Hi everyone, longtime reader, first time poster here. What I have is kind of a technical question about how the hot water bypass valve works. To try to make a long story short, vehicle is a 1989 Firebird Formula 305TPI. I have found recently that my heater core is on its way out (misting, but not puddling... yet). Vehicle is equipped with AC but it's not operational. I have found articles around on bypassing and replacing the heater core, both of which I am considering as long term options, nut not today. What I am wondering is, since I am going to be putting this vehicle away for the winter next week... assuming that my water bypass valve itself is operational, will driving around with the selector switch in one of the AC positions keep the coolant out of my heater core? I have to assume that the dash selector is what actuates the valve as there doesn't appear to be an electrical component to it from what I can see. Any help you guys can offer me would be appreciated, I just want to get this vehicle to the end of its season so I can poke around with it better in the garage over the winter. Thank you all so much!

 

No, the water valve is not 100% internally leak proof and does not completely seal off circulation. Likewise, having the setting on A/C will not help because the valve needs vacuum to be in divert mode, and of course vacuum is only available when engine is running.


Hard bypass of heater is fairly simple in order to avoid water on the carpet.

 

Thanks for the reply. I kind of figured my brainstorm was too good to be true. I think I'll just try connecting the hose from the throttle body into the hose from the radiator with a coupler and see how that pans out for me until I can replace the core. Getting to the firewall looked like it was going to be too difficult to try on my lunch break.
Thanks again!

 

Like eseibel67 said, the engine needs to be running to pull vacuum. I can't remember if the factory diverter valve for the heater core allows you to push in the bypassing valve, but if you can push it in manually then find a way to keep it pushed in manually, then that is essentially the same idea as when the engine is running and it uses vacuum to do it. I installed a 4 way diverter valve from a Ford explorer on mine, and I can push my diverter valve in manually with my fingers but without vacuum as soon as I let go it opens back up. Whatever is sitting in the heater core when you bypass it will still leak out though, assuming it is leaking a little. So it might be a good idea to check and make sure it's not dripping on the floor of the passenger side. Might be a good idea to just pull it for now if it's just going to be sitting.

But if you want a quick solution, then I guess just connecting the heater hose from the radiator to the back of the motor would work.

 

I would not allow a leaky heater core to sit in the vehicle throughout the winter without expecting some mold and mildew issues when I broke it out in the Spring. Even with the hoses disconnected, some coolant is going to remain in the core.

As easy as it is to swap out..

Early model firebirds provide access to the top bolt for the heater core without removing the dash, a relay has to be dropped is all. I do not know for sure about an '89. A search may help, or simply remove the hush panel and have a look. Took me less than 30 minutes when I swapped the core in my 85.

 

I don't know if the firebird and camaro have the same setup for the heater core, but if they do, it's surprisingly simple to swap it out.

I have a 91 camaro and the heater core was leaking last year. I read I had to take the top of the dash out etc but I just dropped the access panel (like 4 7mm bolts.) Once that was dropped, you have access to all the bolts holding the ducting in place in front of the heater core. You do have to get semi creative to get the top bolts out because you can't see them, you have to reach around with a ratchet, but they weren't too hard for me to get.

I think I had mine swapped in under an hour, maybe 30 minutes.

 

do be advised that the correct copper /brass heater core is no longer available. and ,trust me , you DO NOT want that aluminum heater core. its best to have your original core repaired.