Bob Onit

Hi again

Hey all
I cant seem to get any hot air out of the heater/defroster/vents ect: on my 73

I thought it was a problem with the thermostat at first because the temp gauge was barely climing above 100 degrees... So... I bought a new 195 degree thermostat and when I went to install it I found there was NO thermostat installed

Now it's running at 200 degrees but I can get no hot air.
I did find one vacuum control valve coming off the intake manifold but I think it's part of the air conditioning control.

One of the heater hoses is hot and the other is cool (dont recall which is which, it's late, the car is cooled down and im too tired to check )

Is anybody familiar with this heating system so I can have a reference point to start at?

Im also experiencing a chatter from the rear when making either a left or right turn from a complete stop... but thats another topic....

Thanks in advance!!!

djgrelli

I would think that the hot water shut off valve is stuck in the closed postion. I would check that out first before tackling the heater core. As far as your differential making noises try draining the rear end and put in some new gear oil along with a bottle of Limitied Slip Additive. Took me two changes to get mine to stop chattering.

kb2fzq

Easy enough...and unfortunate but true....if one heater hose is hot and the other is cold....the heater core is plugged....I'm sure you didn't want to hear that...sorry
UNLESS...on my car there is a vacuum controlled shutoff down by the passenger exhaust manifold..in line...if the hose is hot on the radiator side of that valve and cold on the other side...that would be the culprit...

Bob Onit

Could you please explain the location of the hot water shutoff valve?

Also, the rear on my 72 is Positraction.
Could that be what's causing the chatter?
I dont know if limited slip and posi are one in the same

Thanks for the reply!

Bob Onit

Hmm......... It sounds like the heater core is not a fun place to work on?

I will look for the shut off where you have suggested

Thanks

SIXFOOTER

The hot water valve in in one heater hose right in front of where the hoses go into the firewall. It will be clear when you look for it. Follow both hoses from the pump and manifold to the firewall. It is either a Vacuum controlled valve, a Manual Valve installed by PO, or a mechanical valve controlled by a cable.
Trace it down and let us know

Easy Mike

It's more likely to be the valve than the heater core.

djgrelli

Limitited Slip is the correct term. Your clutch plates are gummed up. Do a good cleaning and add some LS Additive and it'll clear up. Mine drove me crazy. Thought the rear was going to fall off, especially after a long run.

housegarage

I don't think '73 have heater control valves from the factory. May be a vacuum door issue. With the blower on, where is the air coming out of?

dgruenke

I think it is the heater control valve. If it was a vacuum door, you would still get hot air coming out some of the vents, just maybe not the right ones.

Also, I don't understand how it could be the heater core unless something was plugged up in it. Otherwise, it just acts as a hot device that air blows over. There is nothing else to it.

copter

Why do they have the shutoff valve in the first place?

Bob Onit

Hey!!!!
I located the problem
It was a vacuum valve located on the front of the intake manifold.
It works with the A/C... when you turn on the AC it is supposed to close the valve... it was stuck closed.
I removed the valve and just hooked up the heater hose direct and ...HEAT!

Ill have to get to a dealer and get a new valve.

As far as the chattering goes, I will try changing the rear diff fluid.
I need to know what kind of additive to get and how much I need and also how to add it... mix it with the gear oil, put it in first, last ect.


Once again .... you guys come through!

Bob Onit

You aint kidding.... it almost feels like the ring and pinion are missing a few teeth

It does get worse after Ive been driving for a while... not as bad when the vehicle is cold.

I may start a new thread on the chatter issue just to get as much input as I can.
Maybe someday Ill be able to answer someone elses questions.
I swear, this car is clean and it has a ton of new parts but its Fix one thing and all of the sudden two other things need attention

After all... It is still just a 1973 Chevy

Thanks very much

carl a

i just posted 2 posts for you on the vaccume controls for your car,,,WHERE HAVE YOU BEEN??????????

Bob Onit

I diddnt see them......... oh boy..... now im in trouble

carl a

no your not,,, go up to the search bar .click it,,when the drop box drops type heat,defrost,,,it will pull up the posts i made before on checking the vaccume system,,i cannot find the other one i did for you,,,sorry but my hands are so sore from wrenching it hurts typing and i just dont wanna type all that again!! if you get stumped on the vaccume e mail me and ill walk you thru it,,the accuators can be checked one by one by disconnecting the feed from the switch in your console and feeding them w/ vaccume from a temp line you can run from under the hood,,,,check the search i put a diagram there all color coded w/ the same color tracers as the car has,,,what the heck ill post the photo again,,,its real e z --------------------------------------------

carl a

i had a 77 and when i turned a corner it clattered from the *** end,,,i added 2 bottles of that additive drove some circles in a parking lot and the noise was gone,,clutch plates hanging up

SIXFOOTER

Copter
the valve is there to minimise the heat in the cockpit, no hot water goin thru the heater core = less heat

kb2fzq

Before you drop a load of money ob a new valve...ya might want to make sure the valve is busted...you may have a vacuum problem to that valve...OR...you may be able to lube the valve and put it back...requires a little investigation first before waving that credit card

kb2fzq

Before you drop a load of money on a new valve...ya might want to make sure the valve is busted...you may have a vacuum problem to that valve...OR...you may be able to lube the valve and put it back...requires a little investigation first before waving that credit card