BenCA

I've done a few track days and noticed after bleeding the brake screws on the front that there was some seepage afterward. The rubber caps on the bleed screws would be wet inside after a session, but no drips down the caliper itself. I re-bled them and tightened them hand tight with a 10mm wrench, but they were still wet after the next session and I was experiencing quite a bit of brake fade. This happened two or three track days.

Back home with only normal driving I took it to the dealer and they were only able to get the left front caliper to stop seeping, the right would still pool some fluid in the rubber cap. They replaced the right front caliper and things looked good for a few days but a couple weeks ago I checked and the cap was wet again, probably half a ml of fluid or so. I cleaned the cap out but didn't do anything to the bleed screw itself to try to isolate the problem, then checked a few days later and it was wet again. I cleaned it out again and scheduled an appointment and today I took it to the dealer and the cap was still dry and they couldn't reproduce the problem, so I'm just going to drive it for a week or so to see if it leaks again. No track days since they replaced the caliper a month ago.

Anyone else have trouble with these calipers (or on the RC350 or GS350 which seems to be the same or very similar part number)? I don't feel safe taking it back to the track with flaky brakes. The other three bleed screws are fine at this point but I've never had this kind of seepage or leak on any other calipers especially under street driving.

Pittsy

Wow, thats really interesting. Maybe try installing some aftermarket quick bleed screws, would definitely come in handy if you’re tracking the car.

Is it leaking out of the threads or out of the bleeder hole?

gcmak

Depending on what you have available to you, there's a few things you can try out.

• blow out the bleeder screw once you've torqued it to spec. that should evacuate any fluid sitting in the screw itself during a brake bleed. if more fluid builds up and shows up later, then it's still leaking.
• if you have a legit air compressor with a trigger and narrow rubber tip, you can push that up against the bleeder screw and see if you can see any fluid/air come of the threads around the bleeder screw.

It's actually a little surprising you've only seen the fluid in the cap and nothing running down the calipers - I wouldn't worry about it myself but I can see your concern when the 3 other bleeders don't exhibit the same behavior.
Pretty normal in my experience to have fluid come out of these kind of calipers with track and heavy street use - brembo/akebono etc. I thought it was a problem of mine too till I spoke to race shops and awkwardly poked around the paddock to see the same issue car after car when they come back from a session.
I also made the mistake of over-tightening the bleeder screw before and it was very gutten tight...no more leaks but the screw snapped off cleanly too!

Nice of Lexus to have changed out hardware for you and all too, most other companies would laugh unless it was actively leaking under a brake pressure test.

I've only done some drifting/autocrossing in this car and i just feel like the long pedal travel in general is not confidence inspiring and there's very little heat capacity for the small pad especially, so things will heat up fast! I did do a complete Castrol SRF fluid exchange, not that I needed to as I don't think I will be taking this on the track in any serious way...it's really a GT car that you can enjoy with some motorsport activities but if you're going to go ham, there's a lot of work to bring it up to snuff to handle the weight and power.

iVtecV8

That’s interesting! I track my other car which has a stoptech BBK with 2 piece floating rotors and carbotech XP12 track pads.

One track day I beat my PB after I brake very late and hard, I noticed there’s some brake fluid dripping on the caliper as well. Somehow it wasn’t as tight. I tightened up the bleeder valves and then it didn’t leak anymore. Since then I check for brake fluid at the caliper and double check if it’s tight after every session.

I think if you do a visual inspection after every session you should be fine.

My guess is the car is heavy, and it heats up the fluid and whole system. I wonder if the IS F, RF F, GS F folks see the same issue.