salimshah

I do not have the manual.

Reverse pumping to un-brake (if there is such a term) is very very unlikely. I am always ready to learn new things. If you find something please share.

Please do not misunderstand me .. controlling the pressurized path(s) and getting the boost is a sure way to bleed. The pumps can also suffer from air-locks. [see my earlier post in the same thread].

Since it is hard to lay your hands on some of the equipment available at the dealership, I am merely pointing out the alternatives that exist.

Salim

rcy

Oh, I'd like to know of alternative that work as well, since replacing brake fluid is something I've always done myself. I'd love to do it myself on the RX400h, but as I said the service manual only shows the one way (Lexus diagnostic computer - using electric pump).

I have also read of others that have tried to bleed the RX400h in the traditional way and ended up with spongy pedal and numerous warning lights on the dash, necessitating a visit to the dealer to have the system bled properly.

rcy

I found this in my service manual...

"During normal braking, the fluid pressure generated by the master cylinder does not directly actuate the wheel cylinders, but serves as a hydraulic pressure signal. Instead the actual control pressure is obtained by regulating the fluid pressure of the hydraulic power source in the brake actuator, which actuates the wheel cylinders."

So my guess, based on this, is that pressurizing the master cylinder will NOT bleed the brakes on the RX400h. You must instead somehow power the brake actuator, which will pressurize the line to the wheel cylinder and force the brake fluid out.

This is where the service manual procedure for bleeding the brakes on the RX400h instructs one to hook up the Lexus diagnostic computer and cycle the brake actuator.

The brake actuator is located close to the master cylinder but actually right against the passenger fender wall, with hydraulic lines in from the master cylinder and out (to the wheel cylinders I guess. It's a metal box (cube) with a couple of electric motors hanging off the front.

thomas1

I was wondering if turning the ignition on which is kind of scarey would make the electric pump work normally...? Maybe if the car is up on stands and the engine is running you could bleed the system...I will look at the schematic on the brake electrical and see if there is a way to turn the pump on...manually.

txt

In a non-hybrid car, the brakes and the steering can still function when the engine is off.
Therefore the brakes and steering still work in case of emergency (ie. running out of gas at 65 mph LOL ).

On a hybrid, do the brakes and steering still work in an emergency situation where the engine and batteries are dead ?

thomas1

the engine is not necessary, but the batteries would have to function if you are applying brakes, the hybrid uses electric pumps for pressure... Note I looked at the schematics, and am at a loss to turn the pump on. The intelligent tester to the DLC3 connection is there, but it goes into a mini computer circuit board... still wonder if turning the ignition on will work.?

rcy

When I was looking through my service manual regarding the brakes, I noticed that there is a capacitor (or some sort of battery back up) for the brake actuator. So you would have a limited amount of power to power the brakes. If I recall correctly (I'm not at home right now) there was also a fail safe when the battery back up was out that would allow braking, albeit without the power assist. The steering will still work, but I don't know if there is a battery back up for it (likely not?), so you will have steering without power assist.

rcy

So you're thinking, turn the ignition on, open the bleed valve at the wheel and have someone step on the brake pedal in the vehicle?

salimshah

This is my experience on GS (which has an electric pump).
On depressing pedal, one rear slave bleeds out the fluid. When it bleeds it does not stop. [the non-electrical-pump only lets out the fluid that is compressed by the pedal]. The other side does not bleed. [This is where an over-ride for ABS is needed].

As soon as I find information for the external pump .. I will post the link. These pumps push the fluid down the master cylinder (expecting the return path to be open ... no brake applied).


Ok here it is
http://www.apexperformance.net/cartg...FcW8KgodBQOybw

I am not endorsing the merchant.

Salim

rcy

Will this work though, since the fluid in the master cylinder is only used as a pressure signal to the brake actuator, or are you suggesting to use this with the ignition on, so that the pressure from the external pump activates the actuator, and no need to step on the brake pedal?

If it's as easy as pumping the brakes with the ignition on, why would the service manual have instructions to hook up the diagnostic computer? Are they just trying to force ppl to take their vehicle to the dealer?

salimshah

The diagnostic computer would open all channels (path to all 4 slave) and would require pressure on the brake pedal to activate the electrical pump. [the diagnostic computer may even have a button to turn on the pump ... I am guessing as it is dealer item]

The other option is to use the pressure pump (link). This would work with vehicle turned off and no one pressing the brake pedal. With the brake pedal in released position (not depressed) the slave cylinders have a free path back to the reservoir. The pressure pump then pushes the fluid down the master cylinder to the salve. You bleed one at a time. You need an adapter to the master cylinder.

If you go the web-site of the pressure pump, they have a better explanation.

Salim

thomas1

interesting salimshah, man do i want to buy another tool? Do you have one of these...

salimshah

I was almost going to buy one .. needed to bleed the clutch on son's bmw .. the pedal does not return by spring action .. you pump down and then pull up . Since it was a single destination point, I just let gravity bleed it.

Salim

ps: I was also tempted to make a universal pump with a latex glove as an adater to any master cylinder reservoir and was looking for a cheap bellows type stoking pump connected to the finger. I am on the look out for that trinket every time I accompany my wife to the Asian Import stores.

HF also sells a suction/pump device which you connect to the bleed end. Dont know how good it is.

tonyfern75

Lots of people like this Scanning device. They say it allows you to everything the factory computer does. I bought it with the hopes of bleeding my brakes using the internal pump/factory method.

tonyfern75

I have Star Diagnostic and use it for everything on Mercedes Benz (including brake bleeds), but that costed me around $600. If the Fotga would allow me to only bleed my brakes on the Lexus, I would gladly spend the $24. I haven't attempted to use it yet so do your own thorough research before jumping in. I hear most people run it on Windows XP 32 bit laptops. Most people aren't still using that OS, but one individual said he got it to work on Windows 7 64 bit.