09 2500hd bleed brakes new rear calipers

frased · March 7, 2019

I bled the 2 rear calipers starting with passenger then drivers side.

what am I missing? Still spongey.

Do do I have to bleed all 4 corners even though I only replaced 2 rear calipers?

also I see mention of ABS bleed... didn’t know about this at all. Is that another reason?

casey.mikl · March 7, 2019

Yes you need to bleed all of them. Anytime you deal with opening the brake system, you need to bleed all 4 brakes in order. Passenger rear, driver rear, passenger front, driver front.

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davester · March 7, 2019

No, it depends on what happened when you opened up the system.

If you disconnected the line from the caliper, capped the line right away, then uncapped and screwed in the new caliper so not a lot of air could get in the line, then you only need to bleed that corner.

If you disconnected the line for some time, and just let it drip in a bucket, and the master cylinder went empty, then yes, you need to bleed the entire system.

However, if you haven't flushed the brake fluid in a while (say, in the last 5 years), it would be good to get new brake fluid in the whole system (suck out most of the fluid in the reservoir (but don't try to get everything, as it's better to not introduce air into the system at all, fill it up with new brake fluid, then bleed each corner (furthest from MC to closest) until new fluid comes out, and the rears show no sign of air.

frased · March 7, 2019

1 hour ago, davester said:

No, it depends on what happened when you opened up the system.

If you disconnected the line from the caliper, capped the line right away, then uncapped and screwed in the new caliper so not a lot of air could get in the line, then you only need to bleed that corner.

If you disconnected the line for some time, and just let it drip in a bucket, and the master cylinder went empty, then yes, you need to bleed the entire system.

However, if you haven't flushed the brake fluid in a while (say, in the last 5 years), it would be good to get new brake fluid in the whole system (suck out most of the fluid in the reservoir (but don't try to get everything, as it's better to not introduce air into the system at all, fill it up with new brake fluid, then bleed each corner (furthest from MC to closest) until new fluid comes out, and the rears show no sign of air.

Master cylinder definitely never went empty.

i did the one man bleed in a bottle trick... pump pump until all bubbles just fluid and close. Repeat on other side. But still spongy brakes!

davester · March 7, 2019

You might consider flushing the power steering system (as it's also used to to power the brake Hydroboost part). It helped with the feel of the brakes on my truck when I did it ('04 Sierra 3500).

casey.mikl · March 7, 2019

This may be a stupid question. But I’ve seen it done, on the rear calipers that you just installed, are the bleeders on the top side of the caliper or the bottom?

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frased · March 7, 2019

12 minutes ago, casey.mikl said:

This may be a stupid question. But I’ve seen it done, on the rear calipers that you just installed, are the bleeders on the top side of the caliper or the bottom?

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Bottom

casey.mikl · March 7, 2019

That’s your issue. You have them backwards. Bleeders go on the top. Air rises. So with them on the bottom all the air can’t escape so there’s an air pocket getting stuck in the tops of the calipers, thus giving you the spongy feel. You need to swap them. Meaning put the one on the passenger side on the driver side and vise versa.

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frased · March 7, 2019

45 minutes ago, davester said:

You might consider flushing the power steering system (as it's also used to to power the brake Hydroboost part). It helped with the feel of the brakes on my truck when I did it ('04 Sierra 3500).

This summer I ran dry a couple times before fixing the power steering cooler. But didn’t seem to affect brakes.

this time I replaced both rears and can’t seem to get the pressure back.

question at one point I saw the brake line bolts that attach to the caliper had seapage. Tightened hard as I could! Re-bled. No better luck.

i used the new copper washers too on both sides of the bolt.

Edited March 7, 2019 by frased

frased · March 7, 2019

2 minutes ago, casey.mikl said:

That’s your issue. You have them backwards. Bleeders go on the top. Air rises. So with them on the bottom all the air can’t escape. You need to swap them. Meaning put the one on the passenger side on the driver side and vise versa.

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This is what I get for working on my rear axle until 2 am in the freezing cold!

Wow thanks man man I hope that’s it.

I still have the old frozen calipers I will look at them too to verify.

casey.mikl · March 7, 2019

Look at your front calipers to verify it. The bleeders should be on the top. Unbolt them, swap sides, bolt them back up and re-bleed. You should be good.

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