Strange Rear Brake Line Leak

[DuctTape4Ever]

Last fall, i was backing up going no more than 5 mph and slammed on the brakes (to avoid hitting a big rock). All the sudden the brake system warning light came on, and the brake pedal mashed down a ways, not to the floor. After leaving it sit 3 1/2 months, I drove it and had to add fluid every time I used the brakes. Now it is to the point where if I fill up the brake resovoir the evening before it leaked out somewhere by morning. I brought it to a tire shop to have the bead on one of the front tires re-seated, and the shop said there was a leak on the rear brake lines or hoses. Would bleeding the brakes help, with the leak? BTW, the fluid that is in there is black, and 13 years old (last time they were bled was in '04). The fluid probably is quite watery and rusty

 

[Black_cirrus]

NO, you need to fix the source of the leak then bleed them. In fact bleeding the brakes may make it worse if gunk is slowing down the leak. Don't be surprised if you need a master cylinder if you've been driving it like that.

 

[kennythewelder]

NO, you need to fix the source of the leak then bleed them. In fact bleeding the brakes may make it worse if gunk is slowing down the leak. Don't be surprised if you need a master cylinder if you've been driving it like that.

That's rite, You need to fix the leak first. Then you will need to flush the system with new fluid to replace all of the old black fluid. You will even need to bleed the master cylinder. This will need to be done first. Start by taking out all of the old fluid and replacing it with new. Then bleed the MC several times to flush out the system. Then do a brake line bleed, starting with the rear passengers tire and working you way back to the closest one to the MC. I did the GMT 800 up grade on my truck a few months ago. The old fluid was black just like yours. I bleed the MC twice. Once on the bench, then again on the truck. Then I bleed each wheel 12 times. My fluid is as clear as what is in the bottle, and I never had a better peddle. You could also do a pressure bleed. This forces brake fluid through the system when you crack open the bleeder valve, but takes a pressure bleed system to do this. One can be made with a garden pump sprayer. There are a lot of videos on you tube that will show you how to do all of this.

 

[Dylan1991_1500]

Sounds like you need to replace some lines.

 

[DuctTape4Ever]

NO, you need to fix the source of the leak then bleed them. In fact bleeding the brakes may make it worse if gunk is slowing down the leak. Don't be surprised if you need a master cylinder if you've been driving it like that.

I've only drove it +/- 25 miles since it got bad

 

[DuctTape4Ever]

will the master cylinder be ok?

 

[kennythewelder]

Chances are, yea the MC will be fine after you bleed it. go through some of these videos, and that should help you if you don't understand how to bleed your system.
https://www.youtube.com/results?search_query=pressure+bleeding+master+cylinder
https://www.youtube.com/results?search_query=pressure+bleeding+brakes https://www.youtube.com/results?search_query=bleeding+master+cylinder+on+truck

 

[Justin S]

Should be pretty easy to see where its coming from if its that bad. Just a guess, but if you change those rear lines that go from the junction near the diff cover, just get yourself some new cylinders while you're at it, for $10 each its not worth the hassle

 

[Bob L]

I agree with Justin replace the wheel cylinders now. I am sure the old ones are pitted with rust if the fluid has been in there that long. New wheel cylinders,replace all the lines to the rear including the hose and you will still be under $100.00 bucks. I have had real good luck just gravity bleeding brakes. Drain the master by loosening both lines coming out refill with fresh then pump the brakes by just pushing the pedal enough to move the piston a little not pushing it to the floor till fluid comes out of the fittings on the master. Tighten those fittings and give it a few more short pumps with the bleeders open till some fluid shows up. Then close the bleeders except the farthest from the mast and let the fluid drip till clean then put a clean container under to catch the fluid and let it drip for at least 10 minutes on each wheel while making sure the master doesn't run out of fluid. If you use a clean container and the fluid coming out is clean you can just keep pouring it back in till no bubbles are coming out of the bleeder. I work by myself and this does work most of the time including when I did my 98 400.

 

[Black_cirrus]

I agree 25 miles your probably ok, the risk factor is you've been making the master cyl move into the area its not normally moving and any pitting can damage the seals.