Why do they even have bypass valves? I didn't have one and I ran both the hoses from the pass side directly to the heater core.

I don't remember having the vacuum problem. I have heat at idle. I did take the vacuum canister off though so the car has to be running in order to change the hvac controls. I did have to play around with the hoses a bit.

Check for a faulty thermo as said earlier. It will cool off quick driving and never make decent heat.

 

i think the t-stat is ok cuz i have already changed it. i didnt know that i needed to use both of the outlets on the passenger side of the water pump. i am going to try running the lines to the heater core without the bypass valve.

so then the question is, why does the thirdgen even have the bypass valve?

 

to keep extra heat from inside the car and to bypass the coolant if the heater core leaks, but that doesn't seem to work since my friends 90 Camaro has the bypass valve and he still had coolant leaking into his car.

 

yeah the bypass valve, just likes to break alot, When I bypassed my throttle body coolant passage, the inlet side of the valve, just snapped off, coolant shot everywhere. And what was funny, was it was just before I was going out to a carshow, I guess it was good timing, but it is nice if your heater core breaks, my friend has a 91 z, and he wasn't as lucky, he had coolant everywhere when his heater core failed, sucked to be him.

 

That is exactly how my bypass valve broke, while I was doing the TB bypass. I guess they get really brittle from teh heat and age.