# Can I replace the front piston dust boots without removing the piston from the caliper?



## IJM (Jul 30, 2001)

My front piston dust boots (expandable rubber boot that keeps dust out of the caliper bore) are torn, so I ordered new ones and pulled out the old ones. I easily got them to seat into the ring in the piston, but I can't seem to get them into the inner ring inside the bore. It it possible to do this without removing the piston? I don't have a compressor, so I'm not sure how I'd even remove the piston if I needed to. Fully retracted, the piston still sicks out past the caliper by about 1/4 inch.

I have a track day coming up next weekend, so any help would be greatly appreciated.


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## akid420 (Apr 23, 2009)

bit confused about what youre saying but yah you gotta remove the piston to get new rubber on


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## spitpilot (Feb 14, 2000)

During caliper rebuild, I've always installed dust boots last after pistons with new piston sealing rings are back in the bore:thumbup:....do you have a blunt "pick tool" that can work edge into the mounting groove without damaging the rubber?:thumbup:


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## IJM (Jul 30, 2001)

Sort of. I have a piece of plastic I jerry-rigged to fit into the slot. I greased the rubber part up, but maybe need to try again tonight with more grease and more pressure. It does sounds like it's possible, right?


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## spitpilot (Feb 14, 2000)

Every caliper rebuild I've done..the last step is installation of dust boot...it usually just slides down over top of piston and snaps into grooves on piston and caliper body...haven't done your specific caliper so I can't describe install technique better...:thumbup:


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## IJM (Jul 30, 2001)

I'll give it another shot. If I break something it's your fault.:beer:


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## germancarnut51 (Mar 23, 2008)

You pretty much gotta remove the piston from the bore to get the dust boot seated in the goove inside of the cylinder, before stuffing the piston back in.

Seems scary, and complicated, but it isn't that bad. Besides, you gotta remove the piston to get the piston seal back in before installing the dust boot anyway.

Scrub parts with a green scouring pad, clean everything (except for the rubber parts) with brake cleaner, and rinse with more brake cleaner, not water.

Use silicone brake grease, that way it's easier to focus on reassembling the caliper, rather than where all the corrosive brake fluid you would have been using is landing/splashing. Lube up everything (caliper bore, piston seal, dust boot, and piston). DO NOT USE wheel bearing or any other petroleum based grease or any synthetic grease designed to replace a petroleum based grease, that stuff will contaminate the brake fluid and eat rubber seals (like the ones you're installing).

Following the printed instructions that came with the caliper seal kit, put the piston seal in the lower groove in the cylinder. Slide the dust boot over the piston from the top down. Engage the dust boot lip in the upper groove in the cylinder, and slowly push the piston into the cylinder until the groove in the piston is close enough to stretch the dust boot up and engage the inner lip of the dust boot in the groove on the piston, and press the piston the rest of the way in. You may need to lift the edge of the dust boot to slightly from the goove in the piston before the piston is fully into the cylinder to allow air that is trapped, out from under the dust boot so it will rest properly when the piston is fully pressed into the cylinder. The combination of the new seal, dust boot, and silicone grease makes the space between the piston ring, and the dust boot pretty much airtight.

You are going to need VAG.COM or make a trip to the VW Dealer to bleed the brakes when you are done.


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## IJM (Jul 30, 2001)

Thanks for the detailed advice. I do have a VAG-COM and plenty of brake fluid, so that shouldn't be a problem. Is there an easy way to get the piston out of the caliper without an air compressor? I suppose I could just pump the pedal until it pops out, but that would dump a bunch of brake fluid out in the process.


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## germancarnut51 (Mar 23, 2008)

It doesn't take much air pressure to pop the pistons out of the calipers.

I used a bicycle pump. Put the caliper on the floor. Put a towel rag infront of the piston, point the piston away from you. Hold the airpump hose end up against the opening where the brake line is normally attached, and gently pump. The piston will extend, and then pop right out if you continue to apply air pressure. 

Be careful not to turn the caliper piston into an unguided missle with the application of too much air. The brake fluid creates a mess, but it isn't too bad if you don't overdue the oil pressure.


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