ABS modulator bleeding/air trapped

[asphalt victory]

bled everything replaced a buntch of parts but its not firming up after bleeding. It has to be air trapped in the ABS modulator Is there a way to get the air out of the module at home?

Any advice much apreatiated
Mike

[asphalt victory]

no takers?

[71Corolla]

How specifically are you bleeding the brakes?

[bolink654]

Dunno, I've never fooled with ABS myself... but

I've heard that sometimes if master cylinders get air in them, or go empty... any situation were the pedal goes to the floor really, this is allowing the piston/seal in the master cylinder, to go into a place in the cylinder it's not been before. And sometimes this part of the cylinder can have corrosion, or something, which can mar/cut/gouge the cylinder and seals, which allows fluid to seep back past the cylinder... Which could cause symptoms similar to air, or cause the pedal to go the floor even if everything else is fine.

Could this be the problem? Just throwing it out there. Hopefully someone will come along with more ideas and insight.

[fenixus]

how are you bleeding the brakes?

[asphalt victory]

standard bleeding procidure new master cylinder bentch bleed everything is there It is the abs modulator with trapped air in it AND it is a nightmare

as i understand toyota dealerships can cycle the ABS modulator with a computer I was wondering if anyone knew a trick around this AS 2 hours of toyota shop time is just a bit expensive

[asphalt victory]

hears the story comming home one night a steel line busted open i parked the car came out the next morning and it drained the master cylinder.

replaced the line bled the brakes but the pedal never firmed up so i bled it again still the same

i figured the time the master cylinder was dry of fluid (about a week) the seals went bad so i got a new one bentch bled it put it in bled the system and still pedal to floor

I came to the conclusion that the ABS modulator is the cause as the brakes worked perfect before the line blew

[fenixus]

well ... i did it the ghetto way... bleed the hell out of all 4 corners startign from furtheest to nearest to MC then take the car for a drive ... and make the ABS kick in 5-6 times the longer the better (hard to do in Summer and on asphalt roads) ... then bleed it all around again, repeat again if needed.

however, in first Winter when I really started using ABS on ice a few times it came up that more air got released from ABS, so I had to bleed it again ... then I replaced front calipers ... and was bleeding it again ... man I was bleeding brakes on my car like dozen times in last year ...

make sure you're not loosing any fluid from any connections or something. I never had a problem with pedal going to the metal, only mushy and soft. still is a bit, but I believe actually the old rubber lines are more responsible for that than anything else to be honest.

[asphalt victory]

so what your saying is drive it down the road and slam on the brakes to activate the ABS and this i suppose might force some air out of the module and into a line perhaps where it would easly bleed out?

The only thing is When you slam the pedal to the floor Your kindov "asking" the car to stop

thanks for some feedback

[fenixus]

yup, that's the idea. mind that it's easiest to do on ice or on loose gravel or hardened dirt road. asphalt is very hard to work with (too good traction) and most likely will not open the circuits enough (or not for long enough).

and by slamming, I mean SLAM IT, like you wanted to make the tires to squeak for 3 seconds, but instead the ABS will kick in. make sure there is no other cars behind you though

Originally Posted by asphalt victory

so what your saying is drive it down the road and slam on the brakes to activate the ABS and this i suppose might force some air out of the module and into a line perhaps where it would easly bleed out?

The only thing is When you slam the pedal to the floor Your kindov "asking" the car to stop

thanks for some feedback

[asphalt victory]

sounds like a nice youtube viedo "redneck abs bleeding" ill have to try this ill get back to toyota nation with my results

[fenixus]

good luck!

just do it on a deserted road, possibly industrial/deserted area at night make the abs pump go "wrrrrrrrr"

[Stillrunning]

The little research I did on this shows you need to determine who makes the ABS Module as each one is different and has different internals. If you're getting brake pedal to the floor when parked I would not try to cycle the ABS when moving. I use the ABS cycling method described by fenixus after I have flushed the brake fluid with new, but with no air in the system.

It may be possible to crack each hard pipe connection at the module then slowly press the brake pedal to expel the air from that connection (similar to bleeding caliper), but without further investigation I would not mess with the module without knowing for sure.

Having to bite the bullet and spend for a cycling tool may be the safest thing to do. Unfortunately you'll need to get it towed to the shop.

[fenixus]

yeah, the required pre-requisite is that the pedal doesn't go to the floor... wondering why yours keep sinking even though there is no air, sounds like MC is unable to build the fluid pressure if there is no external leaks?

mind that after actuating ABS module which expels air from inside of it into tthe brake lines, then the pedal will become only softer than already is.

if you can't figure it out, I would suggest a pro take a look. Toyota can do the bleeding service on the system with ABS without driving it though they charge like $200 for the service and that is if all parts are in order.

[JohnGD]

The ghetto method may be the easiest if the necessary safety precautions are taken.

Another would be to find the wiring diagram of the particular ABS module and activate the pressure relieving solenoids that allow brake fluid to flow into the secondary circuit. This is followed by a brief activation of the pump motor for each of the 3 or 4 channels (some systems have one channel for both rear brakes). Denso makes licensed copies of Bosch ABS systems. But Continental Teves systems are quite popular on newer cars and trucks.

The risk is not to power anything for more than a few seconds for risk burning them out. This jumpering method is still workable on older 2-state solenoid designs (like relays). The newer 3-state designs require specific DC current (for example, 2 amps does one thing and 5 amps does another) and is easier with a scan tool.

Some of the later ABS systems are hard to work with because they do a lot more than "anti-lock" and basic traction control. These also do start-up wheel spin control, hill start assist (so the car doesn't roll back), brake proportioning, brake force redistribution, electronic stability control, brake drying, electronic parking brake, and emergency brake pedal pre-charge, etc.

A burned out ABS module is expensive to replace. So see how the ghetto method works first if the pedal is just a tad soft. But as mentioned, don't drive if the brake performance is below par.