geoffucla

This is a cross-post from the GT3 forum, but I thought the experience found in this forum would be most beneficial. See post here.

Thanks--

mitch236

I use the Motive power bleeder all the time with no problem. I use it on my track car. I use it without fluid, so I am careful not to let the res. get too low.

Edward

Been using the Motive for years w/o incident. And I started using it after years of using a vaccuum bleeder (slow and cumbersome IMHO), and those that recommended it have been using it for years. The contention that the power bleeder "forces air into the system" is completely erroneous. It exerts only a mild positive pressure (I use maybe 10-15 psi) just to push the fluid out the bleed nipple ...that's it. I'm no physicist, but it would take MUCH more than 15psi to aerate fluid.

Edward

Noel

Isn't natural atmospheric pressure more than 10psi? I've never had an issue.

Technically you are also introducing water into the fluid at all times it is exposed to air, so if I have a bit of fluid left after my pre-event flush, should I not save it for the following weekend at the track or should I throw it away and then open a new bottle 7 days later to top off my master cylinder reservoir? Come on this isn't Formula 1 here.

M758

Here is what I do... For right or wrong.

When I started DE in my 944-spec car I run the car hard for day with nice strong pedal. Next I'd do an autocross the next week. Well pedal was very soft and I don't like a soft pedal. I really want the brakes to be firm and light touch on pedal makes the brakes work.

So I figured that one day's use cause the fuild to boil a little and a soft pedal. I already ran Super Blue and had cooling ducts in the car. So I simply starting bleeing before each track day.

Now it is ritual. At the start of EVERY track day I jack the car up get all 4 tires off and bleed all 4 calipers with a motive power bleeder. I always get a few air bubbles. This ensures I have firm pedal just like I like it for the day.

Now I commit the biggest sin of all... I use fuild from open containers and never "flush" the system .

Here is why. Firstly Arizona is a dry place so there is limited moisture in the air. I also carefully seal all containers. I will add fuild to the motive bleeder. Bleed the brakes and then dump the remaining back into the can I got it from. Then tightly close the can. I don't have the money to dump a can each day I bleed the brakes and this method while not othrodox does give me the pedal feel I want. I have never done a proper "Flush"

I believe the reason I can get away these sins is that I do bleed every track day. This means I am constantly removing and replaceing 8oz of fluid per track day. So inspite of what moisture may enter the system it is quciky removed. I typically go through 3-4 full cans per year with this approach.

Now you could argue that if I flushed once a year and keep the fluid sealed I would not need to bleed the brakes each day, but there are other side benefits from this.

1) I know the brakes are good before each day. If they get bad after a session I can just do it again.
2) Chance to rotate the tires. Since I use the same tires at all corners I use this time to also rotate my tires for best wear each trackday.
3) Nut/Bolt and visual inspection. This gives me a few minutes to check stuff in the wheel wells and under the car before each day. This way I can notice issues faster and prevent others. Also I run steel control arms. They are cheap, but can crack. I don't worry about them cracking as it takes 3 mintues to inspect these when I do my brake bleeding for the day. If I have and issue I have parts on the truck to fix.

M758

Geoff,
I did not read your other post, just make some general comments.

Here is your orginal post
I have exprience with both style bleeders. My father used have an older diaphram unit. We used a small 12v air pump to pressurize it and bleed away. We would fill it with a full can every now and then and leave the fuild it in it. We would depressurize after each use. After a while the diaphram broke. We replaced it with a motive bleeder. In fact the motive bleeder is on some ways easier. The big one is no need for the air pump. You use hand pump it. Secondly it is also easie to know how much fluid is in it. (Old was metal and you could not tell). It is also smaller too.

Down side is that you can't leve the fuild it in it as it is not an air tight unit. And for some reason it levels the master cylinder a little over full. So we have medicine dropper and pull out a little fluid to keep the reservior at good level.

As for the performance. They both bleed the same and once bleed both give me the same feel on the track. A nice stiff brake pedal.

We went with the motive unit since it was cheaper than fixing the diaphram on.

mitch236

If you don't have a lift, you should jack up the car and remove the wheels before each event to check the brakes and tires anyway. Might as well bleed them too.

Larry Herman

I use a vacuum bleeder that I built from an old freon can. I just use my vacuum pump to pull it down to 30" of vacuum and suck the fluid from the brake bleeder nipple. Works like a charm, but I have to carefully monitor the reservoir, as one time I heard this gurgling, and realized that I had quickly sucked all the fluid & some air into the system.

mdbickell

I have the same ritual as Joe P and love the Motive. I've found that I can't get the pedal nearly as hard using the old fashioned pedal-pump method.

geoffucla

Cool, great thoughts. So it sounds like while in theory, the fluid could become aerated under pressure, in practice it really doesn't seem to make much difference. I am curious, though, as to why some simply use the Motive bleeder as a pressure device, and do not put the new brake fluid in the bleeder.

DrJupeman

Btw, for cars like mine that have a "high pressure hydraulic boost system", Porsche requires the use of a pressure bleeder.

Brian P

I love the Motive Power Bleeder. One tip though... don't use it to flush the fluid while you are also changing your rotors.

Bill Gregory

On a higher mileage car, leave the old fashioned pedal-pump method behind - Use pressure (as you do) or vacuum. What happens on high mileage master cylinders, there are smooth sections within where the seals move with regularity. In the other section, there is corrosion that builds up over time. Pushing the pedal to the floor in the pedal pump method runs the seals over the corrosion, ripping them, and guaranteeing either a rebuild or a new MC in the not distant future. I learned this on a high mileage Volvo years ago.

Interestingly, in the 964 factory manual, Porsche recommends pushing the pedal 4 times for each bleeder nipple, while using 2 bar (30 psi) air pressure. In the 993 factory manual, they added a caution about using the pedal on higher mileage cars.

Dave in Chicago

Love the Motive. My son has been bleeding brakes on my Porsche since he was 10, even gets the clutch while he's at it. One litre, 30 minutes, complete flush and bleed. Hot set-up!

Steve Weiner-Rennsport Systems

Hi:

FWIW,......Pressure bleeding is the only effective way to flush clean fluid through the system and remove any air bubbles.

Over the past 30+ years, I've used the pump method, the vacuum method, and after several varieties of pressure bleeders, its THE only way to go,....

Currently, I have two Snap-on pressure bleeders; one large one for the shop and a small portable one that uses an external air source to pressurize the cannister. Both are diaphram types and both leave the reserviour topped up very nicely.

Using 12-15 psi, these things work really well and leave you with a nice firm pedal, each & every time.

There are some tricks of the trade and one of them is to tap on the sides of the calipers with a plastic hammer while bleeding. This dislodges the tiny bubbles that tend to stick inside the piston chamber walls that always resist higher bleed pressures. Thats one major cause for a spongy pedal, even after bleeding.