heavy85 Posted July 20, 2009 Share Posted July 20, 2009 I'll skip boring everyone with the details and leave that to another thread but at the end of the NASA track weekend the brakes felt odd and weak with more than usual pedal travel. I decided to skip the last session - intuition is a great thing - and in the process of changing tires noticed that one rear 240sx caliper was leaking badly. I limped it home only to find out the other caliper was leaking but not as bad. WTF. One was a reman bought off e-bay and the other was from Advance. I didn't boil the fluid or anything and am only running Hawk HP+ which dont take heat ... and also fade really badly by the way. I'll repeat WTF. Any ideas? I thought many people use these for track days and even remember seeing pictures with heat checked rotors. One last WTF for good measure? Cameron Quote Link to comment Share on other sites More sharing options...
jt1 Posted July 20, 2009 Share Posted July 20, 2009 If you're getting brake fade, either you got the pads hotter than their operating temp, you boiled the fluid, or you've got some moisture in the system and boiled the water. Usually if you overheat the pads, the brakes come back after they cool down. If the pedal was still soft after cooling, it's fluid related. Either way, it sounds like you got the calipers hot enough to cook the seals. A caliper rebuild is in order, then some fresh fluid, something like Valvoline Syntec or ATE super blue. I use both with good results. If you still get brake fade with good fresh fluid, it's time to upgrade the pads, and maybe work on some cooling ducts. Can you tell if it's the front or rear fading? John Quote Link to comment Share on other sites More sharing options...
heavy85 Posted July 20, 2009 Author Share Posted July 20, 2009 With the stock brakes I could go about one lap full out before the pads faded and I went off track - dont ask me how I know. With the new vented, two-piece rotor, 4 piston front & rear disk set-up I can go about three laps before the pads fade and I go off ... but dont ask me how I know that either. Either way these are HP+ pads which as I've found dont take heat well and have a low coefficient so are weak for track duty. I was expecting the new set-up to work much longer but they dont. Anyway this weekend were 25 minute sessions so around 15 laps give or take. Knowing their limitations I managed pad fade by braking WAY early - I mean WAY early - on the long straights and never had an issue until the next to last session. The pedal was always there so I dont think I boiled the fluid it just got progressively softer through the session and I could manage it. I had also just bled the brakes with Motul Saturday night so they had fresh fluid. I've gotten the stock brakes HOT and never had seal issues. I mean smoking burning the paint off kind of hot. I never even smelled brakes all weekend so I really dont think they got THAT hot. If I got the brakes hot enough to melt the seals I would expect to have seen other signs like blued rotors or at least smelled hot braked but I saw no indication at all. My concern is not with the fade as I understand and can manage that it's how do I prevent these seals from failing again. I missed the last session because of it so I dont want these things to leak again. Cameron Quote Link to comment Share on other sites More sharing options...
jt1 Posted July 20, 2009 Share Posted July 20, 2009 I would tear down the calipers and examine them carefully. See if the seals look melted, and if the bore and piston look OK. Look for any signs of scuffing, or a rough piston or bore. Do the pads show any taper? Sometimes if they are wearing tapered, the piston can cock and cause a leak. Excessive caliper flex can also do this, and if could be a combination of both. The mount could also be flexing. jt Quote Link to comment Share on other sites More sharing options...
EMWHYR0HEN Posted July 20, 2009 Share Posted July 20, 2009 Just making sure but, are you twisting in the pistons when you push them in for new pads? and are you lining up the notches on the pads with the grooves on the caliper? Quote Link to comment Share on other sites More sharing options...
johnc Posted July 21, 2009 Share Posted July 21, 2009 Get air to the inside of your front rotors. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 21, 2009 Share Posted July 21, 2009 Seems like the problem now is with the rears. I'd suggest a bigger rear brake upgrade, maybe something with a vented rotor and larger caliper and pad. Just to clarify are you having brake fade or boiling the fluid? Fade = you step on the brakes and the pedal is hard but the brakes don't slow the car. Boiling fluid = pedal gets soft and brakes do nothing. If it's fade, I'd just get the next step up in pads, like a Hawk Black or R4. It's about this point in the pads where you start having to put heat into them to get them to work, so not the best choice for the street. I had a near miss with R4 pads after getting off the freeway. They were cold, and the light was red... Quote Link to comment Share on other sites More sharing options...
zedman240 Posted July 21, 2009 Share Posted July 21, 2009 Never heard of rear brakes on a zed fading? Fronts yes but rears? Where they supposed to be remanufactured calipers? Do you have an adjustable bias valve fitted? I'd say seals have decided to fail and leak fluid. When brakes fade never seen fluid leak; just a soft pedal and rears partially applied.. Get them both redone by someone you know well then that's the only time you know its been done properly! Who needs brakes anyway...they just slow you down! j/k Quote Link to comment Share on other sites More sharing options...
1 tuff z Posted July 21, 2009 Share Posted July 21, 2009 cam, i ran my 24sx rears for years at watkins glen, running sessions up to 40 minutes long and never had a problem with brake fade [although sometimes i do get brain fade ] and am running the same hawk hp+ pads. there must be something else that is causing this issue. for fluid i run an off the shelf, valvoline synthetic. again, no brake fade ever. i had the modern motorsports 13" fronts with the sx rears. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted July 21, 2009 Author Share Posted July 21, 2009 Get air to the inside of your front rotors. That will keep my rears from leaking At least I now have two piece vented rotors so I've gone from one to three laps before they go away. I now have a winter project ... cam, i ran my 24sx rears for years at watkins glen, running sessions up to 40 minutes long and never had a problem with brake fade [although sometimes i do get brain fade ] and am running the same hawk hp+ pads. there must be something else that is causing this issue. for fluid i run an off the shelf, valvoline synthetic. again, no brake fade ever. i had the modern motorsports 13" fronts with the sx rears. You have to remember I'm on full slicks with lots of grip a very good power to weight ratio (~350 hp / 2600 lb) and I drive very hard. Just making sure but, are you twisting in the pistons when you push them in for new pads? and are you lining up the notches on the pads with the grooves on the caliper? Yes Just to clarify are you having brake fade or boiling the fluid? If it's fade, I'd just get the next step up in pads, like a Hawk Black or R4. It's about this point in the pads where you start having to put heat into them to get them to work, so not the best choice for the street. I had a near miss with R4 pads after getting off the freeway. They were cold, and the light was red... My fade is pad fade not boiled fluid. Hard pedal just no torque. Yeah I need to upgrade pads but the whole street drive to and from the track has got me concerned. I would tear down the calipers and examine them carefully. See if the seals look melted, and if the bore and piston look OK. Look for any signs of scuffing, or a rough piston or bore. Do the pads show any taper? Sometimes if they are wearing tapered, the piston can cock and cause a leak. Excessive caliper flex can also do this, and if could be a combination of both. The mount could also be flexing. Just tore one apart. Everything is perfect. Pad wear is even. Seal looks new. Piston looks new. Now I'm really like WTF. Why did these start leaking? They leak just pushing the pedal sitting in the garage so it's not a heat related or dynamic flexing issue. Cameron Quote Link to comment Share on other sites More sharing options...
DiscoPotatoe Posted July 22, 2009 Share Posted July 22, 2009 That will keep my rears from leaking At least I now have two piece vented rotors so I've gone from one to three laps before they go away. I now have a winter project ... You have to remember I'm on full slicks with lots of grip a very good power to weight ratio (~350 hp / 2600 lb) and I drive very hard. Yes My fade is pad fade not boiled fluid. Hard pedal just no torque. Yeah I need to upgrade pads but the whole street drive to and from the track has got me concerned. Just tore one apart. Everything is perfect. Pad wear is even. Seal looks new. Piston looks new. Now I'm really like WTF. Why did these start leaking? They leak just pushing the pedal sitting in the garage so it's not a heat related or dynamic flexing issue. Cameron Is your bleeder valve tight? brake line? mabe it backed off a little at the track I've had this happen before.... expecially after a recent fluid change. Little tip when working alone trying to trouble shoot put a camera in different angles around the car and start video taping and press the brakes until you find where its leaking from. little tip i learned when i started living on my own... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 22, 2009 Share Posted July 22, 2009 I'm starting to wonder about the caliper brackets. Was it mark or jt1 that had the Wilwood bracket flexing and causing the pistons to wear in the bores??? I'm thinking something similar might be happening to you. Are your brackets aluminum or steel? You may think that it's not related because they leak in the garage NOW, but I think maybe they were damaged by what happened on the track, and now leak in the garage. As to rear brakes and heat, I've run my car with 3 drivers at an autox and at the end of the runs the rear rims were too hot to touch, so I think you can get plenty of heat into the rear brakes especially with the sticky tires Cameron is using. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted July 22, 2009 Author Share Posted July 22, 2009 I'm starting to wonder about the caliper brackets. Was it mark or jt1 that had the Wilwood bracket flexing and causing the pistons to wear in the bores??? I'm thinking something similar might be happening to you. Are your brackets aluminum or steel? You may think that it's not related because they leak in the garage NOW, but I think maybe they were damaged by what happened on the track, and now leak in the garage. As to rear brakes and heat, I've run my car with 3 drivers at an autox and at the end of the runs the rear rims were too hot to touch, so I think you can get plenty of heat into the rear brakes especially with the sticky tires Cameron is using. ... but they look perfect. Seal and piston look new? The bracket are from MM and are cast steel and I thought many had good experience with them. Pad wear is also even. Cameron Quote Link to comment Share on other sites More sharing options...
jt1 Posted July 22, 2009 Share Posted July 22, 2009 If the bores and pistons look good, I think I would try and source some o rings of the correct size from Wilwood, Brembo, or AP, and put them in the SX calipers. They are likely of better quality than the rebuilder grade stuff. Then get some higher temp pads and give it a try. The pads will help with the fade, and the higher temp pads transfer less heat into the pistons, caliper, and fluid. Of course, this forces the heat into the rotor, so you may have to improve cooling. I've seen tire worms caught in the caliper and rotor catch fire after a hard session. Jon is right, you put a lot of heat into the brakes on a high HP/sticky tired/aggressively driven car. jt Quote Link to comment Share on other sites More sharing options...
bjhines Posted September 27, 2009 Share Posted September 27, 2009 What happened with this issue? I am VERY WARY of the rebuilt 240sx calipers I have seen. Those calipers are not completely rebuildable without a few highly specialized tools. There are seals behind the pistons(inside the helical pin area) that are next to impossible to replace. I am willing to bet that they were improperly rebuilt and that is the source of your leaks. You cannot completely disassemble those calipers without VERY, VERY, VERY, custom, specific, super, ultra, wicked, inside, snapring, thingamabobbies. I GUARANTEE that the rebuilders don't do SQUAT!!! to address those inside seals, You are just lucky if you happen to get good NON-ocmpletely rebuilt ones. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted September 28, 2009 Author Share Posted September 28, 2009 I'm embarrassed to say I think to root cause was leaking banjo fittings. I had been running them all year with several track events, autox, etc and had no problems at all. Then at the end of one track day while changing back to street tires to drive home I noticed that both rears were leaking fairly bad as fluid was on the wheels and fluid dribbled out when you pressed the pedal. Looking at them you could see fluid dripping off the bottom of the pistons and the dust shields were brittle. Thinking the obvious that the seals were bad I exchanged one at the auto parts store but the other one I got on e-bay so I bought a rebuild kit. I replaced the seals in the one and it still leaked dripping off the piston. Then I started looking REALLY close and noticed that the banjo fitting was wet and that was the source. If the fittings leak the fluid runs down to the top of the piston then runs off the bottom making it look like a piston seal leak. Since the fluid is thin and clear and the calipers are gold anodized it's impossible to see the fluid path but you could feel by hand and trace it. Why both sides decided to leak at exactly the same time after 1/2 years use I have no idea but I noticed you have to crank them down more than I would think is enough to get them to seal. I wonder if the temps caused the copper crush washer/seals to relax? Cameron I'm anxious to see how your car does when you get it complete and on track! Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted September 28, 2009 Share Posted September 28, 2009 To soften copper gaskets and O-rings for reuse, heat them to red hot and drop them in cold water. They will go dead soft and reseal nicely! Mongo Quote Link to comment Share on other sites More sharing options...
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