Have you examined the brake fluid in your master cylinder reservoir? And if you have a hydraulic clutch, have you checked its little reservoir?
Well, most people don’t, even technicians who really should. I’ve been in very high-dollar hop-up and dyno shops and seen reservoirs so dirty, the fluid looked like mud — in 600 hp+ cars! Spend big money to make more power but then neglect the braking system – happens too often!
At the August Cars and Coffee, I talked with a couple of C6 and C7 w/manual trans owners about the problems that can develop with hard, launch control clutch use. In the C6, the puny clutch reservoir is translucent. Even normal clutch use will turn the fluid black after a few years, and you can see it with the cap in place. I kidded that in the C7, Chevy solved that problem – by making the reservoir black. So, my new C7 acquaintance checked his clutch reservoir. It was empty!!
What happened?
- As your brake pads and clutch discs wear down, the actuating pistons protrude further and fluid gradually leaves the reservoir to compensate. And not only is the clutch reservoir very small to start with, but apparently the hydraulic clutch system leads a tough and very dirty life — some of the clutch dust makes its way into the fluid in the slave cylinder. Then every time you use the clutch, fluid goes back and forth in the system and some of the dirt makes its way up into the reservoir. There should be enough fluid capacity designed into the system to compensate for the drop in reservoir levels caused by normal wear, but the operative term is ‘should’.
- Brake fluids, DOT 3 and 4, are hygroscopic – they absorb moisture. Who would want that?? We all do. With the repeated, repeated high and low temperature cycling of a brake or clutch system, moisture is inevitably sucked into the systems. If the moisture was not absorbed by the fluid, it would instead gradually build up in the low spots (in the brake calipers or clutch slave cylinder) and droplets of water would accumulate. When you use the brakes or clutch hard, and they get very hot, that liquid water would vaporize, and your brake or clutch pedal would get spongy, or even flop uselessly to the floor.
Instead, the water is absorbed by the fluid, but that gradually degrades the fluid, darkens it and turns it corrosive. Then corrosion allows greater abrasion of the moving parts. The seals in your master cylinders, brake calipers, and clutch slave cylinder become abraded and worn. That’s how the brake fluid becomes dark and muddy, and that’s only a symptom of problems to come –everything gets worse from there.
Yet, it’s really pretty easy to slow down the whole destructive mess!
Ideally, you’d have your brakes flushed and “bled” every 3-5 years or so. But almost no one does this. And my 2013 manual calls for a brake fluid change at 10 years or 150,000 miles and a clutch fluid change at 30,000 miles. Do you know anyone who does this? And, if you tried, the bleeder fitting for the clutch slave cylinder is essentially inaccessible. But you can still do something about it in your own garage!
Buy a Mityvac® suction pump https://www.skf.com/mityvac/products/hand-vacuum-pressure-pumps/hand-pump-kits/mv8500 for about $100 and suck the old fluid out of your brake and clutch master cylinders and replace it with fresh fluid. Some brake systems call for DOT 3 , others specify DOT4. C6 and C7 clutch master cylinders call for DOT 4. Always use fresh fluid! Puncture the silver seal on the bottle of fluid as shown in the photo to make the pour easier to control.
Cover all your fenders and under hood parts with towels to catch any spilled fluid – brake fluid will ruin paint! Keep clean water on hand to wash off any spills – brake fluid washes clean with water. But cap the open reservoirs first!
If your reservoirs are dirty, it may take multiple suctions and replacements, but you can get back to clean conditions. Then keep after it! Suck out old fluid and replace it every 6-12 months.
If you don’t?
Brake systems are amazingly robust and rarely fail, but corrosion will be eating away at the insides: slowly, insidiously, perhaps even worse on a babied car that sits stored all winter. And your Corvette may be capable of near-200 mph, so treat it seriously even if you don’t go half that! If that’s not enough motivation, have you ever had a nightmare where you’re pressing the brake pedal as hard as you can and your car would not stop? It can happen.
Clutch systems are less forgiving. Complaints of clutch pedals that stick on the floor after launch control abuse can be found readily on the forums, and my buddy with a high- mile C6 has had it happen to him several times. Replacing the clutch slave cylinder means removing the rear transaxle, torque tube and bell housing. Very big money and not DIY. So make it last as long as you can with relatively easy maintenance.
Please pay attention to this commonly ignored topic and keep your Corvette stopping and going safely, providing the extremely high performance you paid for!