School me on flushing brake fluid

Andy Maurer

TJ Enthusiast
Joined
Sep 7, 2018
Messages
136
Location
St. Louis
Last week my right front caliper started sticking so I replaced it... easy enough. When bleeding the brakes I noticed the fluid which was coming out was very dark and had some debris, I have no idea when it was last changed. I don't know if the caliper failed, or if debris in the brake lines clogged something so I would like to flush the lines to be safe. I want to be sure to do this correctly so I have a couple questions below:

Q1: Is flushing the brake lines the correct thing to do in the case where the fluid looks horrible and a caliper recently failed? Is there any chance of making things worse by lodging debris currently in the brake lines?

Q2:
Is the process for flushing the lines as follows: fill up reservoir, connect clear tubing to bleed screw, have someone apply brakes until resistance is felt, open the bleed screw on rear passenger side, as soon as brake pedal hits floor close bleed screw and repeat?

Q3: Is the correct bleeding order for a TJ passenger rear, drivers rear, passenger front, drivers front? Or does this matter?

Q4: I assume I will have to fill the reservoir multiple times to get new fluid to each caliper, do I need to put the reservoir cap on each time after filling, or if I monitor to ensure it does not run dry can I leave the cap off?

Q5: This is all to be done with the engine off correct?

Q6: Anything I am missing?

Before it gets suggested... I would prefer to keep this as cheap as possible and do it the old school way rather than buy a vacuum brake bleeder.
 
Old school works when you have help.

Get the old fluid out of the brake fluid reservoir first. Then fill with new fluid.

Start with the passenger rear first (furtherest away). Then driver's rear. Passenger front. Driver's front.

A piece of tubing from the bleed nipple into a bottle is used to catch the old fluid.

Have your helper put pressure on the pedal. Open the nipple on the caliper, the pedal goes down, your helper should hold the pedal down until nipple is tightened.

Repeat bleeding procedure until you see clear fluid at each caliper.

I put the reservoir cap back on when I bleed.

I check the reservoir after 5 to 7 repetitions of the bleeding process.

Fronts will clear up a lot faster than the rear.

Change brake fluid every 2 years.

I have a lawnmower, motorcycles, cars, a truck, and a camper to take care of. I find that special tools are a time saver (plus I don't always have a helper). I tried a vacuum bleeder but didn't like it. I use a power bleeder now. I think Mr. Blaine (the brake expert) posted in another thread that he like the pedal pump method because the sudden pressure changes are more effective in blowing out gunk. I also have a oil change tool that I can use to suck the fluid out of the brake reservoir.

https://www.motiveproducts.com/coll...er-kits/products/chrysler-dodge-mopar-bleeder
https://www.walmart.com/ip/Trac-7-L...2GyorbyAjV0MEz_GYMDDvflFY-XQRcq0aAhF5EALw_wcB
 
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Good advice on here, but yea start with the side that is farthest away from your master cylinder, it’s just to bleed the system faster. Back will take longer and once you get closer it will all be pushed out faster. As for the crud in your lines.. I can’t think of another way to flush the fluid. If your bleeder nipple were to get clogged that could pose a problem. But you could always replace it if it was clogged. I have seen them rust up and not bleed anymore.. so they need to be cleaned out or replaced! Good idea to flush the old fluid, whenever you put a new part on your brake system.. master cylinder, caliper.. it’s a good idea to flush it.. your already gonna need to bleed everything


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+2 on above methods..I also have the motive pressure bleeder and it is great. It is needed on some of the more modern abs cars, old school method does not work. I need to use it on the wife's Benz when I do the "B" service every 20,000 miles to maintain warranty.
 
+2 on above methods..I also have the motive pressure bleeder and it is great. It is needed on some of the more modern abs cars, old school method does not work.
This is a timely discussion. I need to flush my old brake fluid and am considering both the Motive pressure system and a traditional vacuum style for my TJ that does not have ABS. The Motive was my leading choice until a local friend strongly recommended the vacuum style. What say you and the rest of you?
 
Old school works when you have help.

Get the old fluid out of the brake fluid reservoir first. TheN fill with new fluid.

Start with the passenger rear first (furtherest away). Then driver's rear. Passenger front. Driver's front.

A piece of tubing from the bleed nipple into a bottle is used to catch the old fluid.

It isn't a good thing to let the pedal go all the way to the floor. Put something under it to limit travel.

Have your helper pump the pedal three times, open the nipple on the caliper, pedal goes down, hold the pedal down until nipple is tightened.

Repeat bleeding procedure until you see clear fluid at each caliper.

I put the reservoir cap back on loosely when I bleed.

I check the reservoir after 5 to 7 repetitions of the bleeding process.

Fronts will clear up a lot faster than the rear.

Change brake fluid every 2 years.

I have a lawnmower, motorcycles, cars, a truck, and a camper to take care of. I find that special tools are a time saver (plus I don't always have a helper). I tried a vacuum bleeder but didn't like it. I use a power bleeder now. I think Mr. Blaine (the brake expert) posted in another thread that he like the pedal pump method because the sudden pressure changes are more effective in blowing out gunk. I also have a oil change tool that I can use to suck the fluid out of the brake reservoir.

https://www.motiveproducts.com/coll...er-kits/products/chrysler-dodge-mopar-bleeder
https://www.walmart.com/ip/Trac-7-L...2GyorbyAjV0MEz_GYMDDvflFY-XQRcq0aAhF5EALw_wcB

A few minor corrections. Modern masters like are in the TJ do not respond well to the 3 pump and hold method. All that does is aerate the fluid more than just a single pump with the bleeder already open. And, you don't have to take my word for it. Do it with clear tubing and after a couple of those, watch the fluid. You'll see all the tiny bubbles in it. Has to do with how the fluid gets into the bore from the reservoir. Always open the bleed screw first, have helper push the pedal down ALL THE WAY with some enthusiasm. We are trying to use some turbulence to try and flush as much crap out of the caliper bore as possible.

Even with the single pump with the screw open, that still gets some small bubbles in the fluid which we go back and get out with a couple of bleeds at each corner the next day. Also, any bleeding needs to be done with the key on and parking brake off so watch the dash light for the brakes. If it turns on, close the bleeder, pump the pedal until it goes off and start again with the bleeding.

The myth about not going all the way down with the pedal is a carry-over from old iron masters that have been sitting with contaminated fluid in the bore and rusted the un-used section which then took out the cup seals. None of that is applicable to the TJ master.
 
This is a timely discussion. I need to flush my old brake fluid and am considering both the Motive pressure system and a traditional vacuum style for my TJ that does not have ABS. The Motive was my leading choice until a local friend strongly recommended the vacuum style. What say you and the rest of you?

I bought this little guy a few years back and really like it. I have 6 machines I maintain so it gets regular use and hasn't given me any issues. I just used it to change the TJ's brake fluid this past weekend. I like that it holds plenty of fluid and has a pour spout for disposing of whatever fluid you're changing.

https://www.amazon.com/dp/B07SG4FQX2/?tag=wranglerorg-20
 
when I rescued my jeep from a field all the brake lines needed replace before I could drive it home.
I was pleasantly surprised that the gravity primed all the lines and streamed out of the bleeders with no help.
Luckily it did not empty the reservoir before I noticed the stream.
Not pump and twist necessary.
 
This is a timely discussion. I need to flush my old brake fluid and am considering both the Motive pressure system and a traditional vacuum style for my TJ that does not have ABS. The Motive was my leading choice until a local friend strongly recommended the vacuum style. What say you and the rest of you?
From my readings on the MB forums I needed the pressure bleeder for my C300 a vac was not recommended. Being that I got all the adapters, I use the motive on every one of the 7 vehicles I have even my 74 TR6 and 81 Corvette.
 
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Always open the bleed screw first, have helper push the pedal down ALL THE WAY with some enthusiasm. We are trying to use some turbulence to try and flush as much crap out of the caliper bore as possible.

This is mostly how I've been doing it for some time for flushing. Have the helper (lovely wife for me) push on the pedal, so there is some pressure before opening the bleeder. Open the bleeder and just before she hits the bottom of the stroke, close the bleeder. That way there shouldn't be any chance of the pedal coming up and sucking air before closing the bleeder.
 
This is mostly how I've been doing it for some time for flushing. Have the helper (lovely wife for me) push on the pedal, so there is some pressure before opening the bleeder. Open the bleeder and just before she hits the bottom of the stroke, close the bleeder. That way there shouldn't be any chance of the pedal coming up and sucking air before closing the bleeder.
If you have the helper hold at the bottom and then close the bleeder, you don't have to guess at full stroke and no air will enter the system.
 
A motive bleeder is worth it's weight in gold. They take about 1/4 the time as doing it the old fashion way with a helper.
 
I personally keep the cap on the master and bottle as much as possible to keep any sort of moisture from the air out of it. Probably doesn't make a difference, but I'm paranoid and it can't hurt
 
Not sure what I was worried about here... with the help of my brother in law this was one of the easier things I have done on the jeep. Compared to the exhaust manifold I did last month this was a cake walk! I can see where the motive bleeder would be a huge help if doing the job solo, but with a helper it was easy.

Now onto the next thing... changing the front & rear diff fluid.
 
Not sure what I was worried about here... with the help of my brother in law this was one of the easier things I have done on the jeep. Compared to the exhaust manifold I did last month this was a cake walk! I can see where the motive bleeder would be a huge help if doing the job solo, but with a helper it was easy.

Now onto the next thing... changing the front & rear diff fluid.
even easier...just make sure to loosen the fill plug first. Nothing worse than dropping the fluid to find the fill plug is stripped.
 
A few minor corrections. Modern masters like are in the TJ do not respond well to the 3 pump and hold method. All that does is aerate the fluid more than just a single pump with the bleeder already open. And, you don't have to take my word for it. Do it with clear tubing and after a couple of those, watch the fluid. You'll see all the tiny bubbles in it. Has to do with how the fluid gets into the bore from the reservoir. Always open the bleed screw first, have helper push the pedal down ALL THE WAY with some enthusiasm. We are trying to use some turbulence to try and flush as much crap out of the caliper bore as possible.

Even with the single pump with the screw open, that still gets some small bubbles in the fluid which we go back and get out with a couple of bleeds at each corner the next day. Also, any bleeding needs to be done with the key on and parking brake off so watch the dash light for the brakes. If it turns on, close the bleeder, pump the pedal until it goes off and start again with the bleeding.

The myth about not going all the way down with the pedal is a carry-over from old iron masters that have been sitting with contaminated fluid in the bore and rusted the un-used section which then took out the cup seals. None of that is applicable to the TJ master.

What is the right size tubing to fit over the bleeder screws?
 
I have a Motive pressure bleeder and like it but I've also got a pneumatic brake bleeder (bleeds by vacuum) from Harbor Freight and I have really come to like it. Works great on TJs. I don't use the "auto refill kit" though.

https://www.harborfreight.com/pneumatic-air-operated-brake-bleeder-with-auto-refill-kit-57057.html

57057_W3.jpg
 
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