brake bleed issues

hey guys ive got a 73 cj5 i am putting back together. all the brake components are new.

i have bled the system a few times but still dont seem to get a firm pedal. the pedal offers some resistance but still goes to the floor.

i put the blue plastic plugs that come with the master cylinder for bleeding into the master cylinder and the pedal is firm. ( which makes me think the master cylinder is ok) but i still get a soft pedal when the brake lines are attached.

also the brake fluid has been in the system for about 6 weeks and i have not noticed a drop on the floor and the master cylinder was/is full to the top. so i am resonably sure i do not have a leak in the lines.

my question is.... how long should i bleed to get all the air out? is there a better way? currently i am just using the buddy system. one guy to pump the pedal, the other guy to open the bleeder and close. (all while the pedal is held down)

any help or thoughts would be appreciated!!

tia
jeep

 

My 75 was the same way. didn't think I would ever get the air out. To this day, every once in a while the pedal still goes to the floor for the first use of the day. Tried 2 rebuilt mc's and finaly bought a new one. Still the same. New lines, hoses, hrdwr, shoes, and m/c. I cede to the Jeep gods, not fooling with it anymore. Mine took about a quart of fluid till it got firm and stayed.

 

Go to your local FLAPS and get a set of Speed_Bleeders. If your other components are in good shape it make brake bleeding a one-person job and goes really fast. One of the best investments I've ever made.

 

did you adjust your shoes up before you started bleeding?

 

The rear lines take forever!

 

What about pressure bleeding?

 

I've always had good luck gravity bleeding my new systems. Fill reservior and crack the RR bleeder screw. Shove a piece of clear tubing over the bleeder and leave it alone. Before you know it, you have fluid running. Close that bleeder and go to the LR. Same proceedure. Then RF then LF. Once this is complete, you should be able to do a normal "let the wife help ya bleed each corner.

 

All of the above are good ideas but.....Did you bench bleed the MC?

You can only depress the cylinder rod so far with the pedal. It does not bottom out, so a small pocket of air will remain trapped in the MC.

The MC needs to be bench bled so you can depress the cylinder the full depth. It is really the only way to get all the air out of the MC.

 

I've gravity bled my 75 three times now by myself, after repairs that required opening the brake system, and haven't had to touch the system otherwise. I agree about the bench bleeding and brake adjustment. They have to be done right or the system will never feel right no matter how much you bleed the system.

 

I've done all of the above and still have air in the lines. Never had any problems before, but this time I can't get the air out. Pressure bleeding seems like the last option.

 

You're not using silicone brake fluid are you? Dot 5, IIRC. Drove me nuts bleeding the Harley. It doesn't absorb moisture, but you sure pay the price come bleeding time...

 

sorry guys my internet has been down for a couple of days. i really appreciate all of the responses and ideas.

i did adjust the rear drums.

i did bench bleed the m/c and also if i put the blue plugs in the m/c while it is on the jeep the pedal barely moves at all. making me think their is no air in the master cylinder.

i bought a vacuum bleeder tool tonight (have not had a chance to read the directions or use it though)

finally i did use silicone fluid on a recomendation from my part store. (EVERYTHING in the system was new though.)

thanks for alll the help so far guys!!

jeep

 

The silicone is your problem. Very, very difficult to bleed. You'll probably be a happier man if you spend the $30 or so and get a thing called a Mityvac. The Harley would NOT bleed without it. I know guys who have replaced entire perfectly good brake systems to switch from DOT 5 (silicone). Mityvac (sp?) works on a vacuum hand pump. Pretty slick little deal. Google will be your friend here...

 

Get rid of the silicone and go back to good old DOT3 fluid. There's NO reason to use silicone in a street car (i.e. anything short of full race), especially one that wasn't designed to use it by the manufacuturer. The reason parts guys push it is it's the super cool racing stuff and they don't know any better.

 

I agree with getting rid of the silicone based brake fluid. It aerates extremely easy and doesn't give up tiny air bubbles easily. Go back to dot 3. Nickmil

 

thanks guys.

i did buy a mityvac and bled and bled and bled some more. i am going to try one more time and then switch to the dot 3.

any idea how much of the silicone has to come out and how to make sure i get it all out.

jeep

 

All of it. You can use some de-natured alcohol to flush it all out then flush and bleed with regular dot 3. I've never tried just flushing with dot 3 alone so not sure how they will interact. Maybe someone else can chime in with more of that type of experience.

 

Yep, the mity will take a while on the jeep. It took a while on the Harley, and the brake lines are all of 4 feet long. I sure do understand your frustration.

In the Harley world, best practice calls for replacing MC and calipers, expensive. I would imagine that Nickmil's method would work, you're going to be doing a lot of flushing, the little mity may come in handy yet.

Don't ya just love the level of technical knowledge at your average parts store? This is why if you find a good counterman, its like a gift from heaven...

 

this may be a dumb question but what do you guys mean by bench bleeding? Im putting all new lines on my 68 as we speak. By reading this i dont want to run into the same problem. I have the body off right now So getting to the mastercylinder is cake. Is it possible with it still on the body to get the completely push you guys are speaking of Since there is no floor to stop it? Im going to run regular DOT3 and reading this it appears that is the way to go. Also i have read on here that running the dot 5 you will get a better feel in the pedal? Although i dont know how much feel people want from brakes with no brake booster haha.

 

DOT3 and DOT5 don't play well together. The best bet is to pull the cylinders apart to clean them, and to flush the lines completely. If you don't go this far, be sure to flush the system a couple times with new DOT3 then keep a VERY close eye on the brakes until you're sure you don't have problems.

Besides retaining microbubles, DOT5 also eats some materials used in older brake systems, and unlike DOT3, DOT5 is hydrophobic (or hygrophobic, not sure which term is correct.) DOT3 fluid absorbs and distributes water. That's why it needs to be flushed from time to time. DOT5 forces water to pool. This leads to boiling in the cylinders (which introduces air pockets) and corrosion throughout the brake system. On a race car, the fluid will be flushed after every race, or every few races at the most, so it's downsides aren't an issue.