Leaking front calliper

[bash is300h]

Hi folks

Some advice needed around 10 months ago I accidentally pressed my brake pedal whilst my callipers were removed for q brake job resulting in the pistons being pushed out.

Both front callipers were replaced and full brake system was manually bled.

10 months later I noticed the front drivers calliper was leaking from the piston. 

Replaced and now 3 weeks later the new one is also leaking.

Anyone had this issue before / what could be the under lying issue causing the leak from one particular side. 

Car is is300h 2015

Thank you for your help

[IS300FSPORT]

Brake calipers leaking is usually because a seal was disturbed or potentially worn out.

What brake fluid are you using? Incorrect/contaminated fluid can cause this. 

Where did you source the new caliper from it should be covered under warranty.

Dont automatically assume its the brake caliper itself it could be the brake hose that attaches to the caliper was twisted during installation or a bad washer. Keep an eye on the brake bleed nipple as well. 

Get an assistance to pump the pedal whilst the wheel is off & you have full access to the caliper to visually see where exactly is the leak coming from. Whilst keeping the brake fluid reservoir topped up. 

Keep us posted pls. 

[ColinBarber]

This isn't a common issue reported here. Were the replacement callipers new from Lexus - they would come with a 12 month warranty.

[bash is300h]

Fortunately the first one I replaced was under warranty and so Is this one

The brake system has brembo dot 4 fluid

It's definitely leaking from around the piston the rubber boot is wet and not the brake hose / the connection.

As it is a repeat on the same side with the leak from the exact same component of the calliper I am wondering if there could be underlying issue isolated to purely the NSF?

In general the car brakes exactly as it should 

 

[Notamech]

2 hours ago, bash is300h said:

Fortunately the first one I replaced was under warranty and so Is this one

The brake system has Brembo dot 4 fluid

It's definitely leaking from around the piston the rubber boot is wet and not the brake hose / the connection.

As it is a repeat on the same side with the leak from the exact same component of the calliper I am wondering if there could be underlying issue isolated to purely the NSF?

In general the car brakes exactly as it should 

 

Thats the wrong brake fluid. You are meant to be using SAE J1703 or FMVSS No. 116 DOT3

[bash is300h]

Could this be the cause of the leak? It has been in the car 10 months and what is confusing why is it only leaking from one particular calliper and that to a repeat of the issue. Could any further harm have been done by using the Brymbo dot4

[Notamech]

1 hour ago, bash is300h said:

Could this be the cause of the leak? It has been in the car 10 months and what is confusing why is it only leaking from one particular calliper and that to a repeat of the issue. Could any further harm have been done by using the Brymbo dot4

Unlikely. Its probably something else like an improperly fit piston seal. Better to take it to a dealer or a hybrid specialist. As far as I am aware dot4 can be used in dot3 systems but better to use the correct spec just to be safe. 

[Redefined]

Dot 3 and dot4 are definitely cross compatible. In fact (AFAIR) dot 4 has a better/higher boiling point so an upgrade. I've rebuilt quite a few brake calipers and from what you describe it sounds like a bad piston or rubber seal. The gap between the piston and the surrounding is a fraction of a mm so a worn caliper that has been refurbished (I'd assume with it being a new unit that it is just a rebuilt unit unless you bought it new from Lexus?) might have taken a hit around the housing at some point.

Hope that helps and hope you get it sorted. Goes without saying that a leaking caliper means the car shouldn't be driven until you've got the bottom of it. Which in my mind should be a replacement part from whoever supplied you the calipers. They'll definitely have come with a 12 month warranty so get onto the seller for the replacement.

[Redefined]

https://www.bremboparts.com/europe/en/support/how-to-choose-the-right-product/which-is-the-right-brake-fluid-for-my-car-195105

 

NB seems like brembo have two different types of dot 4. Dot 4 and dot 4 low viscous. Could it be you're using the low viscosity and it's too thin the be retained around the pistons. Just a thought, but then that still doesn't explain why only one side is leaking.

To answer that, again 'maybe', it's just the side that decided to leak when the pressure built up and the seal might have been disturbed on the inside. It's a bit of a labyrinth seal which would need quite a good build up of pressure to really be disturbed.

Interested to see what you eventually figure out. If you are on low viscosity I'd definitely think about bleeding the whole system with standard dot4 and take it from there. Also, don't foeget that dot fluid is corrosive but easily denatured by water. So spray some water all over the areas where it could have splurted out and maybe some brake cleaner thereafter. Just watch where you spray the brake cleaner though as you don't want it entering any grease ports/CV boots or bearings.