BigE

iTrader: (2)

I have air in the system of my 02 Formula thanks to a previous owner. I've bled them a few times after correcting a few PO mistakes (like a brick of a chinese rotor on the front left). I believe they cracked the system up to the ABS block and didn't bleed it properly thereafter. I have access to a Tech II but can anyone tell me the process for bleeding via a the Tech II?

Thanks

NBM-LS1

iTrader: (7)

Plug it up, initiate the bleed process, and start bleeding.

BigE

iTrader: (2)

So it should be readily apparent via the menus?

bww3588

iTrader: (49)

its under the ABS section.

BigE

iTrader: (2)

Just thought I'd post up some more information now that I've hooked it up. I think a lot of people could benefit from this in a search.

First, my problem turned out not to be in the ABS system. After initially hooking up the Tech II, it said to refer to the procedure in the manual to properly bleed the brakes. So I borrowed a service manual and read up on the system. After educating myself a bit, I performed a closer inspection of the master and discovered it was leaking into the booster so my problem was unrelated to the ABS block (GM calls it the EBCM [Electronic Brake Control Module] and the BPMV [Brake Pressure Modulator Valve] - BPMV is the block with valves and pump, EBCM is the controller bolted to it).

Second, looking in the service manual (HIGHLY recommended), the hydraulic circuits from the master cylinder to the wheels are completely uninterrupted when the ABS/TCS systems are not active. If you're not slipping or hard-braking, the system acts like any other non-ABS system. This is significant because the system will bleed like any other system. So if you bleed your brakes and it works well for a short period of time and then acts up, you could have air trapped in the ABS block that is being passed into the system when ABS or TCS is activated (slip, panic stop or when the system initializes after start up). Unless something really goes wrong, most people should not have to bleed the ABS when working on the brake system. However, I would highly recommend capping the system whenever you have to open it but aren't working on it. So if you're doing some work to the rear end and open the brake lines to do it, cap the ends of the lines if you're leaving it for a day/week/month. It will prevent air from traveling up the lines to the ABS block.

Lastly, the Tech II bleed is an AUTOMATED bleed process. The manual instructs you to pressurize the system to 30 psi (via Motive pressure bleeder or similar) before you start the process. Once that is done and you start the process via the Tech II, it will tell you to open X bleeder screw where X is whichever wheel it tells you. It then cycles the solenoids and pump in the ABS block to bleed the block and that particular wheel circuit at the same time. Once that completes, it will tell you to close that bleeder screw and move on to another one. You do that until all 4 wheels are bled. This is as far as I got since I discovered my problem was elsewhere. The reason I think this is important is that, not knowing it was a pressure process, I was hoping to use the Tech II to open the solenoids and then bleed the system with the foot-pump method. I didn't try it, but looking at the way the system works, I don't believe it would be an effective method. So if you have to do this, plan on having a pressure bleeder available.

I am no expert in the use of the Tech II or in the design of the ABS/TCS/brake system. However, through this problem, I have learned the above. I hope it helps someone else if they run into issues similar to those that I did.

Spartan7

iTrader: (7)

I'd be a little leery of using that much pressure. I've read of some guys blowing up their master cylinder reservoir. When I bled my brakes with my Motive bleeder, I only used 15 psi, which was more than enough.

But other than that, great info. Where did you end up borrowing a Tech II from?

BigE

iTrader: (2)

Yeah, the manual actually states between 30 and 35 psi. I was doing a search where someone on cz28 exploded their MC at 25 psi. He stated that the Motive directions tell you not to exceed 20 psi. Again, I didn't use a pressure bleeder so I have no idea what it would actually do. Knowing what I know of mechanics and hydraulics though, almost any pressure differential is going to cause the fluid to flow so I would start out conservatively and see how fast fluid comes out. If it doesn't come out fast enough, up the pressure. But as long as it's flowing, I'd leave it alone.

I borrowed it from work.