Master cylinder reservoirs get really hot

[Caddy Dad]

I now have about 800 miles on my Mk IV roadster and after each drive I do a little post drive walk around and inspection before i put her to bed. I've noticed that the brake and clutch reservoirs get really hot to the touch. Almost so hot you can't keep your hand on it for long. I'm using DOT 4 fluid and I haven't noticed any braking issues. Is this normal? TIA

https://thefactoryfiveforum.com/attachment.php?attachmentid=151418&d=1627660443

[NAZ]

I'd be more concerned with the performance impact on the engine with all that heat trapped under the hood. Brakes convert kinetic energy into heat -- a lot of heat. Brake fluid is designed to operate in relatively high temps. Much hotter than you'll find under the hood. Take a look at the glowing rotors in the photo below. The brake fluid is about a 1/2" away from that rotor that is north of 900F based on the color.

151419

[Desert Cobra]

I thought the same thing, so I built a small U shaped shield below and under the two I have. My theory is that at least some of the heat under the hood is reflective or radiant heat and that the shield reduces that. Sort of a sun umbrella effect. I have never actually measured temperatures.

[JohnK]

I'm more concerned about the long-term effect that heat has on the rubber hoses, so I added some heat sleeves to them.

https://thefactoryfiveforum.com/attachment.php?attachmentid=147795&d=1620879649

[rich grsc]

I'm more concerned about the long-term effect that heat has on the rubber hoses, so I added some heat sleeves to them.

https://thefactoryfiveforum.com/attachment.php?attachmentid=147795&d=1620879649

Thats a joke? What are you doing to protect the radiator hose from the 200* heat of the coolant? Those will be twice the temp of this brake hoses, and even the fan belt get a hotter.:confused:

[JohnK]

Thats a joke? What are you doing to protect the radiator hose from the 200* heat of the coolant? Those will be twice the temp of this brake hoses, and even the fan belt get a hotter.:confused:

I'm not doing anything to protect those, because they're not sitting inches away from catalytic converters.

[NAZ]

Don't forget to wrap your brake hoses, they're attached to the calipers that help generate enough heat to make cast iron glow red.:)

[JohnK]

Don't forget to wrap your brake hoses, they're attached to the calipers that help generate enough heat to make cast iron glow red.:)

Right. Because braided stainless flex lines have the same service temperature as rubber hose. :rolleyes:

The rubber hoses that came with my Wilwood MC's are labeled "Gates Plant Master". Gates lists the service temperature of these at -40*F to +200*F. Not hard to figure out that running a rubber hose at the upper range of it's service temperature will shorten its service life. Having to replace radiator hoses every few years when they've deteriorated is probably fine. Having to get into the upper part of the footbox to replace those hoses is a bit more of a PITA. If spending a few $$ on heat sleeves means I can extend that time, I'm good with that.

[txboiler]

I have been contemplating running hards line from reservoirs to master cylinders using bulk head fittings to pass through the front side of the footbox. I like the look of the hard lines and will use hoses inside the footbox to connect to the master cylinder. I haven’t seen this on many builds.

What am I missing?

[rich grsc]

WHAT heat, those hoses will never see 100*.