Brake fluid seepage troubleshooting

[uwaeve]

OK, posting this on some other boards got me some suggestions, but I'm interested in having you guys that track your cars on a regular basis take a crack at it.

I own a 2005 Nissan 350Z with the Brembo brakes. Calipers are all fixed, 4-pot fronts and 2-pot rears. Rotors are 324*30 mm front, 322*22 mm rear.

Before my first DE event, I went ahead and installed Hawk HP+ pads and flushed/bled new ATE Super Blue fluid.

The first DE even was at NHIS, which is apparently a tough track on brakes (so I’ve heard). This, perhaps exacerbated by incorrect use of brakes (I’m guessing here, no one told me that I was using them incorrectly, but it was my first time on the track) made my brakes fade. I figured I didn’t buy the right compound and just finished the day on less-than-stellar brakes. Not unsafe, but soft pedal. This leads me to believe I either boiled the fluid, or got air into the system during hard braking. When I did my flush and bleed, I never did any ABS stops to flush out that reservoir. Looking at my brakes near the end of the day, though, I noticed a trickle of blue down each caliper. Not a lot, but enough to leave a track all the way down the caliper and leave some drops (not puddles) of baked fluid on my wheels.

Before the next track event, I did another bleed and tried to repeat the problem (probably going through a bunch of pad trying it) on a long and little-used road near my house (not interstate, but 65 mph speed limit). The best I could do was go from 90 to 30 mph over and over again as fast as I could. I went through a fair amount of cycles, but nothing approaching a 20-minute track session. No dice: clean calipers.

So off I went to my next event at Watkins Glen. I watched throughout the day as the problem repeated itself to a lesser extent. First the left rear had a bit of seepage, then it spread to all the calipers and greater amount of fluid. However, the pedal held up a lot better through the day. Still softened, but not near as bad. Also, the amount of fluid we’re talking about barely made the reservoir at the master drop at all (and that would include the volume used to replace the brake pad that I left all over the track) over the day.

So now to my speculation and hearsay.

The first thing I thought of is that I’d taken $1.60 worth of (nice, hard steel) screws and destroyed $4800 worth of (nice, soft aluminum) calipers. When I did the bleeds, I torqued all the bleed screws to 120 in-lb (10 ft-lb), as the specification in the service manual is 9-11 ft-lb. Fairly sure it's not a typo, since it's also specified in N-m and kg-m and the numbers jive. I’ve since called a couple dealerships to verify the torque number, and found that the people I’ve spoken to just hand-tighten them. A couple of mechanics (at local garages, not Nissan dealerships) have said that 10 ft-lb sounds high for bleeder valves, but then again they are not race mechanics.

Someone suggested that I could have gotten dirt in area where the bleeder seats against the caliper. I don’t know whether the fact that it happened to all 4 calipers means the dirt theory is more or less likely. I could argue either way.

So my next course of action is to examine the valves and caliper seats during the next flush, which will probably happen within the next month. Can anyone make suggestions as to how to minimize problems in the process? Can I do this inspection without emptying the caliper? Can I just relieve pressure with the bleeder, remove it, and wick up enough fluid so that I can see into the threaded hole to examine the seat? Any other suggestions on what to do/look for would be appreciated.

Any thoughts, comments, accusations of lunacy? The lunacy would refer to me insisting that I do everything myself. I consider myself organized, conscientious, and fairly handy with these types of things. This is, however, the first time I’ve done a flush/bleed/track.

Thanks in advance.

[billy]

Haven't had a problem with my car at Brainerd or MAM, no fade at all (it's a 996) but I had the dealer flush my fluid, not brave enough yet to do it myself. Like you, I'm a novice, they were my first two HPDE's. I think I was going ok as John was taking little or no time out of me except through the very fast turns where I just didn't push it and for sure, John likes to whip his car.

But, what I find interesting here is Conan had similar problems last year at Brainerd where his brakes faded completely (stock 350Z). I think he's putting on stoptechs this year but given you upgraded your brakes and they still faded, it makes me wonder if inadequate cooling is the problem? I think Conan was hoping the bigger calipers would be enough to dissipate the heat.

Also,
Why is the rear disc bigger than the fronts? Haven't seen that before.

I figure Stacy will sort you out anyway given he tracks 350Z's regularly.

[uwaeve]

Fixed the rear rotor size, there's a typo in the service manual.

I'll be interested to find out if Conan was venting fluid or not.

[uwaeve]

I had the dealer flush my fluid, not brave enough yet to do it myself.

Come on...look at how well it worked out for me.

[Stack]

Originally Posted by billy

I figure Stacy will sort you out anyway given he tracks 350Z's regularly.

HA! I wish!! LOL I have driven a few on and off track, and seen my fair share at our events... some with, and some without brake problems.

You generally won't see any problems with the Brembo brakes - and almost never with an upgraded stoptech system.

I'm curious uwaeve if you could tell where the trickle of fluid was originating? Was it coming from inside the caliper? Outside? Have you changed to stainless brake lines or anything recently where a fitting may be stripped out or anything?

Outside of that, it sounds like a bit of seal faliure to me... but on a 2005 I'd think that would be unlikely.

I've had similar fluid issues on both my '90 Z32 and my '71 240z - so its not uncommon... but on a car that new, should be cause for concern.

Have you posted anything on My350z.com in the track section?

[uwaeve]

I'm curious uwaeve if you could tell where the trickle of fluid was originating? Was it coming from inside the caliper? Outside? Have you changed to stainless brake lines or anything recently where a fitting may be stripped out or anything?

I should have clarified, the seepage came from the bleeder screws. Whether it came from the "outside" of the screws (threaded portion) or the "inside" (where fluid usually comes from when you loosen the bleeders) is a mystery. Basically looks similar to what would happen if I loosened the bleeders with pressure in the system (without tubing/catch can) and just let some fluid run down the calipers, then retightened. Except I didn't.

Have you changed to stainless brake lines or anything recently where a fitting may be stripped out or anything?

No stainless lines, but I did do the flush/bleed by myself. That's why I was a little worried about stripping out the threads inside the caliper. However, knowing how expensive they were, I made sure to torque to spec, not bang the torque wrench past the initial break, etc. Unless it was a typo in the service manual, or 10 ft-lb is not equivalent to 120 in-lb, I followed specifications.

Another thing to note: in the pits after I cleaned up the remains of the initial trickle, I couldn't squeeze any fluid out of the calipers by standing on the brake pedal. Now that I'm thinking of this, the dissimilar coefficients of thermal expansion could be allowing a path for fluid to seep out at elevated temperatures. In that case, maybe I'm not tightening enough, but I clearly need to be wary of stripping the aluminum threads in the caliper. Hmm. Dilemma.

Have you posted anything on My350z.com in the track section?

Nope, tried the "repairing" section without too much luck. I'll try the "Track" section.

[Stack]

hmm... interesting...

Since its happening on all the calipers... I think we can rule out defective bleeders. Maybe they aren't up to HP driving though? Possibly a cost-saving measure from Nissan?

Could be user error... but not sure how - sounds like you did everything by the book

Wonder if it could have anything to do with ambient temperatures when you tightened the bleeders? Cold when you did the bleed vs warm when you were on track, or vice-versa?

Not sure if this is kosher or not, but I wonder if you should try a small bit of teflon tape on each bleeder? See if that helps?

I know I'm just creating more questions than answers here... I know the guys from StopTech are members and sponsors of My350z.com - wouldn't hurt to PM them with the situation as well... they've got enough track time and R&D in the 350z I'm sure they've encountered the problem as well.

As far as your brake fade... it may very well be completely unrealated. If you got a soft pedal (I.E. the pedal will go farther without stopping as well) then yes, you got air in the lines... either from boiling (probably not with AP Super Blue) or from air being let in by the bleeders.

If you had good pedal feel, but no stopping then you glazed the pads, or got some of the fluid between the pad and rotor.

[billy]

I dunno Stack,
Our man Conan boiled ATE in his 350Z , a feat that will go down in the lore of HPDE history

[Stack]

Originally Posted by billy

I dunno Stack,
Our man Conan boiled ATE in his 350Z , a feat that will go down in the lore of HPDE history

LOL ... thing about brake fluid... I don't care what fluid you use, if the car is fast enough, and the brakes small enough... and the driver tentative enough... any fluid can be boiled

Notice how I didn't say aggressive? Its my opinion, that its the tentative drivers that have the hardest time with brake issues... I think what happens is they have a tendency to 'ride the brakes'. It's a natural tendency, but it can be detrimental. If the brakes are applied too soon, and with an easy motion, even if not being applied super hard, in a car with high speed capability, the brakes will overheat faster in this scenario than if driven more aggressively: Wait a little later to brake, apply heavy, but not jerky pedal pressure (fast squeeze, progressively stronger as the car settles into its braking stance.) The trick is to use the maximum braking force without lock-up within the shortest distance... this is called threshold braking. "Going easy" on the brakes tends to have the opposite effect in terms of temperature and brake fade. The only way to "go easy" is to "go slower"

[uwaeve]

and the driver tentative enough

I am pretty sure this is what happened. Didn't have good pedal feel, so I figured I boiled it. In my previous post, I conjectured that being a n00b was harder on the fluid, for the very reason you point out.

More later...