Hi all: I tried to research this on NAM but couldn't find an answer although there are a lot of threads

...this past weekend I bled the brakes on my 2005 cooper s twice. The car is new, build last January. I'm bleeding because I just did a 2 day DE school and will do another in a couple weeks. I used the MOTIVE hand pump tool/method. I put through 4 containers of MOTUL 600. I am not new to bleeding brakes, but have used a Speedy Bleed kit in the past on bmw's but this is my first time bleeding a mini cooper

During the first bleed, the rear calipers appeared to have excessive air bubbles when bleeding, kinda like streaming air bubbles. I turned the bleeder screw to almost closed and eventually the bubbles went away. The front calipers bled fine. I was concerned that somehow I bled the system wrong or introduced air using the motive bleeder, so I bled them again the next day, and again got the damn air bubbles streaming out... and then stopped with the bleed valve almost shut off..... I am wondering did I do something wrong?

The brake peddle appear fine, but I have a few questions about this process if anyone knows...

1) What is the recommended pressure to pump the system up to? I used 15 psi, but heard from a vender that 24 to 26 psi is needed with advanced ABS. 25 psi seems high.... Bentley manual says don't go over 30 psi I believe..

2) Does one have to put the hose that connects to bleeder valve in brake fluid? Could that be the problem causing the excessive air bubbles....I did not put the bleeder hose into brake fluid.

3) Does it matter if the parking brake is on with the MINI as the brake caliper is compressed with the parking brake....

4) Could it just be that the system has lots of air from the factory?

Any other comments would be helpful.. Matt

 

With some bleeding valves I have found that if you open them too much you get streaming bubbles - suggest that you only open enough to allow liquid to flow and be patient.

DO NOT EXCEED 15 psi - I've used the Motive bleeder and kept presure at 12 psi - worked just fine. Just check it periodically to keep presure up.

Not sure about the parking brake - but I'd do with the brake released (make sure car will not move)

Lastly - do not bleed clutch unless you have a way of keeping the clutch fully depressed while bleeding - this is required and will cause problems if not done properly (learned with some helpful hints from other board members).

good luck

 

Glad to hear the streaming bubble thing from other ... Thanks I will re-bleed this time with ATE super blue as no one around boston has motul in stock... $60 worth of motul fluid wasted I guess in my learning how to bleed the MINI Cooper... but want to have confidence in my brakes at my next driving school

I'll try again at 14 psi, opening the valve only a bit.... The on-line instructions from Bavarian Autosport states to pressurize 24 to 26 psi.... so mixed information is confusing to me, but that seems way too high
Thanks again...

 

All,

I have had the exact same experience with "streaming bubbles" in the rear wheel cylinders when bleeding under pressure. I have concluded that the air is in some way leaking around the bleed screw, and that I am not accidentally introducing air into the lines / wheel cylinders. Whew!

Here is what I do quite often: After each track day, I bleed each wheel cylinder by opening the master cylinder reservour cap and letting about 1/4 cup of fluid drain out under gravity. No pressure. I always find a bubble or two in most of the wheel cylinders. By doing this "mini bleeding" (no pun intended) I feel that I am eliminating any boiled and degraded fluid from the immediate caliper areas and replacing that fluid with relatively fresh fluid from the lines and resevour.

When I do bleed the entire system, I use about 15 or 17 lbs. of pressure and am patient. Takes a little longer than higher pressure. e.g. 22 lbs. but I don't worry about leaks of brake fluid some where in the system.

Regarding the clutch slave cylinder, BE CAREFUL. It is easy to bleed under gravity the same way as the wheel cylinders. No problem here. Do this after every track day as well. Don't usually find any bubbles though.

But, woe to you, if you pressure bleed the clutch slave cylinder and accidentally introduce air, as I did once. The clutch fluid inlet is near the top of the brake fluid reservour and once I accidentally drained the fluid below that inlet point. Momini's caution and comment are very, very true. If there is air in the clutch hydraulic system, you must fully compress the slave cylinder and slowly introduce hydraulic fluid and hope that there is not even the smallest air leak around the clutch slave cylinder piston. In my case, I ultimately had to replace my clutch slave cylinder because it would suck air around the piston seal. It would hold hydraulic pressure from the inside, but not seal air from the outside. Anyway, I removed the cylinder from the transmission housing, and compressed the cylinder with a home made compresser. Tne compresser was constructed with two bolts that passed thru the clutch slave cylinder mounting ears and a thick metal bar that pushed on the clutch throw out rod. Even tightening of the bolts pushed on the rod and compressed the clutch cylinder piston. Even loosening of the bolts gradually relaxed the pressure on the piston and the hydraulic fluid flowed into the cylinder.

My track rat friends bleed their wheel cylinders after every track day, too. I think that the frequent wheel cylinder bleeding is a good practice and encourages close attention to this vital vehicle safety system.

Regards,
John Petrich in Seattle

 

Thanks John for the detailed and useful information... In thinking about about it, the air could sneak in if the bleeder is open too much...

Also, appreciate the clutch slave cylinder information... I'll probably just leave that unbled for now, as the system works fine, and fluid only 6 months old....

Its great how a seemingly very covered topic such as brake bleeding can reveal a new bit of information.... great help from NAM folks!

So in summary, i think to bleed using a motive bleeder, I will use about 15 psi, bleed very slowly meaning open the bleed screws only a bit and be patient, and also be sure to bleed into a container with tube immersed in clean brake fluid. Other tips I've noticed include tapping the brake caliper with a rubber mallet to help dislodge air bubbles..

Thanks again...

 

I tried one of those pressure (Vacum) bleeders and had problems with sucking air from around bleeder screws. Tried putting grease arould threads as the manufacturer suggested, different pressures, etc. Never did get it to work properly. Ended up going back to the tried & true using the brake peddle, down/up,down/up process and worked fine.

 

Yes, I would like to do the helper, pump brake method to bleed brakes actually, but my loving wife, is busy breast feeding our 4 month old or chasing around my 2 y.o. when I am under the NEW MINI (whether I'm bleeding the brakes, swoping race/brake pads, changing oil, installing a sway bar etc, etc..), so it's hard to convince her to sit in a 6 month old car for 30 minutes, pumping the brakes... Hey... maybe I should try using her breast pump instead of the MOTIVE pump???

Actually......... after all of this, I'm gonna re-bleed with the motive, and just opening the bleeders a tiny bit and being very very patient.....

Thanks for the help all...

Matt

 

I have speed bleeders for my MCS from piloracing.com. They replace the stock bleeders and make bleeding the brakes a one-man job. They are well worth the $!

I bleed with ATE Super Blue or Typ 200 after every track day.

Aaron

 

just letting folks know that the two person, one pumping brakes and one bleeding works great and gives a very firm peddle.... Once that is done, then using a pressure bleeder works.... I plan to do the two person method in the spring prior to the driving school season, and use the pressure bleeder for intermittent bleeds.... If the peddle feels not very firm post pressure bleeding, then I will do the 2 person method....

 

I agree with most everything that has been posted here. Except: I would not bleed the clutch at all. The brakes experience intense heat and usage on the track. This is why you need/want to flush the fluid. Every track day is overkill; back in the days when I was at the track every weekend, I'd bleed the brakes every month or so. If I boiled the fluid, then of course I'd bleed them, but if you're boiling fluid regularly you've got other problems and you need to address them (cooling ducts, different brake pad compounds, adjust your driving style, etc.) first.

The clutch is not taking the abuse or heat that the brakes are, so I would only bleed that as part of normal maintenance when called for (I don't know what that is).

Pressure bleeding is great if you are by yourself, and the bleed screws will let in air into the discharge hose so that it "appears" that you are getting air out of the system when actually you are not. But the air won't get sucked back in, so you'll be OK.

Speedbleeders are OK, but only for people that don't have a pressure bleeder. I'd rather see a pressure bleeder; speedbleeders can let air in.

If your wife/SO will not or cannot help you bleed the brakes, then do it at the track. There are always people around willing to help.

HTH,

Michael