How do I bleed the system?

[zach9989]

I am having some trouble with my brakes in my 1992 Explorer 4X4. I had the rear brakes checked out and adjusted... they are fine. The front pads are a little better than half.

My break pedal is very loose, it goes practically all the way down. It will stop the truck, but it is risky. A mechanic that did other work for me told me that he believed it was the master cylinder, he said something about an internal leak or something. The brake fluid reservoir is still full. I read somewhere that it could be solved by bleeding the system and checking the vacuum lines.

I can't afford to ave the mechanic do it, and I don't want to replace te master cylinder if I don't have to. The MC has "Bendix" on it, which makes me assume that it has been replaced before.

What should I do, and how do I do it?

 

[ExplorerDMB]

Two ways: gravity bleed and normal bleed.

To gravity bleed, you go to each wheel, break open the bleeder screw so that fluid will come out and let it drip for a few minutes then close it off. Then do the other three.

To normal bleed, you will need to go to each wheel (rear first usually), get someone in the vehicle and have them pump up the brake and to hold it down (if it will - you said it goes to the floor), and then while they are holding it, open the bleeder screw and let the fluid come out (watch out for air in the lines, the splatter can blow it in your eyes) - but after the pressure has stopped coming out, close it off and have them pump it up again and repeat. Do this atleast 3 times per wheel. The time elapsed from when you open the bleeder screw to when you close it should be like 2-4 seconds!


Good luck. Your vehicle should be in park and not running! And be sure to have some brake fluid so after you are done bleeding you can fill up the master cylinder. You may have a leaky wheel cylinder -- how many miles are on the vehicle?

-Drew

 

[zach9989]

The vehicle has a whopping 186,247 miles. I don't know where the bleeder screws are. How much fluid am I losing in this procedure? Reason being, I have a bottle just over half full, do I need more?

 

[zach9989]

ExplorerDMB, how much were your wheels?

 

[Rhett]

My break pedal is very loose, it goes practically all the way down. It will stop the truck, but it is risky. A mechanic that did other work for me told me that he believed it was the master cylinder, he said something about an internal leak or something. The brake fluid reservoir is still full. I read somewhere that it could be solved by bleeding the system and checking the vacuum lines.

I can't afford to ave the mechanic do it, and I don't want to replace te master cylinder if I don't have to. The MC has "Bendix" on it, which makes me assume that it has been replaced before.

What should I do, and how do I do it?

First of all, I believe OEM Master cyls on 1st gens were made by Bendix. So it may be original.

Second, *if* your master cyl. has an internal leak then your best way to fix it is to replace the master cylinder. I hate to say that but in my experience when they leak like that it's just easier to replace, else you'll be fighting the low pedal problem periodically for a long time.

If your master cyl is fine, then as you say you could need nothing more than a bleed job, and to check all the lines for leaks. If you can't find any other leak problems in the brake system (proportioning valve, hoses, calipers, etc.) then it may very well be the master cylinder as your mechanic said.

 

[zach9989]

You may have a leaky wheel cylinder -- how many miles are on the vehicle?

What all do I do to check this? I also have another concern... wouldn't the reservoir drain as the fluid leaked? I may change the master cylinder, but I am broke and I am trying to avoid unnecessary charges right now... college student's budget.

I just need to know where the bleeder screws are. Thanks alot for all the help thus far.

 

[MrShorty]

Bleeder screws are at each wheel. On the rear they will be on the back side of the drum backing plate near the wheel cylinder. On the front they will be on the back side of the caliper.

 

[zach9989]

Thanks, just changed my oil, headed out to do that now, Will let you know.

 

[ExplorerDMB]

ExplorerDMB, how much were your wheels?

4wheelparts.com -- I believe they were like $135-150!

-Drew