1993 brake master cylinder replacement

[DrewSmith007]

I've got a 93 4wd Ex, and the master cylinder is in pretty bad shape. the brakes are squishy and I want to replace the MC before I do any brake work.

My Haynes says to not attempt at a home shop because it is "impossible" to properly bleed the MC.

I hear there is a special tool (on a ford? surely not...) to bleed the MC. Anyone know what this tool is, looks like, or does?

Is this something I really can do at home, and the Haynes guys just didn't want to bother with it?

 

[FR-425]

Read this thread, you will see that the issue is not bleeding the master but getting any air out of the ABS pump/actuator/valve thingy. (HCU)
http://www.explorerforum.com/forums/index.php?threads/bleeding-abs-brakes.35821/

My solution to this problem and the fact that the special tools are no longer available was this:

I use a rotor with a broken tone ring on one front wheels to activate the ABS repeatedly to push the air through. Then one final "normal" bleed at the calipers/wheel cylinders to get the air the rest of the way through.

As you can see I purposely broke off one of the blades on this tone ring. It's a bit lengthy process but gives the best result. (and you need a junk rotor lay'n around)

The gap causes the ABS to engage for an instant each time the gap passes by the sensor. Thump - thump - thump. DO NOT drive faster than 25mph when doing this.

P.S. You only need to do this for 40 "thumps" or so to get all the air out. So about 10 brake applications at 20mph will do the trick.

 

[DrewSmith007]

Thanks. I'll give that a shot if the gravel stop method doesn't work out.

I also picked up an ABS hydraulic control unit at the local LKQ's black friday sale, along with both electrical harness connections. I'm going to clean it up and play around with it to see if I can figure out a way to trick it into bleeding itself.

Are the schematics for this HCU available anywhere? They're either not in the Haynes, or I just can't find that part.

 

[FR-425]

Can't recall the Bedix part number but these HCU's were first use in Boeing aircraft such as the 737 to control the spoilers and ailerons..

It was adapted for use in the automotive industry for ABS. Point being you will get better info from Bendix. Just need that part number.....

 

[larrydd999]

I guess dumb luck still exists. A few years ago I replaced the master cylinder on our '92 and other than filling the reservoir nothing else needed to be done.

 

[FR-425]

92"s don't have
four wheel ABS. It's not an issue with RABS