450hplt1

Just got my camaro on the road and everything is going great except my abs light is on and it feels like i have no power brakes. I bled them starting at the unit and then all 4 wheels. The car stops and i have been driving it that way but i know its not right. I don't even know where to start. Any help?

pgerst

Is the ABS light on? If not and brakes are not soft, could be vacuum assist (unit and/or hise.) Not sure exactly what you have changed on the brakes but a new master cylinder should be bench bled (can be done in car with sections of clean new brake line looped back into reservoir), there are also two bleed screws on the valve/abs unit at the left front fender that need to be bled as well before you start at the calipers.

450hplt1

Yes abs light is on. The brakes aren't soft either. Where is the vacuum assist unit? The hose is connected from the intake to power booster. Thanks.

450hplt1

Any ideas???

pgerst

the assist is between the master cylinder and firewall, there is a large 3/8 inch vaccuum hose to left rear of manifold that supplies manifold vaccuum to the power assist unit. http://shbox.com/1/master_cyl.jpg. Not sure how you test the vaccum assist unit, possibly some sort of leak down test? (If you have swapped in a hot cam, you might have issues with low manifold vaccuum which can cause no power assist)

Couple items that are the usual suspects in abs light are: center rear brake light bad, front hubs/rear axle speed sensor/wiring, and low battery voltage. If all these are OK, you may need to get it to a dealer and get him to test the abs for codes and possibly rehome the abs unit but I think that is a fairly rare failure so one of the easy fixes should be the ticket.

450hplt1

Ok, power assist unit = brake booster, right? I assume that its bad but if it was would that cause my abs light to come on? Thanks.

Procharged94Lt1

The abs light comes on when there is a problem like was stated above. It could be as simple as a speed sensor out of whack or something in the module itself.

Is it hard to stop the car or is the pedal just at the top and gets firm quick? If you have completely bled the system properly it shouldn't be an issue. If there was air in the lines the pedal would travel without any resistance which is the opposite of what you are trying to describe.

Easy way to make sure the booster is working is take the hose off of it and drive the car. If it is really hard to stop the car and you need to stand on the brake pedal then I would say the booster is working and your problem lies elsewhere....

pgerst

I will check the shop manual tonight but I think the only failure modes that cause an abs light are abs related. I think if you had air in the system, that would cause the brake light to go on due to pressure differences in the two circuits. I will check and see if a bad assist unit even triggers a light (abs or brake).

Injuneer

Once the "BRAKE" light goes on, it would be logical to deactivate the ABS.

pgerst

Read through the manual a bit. The brake light indicates: pressure differential in circuits, parking brake on, as well as some serious ABS failures which light both ABS and brake light. There is no monitoring (and no warning light) for the power assist unit; also no signal sent to ECBM or ABS from assist unit. So an assist failure would just be no power brakes, hard pedal feel with no electronic warning/diagnosis.

Three ABS light modes controlled by the ECBM: solid ABS, ABS and Brake, flashing ABS (which means the EBCM can not light the brake light for some reason.) The ABS and Brake light combo is caused when ESB can not hold ABS pistons in home position for a number of reasons (can be mechanical or other electrical which causes failure.)

I could not find anywhere where the manual indicated that the ECBM would not engage ABS when a pressure differential exists in the circuits so it seems that ABS will still function if the brake light is on (absent another failure with the abs)?

While it was interesting to learn about the abs, not sure how much this helps the OP other than probably narrow the failures down to two, ABS and assist. If the usual suspects don't work to fix the abs, the codes can be accessed with the Tech 1 tool by the dealer.

450hplt1

Ok let me clear these few things up. I have bled the brakes starting at the abs unit and the brakes will stop the car but obviously the power assist is not working because they are very tough. I have a couple parts cars but just didn't want to start swapping boosters and abs units unless it was completely necessary. I may buy an abs delete kit but i still need to get the power brakes working so I guess I'll start with the booster...

Injuneer

Why not have the EBCM codes read? Chiltons indicates you can not successfully bleed the brakes if you have ABS codes, unless you "home" the motors.

450hplt1

Sounds like a good idea to me but i have no idea what to get to read them or where to take my car?

pgerst

Need a Tech 1, which is probably the dealer or a well equipped brake shop.

Did you have a code before you did the bleeding? If not, I have flushed and bled mine every 2 to 3 years and have never had a code as a result of flushing/bleeding so I don't think the light is a result of the bleeding. I use a pressure bleed system so dont touch the brake peddle or power the ECBM/ABS (key off); if you energize the ECBM and/or use the peddle to flush, that might have caused an error?

I have picked up abs light for bad third brake light as well as low voltage on the battery which self-clear the abs light when corrected. Have you checked the brake light, battery voltage and speed sensor connections as those are the usual suspects before you pay money to the dealer.

450hplt1

Thanks for the info. I have checked everything that you listed and it all seems to be fine. The abs light was on before i bled the brakes, but i think i bled them with the key off. I still do not understand why the abs would cause me not to have power brakes, but i have a fairly good shop in town that i'll probably take it to because they know me pretty well and won't rape me like the dealer.