Yesterday I was putting in braided steel brake lines and planning to flush and bleed the brakes after (obviously), and believe it or not, a brand new banjo bolt sheared in the caliper was the least of my issues...

Doing the brake lines, I had the brake pedal engaged (with bricks) just so I wouldn't leak too much fluid before I was ready to flush. I totally forgot about this as I was getting ready to flush them with my new Motive Power Bleeder and I think that was my demise. Following the instructions I first tested the pressure bleeder at 15 psi and there were no issues - mind you, the brake pedal was still engaged. So I fill the reservoir and start pumping it to ~20 psi and *pop* instant decompression and brake fluid all over that part of the engine bay. Not all the brake fluid in the reservoir was leaked/spilled - just all that was above the seam (where the max line is).

So I'm pretty sure I busted the plastic reservoir right in the middle of the seam with too much pressure and am just hoping I can replace the reservoir.
Does this sound accurate? Or did I do any more damage? Any seals that could have been busted from too much pressure? Thanks!

 

Typical brake reservoirs just get pushed into a gasket that holds them on to the master cylinder. perhaps it didn't split and the pressure just pushed the reservoir out of the gasket. But even if it did split it its a pretty simple, relatively cheap repair. It may be that you didn't even push any air into the master cylinder.

Tips(such that they are): when ever I use a power bleeder I always tie the reservoir down to the master cylinder so I don't have it blown off. Couple wraps of twine/kite string work great.
I have had them leak from the gasket seal(s) between the master cylinder and the reservoir. That was enough of a clue for me. I also purge between 15 and 20 psi. I don't put any brake fluid in the Motive power bleeder (less stuff to be squirted in case something else happens). I usually do two wheels before depressurizing and topping up the reservoir. Although the MINI looks like that will be just one wheel.
And when you get a chance replace that surgical tube the power bleeder uses. IT breaks under pressure within a couple of uses. Brake fluid breaks it down. Get the clear polyethelyne at lowes (1/4" ID) You can zip tie it to the bleeder.

If you have to replace the reservoir, Look your car up in REALOEM and drill down to the reservoir and its gasket(aka plug sometimes) to get part numbers.

Good Luck
Bruce

 

Thanks Bruce - a lot of great info there and it's all very much appreciated.
I wanted to post a follow up to thank you and to just say that I'm lucky and it was just the reservoir that indeed did split at the seam - making a relatively easy job of just replacing it (although now I have a spare master cylinder since it was cheaper to get the two together used than a new reservoir lol). Ok, not as lucky as you made me hope I would be, but still not a huge deal. I do have to bleed the brakes again though because I'm pretty sure I got air in the ABS system :/

So word to the wise - make sure the brake pedal is free when you're using a power bleeder otherwise you'll blow the reservoir! (And they're surprisingly not that cheap nor readily available)

 

This just happened to me Friday when I was using my new Motive Pressure bleeder for the first time, and I was replacing and bleeding the clutch slave cylinder. Scared the crap out of me, fluid sprayed all over. I had the car towed to my mechanic, although now it does not sound that bad. My reservoir is still holding fluid in it, so I am assuming the connection(s) to the brake master cylinder probably came undone at the o-ring seals.

 

Interesting. I have been thinking of getting one similar but have never given much thought to what max pressure should you apply. I infer you only need no more than say 10 psi over atmospheric. Did you note what pressure did it happen?

Professional pressure bleeding equipment has been used by dealer for a long time.

 

What a bummer and a mess to deal with.

The pressure bleeder I've been using on the cars has a gauge and I typically flush at 15 psi. Never had a problem the mini, P-cars, and others.

I thought the Motive has a gauge?

 

Brake fluid will eat paint, so make sure you get everything cleaned up real well ASAP after the explosion.