh113]

I think that the only connection between the braking system and the engine (running or not) is the brake booster. 

You might want to check the plastic fluid trap in the air line between the booster and the intake manifold, and see if it is loaded with brake fluid.  Not sure how this could cause the problem, but would indicate something failed within the booster.

Could be that the engine vacuum is fully triggering the brake booster (full braking), or the booster is seized in full braking mode, and that is why there is no pedal left.  Is there pedal feel when the engine is turned off?

You should be getting good flow out of the rear bleed nipples.  Did you replace the rubber brake hoses?  Those could be old and blocked.

regards -- Roger

[RobParkerMB]

Thank you. I will check that fluid trap, although as you say I can't see why it would cause my issue.
I can't even see if the booster had failed that it would cause my issue, I would think it would give a hard pedal.
I wonder if with the power of the booster it's emphasising air in the lines that haven't bled properly.
Yes all hoses are new. It's abit of a head scratcher

[hemibeep]

I am also working through new brake system.

Master cylinder was hard to bleed.

If you have pedal with engine off, then no pedal with engine running, you probably still have air in system. Booster is power assist and multiplies pressure to MC.

The front brakes are easy to bleed by simply turning the wheels one at a time. perhaps try with car running.

Should always start with passenger rear, then other rear, then pass front.

good luck

[RobParkerMB]

You wouldn't think bleeding brakes would be so hard! Had the same trouble on a 203 years ago.

Good luck to you as well

[mdsalemi]

My guess is you were not using a vacuum or power bleeder?

[Raymond]

Even with a bit of air in the system, you should be able to pump up the pressure.  With no pedal resistance at all, I'd suspect a blown booster. 

[AndrewB]

Not sure if you have LHD or RHD Pagoda, I believe the boosters are different

However, Colin Ferns can rebuild both types

[Cees Klumper]

Maybe bleed the master cylinder again, before anything else?

From memory, when I did one a few years ago it was basically attach a hose to the outgoing 'port/nipple' that feeds straight back into the fluid reservoir - pump the pedal/rod several times so that the fluid recirculates and expels any air from the master cylinder.

[RobParkerMB]

I'm going to try and re-bleed the new master first.

Wouldn't a blown brake booster result in no vacuum and therefore a hard pedal as apposed to no pedal?

[BobH]

Maybe you're sucking in air from a joint or even a wheel cylinder, even if you've replaced them.  When the engine is running the leak may be exaggerated

[rogerh113]

I think if the car is  'sucking air' from a cylinder, then the only path out for the fluid is the fluid trap (and input manifold).  If the fluid trap is not rapidly collecting brake fluid, then likely 'sucking air' is not the problem unless the displaced brake fluid is collecting in the brake booster (failed).

When I redid my brakes years ago, the master was a bit fussy and I did end up bleeding it.  That soft pedal issue was without ever starting the car. 

Useful to eliminate the easy, inexpensive possible issues before addressing the brake booster.

[BobH]

Have you replaced the calipers on the front?  if so are they fitted correctly, with the bleed nipples at the top, not the bottom?

[RobParkerMB]

I think I've found the issue.
On my way around re-bleeding, one of my new front calipers was leaking from the joint between the two Half's. I've never seen one leak from there before, didn't spot it before. Hopefully the shop I bought it off will send me a replacement.