83 c-10, spongy brake pedal

[knockretard]

Hey everyone, I have a problem. First let me give you the details. It's a 83 c-10, long-bed. It has a 305 and 700r4. I purchased the truck with a spongy brake pedal. I have since replaced both front calipers and brake pads. I can't find any leaks with the system. I bleed the heck out of the thing and it fill get firm for maybe 3 pumps and thing "leak down". Also the truck has front disc brakes, but no power brakes.

Maybe someone jas had this problem before?? Any suggestions would be great.Thanks in advance.

[old Rusty C10]

im thinking the master cylinder

[78 Big10 454]

I'm with old Rusty c10 on this one.

[silvereagle07]

Could be leaking internally. Remove it and check the rear seal.

[N2TRUX]

Yep, sounds like it. While you are rebuilding the system consider replacing the rubber lines at the caliper. They are prone to create a soft pedal as well. Not a leak down as is the case here.

[knockretard]

thanks guys, it def. feels more of like a "leak down" than a spongy feeling. My next thing is too replace the front caliper rubber lines and the master cylinder, probly this weekend.

[N2TRUX]

Report back with your results...

[Joe R]

Whats your fluid look like, is it still clear or is it black. I had a similar problem with mine and replaced the booster and master cylinder. That made it better but still felt strange. I pumped out the old black fluid and replacing it with fresh fluid and now it feels like a new truck.

[silvereagle07]

Joe R , replacing your brake fluid will make the truck perform better. Over time the fluid will absorb moisture and causing it to reduce it's boiling point. Moisture in a brake system can cause components seals to fail, pitting in calipers and wheel cylinders and it breaks down all rubber components (hoses). I usually change my fluid every year. Most maunfacturers recommend between 25 and 30k miles.