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ManInBlack · 06-04-2018, 06:48 PM

Let me try to summarize what I'm dealing with as succinctly as possible, so that I may begin drawing answers from those more experienced...

86 Gulfstream Sunstream on a GMC P30 chassis, with a 454.

Drove to the end of my driveway noticed the brake pedal when down WAY further than normal, loss of braking power, and it now makes a "belt squeeley" noise when I push real hard. Brake warning light is now on.

Parked it, crawled underneath, can't find a leak or blown line anywhere.

Performed yoga to open the master cylinder. Rear fluid chamber looks normal. Front fluid chamber looks empty, but has some grainy soft gook in the bottom.

Scooped out the gook as much as possible with a paper towel, filled chamber with fluid. Pressed the brake pedal and saw air come up into the fluid chamber, for about 4 presses, then no more air coming into the chamber.

Brake pedal feels better, still made a bit of a squeeley sound when pushed real hard. Brake warning light has now turned off.

Attempted to bleed the brake lines, but the bleeder valves are rusted pretty tight and I may have rounded one off a bit. Will let the rust penetrating spray sit on that a couple more days before trying again.

So...

Why did my fluid turn into a squishy, grainy substance?

Is it possible the seal on the master cylinder went bad and exposed the front chamber to weather?

Is it that the fluid mostly evaporated off over a period of years or is it still likely I have a leak somewhere?

Thanks.

Bob_C · 06-04-2018, 07:02 PM

I'd be look'n at the rear wheel cylinders....Try using a small pair of vice grips or a 6 point socket...on the bleeders

ManInBlack · 06-04-2018, 07:05 PM

Quote:

Originally Posted by bob caldwell

I'd be look'n at the rear wheel cylinders....Try using a small pair of vice grips or a 6 point socket...on the bleeders

Do you think the rear cylinders are the problem, or are you just suggesting I check them?

Bob_C · 06-04-2018, 07:30 PM

Fluid went somewhere....can you see the backing plates?

ManInBlack · 06-04-2018, 09:48 PM

Yeah, unfortunately no evidence of fluid anywhere.

Viciousharp · 06-04-2018, 10:18 PM

May have a leak at the combination valve. It's super well hidden and is a lot of times the problem in this system. The brake light being on means you lost pressure in half the system. Brake fluid does evaporate off over time so it could just be you were low.

ManInBlack · 06-05-2018, 05:58 AM

Quote:

Originally Posted by Viciousharp

May have a leak at the combination valve. It's super well hidden and is a lot of times the problem in this system. The brake light being on means you lost pressure in half the system. Brake fluid does evaporate off over time so it could just be you were low.

Does the combination valve look like a metal block that the lines run to? I found something like that somewhere between the front wheels. Didn't seem to be leaking.

MotorPro · 06-05-2018, 07:28 AM

Brake fluid does not evaporate . Likely a leaking master cylinder.

ManInBlack · 06-05-2018, 08:05 AM

Anyone have an idea why it turned into a grainy thick goop?

raccoonman · 06-05-2018, 08:19 AM

Brake fluid is hygroscopic. It absorbs water, and when you have a leaking cylinder, brake fluid goes out, air(and therefore, water vapor) is sucked back in. Even in a line as small as brake line, air seeks the highest level just as water seeks the lowest. Eventually, all the fluid is replaced by water and that's where the "goop" comes from. Literally, it's algae and rust. You have bad wheel cylinder seals or soft brake line leaks somewhere. Rig is thirty years old; time to give it a thorough examination underneath. The Master cylinder could also be leaking internally. One piston, two chambers, one chamber could be back feeding to the other, or leaking into the power booster(if vacuum) or past the hydrovac unit.

twinboat · 06-05-2018, 08:20 AM

Someone may have added power steering fluid.

Complete rebuild and flush is only cure for that.

60sumtin · 06-05-2018, 08:37 AM

If you think the brake fluid disappeared over a period of years, not months or weeks, it sounds like it hasn't been checked for a long long time or maintained properly. Brake fluid doesn't just disappear, it leaked somewhere. Your rig is over 30 years old. I'd be doing a complete brake overhaul front to back. At a minimum new wheel cylinders, callipers if disk, master cylinder, and a complete flush. While you are at it it gives you a chance to clean, lube and inspect the drums, shoes, rotors, pads, and look for broken parts. Check the parking brake mechanism while you're at it. Brake parts are not expensive and kinda important they work properly.

ManInBlack · 06-05-2018, 09:58 AM

Any suggestions where I should look for parts? Do I just search for Chevy P30 parts?

shrekchatou · 06-05-2018, 10:34 AM

On my p30 National Dolphin i have a low brake pedal and low oil brake level in compartiment no leaking on floors... we find a tinny tinny hole on a brake hose very few drop of oil was comming out. The mecanic guy changed that part of hose fill up oil and bleed and everything is ging back on. If that can help you find your trouble !!!!