1990 Lebaron brake distribution block spays fluid

That's the combination valve. It's an extremely low-failure item so a used one from the salvage yard should work fine. The part you have shown appears to be the metering valve. That prevents any pressure from going to the front calipers until about 10 pounds of pressure goes to the rear drum brakes first to push the shoes out to the drums. That way all four brakes start to apply stopping forces at the same time. Without that valve, the front brakes would do all the stopping under light pedal pressure and the rears wouldn't do anything.

Be sure to get a valve from a similar car. The proportioning valve that's built in limits the maximum fluid pressure to the rear brakes to reduce easy wheel lockup. It's calibrated for the weight distribution of the specific vehicle.

Any salvage yard. This is not a high-demand part so no dealer or parts store is going to offer it. The dealer can special order it for newer cars but not likely for one that's 20 years old.

If you live anywhere between Indianapolis to southern Georgia / Alabama, there is a real nice chain of yards called "Pull-A-Part". You can do an internet search for them. The yards are all real clean and well-organized. The people are friendly, parts are REAL inexpensive, and they bring in two new rows of cars at each yard every few days. You pay your buck, throw your tool box in one of their wheel barrows, and you can spend all day there. You can do a search too to see which yards have cars like yours. The searches won't show up paint color, options, or which parts have been removed already. I did a real quick search and found one in Indianapolis and one in Atlanta. Those are the only two cities I checked. There are other similar yards all over the country. I visited one in St. Louis a few years ago but he was rather proud of his parts. He wanted $250.00 for a dented lift gate for my '88 Grand Caravan. I got the lift gate and a sliding door from Pull-A-Part for around 90 bucks for the pair, tax included. Pull-A-Part also has people running around with vans or motorized carts to help you haul out larger items.

I should mention too to be careful when unscrewing the steel lines from that valve. If the soft brass nuts don't spin freely on the metal lines, those lines will twist off causing you more work. Use a flare nut wrench to prevent rounding off the nuts. When you remove the valve from the junk car, consider unbolting the two lines right at the master cylinder. In fact, you can even unbolt and remove the entire master cylinder a lot easier.

Being from Wisconsin, the road salt capital of the world, everything gets corroded tight. I removed a rear spindle and brake assembly for my Caravan from a van in Tennessee, and the line came loose with a simple twist of a tiny wrench. I'm not used to that. Don't use any type of penetrating oil or any other petroleum product near brake fluid or brake parts. The slightest hint will destroy ALL rubber parts in the system that come in contact with brake fluid.

Be aware too that you might have a damaged master cylinder. When it sprung a leak or when you bled the system, if the brake pedal went more than half way to the floor, the lip seals could have gotten torn on the crud and corrosion that builds up in the lower halves of the two bores where the pistons don't normally travel. When you bleed the system, never push the pedal more than half way down to the floor.

You can also avoid having to bleed at the wheels. Keep the replacement master cylinder full of fluid and sealed until all of the lines are connected. Loosen the lines going to the wheels just a little, then have a helper push the brake pedal very slowly half way to the floor. It should take about 10 - 15 seconds to do that. You'll see air bubbles coming out at the loose nut. Tighten the nut, THEN tell your helper to let the pedal come back up quickly. Do the same for the second line. You might want to do each one two or three times until you don't see any more bubbles. When the pedal is pushed slowly, the air comes out by the loose nuts. When it's released quickly, the fluid coming back to the master cylinder washes any remaining air bubbles back into the reservoir. You might have a slightly mushy pedal for a few days, but eventually those bubbles will work their way back up to the reservoir.