Probably easy question, on brake caliper pistons

[Richard]

Newer caliper pistons (ie, my 2012 Accord) have a ‘closed-head’ piston with a cross design, like a very large phillips screw head, rather than the open head piston I’m used to seeing, and like in Eric’s ’97 Subaru video. Also like my former 2000 Civic.

Does one push a cross-head piston to compress it, or turn it? My assumption would be that it must compress just like open-headed pistons, but they can be turned like a screw with the right (or the wrong) tool.

If it won’t compress into the caliper by turning or by squeezing with a c-clamp, then I guess it’s messed up?

I have other signs of bad caliper anyway, notably the inner rear pads are down to almost nothing, while the outer pads aren’t nearly as worn. Rear pads should last much longer than 45K miles.

Thanks!

Topic

[dave]

This is the golden rule, that works for all calipers all the time:

Front calipers: will always need to be pushed back.

Back calipers: will always have to be screwed back in.

This is the way it was, is, and always will be.

[Its me]

It should be turned to get it back in…Like this…

You can also get a kit like this, but sometimes, It is just easier to use the cube….

Karl

[Richard]

Thanks, both of you, didn’t know the golden rule! If I were to cheat, and try to use something like a screwdriver blade across the piston head, how difficult should it be to turn the piston back into the caliper? About the same resistance as pushing in a front caliper piston?

[Bill]

I assume you’re talkin about the rear calipers. A good rule of thumb is if the park brake is actuated by the caliper you need to thread the piston back in. If the park brake is inside the rotor you can push them in.

There is a special tool to accomplish threading them in. Perhaps you can rent one.

In regards to the uneven pad wear make sure that the guide pins are will lubricated with silicone brake lube and that the metal contact area on pads is lubricated with high temp brake lube and that the calipers move easily on the pins. The pads need to be snug in the brakets but not tight.

[Richard]

Off to get “the Cube” and some silicon. Can’t find it. Have the anti squeal packets.

Thanks for your help!

[Richard]

One more question to anyone — where/how does one lubricate the caliper bolt holes (with the rubber seals around them)? It’s not obvious to me. Do you just lube the bolt and that takes care of it? Or do you need some lube inside the hole?

The old caliper is not stuck. Using the Cube, I could ratchet that thing right back inside. But the top caliper bolt hole doesn’t spring very much. The bottom one is better, more springy.

Thanks!

[twiggy]

[quote=”Wrench Turner” post=66045]This is the golden rule, that works for all calipers all the time:

Front calipers: will always be able to be pushed back.

Back calipers: will always have to be screwed back in.

This is the way it was, is, and always will be.[/quote]

I just changed the rear pads on a 2002 Honda CRV following the service manual which calls for simply pushing the calipers back in.

I’m sure your golden rule is true 99% of the time though.

Edit – just read the post from wysetech he is right as the crv I worked on has the parking brake inside the rotor.

[dave]

Perhaps the golden rule should be edited:

Front Calipers: will always have to be pushed back.

Back Calipers: could be push back or screw in.

[Richard]

Alright. So here’s a brief history of my situation.

1. This is a 2012 Accord SE, with 45,xxx miles on it. It’s 21 months old.
2. Last few weeks, we were hearing a high-pitched whine noise from driver-rear wheel on reverse, and when braking in reverse. No noise forward. Sounded to me like a pad issue or something loose that was rubbing or vibrating.
3. Yesterday removed driver-rear wheel, and the caliper, and found the inner pad was down to the wear indicator, and the outer pad was better, but still more worn than I expected for a rear pad of that age.
4. Figured I’d probably change pads, but found I couldn’t get the caliper piston back into the caliper, by squeezing with a C-clamp. Was able to get the piston turned, with some difficulty, using a screwdriver blade across the slots. Turned OUT, though, not back into the caliper. In fact, got it out to the point where it was loose in its boot.
5. Attempted to screw it back in, or push it – and couldn’t on either count.
6. Assuming caliper was stuck, and being prudent about the other (untested) caliper, took other vehicle and bought two new calipers, a set of pads, a gallon of brake fluid, expecting to change the calipers. Left all this overnight.
7. Today, after watching Eric’s youtube video on the ’97 Subaru, decided to give it a go.
8. Came here to ask my question about how to properly move the piston. Bought a cube and silicon lube.
9. Discovered that using the cube, it was pretty easy to screw back the piston, all the way into the caliper. So figured maybe it wasn’t bad after all. Put on new pads, put back the old caliper with newly lubricated bolts (Silicon lube).
10. Removed other wheel, and its caliper. COULD NOT MOVE THE PISTON EITHER WAY with the cube.
11. Actuated brake pedal a couple times. Piston came out from the caliper further. NOW I was able to screw the passenger-side piston back into the the caliper. Changed pads, replaced caliper with lubricated bolts.
12. Put both wheels back on, put car on the floor.
13. Started engine, pushed pedal, seemed to build pressure.
14. Test drove in neighborhood street. Found that pedal would build, then lose pressure. Had to pump pedal to build pressure. Car will stop but pedal will lose pressure. No idiot lights are on.
15. With car back in garage, engine running, spent several minutes pushing brake pedal, with no change in behavior. It loses pressure.
16. There is no leaking fluid from the rear wheels at all. I earlier had added about 2-3 ounces of fluid to the master cylinder, which anyway was well above the MIN mark. Secured its cap.

Why am I losing pressure if there is no fluid leak? I don’t notice any fluid leaks at the master cylinder, either. The car did not lose brake pressure until I did all this, it just made a noise. With the engine off, it does not lose any pressure.

[dave]

Why am I losing pressure if there is no fluid leak?

You have an internal fluid leak; brake fluid is bypassing one or more of the seals in the master cylinder.

[Its me]

Did you push/screw the caliper back without opening the bleed valve? If so, I have heard of Honda master cylinder seals “rolling” and not sealing properly….Haven’t seen it myself though….

Karl

[Walter Cheryba]

In your step no. 11 you said you pumped the brake pedal and dislodged the piston. I assume the pads were not in place in the caliper and that the caliper was not bolted to the mount. You may have allowed some air to enter the system doing that and it would have occurred when you released the brake pedal after the piston dislodged. I know-there should have been a fluid loss for air to get in. But I would gravity bleed the rear brakes starting with the passenger side rear first, then the driver side rear and see if that helps-it won’t hurt. Observe the bleed, you might just see some air bubbles. Bleed about 2-3 ounces from each rear wheel and keep the master cylinder full during the process. You should not have any air in the front brake lines but if the pressure problem does not go away after bleeding the rears then do the fronts too as a try.

[Bill]

You have to remove them. pull down lightly on the rubber with your thumb and slide the pin out.

[Richard]

End of Day Update:

Spoke to my mechanic, who’s willing to give me advice. His advice – like yours – bleed the brakes. Some air got in there. Probably in step 11 like was pointed out upthread (thanks!).

So my friend and I bled the brakes LR-RF-RR-LF and we got a good bit of air from the RR, lending credence to the step 11 theory. Test drive showed improved, but not ideal, pedal response. And I could feel the rear brakes operating.

In about a month, my friend will help me replace the calipers, since I’ve bought them and you can easily find reports in a google search about issues with Accord and CRV rear brakes in recent model years, that Honda is deflecting. So prudence dictates replacing the calipers while the pads are still pretty new.

You guys have been awesome, thanks to all!

[Walter Cheryba]

Congrats! Sounds like you are making progress. Just a personal note-when I bleed an entire system (all 4-wheels) I always start with the wheel furthest from the master cylinder and then the next furthest etc. At this point before you bleed again it would be good to open the fittings at the master cylinder one at a time and allow it to gravity bleed-don’t pump! Again just a few ounces here at each fitting. Be sure to put rags etc. below the area to catch all the brake fluid-it does not play well with many things. Let us know how it all turns out.

BTW-you know your car best but perhaps the difference you are feeling in the brake pedal now is because the rear caliper pistons are now moving freely. I’m not there driving it so it is just a thought.

[Author]

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