This is my first post on here... Hopefully someone can help because my new CJ5 is not going anywhere until I figure this out...
I purchased a 1978 CJ5 a week ago. I had mushy brake symptoms intermittently, the only way I could come to a good stop was by pumping the brakes to build up pressure. I assumed the brake lines had a little air inside. When I opened the Master Cylinder I noticed that the brake fluid was very corroded. Very brown with rust flakes.
I did a little research on this forum and I determined that the best thing to do would be to bleed the brakes. First I attempted the method below.
1. Fill the reservoir and replace the cap. Fasten it down.
2. Give the brake pedal a couple of hard and fast stomps to reset the proportioning valve. Do this only if your system was dry. If not, you shouldn't need this step.
3. Make sure the reservoir is full and put the cap on lightly.
4. Have a friend with the right size wrench at the brake you're bleeding.
5. Push the pedal in all the way and hold it. Don't get too excited as you don't want to spill fluid out of the reservoir.
6. Have your friend open the valve and check for new fluid coming out.
7. Have your friend close the valve.
8. Let up off the pedal.
9. Check your reservoir fluid level - DO NOT LET IT EMPTY or you'll have to repeat the process.
10. Repeat at step 5 until you get new, clean brake fluid coming out.
11. Move to the next brake (driver rear) and repeat the process starting at step #3.
This helped clear out the dirty fluid. But the brake lines still felt like they had air in them. I think it was because I accidentally ran the master cylinder dry a few times while doing this.
So today, I tried this method (Gravity Bleeding).
Fill Master Cylinder with proper brake fluid (Dot 3) leave lid off,start at wheel furthest from the Master Cylinder (Right Rear) open bleeder screw & let drip till no more air I usually let it drip for quite a while to get fresh fluid through out the system (you can attach a hose to the bleeder if you want) after bleeding the Right Rear close the bleeder & move to the next furthest wheel and so forth all the while keeping the Master cylinder topped off.
Now I have no brakes and there is no a pressure at all. I checked all the nipples to make sure they were tight and not leaking, all look good. The fluid level is not dropping so I don't think there is a leak. I didn't touch anything with the brakes on the wheels. Just loosened/tightened the nipples.
Any ideas what I have to do here??? This is new to me but I am a major Do-It-Yourself'er and can usually fix stuff by myself. I just got this this licensed and the weather is getting warmer and I already broke it. Any help or guidance would be appreciated.
Also, when I did the gravity bleed method, the fluid steadily dripped from each nipple. I let the fluid drip for about 30 min per brake. Went through about a bottle and a half of brake Dot 3 fluid but I wanted to be sure that the old gunky oil was completely gone and all air was pushed out. Here is a pic of the master cylinder with the cap off. This looks pretty basic. I am probably missing something simple..
I have the best luck using tight fitting clear tubing from the bleed screw going into a catch can with brake fluid higher than the end of the tubing. Open the bleeder just enough to allow fluid to flow. Bleed until there are no bubbles in the tubing and tighten the bleeder. Repeat 3 more times (moving long to short lines). If you run the master dry, start over.
"Peace is that brief glorious moment in history when everybody stands around reloading" Thomas Jefferson
"Nearly all men can stand adversity, but if you want to test a man's character, give him power" Abraham Lincoln
...If you run the master (cylinder) dry, start over.
x2 on this. I've run into this same problem almost every time I've bled my brakes. It's very easy to let the MC fluid level get too low. If one of the compartments in the master cylinder goes too low, then you introduce more air into the line and you have to re-bleed again from the beginning.
I never did bench bleed my MC until I installed a new one, but if I had a condition where I couldn't get all the air out of the system, I wouldn't hesitate to pull the MC and bench bleed it.
If the MC had flakes of rust in it, I would be worried about it anyhow. I would think the rust flakes would grind away the seals in the MC.
"I give you a republic, if you can keep it." - Benjamin Franklin
Thanks for the help guys. I bench bled the master cylinder and it is a little better but not safe to drive. I hear swishing around in the master cylinder when I pump the brakes. I think the seals are bad from the old oil and rust. Ordered a new one on ebay for 95.00$ (cough cough).
Hopefully that will fix this. Crossing my fingers...
Be sure to bench bleed the new MC before you put it on. I think I pumped mine about 200 times before I installed it. Luckily, the install was trouble free. After reading so many threads about problematic brake work, I didn't want to take any chances.
Also, you might do a search or the brake proportioning valve. This is one piece of the brake system that seems to cause confusion. According to the factory service manual, you are supposed to use a tool to hold the valve open while performing brake service.
"I give you a republic, if you can keep it." - Benjamin Franklin
Ken, i think you are on to something by mentioning the proportional valve. I did some research and it seems that some people have replaced their entire brake systems and still have no pedal by skipping this step. Apparantly you need a "tool" to keep the button depressed while bleeding. My "tool" will be a quick clamp with a small bolt coming through the rubber on one end of the clamp to depress the proportional valve button.
My brake light stays on when I drive so that must mean that there is air trapped in the propotional valve. In theory...
Im going to give this a try tomorrow while I impatiently wait for the new MC to get here...
There is a lot of information about if the proportioning valve should be pulled or pushed during bleeding. There may be a definite answer depending on a Jeep's specific hardware, but I don't know what it is.
Well, a new master cylinder did the job. I did confirm that for the 78' CJ you need to hold the Brake Proporsional Valve in a depressed position when bleeding. I also wanted to make sure all the air was out so I got a loaner brake vacuum power bleeder from Advanced Auto. Highly recommended.
Now a new problem. The piston in the new Master Cylinder is apparantly shorter so my brake pedal no longer sticks out so far. I prefer this since the CJ5 a tight fit. However, now my brake lights wont turn off unless i manually grab the break pedal and pull it out further. I need to find where the heck the sensor is and adjust it. I think i will have to pull the dash to find it.
On my '83 the brake sensor is above the steering column between that and the top of the firewall. There are threads on the sensor so you ought to be able to tighten/loosen it as needed for your brake pedal. I don't know how different our wiring is for the MY but I can access mine best from the pass side of the steering wheel. I pulled my interior wiring harness this weekend (I'm still not sure why) and my sensor doesn't have the rings on it to adjust. It must have just been jammed up there in place.
2013 JK (see info on left)
SOLD: 1983 CJ7
Utah Jeep Crew #178
..Now a new problem. The piston in the new Master Cylinder is apparently shorter so my brake pedal no longer sticks out so far. I prefer this since the CJ5 a tight fit. However, now my brake lights wont turn off unless i manually grab the break pedal and pull it out further. I need to find where the heck the sensor is and adjust it. I think i will have to pull the dash to find it.
I don't know if the '78 is exactly like the '85, but I had to replace the brake light switch on my '85 and it was not easy. It's very hard to get to and difficult to see. If I remember correctly, you can adjust how far the thing sticks out so you might be able to fix your problem if your hardware is the same.
This post has some photos and commentary, but it will only get you so far because the area is very hard to photograph because it's buried to deep inside the dash.