caliper cylinder boot is bulging

[Rolomoto]

I am doing my front brakes and when I pushed the caliper cylinder back with the tool shown and a used brake pad the boot around the cylinder started to bulge out and won't go back in flush. Is this an issue, if so what can I do? I try to squeeze it back in but it doesn't hold or another spot will bulge out once I get one spot flush. I can close the caliper down over the pads but wonder if I would be damaging that boot using that way. Thanks cylinder boot pic 01 cylinder pic 02 tool

 

[wirelessF]

It's probably trapped air in the boot. I've used a pick or similar slim tool in the middle groove to help push the boot back in.

 

[Tegger]

Originally Posted By: Rolomoto

the boot around the cylinder [piston] started to bulge out and won't go back in flush.

Trapped air. Just "burp the boot by briefly pulling it away from the piston with your fingers or some other tool that won't poke through rubber. You can use your fingers to "pinch" the boot to create a slight gap for the air. Do not put the caliper over the boot when it's like this. You may tear the boot, which is a Bad Thing.

 

[29662]

Sounds like the piston may be cocked. Either replace or rebuild the caliper. They're too cheap to risk your life.

 

[Trav]

As others have posted its just aa little air, pull it with your fingers. I see you just removed the lower pin bolt to flip the caliper up. While this makes for a quick hob the upper pin is not being serviced. I strongly recommend you remove the top pin and lube it.

 

[JTK]

I've had this happen and it was trapped air. Like suggested, I just tugged the boot away from the piston and the air bled out. I usually spray some silicone spray lube on a rag to wipe down the outside of the boots real good and then rub some silicone grease around them.

 

[Rolomoto]

Burping it worked fine, thanks! As Trav suggested, I would like to lubricate the upper caliper pin however I can't fit a 14mm wrench over the pin to hold it steady when unscrewing the caliper bolt. There is a little steel lip that the boot pushes up against and there isn't enough space between that and the other side for me to fit the wrench in there. When I turn the caliper bolt it just spins, I need to hold the pin steady. pic of what I'm talking about

 

[Trav]

You need a thin profile wrench. You can take a cheap one and sacrifice it to make your own with a grinder. I have plenty of wrenches that have been ground, bent and twisted for different stuff. You may be able to just pull the caliper off the pin, lube the pin and put it back on.

 

[Rolomoto]

Thanks Trav.

 

[Tegger]

Originally Posted By: Trav

I have plenty of wrenches that have been ground, bent and twisted for different stuff.

I have a few, too. Here are a couple of them. They are used together to perform on-the-car adjustment of the brake master cylinder pushrod on older Hondas. They started out as ordinary Craftsman combo wrenches.

 

[Trav]

Nice. Well done!