Littlebeefy Posted September 14, 2021 Share Posted September 14, 2021 I tore out the whole original vacuum system with the exception of the hose that runs through the firewall and connects the dump valve on the pedals to the speed control. Now I'm trying to plan on putting back in a new system for only the two vacuum related items I have left: the HVAC and the cruise control. I have an 84 Bronco and my heater has the check valve tee installed between the HVAC, the reservoir and the vacuum manifold. My understanding is that the check valve is isolating the reservoir and HVAC from higher pressures when the engine vacuum isn't available. Is that right? Also, it looks like the way my system was set up before I pulled it out, the speed control servo was connected directly to the vacuum manifold and does not have an external check valve or reservoir. Is that correct? If so, how does the cruise function without those, or are they internal to the system? When I put in the new system I would like to put in a reservoir with a built in check valve to the vacuum manifold. I know I would need to connect the reservoir for the HVAC. Would I also need the reservoir for the cruise system or would it operate directly from the vacuum manifold? If it does require a reservoir, would I need to add check valves to isolate the HVAC from the cruise? Thanks! Link to comment Share on other sites More sharing options...
FuzzFace2 Posted September 14, 2021 Share Posted September 14, 2021 I know the HVAC needs a check valve on its system. As for the speed control I am not sure as I have not looked into that system but here is my thinking. It cant be tied into the HVAC system because when it dumps when you hit the brake or clutch it would dump the whole system is the way I see it. Dave ---- Link to comment Share on other sites More sharing options...
ratdude747 Posted September 15, 2021 Share Posted September 15, 2021 I know the HVAC needs a check valve on its system. As for the speed control I am not sure as I have not looked into that system but here is my thinking. It cant be tied into the HVAC system because when it dumps when you hit the brake or clutch it would dump the whole system is the way I see it. Dave ---- ^The cruise can be with the HVAC as long as you tie it in before the check valve. It uses a larger line size though as it needs more flow/volume. One option would be to run a line to cruise, and tee the check valve feeding the HVAC and vacuum reservoir from that line. My cruise is straight to the manifold... I think the idea was that if you're mashing the throttle enough to drop vacuum to the point of the solenoid letting go, you're beyond what the cruise was meant to control (a built in safety I guess?). Link to comment Share on other sites More sharing options...
Littlebeefy Posted September 15, 2021 Author Share Posted September 15, 2021 ^The cruise can be with the HVAC as long as you tie it in before the check valve. It uses a larger line size though as it needs more flow/volume. One option would be to run a line to cruise, and tee the check valve feeding the HVAC and vacuum reservoir from that line. My cruise is straight to the manifold... I think the idea was that if you're mashing the throttle enough to drop vacuum to the point of the solenoid letting go, you're beyond what the cruise was meant to control (a built in safety I guess?). Good stuff, guys. This is what I was hoping for. It sounds like the HVAC needs a check valve to keep its vacuum isolated from the dump valve on the cruise, just like it's set up now. If I follow your plan, which is excalty what I wanted to do in the first place, the cruise is not isolated from the HVAC because of the one way nature of the check valve. If I do it that way, an increase in pressure from the HVAC side would impact the availability to vacuum for the cruise. I know the HVAC doesn't have a dump valve like the cruise, but will its operation affect the cruise servo? Can the HVAC even affect the vacuum at all? Gary's notes on Vacuum Reservoirs said that the cruise and HVAC have separate reservoirs, but I couldn't find a second reservoir in the engine bay when I took everything out. Does that mean it was removed by the PO? Or is it possible that it never had one? Link to comment Share on other sites More sharing options...
FuzzFace2 Posted September 16, 2021 Share Posted September 16, 2021 Good stuff, guys. This is what I was hoping for. It sounds like the HVAC needs a check valve to keep its vacuum isolated from the dump valve on the cruise, just like it's set up now. If I follow your plan, which is excalty what I wanted to do in the first place, the cruise is not isolated from the HVAC because of the one way nature of the check valve. If I do it that way, an increase in pressure from the HVAC side would impact the availability to vacuum for the cruise. I know the HVAC doesn't have a dump valve like the cruise, but will its operation affect the cruise servo? Can the HVAC even affect the vacuum at all? Gary's notes on Vacuum Reservoirs said that the cruise and HVAC have separate reservoirs, but I couldn't find a second reservoir in the engine bay when I took everything out. Does that mean it was removed by the PO? Or is it possible that it never had one? I dont ever remember seeing one on a speed control I wonder if the bellows with the chain is what they and calling a reservoir? Dave ---- Link to comment Share on other sites More sharing options...
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