• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

E-Type, Series 1, 3.8L. Clutch hydraulics.

Share this page

TroyThunder

TroyThunder

Freshman Member
Country flag
Offline
Greetings fellow British motorists.

I have a conundrum. Over the course of 100 miles or less, and following a complete bleed of the clutch hydraulic system, the pedal will be going soft; it will extend all the way to the floorboard while barely affecting the clutch. Requires multiple pumps to get adequate activation of the clutch system.

At that point, bleeding the system at the slave cylinder, the fluid comes out black (until a fresh supply reaches the bleed screw from the master reservoir.)

Things I've already done: I replaced the master cylinder. I flushed the hydraulic tubing between the master cylinder and the slave cylinder. I double-checked and triple-checked that I am using the correct dot-spec fluid.

Cogitations: does the hydraulic fluid tubing run too close to the header on the engine? And would that kind of heat lead to blackening and disruption of the fluid itself? Answer seems to be "no" to both questions. Could a trace amount of air in the line cause this? Certainly air by itself can cause this soft-pedal effect, but doesn't explain the blackening of the fluid ... does it? (I am making the assumption that the blackening of the fluid coincides with the system failure; presumably a change in fluid viscosity or compressibility. When the system is freshly bled with clean fluid throughout, the system works precisely as it should. No softness. The softness develops over time, presumably as the fluid turns black.)

Does this sound familiar to anyone? Any guidance would be very welcomed.

Cheerio.
 
Hello,
Sounds like the fluid is bypassing in the system, hence the blackness of the fluid. Probably one of the cups is coming apart. Would recommend new slave and hose, bring how the master is new.
I have yet to have any issues with heat build up in a factory clutch system.
What fluid are you using?
 
Grantura_MKI said:
Hello,
Sounds like the fluid is bypassing in the system, hence the blackness of the fluid. Probably one of the cups is coming apart. Would recommend new slave and hose, bring how the master is new.
I have yet to have any issues with heat build up in a factory clutch system.
What fluid are you using?
Click to expand...
Hi Grantura -- Using Castrol React SRF. Since my initial post, I have systematically disassembled the clutch hydraulics. Fluid in the reservoir was clean as silk. Fluid pumping from the master cylinder, ditto. Fluid coming from the bottom of the flex hose, prior to the final pipe run to the slave cylinder, also nice and clean. I pulled the slave cylinder. Disassembled. The rubber hydraulic plunger-cup appears fine, but is surrounded by black-ish tarnish in the cylinder bore ... so if the hydraulic plunger is failing, it is in a very subtle way. Or is it possible that this blackish contamination is arriving in the slave cylinder simply by having greater specific gravity? And still coming from upstream? Given the sequence in which I disassembled, seems unlikely but maybe? I have a new slave cylinder coming in the mail. We shall see. Thanks for your input
 
That’s good fluid, but beware of the change out instructions.
I would suspect the hose and slave are failing. Switch both out just to be safe and knowing that the system is all new.
Good luck with it.
 
Back
Top