After my engine rebuild I have no heat ? What is the vacuum line going through the firewall for ? And should it go to manifold or ported vacuum ? Thanks a lot for any suggestions

 

The main vacuum line comes off manifold vacuum, from there the line goes to the vacuum reservoir attached to the firewall out under the drivers side fender, then the line from the reservoir goes thru a grommet in the firewall behind the master cylinder to the vacuum switch under the dash, then the line to the heater valve comes back thru the same grommet in the firewall and goes to the valve ... found this on another camaro forum, so not 100% on where everything is located, but it should all be about the same

 

Do you have an air bubble? The heater is up high and might not be filled with water. Are the heater hoses both too hot to hold?

 

the 2 parts listed in post #2
http://www.ebay.com/itm/87-92-V6-V8-Camaro-Firebird-Heater-Control-Valve-NEW-/380685436327?pt=Motors_Car_Truck_Parts_Accessories&hash=item58a29ec5a7
http://www.ebay.com/itm/87-92-Camaro-Firebird-Heater-Control-Vacuum-Tank-NEW-GM-/291035131999?pt=Motors_Car_Truck_Parts_Accessories&hash=item43c30bb05f

 

The vacuum lineto the firewall goes to your hvac controls and allows you to select which vents you want airflow from. Without it air will only blow through the defroster vent.

 

that is only true if it is the line that is going to the hvac, not coming from it, right ... not 100% on the setup of the hvac anymore, been a while sense i have one opened ... is there not one that runs to the control valve from under the dash as well?

 

That was my experience. Dont plug it in and air blows through the defrost vents. plug it to manifold vacuum and air goes where you set it to go assuming no problems with your switch. I also dont really understand why there would be a line coming from it, as in a vacuum return line, but if that was the case it would be a massive vacuum leak and you could tell.

 

it is not a return vacuum line (not that i have ever heard of such a thing) i was referring to, but what tells the Heater Control Valve (the one with the hoses going from it to the heater core) when to open if one does not come back out from the dash?

 

I think I found my problem ...
I have vacuum to the controls in the car because my vents floor defrost etc. work but I have NO vacuum to the HCV in engine bay ? What could this be ?

 

lose or broken line, lines hooked to the wrong spot, bad check valve (if there is one , i am not sure), and i know this is going to sound silly, but did you have it turned to "hot" when you checked for vacuum at the HCV? (i know i have overlooked things that simple before)

 

Yes it was on hot and I have no vacuum leak anywhere .. So where does the vacuum line come from that goes to the HCV ? And another thing is the vacuum resevoir that was under the fender is now gone ... I removed it a long time ago .. Oops !

 

not real sure, but it should be coming from under the dash, from the heater controls

 

No Problem,..... That's a Cruise control vacuum reserve tank.

No heat is the result of no hot coolant in the heater core. If there was hot coolant in it, it would blow hot air no matter where it was blowing from.

On 87? and later cars Chevy installed the "Heater Control Valve" on A/C cars. Those cars had 2 HVAC lines that ran through the firewall connector. ( 1 for "mode" = 90 Degree fitting, & the other for the heater control valve = straight fitting. ) Many people do not reinstall the control valve after a rebuild, but some do. If you re-installed it than be sure that the hoses are right.




There could also be a blockage, could be air in the system, could be a Thermostat stuck OPEN, could be a working 160 T-stat installed, could be no T-stat installed, could be a fan that runs constantly, miss-placed cooling hoses, & how the system was re-assembled after the engine was rebuild could also be responsible.

 

I figured out y the best isn't working ! The factory intake manifold had a coolant crossover it the rear by the dizzy which the new one does not have so I just removed the plug in the top of the water pump and put a nipple in .. so both sides of my heater core are seeing positive pressure .. duh face palm .. so where can I hook up that hose ? The one that went to to back of the stock intake manifold .. thanks !

Sent from my XT907 using IB AutoGroup

 

I'm having the same issues with my heat. I just flushed the heater core out and I was getting terrific heat! I thought I solved the problem until after having the car idle for 5-10 minutes and all of a sudden it started blowing very cool air???? I'm baffled. My car stays around 190 degrees all the time. Is that an ok temp where I still should be getting good heat?

 

Anyone have any further insight? I just want some heat.