Why is my brake reservoir leaking

[dlisabeth]

I have a 1965 C10 with the following brake setup: 85' C10 front discs, stock rear drums, '97 S10 brake booster, '85 C10 proportioning valve, and '85 C10 master cylinder.

I am having an ongoing issue with the '85 C10 plastic brake reservoir leaking and ruining the paint on my inner fender and frame rail. I purchased a new brake reservoir, cap, and seal in hopes that it would correct the problem, unfortunately it did not. I have now cleaned up the mess and repaired the paint 3 times and am out of ideas. What could be causing the reservoir to leak? The brakes work great and there is no indication of a problem until I open the hood and see the damage that has occurred again. The only thing that I have noticed is small geysers (no air bubbles) in the reservoirs when the brake pedal is pressed with the cap off. I have done some research on this and it seems very common. Does anyone have any thoughts? I would love to solve this issue so that I can drive and enjoy my truck without constantly wondering how much brake fluid is leaking.

Thanks for the help

[tubbedII]

Do you see exactly where where it's leaking from when you run into the problem?

[dlisabeth]

Originally Posted by tubbedII

Do you see exactly where where it's leaking from when you run into the problem?

It looks like it is leaking under the reservoir cap and running down the side of the reservoir.

Could something be causing pressure to be built up in the reservoir and force fluid out?

[tubbedII]

I'm sorry, since you have replaced the all the parts that are causing the leaks I'm at a loss. Dumb questions, but are you possibly over filling the reservoir?

[starvinartis]

The push rod from the booster to the MC may be too long, (there are 2 lengths OEM) which would put too much pressure to the MC, tho its possible you just have too many different apps there too. Maybe try the matching 97 MC?

[68_chop_top]

What is the quality of your brake pedal feel? Is it really hard with so-so braking response? The reason I ask is I just replaced by small block with a big block with headers. The brake lines are very close to the headers (inside frame rails) and when the motor is warmed up, the brake lines are hot and boil and over-pressure the master cylinder and squeeze past the cover and onto my inner fenders.
I am changing out my brake lines to outside the frame rail hoping to prevent this.
Maybe this might be your problem.
Thought I would share.