Brake bleeding

MBDiagMan said:

Okay, vacuum bleeders have been around for decades, how long have ABS brakes been around?

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Almost 50 years, but Bosch started development in the 1930s.
The automotive industry saw more widespread use in the late 70s, but apparently KH/TRW had a rear ABS system available for the 1970 Lincoln Town Car. I recall quite a few vehicles with early ABS systems in the late 70s and early 80s.

Your assumption doesn't make any sense because the ABS mechanical system does not activate until the wheel speed sensors tell the ABS module that the valves should start actuating. Until it does this, the ABS pump works like a traditional proportioning valve (remember those things?) Unless you have the special Ford diagnostic tool to cycle the ABS pump, a pressure bleeder would simply be pushing fluid/air through the inactive ABS pump (just like sucking fluid/air through the inactive ABS pump). You're assuming the pressure bleeder will push the fluid/air through the closed valves as well, which is incorrect based on how the TRW engineers explained the functions of the ABS pump.

Maybe I should have phrased my question asking about wide spread use of ABS. I remember reading an article in the very early seventies about ABS brakes on aircraft although they called them something else.

All I know is that I have read in several manuals for ABS brake systems to use a pressure bleeder. I also was told by a friend of mine that he had a heck of a time with an ABS system that had gotten air in the system by a DIYer. The MityVac type bleeder is commonly used by DIYers.

I have, many times, made do with what I had to work with. In this case if a vacuum bleeder is all that you have to work with and don't have a helper to pump the pedal for you, then field expediency prevails.

MBDiagMan said:

All I know is that I have read in several manuals for ABS brake systems to use a pressure bleeder. I also was told by a friend of mine that he had a heck of a time with an ABS system that had gotten air in the system by a DIYer. The MityVac type bleeder is commonly used by DIYers.

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Which manuals said specifically not to use a vacuum bleeder? My Ford FSMs say to use a pressure bleeder, but nothing about NOT using a vacuum bleeder (big difference).

Once you get air into the ABS pump, it's nearly impossible to bleed out without getting a new ABS pump (according to the TRW engineers). The factory diagnostic tool can only do so much on certain ABS systems but there would still be air retained in the pump. I have not read anything that indicates a pressure bleeder can solve this problem or push out all of the air in an ABS pump.

If you remove the ABS pump from the equation, the brake system is the same as a non-ABS brake system w/o the proportioning valve.

Since the master cylinder and the ABS pumps are located higher above the bleeder screws, air isn't going to readily travel upstream into the ABS pump due to gravity (where gravity bleeding comes into play, but I'd rather do the vacuum bleed or even the 2-person bleed methods than gravity bleeding).

I've been itching to buy a Motive 0107 pressure bleeder to try on our Fords since they all use the same style cap. I suppose I can't have too many brake bleeding tools :SNSign:

Sorry to beat a dead horse, but I measured the cap on a new 05-up GT and it is NOT the same size as the standard 3-prong Ford reservoir cap (it's smaller). Ford also has a problem with making the correct gasket for the GT cap, so everyone's reservoir is dripping/dribbling with brake fluid. The MityVac remains to be the most universal brake bleeding tool. I haven't tried the Motive Pressure Bleeder on a 05-up GT, but seeing how the undersized gasket isn't capable of preventing brake fluid from leaking out of the reservoir, I doubt you will get a good seal using the Motive.

Okay, thanks for the information. I will just stick to the two man method when the time comes. It's quick, easy, sure-fire and cheap.

To each his own. I've used the two man method in the past for years before I switched to the MityVac. The end results, in my experience, are the same if not better.

Some GT owners noted that the leakage comes from poorly made reservoirs (the mouth isn't perfectly flat) and that a thicker gasket or teflon tape wraps are just band-aid fixes. Whatever the reason, if you want to use the Motive or another pressure bleeder, you will need the correct adapter (smaller 3-prong Ford cap) assuming you can build up pressure in the reservoir without a leak.