Sticky front hydraulic brake

[Yellow Fang]

I have rather a sticky front hydraulic brake. I wonder whether it's a bike shop job. The brake pads don't look too worn to me, but it has been about a decade since I changed them. I have not bled the brakes in that time neither. I bought some Castrol GTX oil the last time I needed to fill up the brake reservoirs, but I have just watched several YouTube videos and it looks like they use dot fluid now.

 

[Slick]

I have rather a sticky front hydraulic brake. I wonder whether it's a bike shop job. The brake pads don't look too worn to me, but it has been about a decade since I changed them. I have not bled the brakes in that time neither. I bought some Castrol GTX oil the last time I needed to fill up the brake reservoirs, but I have just watched several YouTube videos and it looks like they use dot fluid now.

Ooft, they will definitely need bled and with what depends on what type you have. Also, your pads will almost certainly be worn unless you rarely use your brakes.

 

[Rickshaw Phil]

Some manufacturers use mineral oil and some use DOT fluid. Don't put the wrong stuff in or you will ruin the seals.

Seizure is possible after ten years, especially if they've never been serviced. Most likely the caliper pistons. As above, I'd expect the pads to be worn too. I've changed Shimano calipers and found them a pretty straightforward bolt-on item. You obviously mustn't get fluid on the braking surfaces and having the right bleed kit will save a lot of time and blue air.

It is of course a safety critical item so if in doubt, get the bike shop to do it.

 

[rogerzilla]

Castrol GTX

 

[Milkfloat]

If you have sticky pistons, then you can remove the pads, pump the brakes bit to get the pistons to protrude (but don't go too far), then use Isopropyl Alcohol to clean the sides of the protruding pistons. Gently lever the pistons back in with something soft like a plastic tyre lever and repeat as necessary. I have heard of people successfully using baby oil before, not sure if Castrol GTX is recommended though.

 

[Jody]

Castrol GTX

This pretty much sums it up. OP I'm hoping you're on a wind up.

First job is find out what brakes you have, what fluid they should have in them, buy a bleed kit, flush them properly and hope you haven't damaged them.

 

[Electric_Andy]

As above, they are well overdue. Usually they stick because the seals are knackered, and/or there's crud on the sides of the pistons. If you have the correct tools it's not a hugely daunting process if you watch some YouTube videos first. The same principle applies to nearly all types of hydraulic disc brakes. At that age I'd be ordering a new seal kit and doing a full rebuild anyway. It's a lot easier to clean them properly if they're off the bike. You could try the above advice first (pumping out the pistons and cleaning them in situ, then doing a fluid change), but in my experience this is sometimes only a short term fix until it happens again.

I hope when you pump the piston out, your seals don't come out with it. But if they do then you'd have to do the full job anyway.

Regarding the fluid, yes certainly check what type you should use. Use caution and read up on it first, but don't let it put you off, many people are put off doing brakes but they can be done very safely if you have the knowledge, the right tools and follow advice carefully.

 

[faster]

If this is a system designed for DOT fluid and you've put Castrol GTX in it, I suspect you'll need to replace every rubber part in the system and clean everything meticulously, as the (likely) EPDM seals swell on contact with mineral oils. Probably easier to throw it all away and start again.

If it's a system designed for mineral oil, you may well get away with it.

 

[rogerzilla]

I doubt GTX has the requisite viscosity, boiling point and seal compatibility for any brake system. It would be about as good an idea as frying your chips in it.

 

[figbat]

1. Make and model of the brakes?
2. Was the GTX simply added as "top-up" or was it bled through?

A few things come to mind:

If it is a brake that needs DOT 4/5.1 brake fluid then there's a good chance the seals are ruined at the master cylinder and caliper.
If the GTX was mixed with DOT 4/5.1 fluid then there's the additional possibility of fluid incompatibility leading to deposits or other unwanted interactions.
If the brake is meant for use with mineral oil then things are less bad, but the seals may still be affected as GTX uses additives that these seals are not meant to see.
If GTX was added to mineral oil there is virtually no chance of any fluid incompatibility.
GTX comes in a variety of versions and viscosities, but even the lowest viscosity variant will still be thicker than whatever fluid is supposed to be in there.

Any way around I'd reckon on a complete flush and refill with the correct fluid, plus new seals all-round. Or replace the lot.

 

[Yellow Fang]

Castrol GTX

No, actually I have the bottle in front of me, it was Castrol Response synthetic brake fluid DOT 4. I did buy it from a petrol station though.

 

[figbat]

No, actually I have the bottle in front of me, it was Castrol Response synthetic brake fluid DOT 4. I did buy it from a petrol station though.

Assuming the brakes use DOT 4 fluid then this is OK. One issue could be water ingress, as brake fluid is hygroscopic (absorbs water over time) which can lead to corrosion and hydrolysis (reaction) of the fluid. Or it could just be that the pistons are a bit dirty and just need a clean, plus a fresh charge of fluid.

 

[Jody]

No, actually I have the bottle in front of me, it was Castrol Response synthetic brake fluid DOT 4. I did buy it from a petrol station though.

Less worrying than engine oil

 

[Slick]

No, actually I have the bottle in front of me, it was Castrol Response synthetic brake fluid DOT 4. I did buy it from a petrol station though.

Some good stuff on this link. If you decide to try bleeding them yourself, it could take 3 or even 4 times to do it right but it is worth the effort.

https://epicbleedsolutions.com/