Brake Fluid Leak Help!

[jasone3178]

Hello, i've recently done a turbo brake conversion on an n/a, all seals replaced and caliper bores and pistons cleaned before installation. but when i took the first drive there was a sound in the rear like fluid being forced out, upon stopping there was fluid on the outer lip of the disc and fluid all around the wheels, not enough to be dangerous but eventually. so i put it down to a faulty caliper as it had a speck or two of surface rust and replaced them with better condition ones, these have the exact same problem and im so confused, im assuming its the piston leaking but im hoping its the new HEL braided lines i installed as the 34 gtt lines have a little bit of thread exposed from the caliper
Any help would be really appreciated because i need to drive it and done wanna pay drug money for a shop to look at it

[Dark26]

Take your wheels off where it's leaking and clean the discs, calipers and lines with brake cleaner. Once it's all completely dry, start the engine and pump then hold the brake pedal a few times. Then go back to the brakes and have a look where the leak is coming from. You may be able to see if it's coming from the line itself, the connection of the line to the caliper or the piston.

[jasone3178]

The problem is it never leaks when the car is stationery, when it picks up speed and I brake there's the hissing noise and it spits fluid, but only when it's moving

There's a little fluid around where the line goes in but there's fluid on the edge of the disc aswell and I can't see how the lines could leak onto the disc

[MrStabby]

It doesnt make sense that it only does it when you're driving. Follow Dark26's excellent advice, just make sure you press the pedal as hard as you would when driving. Also don't discount that it could even be the new lines.

[Duncan]

the thing is, nothing that leaks changes when the car is moving....it should be able to make the leak occur when stationary no matter what

[Duncan]

lol adam got in first

[jasone3178]

I sat there and pumped it for a while and I can feel a tiny amount under the lines, so I'm replacing the lines, I agree it doesn't make sense but whenever I try it never gets at wet as I expect so I just dismissed it.

Still I'm baffled that fluid from the lines can make there way onto the rotor

[Dark26]

I'm gonna guess that you're using more pedal effort while driving than in your driveway since you actually have to stop.

[jasone3178]

If you pump it up a couple times how is it any different to braking while driving? The only difference is the pads are doing their job

[Ben C34]

Is the car on when testing in the driveway?

[jasone3178]

Yep

[Dark26]

If you pump it up a couple times how is it any different to braking while driving? The only difference is the pads are doing their job

It's not exactly different but you may be braking differently in your driveway than when you're driving. You haven't said how long you were holding the brakes in the driveway so I'm assuming that while driving you're holding the brakes longer for stops. If I went for a short drive for testing, I would probably slow down to almost stopped from 60 about 5 or so times by the time I make it back around from all the T intersections/corners I have to turn at. It may not seem like much but you may not be braking the same amount in your driveway as you do while driving, that's where I think the difference is. Try pumping the pedal a few times and then hold it down with firm pressure for about 10-15 seconds, if you don't notice anything repeat this a few times.

[jasone3178]

Well my current thinking is the lines, I did find paint flaking from the area and looked into whether the 34 lines are right for the conversion and it seems the 34 calipers have a much deeper fitting for the lines, I'm thinking this isn't making a good seal since half the thread is exposed

33 lines are ordered so we'll see if that's it because two sets of good Nick calipers failing can't be a coincidence

[KiwiRS4T]

Are your new lines the same type of connection as the calipers? When I fitted some GTT brakes some years ago I had to convert from banjo to screw in type (or the other way round - can't remember now) and had to remove the olive from inside the caliper.

[jasone3178]

The hel lines just ditch the stock bracket thingy and screw in straight to the caliper

[Duncan]

Well my current thinking is the lines, I did find paint flaking from the area and looked into whether the 34 lines are right for the conversion and it seems the 34 calipers have a much deeper fitting for the lines, I'm thinking this isn't making a good seal since half the thread is exposed

33 lines are ordered so we'll see if that's it because two sets of good Nick calipers failing can't be a coincidence

Are your new lines the same type of connection as the calipers? When I fitted some GTT brakes some years ago I had to convert from banjo to screw in type (or the other way round - can't remember now) and had to remove the olive from inside the caliper.

I think Bob's on the right track.

There are 2 fitting type, one has a flare on the end of the brake line with an angled end that seals on a similar angled end in the caliper (the "olive" Bob mentions). The other type uses a banjo bolt that seals with a copper washer between the head of the bolt and a (hopefully) flat part on the caliper where the bolt screws in.

If your brake line has the copper washer/banjo setup it needs to seal tightly to the caliper, and it won't be able to do that if the banjo bolt bottoms out on the original fitting before it is tight.

So to check that you can look at the copper washer; they are designed to crush a little when they are tight.

[jasone3178]

The stock ones didn't use a banjo bolt, just an unnecessary bracket thing, but they screwed in fully whereas the new lines have this hardline tube coming from the threaded part which stops it screwing in more than halfway

[Duncan]

I think we need pics....but it seems likely the leak is at that fitting