Brake bleeding—Did I empty the master?

[f22beaver]

Paging mrblaine.

I really need to get off the internet because sometimes you can read too much. I replaced all 4 calipers, I got out about 18 oz of fluid. And so this is where the dumb questions start.

1) It's very clear to me I shouldn't let the master get empty, did my 18 oz do that? My reservoir is empty, does that necessarily mean my master is empty?
2) I've read your "Open screw, pedal to the floor hard and fast, close screw, let pedal up, repeat." advice multiple times. Do I just keep doing this at each corner until fresh fluid comes out? I keep seeing references to modern ABS systems being "weird" when being bled. I don't know how serious those are.
3) Does the fluid I put in matter if I don't know what's in there? I've read about how 5 doesn't play well with 3/4/5.1 because of silicone. If I'm flushing all the way through each caliper does it matter?
4) Do I need the key in the on position for this? When you've helped some others trouleshoot you've had a few of them look for brake lights to turn on the dash, though I'm unsure what exactly that's for.

 

[Gilaguy23]

Can DOT 5 Brake Fluid Be Used Instead of DOT 3 or 4?​

Always refer to vehicle owner's manual for what the manufacturer recommends or warns against. As a rule, vehicles equipped with anti-lock brakes (ABS) should not use DOT 5 brake fluid.

DOT 5 brake fluid is silicone based. DOT 3 (standard) and DOT 4 (heavy-duty) are glycol-based. It can be distinguished from conventional brake fluids by its purple color (which comes from a dye).
If you are emptying the res then you likely have taken air into the MC bore as well or its to close to take a chance as air may have entered the system. Generally you want to start with the furthest caliper/brake cyl which would be the right rear. Personally I use a Mighty vac 90% of the time or a power bleeded. Doing as you say likely will cause air to enter the caliper/cyl when you lift your foot off the pedal.

 

[mrblaine]

Paging mrblaine.

I really need to get off the internet because sometimes you can read too much. I replaced all 4 calipers, I got out about 18 oz of fluid. And so this is where the dumb questions start.

1) It's very clear to me I shouldn't let the master get empty, did my 18 oz do that? My reservoir is empty, does that necessarily mean my master is empty?

Doesn't matter, you never let the reservoir get low enough that you have to guess.

2) I've read your "Open screw, pedal to the floor hard and fast, close screw, let pedal up, repeat." advice multiple times. Do I just keep doing this at each corner until fresh fluid comes out? I keep seeing references to modern ABS systems being "weird" when being bled. I don't know how serious those are.

Do you have ABS?

3) Does the fluid I put in matter if I don't know what's in there? I've read about how 5 doesn't play well with 3/4/5.1 because of silicone. If I'm flushing all the way through each caliper does it matter?

Stop, just use DOT 3 or 4 and you won't have an issue.

4) Do I need the key in the on position for this? When you've helped some others trouleshoot you've had a few of them look for brake lights to turn on the dash, though I'm unsure what exactly that's for.

Later models changed the plunger switch so it trips easier when the shuttle moves.

 

[f22beaver]

Doesn't matter, you never let the reservoir get low enough that you have to guess.

I know, I screwed this one up. Cat was out of the bag before I realized I done f'ed up. I think it's empty.

Do you have ABS?

Learn something new every day. I guess I don't. I assumed it was a standard thing. But the pic attached is what I have, no ABS module there.

Stop, just use DOT 3 or 4 and you won't have an issue.

Fair enough. Thanks.

Later models changed the plunger switch so it trips easier when the shuttle moves.

Thank you for that.

 

[Gilaguy23]

Gee Bev...Id be thinking about the master ripping off the booster with that rust.

 

[WSS]

Ya, enough force and those last molecules could give way. I would consider a booster swap while your at it.

 

[f22beaver]

Ya, enough force and those last molecules could give way. I would consider a booster swap while your at it.

Gee Bev...Id be thinking about the master ripping off the booster with that rust.

Yeah, appreciate the advice guys. My plan is to do it this winter. I just got it back from frame repair so I went after brakes, oil pan, trans pan, sway bar end links (death wobble FTW!!!!) and some coolant work to make it drivable. I've never even really driven the thing without known issues causing driveability issues.

 

[f22beaver]

Thanks for the questions and responses here everyone. It's lead me down an informative path on bench bleeding.

It's left with me two follow ons;
1) it looks like some people just skip the bench and only bleed the calipers. Recipe for trapped air in the master?
2) when I pull off the temp hose to bench bleed, what stops fluid from rushing out before I get the brake lines on? Do I want to leave the piston in or out based on that?

 

[Gilaguy23]

Ive bench bleed MC's to start it going,when pretty done I pop the plastic caps back into the line holes to help fluid from dribbling out.. After you get the bore filled with fluid,MC mounted, you still need to finalize a bleed by doing all 4 wheels. I recall you mentioned a 16 oz bottle getting used up. I think last time I did a good flush I burned 2 quarts. I think all CJ,YJ,Tj's used DOT 3 ONLY or 4 which has a but higher temp rating. You really need to flush out that silicone D5 If thats what you put in the system as I believe it will destroy all the caliper seals and rubber parts designed for the D3 fluid. I now it will be a PITA but its you and others potential lives on the line here.

 

[f22beaver]

Ive bench bleed MC's to start it going,when pretty done I pop the plastic caps back into the line holes to help fluid from dribbling out.. After you get the bore filled with fluid,MC mounted, you still need to finalize a bleed by doing all 4 wheels. I recall you mentioned a 16 oz bottle getting used up. I think last time I did a good flush I burned 2 quarts. I think all CJ,YJ,Tj's used DOT 3 ONLY or 4 which has a but higher temp rating. You really need to flush out that silicone D5 If thats what you put in the system as I believe it will destroy all the caliper seals and rubber parts designed for the D3 fluid. I now it will be a PITA but its you and others potential lives on the line here.

Thanks for the tips. I went ahead and got the 2 quart bottle just to be sure.

Also, I probably didn't use my words well earlier. I've not put anything into the system yet, all I've done up to now is empty it which is where the 16 oz number comes from. I have no reason to think there's DOT5 in there now. My question was more about, since I don't know what's in there how should I proceed. The fluid that came out is almost certainly original, it's a dark brown and the calipers I pulled off still had Chrysler markings on them so I'd imagine this system has never been touched.

 

[JEEPCJTJ]

Paging mrblaine.

That was a great idea.

2) I've read your "Open screw, pedal to the floor hard and fast, close screw, let pedal up, repeat." advice multiple times. Do I just keep doing this at each corner until fresh fluid comes out? I keep seeing references to modern ABS systems being "weird" when being bled. I don't know how serious those are.

Reading this whole thread fairly quickly I didn't see any mention about this so here's my take.

I don't know if hard and fast would help or hurt anything but soft and slow certainly won't either, just use reasonable pedal pressure and speed.

Opening the screw will allow the pedal to the floor but isn't really what you're looking for. where to start.

With the bleeder screw still closed you want to pump the pedal two or three times. As you do it will compress any air in there and you'll eventually feel the pedal stopping higher and higher. With a lot of air the pedal may not get higher for the first few bleeding cycles. Then while the pedal is being held down, loosen the screw. The pedal will drop while it pushes the fluid and/or air out. The harder the pedal is pushed the faster this happens and it doesn't need to be fast. When the pedal is all the way down, it needs to be held there until the bleeder screw is tightened.

Repeat that whole paragraph until the pedal doesn't get higher when pumped. That may be half a dozen times or more on each caliper so double check the fluid level at least when moving to a different caliper. Checking twice as often would be better.

4) Do I need the key in the on position for this? When you've helped some others trouleshoot you've had a few of them look for brake lights to turn on the dash, though I'm unsure what exactly that's for.

Power brakes are easier to bleed with the engine running, so key in the on position. mrblaine did mention about how the dashboard brake light works. I've never paid any attention to that light unless it came on while trying to stop and even then it was only after the pedal went too far down.


The rusty booster is something I'd hit with a wire brush, spray with brake cleaner then prime and paint. It's either not made of body sheet metal or, if it is, the master cylinder is bolted to a somewhat heavy metal structure inside the sheet metal. Either way it's pretty strong.

 

[mrblaine]

That was a great idea.




Reading this whole thread fairly quickly I didn't see any mention about this so here's my take.

I don't know if hard and fast would help or hurt anything but soft and slow certainly won't either, just use reasonable pedal pressure and speed.

Ever look at a carbonated beverage and notice the little bubbles sticking to the inside of the glass? The hard and fast pedal movement creates some turbulence which has a better chance of dislodging any of the small bubbles that may want to be stubborn plus it stirs up and hopefully carries out any crap that has settled in the caliper piston bore.

Opening the screw will allow the pedal to the floor but isn't really what you're looking for.

No, it is exactly what you are looking for. You want to move as much fluid as possible through the piston bore.

With the bleeder screw still closed you want to pump the pedal two or three times. As you do it will compress any air in there and you'll eventually feel the pedal stopping higher and higher. With a lot of air the pedal may not get higher for the first few bleeding cycles. Then while the pedal is being held down, loosen the screw. The pedal will drop while it pushes the fluid and/or air out. The harder the pedal is pushed the faster this happens and it doesn't need to be fast. When the pedal is all the way down, it needs to be held there until the bleeder screw is tightened.

Repeat that whole paragraph until the pedal doesn't get higher when pumped. That may be half a dozen times or more on each caliper so double check the fluid level at least when moving to a different caliper. Checking twice as often would be better.

That's great, what you missed is modern masters aerate the fluid when you do that. Next time you do a bleed with a clear hose, watch it closely and after several pumps you will start seeing tiny bubbles in the fluid that don't ever stop coming out. The more you pump and hold, the more bubbles you get. Also why one should go back the next day and do a 1-2 quick bleed per corner after the bubbles have settled out.

Power brakes are easier to bleed with the engine running, so key in the on position. mrblaine did mention about how the dashboard brake light works. I've never paid any attention to that light unless it came on while trying to stop and even then it was only after the pedal went too far down.

No one has ever recommended bleeding with engine running until now. Absolutely no need to ever do that. The pedal went down too far because you had something wrong in the brake system.

The rusty booster is something I'd hit with a wire brush, spray with brake cleaner then prime and paint. It's either not made of body sheet metal or, if it is, the master cylinder is bolted to a somewhat heavy metal structure inside the sheet metal.

 

[JEEPCJTJ]

Ever look at a carbonated beverage and notice the little bubbles sticking to the inside of the glass? The hard and fast pedal movement creates some turbulence which has a better chance of dislodging any of the small bubbles that may want to be stubborn plus it stirs up and hopefully carries out any crap that has settled in the caliper piston bore.

OK, I never thought about dislodging and stirring stuff up to hopefully get it out. Sounds like a good idea.

2) I've read your "Open screw, pedal to the floor hard and fast, close screw, let pedal up, repeat." advice multiple times. Do I just keep doing this at each corner until fresh fluid comes out? I keep seeing references to modern ABS systems being "weird" when being bled. I don't know how serious those are.

Opening the screw will allow the pedal to the floor but isn't really what you're looking for. where to start.

No, it is exactly what you are looking for. You want to move as much fluid as possible through the piston bore.

In his post, the "Open screw, pedal to the floor..." looked like a starting point. Maybe I didn't read that part correctly but I just wanted to make sure the procedure started before that. I'll be rewording that part of my post.

That's great, what you missed is modern masters aerate the fluid when you do that. Next time you do a bleed with a clear hose, watch it closely and after several pumps you will start seeing tiny bubbles in the fluid that don't ever stop coming out. The more you pump and hold, the more bubbles you get. Also why one should go back the next day and do a 1-2 quick bleed per corner after the bubbles have settled out.

I never knew that modern masters aerate the fluid. Do we avoid those tiny bubbles to some degree by pumping less?

No one has ever recommended bleeding with engine running until now. Absolutely no need to ever do that. The pedal went down too far because you had something wrong in the brake system.

I thought having the engine running would make the pumping somewhat easier. Should it be avoided?

As for my pedal going down, there was a huge problem, a blown rusty brake line long before I even owned a Jeep.

 

[mrblaine]

OK, I never thought about dislodging and stirring stuff up to hopefully get it out. Sounds like a good idea.





In his post, the "Open screw, pedal to the floor..." looked like a starting point. Maybe I didn't read that part correctly but I just wanted to make sure the procedure started before that. I'll be rewording that part of my post.

Open bleeder, push pedal to floor hard and fast, hold at bottom, close bleeder, let pedal up.

I never knew that modern masters aerate the fluid. Do we avoid those tiny bubbles to some degree by pumping less?

Yes, each pedal pump adds more bubbles, little tiny ones. You can also use that to tell when you have fluid from the master to each corner.

I thought having the engine running would make the pumping somewhat easier. Should it be avoided?

No reason to have the engine running.

As for my pedal going down, there was a huge problem, a blown rusty brake line long before I even owned a Jeep.

Yes, that is a problem which will trip the brake light. Also why you should bleed with key on, parking brake off.

 

[Artsifrtsi]

@mrblaine , what are your thoughts on vacuum bleeding the brakes, when you do not have a helper available? Anything special/extra need to be done?

 

[mrblaine]

@mrblaine , what are your thoughts on vacuum bleeding the brakes, when you do not have a helper available? Anything special/extra need to be done?

I don't do it.

 

[pagrey]

Also why one should go back the next day and do a 1-2 quick bleed per corner after the bubbles have settled out.

The number of posts you make that I have to randomly bookmark so I don't forget continues to grow.

 

[Mike_H]

Yes, each pedal pump adds more bubbles, little tiny ones. You can also use that to tell when you have fluid from the master to each corner.

HA! I was going to call tomorrow about this exact thing. What's the solution here? Just wait for them to congregate and push them out in a day or so?

 

[mrblaine]

HA! I was going to call tomorrow about this exact thing. What's the solution here? Just wait for them to congregate and push them out in a day or so?

Next day usually works. Only 1-2 pumps per corner.