Losing Brake Fluid after Mechanic Bleeded Brakes

[oversite]

Hi all,

I had my mechanic bleed my brakes last week as they were a little spongy, I checked after it was done and the brake fluid was full.

This arvo when i got in to start the car I had no pressure in the pedal and when I checked the fluid it was empty.

I refilled the fluid and pumped the pedal and it kept going straight to the floor.

Caught a cab to work

Came home tonight and the fluid has dropped a little from where it was but there is pressure back into the brake pedal!

So my question is what do you think has caused this?

Is it possible that the mechanic had left the bleeder nipple nut open and fluid has been slowly leaking out?
OR
Is it likely that I have ripped a brake hose off somewhere?
OR
Is it something else entirely?


Im fairly mechanical but have little experience with Rovers, when bleeding the system is it just the 4 wheels that have bleeders?

Thanks for any advice!

[Kevin B]

Did you see any fluid on the ground or on the wheel, ?

[Blknight.aus]

not an uncommon failure.

with the vehicle stationary and chocked pump the brakes a few times. look on the ground for fresh brake fluid. Im tipping you wont find any.

Where its going is into the brake booster.

Whats most likely happened is that as part of the bleeding the brakes the MC pistons have been made to move past their normal range of movement, and the aged seals have lifted on the lip thats been worn into the MC. Thats let the brake fluid out.

To test theory remove the vac line on the booster and very carefully insert a long ziptie in a downwards direction through the hole if it comes up wet with brake fluid you have failing seals on the MC.

Dont drive it till you fix this, once it happens once it can happen again at any time without any warning.

[oversite]

Thanks Heaps Dave.

If it is the master seals is that an easy fix?

Just rebuild the booster?

[Blknight.aus]

Define easy?

for me yes, its easy. and takes about 2 hours go to woah to
strip out the MC+ booster,
clean the booster
Strip the MC
hone it if required and make the judgement on replace/repair
reseal it
put it all back
bleed the brakes.

[oversite]

So I couldnt get away with just doing the seal?

[Blknight.aus]

only if you're willing to accept a higher risk of brake failure than doing the job properly.

the difference in time saving from just doing the seal as opposed to doing the extra 3 or 4 things required to do the full job is maybe 15 minutes.

it takes about 2 minutes to put a brush hone down a MC to get it ready to take new seals (you have no choice but to strip it down this far anyway)

it takes about 10-12 minutes to undo the 2 nuts and pin holding the booster in place, clean it via hosing out the vac side to get rid of the brake fluid thats trapped in there then put it back in.

[bee utey]

Another common failure is the seal at the base of the reservoir, the one nearest the booster. If the mechanic moved the reservoir at all, the perished seal breaks and all the fluid runs out down the face of the booster. (Yes I did this and finally found a source for this seal.) Its the dogleg section of the seal that supplies fluid to the port recessed into the face of the booster, the rubber here is very thin.

There is a brake shop in SA that stocks these seals loose. They will post.

Power Brakes South Australia for brake parts and service you can't get anywhere else (http://www.powerbrakes.com.au/)

https://www.aulro.com/afvb/

It takes about 15 mins to do, although its very fiddly to get the bottom bit lined up.

[oversite]

Ok Im going to pull the booster apart right now. Im sure Im going to have some questions!

[oversite]

OK so now Im really lost.

I pulled the master cylinder of the brake booster (2x 13mm bolts) and found nothing in the booster? I had a good look and dipped a cable tie all around and there is no fluid and no evidence that fluid was ever there???

I again checked all wheels and ran all lines from the cylinder to the proportioning valve and then to the wheels and I didn't find anything!

There is no sign of a leak around the booster/master cylinder itself either

This truck leaks diff oil, transmission fluid and oil but I cant find any brake fluid!!!



Any advice as to where I should go from here?

[Blknight.aus]

usually the case as bee utey has pointed out is easy enough to spot from the dirty great wash of brake fluid under the booster. (since you didnt make mention of the presence of brake fluid under the reservoir and on the split conduit under the MC I discounted the leaking top seal)

if you have a drain hole through the firewall the fluid can be pooling where you cant see it but with the wetness over the MC and under the reservoir in your pic and the wet mark on the split conduit thats under where that point on the MC would be Id say that your current most likely cause is the top seal on the MC to the reservior.

next step is to closely inspect the MC for leak points.

[oversite]

Thanks blknight,

I didnt think It was leaking form the master cyliner but I will give it a full inspection tomorrow.

I have never bled the brakes in a Rover, are there just 4 nipples on each wheel?

And is the order Back Right, left, front right, left?

Thanks for any advice.

[Blknight.aus]

pretty much any order is ok with the dual line brakes,

[Tank]

What model and year? the early Discos 93 and earlier had 2 brake lines to each caliper and a 3rd bleed nipple on the top outside of the caliper (nearest wheel), wheel needs to be removed to find this front caliper nipple and special method of bleeding also, Regards Frank.

[oversite]

Thanks frank, Mines a '93 model but there is only one brake line to each caliper