Brake system flush: can it be done with front calipers off?

[Rcroane]

Hey folks.....I need to replace my front calipers (stock '06 TJ). Calipers have been ordered from BMB. Long (embarrassing) story, but the calipers are off the vehicle (brake lines still connected), but the piston cannot be compressed...if you need to know, I'll explain why but that's the really stupid/embarrassing part. I know it is advised that the entire system be flushed BEFORE I mount the new calipers. I've never done a complete flush on any vehicle, so is it possible to flush the system with the old calipers unmounted?

Thanks.

 

[Woodrow]

The problem with pressurizing the system with calipers off is nothing restrains the pistons and they push all the way out. This could result in them jamming at the end of their travel or possibly pushing entirely out of the bore if there isn't anything restraining them (I've haven't disassembled TJ calipers). If you are tossing the calipers and have already flushed the system, then just put in the new calipers and bleed.

 

[Rcroane]

The problem with pressurizing the system with calipers off is nothing restrains the pistons and they push all the way out. This could result in them jamming at the end of their travel or possibly pushing entirely out of the bore if there isn't anything restraining them (I've haven't disassembled TJ calipers). If you are tossing the calipers and have already flushed the system, then just put in the new calipers and bleed.

The calipers are getting tossed. I want to flush the old fluid out before I mount the new calipers. Then I will bleed again. So, I'm just wondering if I'll be able to pull fluid through the calipers that aren't mounted. I guess I could block the pistons so they won't pop out during the process.

I might as well fess up....the reason I'm replacing the calipers is that I stupidly pumped the pedal after I had removed them from the rotor. Like you said, they were unrestrained and now jammed. One of them also has a torn boot, so a good time to start with fresh ones. 160,000 miles and 19 years on these.

 

[srimes]

Yes, you can gravity flush without pressurizing anything. It's slower but super easy, and also works for bleeding brakes. Definitely my favorite car-maintenance task! Make sure to have a comfy chair handy.

Starting with the brake farthest from the master cylinder (passenger rear), open the bleed valve and MC cap, and wait. Drink 3-4 beers. Let it drain until clear, making sure the mc reservoir doesn't get too low.

Once the fluid turns clean close the bleeder and move on to the next farthest brake (driver rear), which will go more quickly, so you'll only have time for 2-3 beers on that one.

Repeat for the front passenger next (2 beers) and then front driver (only 1 beer).

Tell the wife you're tired from working on the jeep and take a nap on the couch.

 

[Rcroane]

Yes, you can gravity flush without pressurizing anything. It's slower but super easy, and also works for bleeding brakes. Definitely my favorite car-maintenance task! Make sure to have a comfy chair handy.

Starting with the brake farthest from the master cylinder (passenger rear), open the bleed valve and MC cap, and wait. Drink 3-4 beers. Let it drain until clear, making sure the mc reservoir doesn't get too low.

Once the fluid turns clean close the bleeder and move on to the next farthest brake (driver rear), which will go more quickly, so you'll only have time for 2-3 beers on that one.

Repeat for the front passenger next (2 beers) and then front driver (only 1 beer).

Tell the wife you're tired from working on the jeep and take a nap on the couch.

This I can do!

 

[Woodrow]

Yes, you can gravity flush without pressurizing anything. It's slower but super easy, and also works for bleeding brakes. Definitely my favorite car-maintenance task! Make sure to have a comfy chair handy.

Starting with the brake farthest from the master cylinder (passenger rear), open the bleed valve and MC cap, and wait. Drink 3-4 beers. Let it drain until clear, making sure the mc reservoir doesn't get too low.

Once the fluid turns clean close the bleeder and move on to the next farthest brake (driver rear), which will go more quickly, so you'll only have time for 2-3 beers on that one.

Repeat for the front passenger next (2 beers) and then front driver (only 1 beer).

Tell the wife you're tired from working on the jeep and take a nap on the couch.

I'd prob fall asleep in the chair and drain the MC

 

[Strizzo]

You could just set them over the rotors to keep them from popping the piston out. Also you're going to flush a bunch of fluid through the brake lines while you're swapping the calipers. You could just let them run until the fluid comes out of the hose clear when you're swapping them over.

 

[mrblaine]

The calipers are getting tossed. I want to flush the old fluid out before I mount the new calipers. Then I will bleed again. So, I'm just wondering if I'll be able to pull fluid through the calipers that aren't mounted. I guess I could block the pistons so they won't pop out during the process.

I might as well fess up....the reason I'm replacing the calipers is that I stupidly pumped the pedal after I had removed them from the rotor. Like you said, they were unrestrained and now jammed. One of them also has a torn boot, so a good time to start with fresh ones. 160,000 miles and 19 years on these.

Pop the dust boots off and toss them. Square the piston up and push it back in, set over the rotor and continue on with your happy self.

 

[Rcroane]

Pop the dust boots off and toss them. Square the piston up and push it back in, set over the rotor and continue on with your happy self.

This is what the piston looks like now after I cranked down on the C clamp trying to compress it. Even more crazy, the C clamp body actually snapped in half . Pretty damn stupid, I know. Believe it or not, I've actually replaced these brakes before with no issue.

 

[Rcroane]

And FYI Blaine, the clamp was pushing on one of your pads......the clamp broke, the piston broke, but your pad (which had no meat left on it), remained intact!

 

[TJ Jim]

Vacuum bleeder.

 

[KennethS]

Pop the dust boots off and toss them. Square the piston up and push it back in

I see a dust boot still installed. Can’t tell if the piston is aligned properly.