Strange, lack of brake fluid flowing when hose disconnected

[MisterCruiser]

I put a new brake hose, the flexi part on the front of the cruiser and was expecting to lose some fluid and was dreading having to bleed the brakes as some of the bleed nipples are seized. Anyway, when the hose was disconnected no fluid ran out at all, I refitted the new hose and was expecting the brake pedal to be soft but it wasnt, the pedal was the same as before I started and didn't need bleeding.

Anyone have any ideas why would it be the case that there was no fluid loss and didn't need bleeding?

 

[tim falce]

No idea why you wouldn't lose any fluid but it will need bleeding as you've introduced air into the system. Are you talking about the hose to the callipers? It sounds like you have a blockage somewhere, is the calliper actually working?

 

[Sag]

Hi buddy,
I would of thought it needs bleeding as you have just fitted a new flexi so that won't have any fluid in for one and you will find it will go spongy after a bit if you don't when the air in the system gets round.

 

[MisterCruiser]

I actually fitted it about 2 months ago, yeah its the hose from the hard pipe to the caliper. Only posted now as have been wondering about it. The pedal doesn't go spongey during driving, the pedal has remained the same as before. So does this man there already was a problem like a blockage or something before I even changed the hose. Ill have to check if the caliper is actually working.

 

[mallster70]

i would be very tempted to just get and bleed the whole system through, with fresh oil too.

you cant take chances with brakes. jack up that corner and check out that caliper. you should know by driving it, if it is working. it will be pulling like mad to one side.

 

[wobbly]

Why did it need a new brake hose?

 

[MisterCruiser]

Why did it need a new brake hose?

The Doe, (Mot) tester said the cable was twisted so I had to renew it. It drives and brakes the exact same as it did before and after fitting the new hose. Ill investigate it further next weekend, I might try and draw fluid through the nipple with my 1 man bleeder kit running off the compressor. That's if I can open the bleed nipple.

 

[Towpack]

Sound very much as though there is indeed a blockage and the affected calliper isn't actually working but I just can't believe this wouldn't be noticeable when driving! Does it have ABS?

 

[Shayne]

I would be looking for air in the line rather than a blockage , a trapped bubble could prevent the leaking you expected and wouldn't necessarily effect braking at all .

 

[Chris]

... a trapped bubble could prevent the leaking you expected and wouldn't necessarily effect braking at all . Errr, I doubt that very much Shayne. Air in the system that doesn't affect braking? That really defies the laws of physics. There's something not right there. Bit odd that it's the front brake. My back brakes didn't let fluid out the other week when I split the lines, which I thought odd until I found the LSV was stuffed and not letting any fluid through. If that was the case then neither back brake would work and the car would still stop in a straight line. But on the front if you have a caliper not working then it would pull to one side UNLESS both front brakes aren't working and all you effort is coming from your back brakes. But to crack a line and not have to bleed your brakes is just not possible.

 

[Shayne]

I don't see why not ? If you open the filler cap you allow air into an otherwise sealed system , replace the cap then undo the pipe at the caliper and it will try to pull the air through creating an air lock which would stop the leak . Fasten it all back up again , pump the brake and the air returns to sit harmlessly on top of the oil in the reservoir . Just a theory of course but nothings more maddening than searching for a problem that's not actually there .

 

[Chris]

Sorry Shayne. No. The air on top of the fluid in the reservoir can't get past the main seals in the master cylinder and in any case atmospheric air can't get into the fluid like that. The top up cylinder isn't sealed in any case. it's a good fit but it's not sealed. But it can't pull the air though the fluid, that's just crazy talk. it will pull the fluid through until there's none left, then the pipe will be empty.

You can't block a brake pipe with an air bubble. If the air just went back up the pipe, through the main seals on the master cylinder then up into the reservoir, we wouldn't need to bleed brakes ever - which we do all over the world, and I'd live in a glade in the Enchanted Forest!

One thing that you will notice is that fluid is less inclined to run out if you leave the cap on. Air pressure is basically pushing the fluid up the pipe from the open end and with the lid on, the weight of the fluid trying to run out is countered by the vacuum that that it would create in the master cylinder. Take the lid off and you may see some come out, but if the MC seals are good, you may still not see any. Open the bleed nipple on the MC and then you'll break that equation and all the fluid will run out.

 

[MisterCruiser]

I'm pretty sure the caliper is working as the disc isn't rusty from lack of use and the cruiser isn't pulling to any side. I thonk the best thing to do is ill try the 1 man bleeder to see if fluid will draw through the nipple and maybe the problem fixed itself.