Have to Pump Up Brakes after Caliper Compression?

[thompsdw]

We did a brake job on my daughter's Ranger over the past several days. It's been a while since I have done a break job and a lot of things have changed LOL. But the one that puzzled me the most that I wanted to get some opinion on was that after completing the job, I was a bit surprised that I had to pump the pressure up on the brakes. On newer vehicles, when you compress the calipers, is there something in the master cylinder that releases pressure causing you to need to re-pressurize? Ive just never had this happen unless you break into the system.

Just wanted to have the info in my knowledge bank for next time ......

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[GhostStrykre]

I've only ever done brake changes on modern vehicles and i've always had to press the brake pedal a number of times to build up pressure prior to driving. i'm not sure if it's building up pressure in the lines, necessarily. i actually always thought it was because there was a small gap between the new pads and the rotors that the calipers needed to squeeze. if that gap wasn't there it wouldn't have been easy to slide the calipers/pads over the rotors.

there are a number of folks here on the forums who can give a detailed response (or correct me if i'm wrong -- entirely possible), but i've always had to pump the brakes a few times. so i think that's normal. just my read on your situation!

also, props to you for helping your daughter save some coin! i can't believe how much brake service visits cost at shops now!

 

[thompsdw]

Yea, what happened was that we were driving over a mountain pass 2 days before they were going home. After the brakes got hot we felt the truck shimmy some on braking. I wish we would have noticed it earlier due to it being somewhat of a fire drill. Strange thing is that we didn't feel it in the pedal (assumed slightly warped rotors) at all.

We were over $400 in parts alone out the door. Can't imagine what a shop would have charged, but we did go with new rotors versus turning them (didn't have enough time).

 

[thompsdw]

actually always thought it was because there was a small gap between the new pads and the rotors that the calipers needed to squeeze

That makes sense. As tight as they seem when you are sliding that caliper into place, there has to be some piston movement. Thanks!

 

[LawnMM]

It's the pads moving into position, you compressed the piston during the change, now it's moving back out slightly to position the new pads

 

[airline tech]

Its normal for all Caliper Brakes - When you compress the piston you are pushing the brake fluid back into the Master Cylinder, you MUST hit the brake pedal a few times to push the fluid back down to the piston / pistons, this pushes them out to close the gap between the pads and rotors.

In fact, on some vehicles, if you do more than 1 caliper at a time, you have overflowed the Master Cylinder and dumped fluid all over the place.
So, it is best practice to do 1 - Then get in a hit the pedal and then move to the next caliper, but this depends on the size of the Master Cylinder and how much fluid has been added as the caliper pistons expand over time your fluid level is dropping in the master cylinder. So, when all is done, you may have to suck some fluid out of the master cylinder to bring it back down to proper level, if fluid had been topped off at some point.

 

[thompsdw]

That’s a great idea. I hadn’t ever thought of doing it that way. I do always watch the reservoir as we compress but that makes a lot of sense.

 

[ctechbob]

It's the pads moving into position, you compressed the piston during the change, now it's moving back out slightly to position the new pads

Yep, that's all it is. Always a good idea to pump the brakes any time you've changed pads or rotors and before you move the vehicle. Or else you could be in for a fun surprise the first time you try and move the thing and it doesn't stop and you end up with a car poking out of the garage wall.

 

[5thranger]

We did a brake job on my daughter's Ranger over the past several days. It's been a while since I have done a break job and a lot of things have changed LOL. But the one that puzzled me the most that I wanted to get some opinion on was that after completing the job, I was a bit surprised that I had to pump the pressure up on the brakes. On newer vehicles, when you compress the calipers, is there something in the master cylinder that releases pressure causing you to need to re-pressurize? Ive just never had this happen unless you break into the system.

Just wanted to have the info in my knowledge bank for next time ......

What happens is as the pads wear if you add fluid to master cylinder to keep at full line when you compress the pistons it all comes flowing back out of master cylinder. When I replace brake pads, I suck the master cylinder level down then compress the pistons and then when done fill master back up and pump brakes with lid back on master.

 

[airline tech]

Yep, that's all it is. Always a good idea to pump the brakes any time you've changed pads or rotors and before you move the vehicle. Or else you could be in for a fun surprise the first time you try and move the thing and it doesn't stop and you end up with a car poking out of the garage wall.

TRUE - I do not remember all the deatils on this but:

Truck was on a - Ramp Style - Alignment Rack
Multitasking - Jobs (Overlapping)

Brake Work and Motor Mount
Brake Work - Complete
Task - Ident the Motor Mount (Thats Bad)

Truck was started and placed in gear - and hit gas
Brakes were not bled or pumped up - I do not remember the details (which)

Truck - Lunged FWD and off the Rack - Pinning the tech against his toolbox and wall, killing him.

This is an actual event - so YES (ALWAYS) pump the brake pedal and or bleed the brakes after any work that may compromise braking - BEFORE you place in Drive.

 

[fusseli]

Its normal for all Caliper Brakes - When you compress the piston you are pushing the brake fluid back into the Master Cylinder, you MUST hit the brake pedal a few times to push the fluid back down to the piston / pistons, this pushes them out to close the gap between the pads and rotors.

In fact, on some vehicles, if you do more than 1 caliper at a time, you have overflowed the Master Cylinder and dumped fluid all over the place.
So, it is best practice to do 1 - Then get in a hit the pedal and then move to the next caliper, but this depends on the size of the Master Cylinder and how much fluid has been added as the caliper pistons expand over time your fluid level is dropping in the master cylinder. So, when all is done, you may have to suck some fluid out of the master cylinder to bring it back down to proper level, if fluid had been topped off at some point.

The better way to do that is to crack the bleeder valve and put a hose on the caliper bleeder so when you compress it you drain the HOTTEST/MOST BURNED AND MOST WORN FLUID directly out of the caliper rather than shove it backwards in the brake system. You should bleed the calipers after final assembly before putting the wheel back on, anyway. Easy peasy.

And yes it have been normal for 40+ years to have to pump the brake pedal after new pads to reposition the calipers.

Also, when I flushed 1qt of DOT4 in my 2019 the other day about a pint came our dark gray tinged from the fronts, I think that's wear metal from the ABS / traction control / master cylinder in the brake fluid. It's a good idea to flush a whole quart through the Ranger because with effectively open diffs the ABS module is doing a lot of work for traction control if you offroad or live in icy and snowy winters. Owner's manual says to do it every two years. Nevermind that I waited 5 years LOL. Also, I can confidently say that premium aftermarket pads and rotors and fresh DOT4 feel better than stock. My Ranger's brakes feel better than ever with this work done, more grabby and definitely smoother and quieter than the factory brakes ever were. If you want a brake upgrade don't wait to do the brakes on a 5th gen and do them early if they have never been done before.

 

[Dereku]

First brake job I rolled away because I didn’t pump the brakes. I was 14. No one seen and I didn’t hit anything. I have always pumped ever since.

 

[harringtondav]

I agree with all above. Pumping up after a pad change is normal. Also I learned the hard way about the reservoir puking when the pistons are shoved back. I was more anal back then and took topping off fluids seriously. As long as you don't have a brake fluid leak, the reservoir drops with normal pad wear.
Also I recently learned brake fluid change/flush intervals are 2-5 yrs depending on your driving and brake use. I didn't know this and had to replace rotted steel lines in two vehicles. ....now I know why. I don't recalling this in the PM section of my owner's manual.

 

[thompsdw]

All great info. Its amazing to me how you "loose it" if you don't "use it". Either that or I am just getting old. LOL

 

[dtech]

Well now pumping the brakes brings back memories of changing drum brakes , if you didn't bother to adjust the star wheel and just drove off you might be in for the unpleasant surprise of long pedal travel, I would always back up multiple times applying the brakes to snug the brakes up.
I've never overflowed a master cylinder doing a brake job, but always do what a previous poster recommended - open the bleed screw with hose attached when compressing the piston and when the new pads are on using the hose and old fluid in a jar to bleed till no more bubbles are seen. This is how my dear old dad taught me 6 decades back and he used vice grips to stretch those springs out and sometimes the springs would slip from the pliers, I eventually invested in the tool for those springs.

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