Clutch Hydraulic Problems

[jhv48]

So, just how long does it take to boil the hydraulic fluid?

Just sitting and idling with no air circulating in the engine compartment is more than enough time to boil the fluid. The headers can reach temps much greater than the boiling point of most brake fluids if not shielded from radiating their heat directly onto a metal hydraulic line. Shoot a laser temp gauge directly onto the line after the car has been idling for ten minutes and see what the exterior temp reads. You may be surprised.

And, once the fluid is boiling, your clutch becomes useless until the fan comes on and blows some air on the lines to reduce the temp or you take the car for a drive and the air circulating around the engine brings the temp down.

That's why so many of these cars have troubles when stuck in traffic but operate fine once on the hiway.

Don't rule out the m/c just yet either.

[bobinyelm]

Originally Posted by jhv48

So, just how long does it take to boil the hydraulic fluid?

Just sitting and idling with no air circulating in the engine compartment is more than enough time to boil the fluid. The headers can reach temps much greater than the boiling point of most brake fluids if not shielded from radiating their heat directly onto a metal hydraulic line. Shoot a laser temp gauge directly onto the line after the car has been idling for ten minutes and see what the exterior temp reads. You may be surprised.

I am sure you're right, and maybe having the hood open was not a better way to try to encourage airflow. Maybe hood down with the radiator fan on would have been better.

I repeated the experiment tonight (engine idling, hood open) and tonight no problem-clutch as smooth as butter.

I did notice that even with the two BDR shields in place, the vacuum brake booster and the short brake line runs from the brake master through the inner fender were too hot to touch in 5 minutes flat.

The shields were burning hot, and despite being silver (low emissivity), were radiating an amazing amount of heat up at the hydraulic cylinders. I may try to find some of the thin wool insulation with silver foil on on side (often sold for firewalls, transmission tunnels, or undersides of hoods) to mount foil-up on top of the shields to cut down on the radiation.

The idea of putting some kind of fan in there blowing cool air in (or hot air out of the side grill) makes more sense than ever to me as well.

And, once the fluid is boiling, your clutch becomes useless until the fan comes on and blows some air on the lines to reduce the temp or you take the car for a drive and the air circulating around the engine brings the temp down.

That's why so many of these cars have troubles when stuck in traffic but operate fine once on the hiway.

I didn't know that was a problem until these postings, actually.

Don't rule out the m/c just yet either.

Yep. Nothing's off the table. Strange that whatever happened last time didn't happen tonight, though the outside air temp was 15 degrees cooler than the last time.

Bob

[jhv48]

I had to fabricate metal heat shields with reflective heat tape on one side to shield my hydraulic lines from the heat of the headers. Actually wrapped the last foot to the slave in a high temp sleeve.

You might have to do the same. A few pieces of sheet metal from Home Depot and a Dremmel with a cutting wheel can make great heat shields when covered with reflective heat tape on one side to reflect the radiant heat away from the hydraulics.

You might have to replace the m/c just because the heat has partially destroyed the rubber seals. Don't replace the master till you reduce the heat first, or you'll kill the new one too.

[Blittleton]

I have seen alot of masters cylinders go bad, with very little miles on it. It isn't the heat problem anymore. Maybe just the Master cylinder could be faulty. I definitely seen some faulty slave cylinders. Backdraft has added the shield and routed their lines away from the headers. They have made adjustments to make these more reliable. I have tried several different models of slaves cylinders and have problems with all of them except the ones I'm ready to put out in my store. It has been the most reliable and has a slightly longer throw.

I can understand your concern that the master didn't last very long, but you will find a bad one every now and then. Just this week I sent a car to MN and the car drove perfect and never had any issues until they backed it off the truck and the starter shorted and lost all power to the car. So you never know if something will just give up or the gremlins are out there. If you need any help with your setup let me know. Maybe I can get you a slave setup that will work better for you.

Bill