Rep Power: 0

I bled my brakes a few days ago now. The next day drove it and the brakes were fine, except once the pedal became very hard to press down. The next morning (about 31°F out) I went to drive the car and no matter how hard i pressed, i barely had any braking power. I didn't touch the car all day. This morning (41°F out) I just preformed these checks http://www.norcalcrx.org/tyson/pics/braketest.jpg and everything was fine. Any reasoning to the hard brake pedal? I thought I would have a faulty booster or check valve, but that didn't seem to be. What other checks can I do?

 
Rep Power: 0

Here is some more info. So the brake pedal was rock hard again this morning, I took off the brake booster vacuum hose, started the car (heat was on 2) and there was no suction at all. Shut the heat off and the valve had a suction. From the link I posted above, this tells me that the check valve is no good. The check valve is inside the vacuum hose for 98 Civic DX, so just replace the whole hose i'd take it. Now the strange thing is that I have noticed that the brake pedal only seems to get hard when the heat is on. Is the just a coincidence or do they have some kind of relationship to one another?

 
Rep Power: 517

Vacuum check valve froze.
I'd replace the vacuum hose assembly for the booster.

IDK what your heater has to do with this, it is not connected to brakes nor booster vacuum hose in any way.

 
Rep Power: 0

replaced the vacuum hose with the check valve in it, problem seems to be solved. thanks