Air locked caliper pin

Joined
Oct 15, 2021
Messages
76
Any tips and tricks for an air locked slide pin? As in, I push it in and it pops right back out? It’s the rubber sleeved one so the air is trapped in the bore not the boot.

I tried shimmying it and rotating it for at least a half an hour with the boot pulled down. Even tried lodging a pick in there to angle the pin as it slid. Finally got it to within a few mm of the caliper’s resting position after all of that and decided to run it but there’s still decent pressure exerted on the pads. Checked it again after a long test drive, hoping the caliper motion would burp it but it’s still firmly there.

I used super lube silicone with PTFE for the slides. I experimented with cleaning out the bore and using a lot less lube but no luck.

I am wondering if the rubber sleeve loosened up over time and isn’t allowing a gap. I have a new OEM pin on order from Nissan so hopefully that does the trick but always curious to learn tips and tricks in case it doesn’t.
 
Happens all the time on my Fords when I service/lube the pins. Just wiggle, twist and pump them a little bit and the air will work its way out. I like to burp the boots after to eliminate as much water collection space as possible.
 
and using a lot less lube but no luck.
I was going to suggest to use a minimal amount of lube but you already tried that with no success.

You could try without the rubber bushing/sleeve just to see if it resolves it. Those are only for 'noise' abatement, to my knowledge. I always make sure they're in the right position and have replaced old ones but the brakes will work properly without them.
 
The rubber bushing is likely swollen/deformed a bit, creating the seal.

You might be able to grind a little relief in it, or just replace it.

On these types (or all types) of slide pins, only grease the pin...do not put anything in the hole. I've seen grease in the hole with a swollen bushing that creates a seal like a hydraulic ram....once thing heat up it starts pushing the pin out of the hole and putting a side load on the rotor and they can sometimes break off of the hat.
 

Clamp idea seems easy enough to give a try. Love SMA.

The rubber bushing is likely swollen/deformed a bit, creating the seal.

You might be able to grind a little relief in it, or just replace it.

On these types (or all types) of slide pins, only grease the pin...do not put anything in the hole. I've seen grease in the hole with a swollen bushing that creates a seal like a hydraulic ram....once thing heat up it starts pushing the pin out of the hole and putting a side load on the rotor and they can sometimes break off of the hat.
Hoping the new pin does the trick. Interestingly the entire pin was cheaper than the bushing from Nissan since it required buying a caliper rebuild kit to get the bushing. The other side went in easy making me think this one was swollen ever so slightly.

The thought of air heating up and potentially expanding is what’s motivating me to fix it.

Thanks for the tips, everyone
 
If it moves freely and just has a little bit of springiness to it,
OP says it "pops" back out. That's definitely air and I'm guessing it's not possible to even push the pin in all the way (easily).
 
OP says it "pops" back out. That's definitely air and I'm guessing it's not possible to even push the pin in all the way (easily).
I took at as it moves out on its own. If it pops out with some force to it, as if it was spring loaded, then that would be abnormal. But I don’t think that’s the case.

And if he can install the caliper, it doesn’t matter, the pin will only come out as the pads wear down.
 
I also ignore it. The air will escape
It usually doesn't.
I took at as it moves out on its own. If it pops out with some force to it, as if it was spring loaded, then that would be abnormal. But I don’t think that’s the case.

And if he can install the caliper, it doesn’t matter, the pin will only come out as the pads wear down.
It's a floating caliper. It will not come out as the pad wears down. It's going to drag your brand new brake pad until the air comes out of the bore and gets trapped in the boot. Then the air trapped in the boot will limit float in the opposite direction. There's no reason to drag your brand new brake pad. Just take a minute or two correctly greasing and installing a slide pin.
 
It usually doesn't.

It's a floating caliper. It will not come out as the pad wears down. It's going to drag your brand new brake pad until the air comes out of the bore and gets trapped in the boot. Then the air trapped in the boot will limit float in the opposite direction. There's no reason to drag your brand new brake pad. Just take a minute or two correctly greasing and installing a slide pin.

The very reason it’s floating is that so it self adjusts for brake pad wear on the side that doesn’t have the hydraulic piston. That’s the only reason they “float”.
 
The very reason it’s floating is that so it self adjusts for brake pad wear on the side that doesn’t have the hydraulic piston. That’s the only reason they “float”.
There's nothing that self adjusts on a floating caliper. It's floating constantly. On brake application and release.
 
Replaced the pin today with a new one with a fresh rubber sleeve. The new sleeve was much tighter and did not seal the bore like the worn out one. Interestingly when I opened the caliper to do this, the air had already worked itself out of the old one as some had suggested. Again, this thing was spring loaded and hard to compress when I put it in but one week of sitting there did it. Replaced the pin anyway.
 
Replaced the pin today with a new one with a fresh rubber sleeve. The new sleeve was much tighter and did not seal the bore like the worn out one. Interestingly when I opened the caliper to do this, the air had already worked itself out of the old one as some had suggested. Again, this thing was spring loaded and hard to compress when I put it in but one week of sitting there did it. Replaced the pin anyway.
I agree since you were already in there, might as well replace the parts, but, yeah, it works itself out as you learned.

This is more of an incidental seal(ing of air) that just so happens to occur as a result of other factors, but it's not built to actually maintain a seal long-term like an air system would be. Through movement, vibration, temperature changes etc the air escapes in relatively short order.
 
Back
Top