Fluid type and bleeding Hydraulic Clutch

[TimG427]

I'm afraid I've lost pedal pressure in my hydraulic clutch. It sounds like the correct fluid is DOT 3 or DOT 4 fluid. Is it difficult to bleed the hydraulic clutch if air is in the system? Sorry for the novice questions, I've never had to service the hydraulic clutch before.

[cycleguy55]

Get yourself a small vacuum bleeder like this one and it's a piece of cake. It will come with instructions, but it's a pretty simple operation.

The most important thing while bleeding is to watch the master cylinder reservoir level - don't let it run dry or suck air while bleeding or you'll need to start over.. Top up the reservoir when you're done and enjoy.
Brake Bleeder and Vacuum Pump Kit

[philminotti]

Tim-

Like the brake system, a hydraulic clutch system doesn't fail for no reason, so just trying to bleed it seems premature until a diagnosis is made. Is the clutch fluid reservoir still full? Does your car use a slave cylinder or a hydraulic T.O. bearing? I expect that it uses a slave cylinder system, with the primary cylinder being in the pedal box. Have there been any puddles under the car? If a seal on the primary or slave cylinder has failed, or if a hydraulic line has leaked, it should be obvious. Could the linkage from the pedal to the primary cylinder have broken or become disconnected? The clutch system can't just "acquire" air for no reason unless you've been driving inverted for a prolonged period of time, such as on the roof of a tunnel.

Just my $.02.

[TimG427]

Good questions, this is a CSX4000 series with slave cylinder. The car just arrived by transport. Fortunately, the clutch worked for unloading. I did look and drive the car before acquiring it. The canister is empty, no fluid, but it’s been in my garage for only two days. I do have a suction bleeder, so I'll refill the system and bleed it.

Thank you for the advice. I was truly going for my maiden trip yesterday since the rain cleared a bit.

[jhv48]

First, crawl under the car and see if there is any fluid on the slave cylinder. If everything is dry, then fill the reservoir and bleed the system.

If the bleeder is on the top of the slave, all you need to do is open the bleeder valve and pour brake fluid into the reservoir. Gravity will bleed it for you. Just don't let the reservoir go empty while it bleeds itself.

[Clois Harlan]

I think you said this but be sure and ONLY use Dot 3. I believe many of the Dot4's are synthetic. Your seals will fail with synthetic brake fluid. Once you fill your reservior lay your bleed line down in a jar 1/2 full of fluid and open the bleeder. First allow the fluid to gravity feed out and then submirse it into the jar below the fluid line and then pump your clutch with your hand slowly. Then try and close the bleeder while it is still submerged. Get an assistant to help you by pumping the pedal and holding it down while you crack the bleeder to purge any remaining air (tap on the feed line with a screw driver to dislodge any stuck air bubbles). Takes about three time to get a good firm pedal. My appologies if this is too simple of an explanation.

[TimG427]

Not at all, thank you.

[cycleguy55]

No problem mixing 3 & 4, in a clutch system anyway.

"DOT 3, DOT 4, and DOT 5.1 brake fluids are glycol-based compounds that are compatible with one another. On the other hand, DOT 5 brake fluid is silicone-based and should never be mixed with any other type of brake fluid. DOT 3, DOT 4, and DOT 5.1 brake fluids will damage painted surfaces. DOT 3 and DOT 4 fluids have lower boiling temperatures than DOT 5 and DOT 5.1. Furthermore, DOT 3, DOT 4, and DOT 5.1 fluids are hygroscopic--they absorb moisture from the air. This causes the fluid to turn dark, indicating that it is time for the brake fluid to be replaced. DOT 5 fluid will not damage paint, has a boiling temperature in excess of 500 degrees F, and is not hygroscopic. "

Source: http://www.summitracing.com/expertad...ive/answer/414

[TimG427]

Good and bad news, I filled the reservoir and pumped the clutch pedal. The pedal pressure came back very well and I took the car for its maiden trip. What a beast. The bad news is the system is leaking quite badly from the portion that pushes the fork.
It looks like that needs to be replaced or rebuilt. It's some tight quarters up there, but it needs to be done.

[cycleguy55]

That sounds like a slave cylinder - it may be tight quarters but it's a lot easier than replacing a hydraulic throwout bearing.

[rodneym]

TimG427,
Depending on what the installer used, I'd consider an upgrade. If he used a generic Chevy, Ford, etc, and it's years old, a replacement could have questionable origins. If it's a slave like a CNC or Wilwood, you can rebuild them, and they're nice.
Call Mike Forte. He can hook you up with a beautiful bracket, slave, etc.

[TimG427]

Thank you for the lead. The car was built by Shelby/Sanderson in Plano, TX in 2004, so it's over 10 years old.

[TimG427]

It looks like the clutch cylinder is made by AFCO, I'm searching for a replacement.