So I have a 95 EG hatch DX. Yesterday I was working on it, changed the thermostat, and then replaced the left rear brake line because it was leaking (I have discs). Anyway after the thermostat was changed, I started the car and everything was fine. Then I went to do the brake line and bleed the breaks, started the car, and the brake pedal didnt have any pressure, and my idle kept jumping up and down between 1 and 2k, but was fine when I started it after the thermostat install. Also, when the engine is off and I bleed the brakes I can get a solid pedal feel but after its started, I barely have any pressure, I can still stop the car but the brake travel is really long, yet when I turn off the motor it pumps up just fine. I don't know if the two problems are related, while they wouldn't seem to be, they both appeared after I changed the brake line. Any help anyone can provide would be helpful.

 

The idle problem could be air pockets in the coolant. If your brake fluid got too low from the leak your master cylinder might have gone bad if the seals over travelled

 

I bled the coolant again, and it fixed the idle problem. Still have the brake problem though, and IDK if its relevant but at idle its below 1k, and when I press and release the brake it jumps up to 1000 and then back down.