The pump & hold method mentioned above can cause problems if you bear down too hard on the pedal. Many believe you need to do this to flush/bleed effectively. Not true.

I've used the pump & hold method and have also used a pressure bleeder. The pump & hold worked as well, if not better. The bleeder I bought was one of the typical diyer units that connects to a tire. I doubt that any of these $50-$100 units is as effective as a professional model that can apply more pressure.

My 2 cents.

So if I made my own, does anyone know what PSI is recommended for flushing? Maybe 10 or 20 psi??

MP

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I found out my local autozone loans out brake bleeders. They said it's the vacuum type that you basically connect at each wheel's bleeder valve and suction the fluid out. Besides the fact that you have to manually keep refilling the master cylinder, are these any better or worse than the types that apply pressure from the top?

A respected tech on another site once said you're wasting your time with pressure bleeders unless you can get at least 30 psi out of them. Professional units can go that high easily. The instructions with my unit said to set it to 15 psi. I never felt that I got as firm a petal with this unit as I did with my foot.

Again, my 2 cents. I suppose not all bleeders are created equal.

Yes if you need to BLEED, then more pressure is better. The thread here, though, is talking about FLUSHING. For flushing, 15 or 20 PSI works great. If you have air in the system, then you need to BLEED and you will need to use the two man method or a higher pressure bleeder.

Merry Christmas,

That's every 2 years on a 124, the coolant is every 3 years.
Gilly

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You need to be careful with pressure. Recently I watched a friend hook up a pressure bleeder to his Honda and pump it up to about 30 psi at which point the plastic reservoir blew off the aluminum m/c, and its contents flew far and wide. (What a mess!) I think our Merc's reservoirs are held in place by a couple of thick O-rings that fit in recesses in the m/c and reservoir, and at some pressure differential the plastic reservoir will either blow off or fracture and explode.

If you have an integral master cylinder/reservoir like the old GM cast iron units from the sixties and seventies you can probably use more pressure, but I really don't think it's necessary, and you need to use caution when dealing with a modern m/c that has a plastic resevoir.

I noted on the instructions for my buddy's pressure bleeding kit that is said to use 20 psi, but I would start with 15 psi, which should be plenty to rapidly purge fluid and air.

The recommended fluid change interval appears to be different for some years, but it represents an average for all climates and use. If you live in a very dry climate, like the southwest desert, it's probably okay to extend the change intervals. If you live in a damp climate (most of the rest of the U.S. other than the desert southwest), then it's probably a good idea to follow the recommended change interval if you want to maximize the life of the hydraulic components by preventing internal corrosion due to moisture or reducing the boiling point of the fluid, which can cause lose of pedal due to the water forming vapor at high temperture under severe brake useage.

Duke

So are you saying that low pressure flushing will introduce air into the system? If that is the case then why would anyone do it? Do you flush and then bleed?? How much do the professional units cost and what about the vacuum type?

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

The idea is to move the fluid fast (w-high pressure) so that any trapped air, which would naturally be at high points in lines and cylinders, will be pushed on out. At a lower pressure (slower fluid speed) the trapped air may be able to stay at the high points and therefore contribute to a soft pedal feel.

OK to flush a perfectly working system with moderate pressure, but if components are replaced or if you have a soft pedal then you need higher bleed pressure to ensure that all air is pushed quickly on out.

I had to have 28-30 lbs even to flush-replace my 95 S420. At lesser pressure it would have been a painfully slow flow at the wheel bleed screws. I suspect there is something in the ABS braking system which requires this much pressure. Older cars w-o ABS may work with lesser pressures. I also remember reading somewhere that some new models may not work at all for the DIYer and require dealer procedure and special equipment.

DanielW

And then, there's Mity Vac's version that pressure bleeds backwards, from the caliper bleeders back up to the master cylinder. I think they call it a power-shot or something similar. Their theory is that the ABS and other regulating devices slow down fluid going to the wheels, but allow free return. And, that's the way bubbles naturally travel, so less velocity is needed to sweep the system clean of air. Never tried it myself, but it sounds like a good idea. It might even be do-able with the homemade jobby. I can just see it now, a geyser of brake fluid spouting out of my m/c all over the fenders.

With a simple google search, you can find almost anything. Try it out.

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Norm in NJ
Next oil change at 230,000miles