chris f

When I used one of these pressure bleeders, as i connected it up to the air supply, it bubbled into the fluid canister and aerated it.

beaker

Bubbled into the fluid canister? How exactly?

Most of the pressure bleeders I've seen use a pump, but there are some that connect to an air compressor. Even on those, however, the air connection doesn't "dip into" the fluid in the canister. Did yours?

JPJ

I've never had any problems with my pressure bleeder introducing bubbles. The pressurized air is only above the fluid in the bleeder tank, so I'm not sure how air could get ever get down through the fluid and the hose to reach the master cylinder? I'm not disagreeing with you that professional garages probably prefer a vacuum system. However, as a home DIY the pressure bleeder has worked very well for me at a reasonable price -- better than having someone pump the pedal when trying to move that much fluid through the system.

Topping off the reservoir and bleeding down to the proper level will work fine when just bleeding the brakes, but the original question was about completely replacing the fluid. For this you have to get the old fluid out of the reservoir (a turkey baster is the tool of choice). No air will get introduced to the system if you don't activate the brakes while the fluid is low, so just get out as much as possible then refill with fresh.

Someone listed the order differently than I do it. Concept was correct in starting fartherest from the master cylinder and working in, but I do right rear, left rear, right front, left front (this is for a car with the master cylinder on the left -- don't know if they have to swap it to the other side for right hand drive cars). If you have a manual transmission the fluid to the clutch should really be bleed out as well.

I recommend ATE Super Blue Racing brake fluid. It has good specifications and with the color change from the BMW fluid you can easily see when you have fresh fluid fully through the system.

chris f

All valid points I must say, but still impossible to finish the bleeding without assistance to ensure a proper job is done, the vacuum system does not have that issue, and its about the same price.
I could never get it to seal properly either, the mere thought of pressurised brake fluid under my bonnet is scary, if you saw what it does to paint, even a small amount, you'd be scared too!!
I just have visions of it springing a leak or bursting.

As for where the master cylinder/servo is, its attached to the pedal, so on a RHD car its on the right. (FYI)

beaker

Funny - that's why I don't like vacuum systems. The pressure one I have has a screw-on cap that fits nice and tight on the reservoir, with a very solid connection going from that to the fill/pressure tank. If I used something like a MityVac vacuum system (and use the gravity fill bottle attached to the reservoir), I'd have to use a plate on top of the reservoir, attached with something like bungie cords. Too much hassle to set up.

Sure, I could just manually fill the reservoir as it goes down instead of setting up the gravity fill, but if I mess up, then I could introduce air into the system. With the pressure bleeder, it's not a problem.

The best thing about all this? We've both found procedures we're happy with.

ernst28

What color is the OEM brake fluid? I just had mine changed by the dealership and the color looks to be like old brake fluid (orange with swirls of clouding liquid that appears to be water droplets). I am curious to know if they just told me they change the fluid...which is what I am assuming right now.

beaker

I don't know if they always use the same stuff, but my OEM fluid was yellow.

pa550

I unfortunately experienced a poor seal with my pressure bleeder on the master cylinder. The result was a quart or so of brake fluid flowing down the firewall and seeping through various panels under the car while I was bleeding the clutch. Of course I freaked, thinking the e-coat and seam seals would be shot. I hosed everything off under the hood and the car and unbelievably there was no damage. I was using Valvoline Synthetic fluid, and the only thing I could figure was it's not as caustic as the traditional brake fluid.

flyhigh_l

Hi Guys,

Just wondering if I can just pour in the brake fluid dot 3 or 4 when my break fluid is low instead of changing the whole thing?
Is there a brand that you can recomend or I have to buy it from BMW?

Thanks,

chris f

You'll need to add the same spec fluid, normally DoT4. Don't brim it though as the fluid level goes down as the pads wear, so when you fit new pads there will be too much fluid and it will overflow.
The system is designed to accommodate the wear and drop in level.