oldsguybry

Ok , my heater blows cold air , I replaced thermostat ... that wasn't the problem . If I flip the selector from cold to hot a few times I get heat for 10 seconds then it goes cold again.... it worked fine before I put different engine in , so do you think this could be the heater core or the heater switch? You have to access heater core under dash right ?

m371961

Did you use the restricted fitting where the heater hose enters the manifold at the rear?

rocketraider

Is it an A/C car or heater only? My guess is a vacuum leak. Since engine has been out, make sure the vacuum storage ball underhood is there and connected. One side to manifold vacuum, the other goes to the HVAC control head.

Could also be the vacuum operated hot water valve at back of engine if it's an A/C car. It should stay open unless selector is in MAX A/C. That's only time it's designed to shut off water to heater core.

oldsguybry

Where or what is this HVAC control head you speak of ? The water valve is new , I put it on when I installed engine because the other one came apart where it's fitted together ... I can take some pictures of what I think you're referring too . Thanks

oldsguybry

I wish I could remember if I used heater at all after putting different engine in car . I took the entire heating / AC unit out from under the hood soon after installing engine because of limited space when I was dealing with the rear spark plug and wire among other things , so I probably never tried using it ... It's kind of strange how I can get hot air to blow for a little bit if I flip from warm to cool a few times on the heater itself inside the car .

Gary M

Gary M

rocketraider

Control head is the control on the dash.

Did you get the correct hot water valve? Some GM Divisions water valves worked backwards from Olds and had to have vacuum to open.

oldsguybry

I'm hoping I did . I usually order parts under 68 Toro 455 when it's motor related and 72 CS 350 when it's anything else ... I'm checking all the vacuum lines first , then I'm going to order a new water valve if that don't solve it . It seems I can put the climate slider over on cold for about a minute , and when I put it all the way over on hot the heat blows real nice and hot for about 10 seconds , then slowly goes back to cold .... it seems to me that something is clogged or the valve ain't staying open .

I will then inspect the control head as a last resort .

RetroRanger

I think the early valves worked one way while the later valves worked opposite as raider said. So by getting an early valve it may not work right w your 72 controls.

If that is case I would order the 72 455 valve, you may need an adapter to fit in the manifold as I * think* they are different sizes

oldsguybry

Thanks for that ... that could very well be the issue .

RetroRanger

Should be able to test it w vac see if it heats, w no vac see if it heats

oldsguybry

Thanks everyone for the input on this , it turns out that it was the heater valve . I took the old one off the 350 , put a adaptor on it , hooked all the hoses up and it works now .

rocketraider

Just in time for summer! It hit 74 here today in Southside Vajenya!

oldsguybry

Yeah that's what I was thinking . I'm hoping for cold weather here now so I can enjoy my heater ...