Fast Eddie I

I have a '07 Z06 with low mileage. I noted today that brake fluid had forced past the seal in the brake reservoir cap. The cap was tightened to its limit. Upon inspection, the seal appears OK as well as the mating rim on the reservoir.

The volume of fluid leaked was sufficient enough to flow down onto the frame rail. I must have caught [and cleaned] the leaking fluid soon enough as the black frame paint does not appear marred or lifting.

I have changed my fluid several times for HPDE sessions and converted to DOT 4. This is the 1st time that I experienced any leaking despite past heavy braking use.

Has anyone experienced a similar problem? Is the correction as simple as acquiring a new cap or could a design problem exist?

Happy Holidays.

timd38

I did when I over filled it. How is the level?

Fast Eddie I

Good question. Right or wrong, I normally refill the reservoir to the 'MAX' line and have had no previous problems. That is why I suspicioned a seal or other mechanical problem.

The last flush/refill was approx. 2,000 miles ago and includes some HPDE use.... all with no sign of leakage.

The present level (following leakage) is slightly above the 'MIN' hash mark.

LEAVINU

Just noticed the same with mine the other day oddly enough. I had just syphoned some old fluid out and filled with new just as a quick "flush" until I bleed the system in the near future. I did notice the rubber underneath the cap seemed like it was deformed and possibly could have been pinched not completely sealing the res when tightened. I've cleaned and re-installed and will check once driven again.

I filled mine just a tad under max as I always do and this is the first I've seen this.

musicmankeb

I also noticed that mine leaks as well, not a whole lot but it leaks down from the cap and onto the seem that goes all the way around the plastic container. I'm thinking of purchasing a new cap unless there is another fix?

Gearhead Jim

Free bump, and awaiting further posts.

JCtx

It seems like a pretty cheap cap. And the only thing that can be wrong is the cap (or more specifically, the rubber gasket), so just replace it. Fluid is sloshing around in the reservoir all the time, so if the cap doesn't seal properly, it's going to make a mess. And you do not want brake fluid on painted parts. And on many other parts. Good luck.

Fast Eddie I

[QUOTE=Gearhead Jim;1582487890]Free bump, and awaiting further posts.

I beleive that my original problem stemmed from removing the cap too many times during regular flushes. During 2012, my dealership installed a new reservoir cap. The tightening action now is really tight as compared to the OEM cap. It may pay one to replace this cap periodically as thread loosening is detected.

To be safe, I now normally put duct tape over the cap during HDPE sessions to protect against loosening. With or without the duct tape, I've experienced no problems since installing the new cap.

JCtx

There're no threads man; it's just a 1/4-turn ramp-up design. And I doubt it matters if the cap is removed many times or not. When the rubber gasket deteriorates (it happens due to age and heat cycles), it simply fails to make pressure against the reservoir anymore, and it leaks. It'd help to post mileage and age of car to judge when we need to replace it .

ErnieN85

Check the center of the rubber diaphram............it has a small cut in it from the factory (unless it's been change recently) I found that on my 2002, I bought a new cap it had it also.
Checked my 2009 same thing. it is hard to see but it is there a small v shaped cut

vette6500

mine leaked fluid past the seals during hard braking at end of autocrosses.
you can buy just the replacement rubber seal from autozone for very cheap like two bucks or something, made by one of those generic makers.
super easy to replace, just squeeze the sides of the old seal and pop it out of the cap's simple detents, then squeeze/pop in the new seal.

the cap's tightening action should instantly feel tighter. no leaks since.

JCtx

You NEED that, to avoid a vacuum condition when reservoir level goes down. Since brake/clutch hydraulic systems are vented, that's why you need to change your brake fluid every 2 years max (regardless of mileage), due to moisture absorption. Hope this helps.

ErnieN85

the older caps had a bellows which decended as the fluid level went down and sealed compleatly. the cut is a bean counter (cheap) way of doing it and causes contamination forcing you to change fluid most people will not eventhink about it
the contamination is also caused by the moisture leaking around the seals in the calipers and the slave cylinder on the clutch

JCtx

Cheap parts is a given on this car man . But pretty much all cars have a vented brake/clutch systems. Only motorcycles use a diaphragm since they don't have hoods . And you're also absolutely correct about the rest of the crappy parts; that's the reason it gets contaminated, not the fact it's ventilated. I have to change the clutch fluid in my car every few weeks. Have been doing it since day 1, and it keeps getting dark after 9 months. Wish I could just bleed it properly, but can't. So have to do the half-a$$ method of just sucking the reservoir dry every few weeks. Have done it like 10 times in 3K miles. It's still oily and getting dark every time I change it. Not black dark, but brownish, with only a few hundred miles. It should get better over time, according to some. We'll see. Take care.