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Do I need a heater control valve? Can't I just let the coolant flow through the heater core, since the hot air coming into the cockpit is controlled by a vacuum operated door. Isn't it so that when the "Heat" is off, the door is closed, and no heat enters the cockpit? Why bother with a valve that shuts off coolant thru the heater core, leaving it all wet and more likely to corrode? So why not have coolant flowing thru the core all the time?
When my '86 heater control valve began leaking several years ago, on advice i found right here on this forum i eliminated it.
I put a plug in the vacuum line and have not missed it at all. I used straight hose.
why not have coolant flowing thru the core all the time?
Exactly. WHY NOT? GM figured it out (eventually) on the later C4's and eliminated the valve. The blendair door, if adjusted properly should completely seal off heated air from the incoming "vent" air. Ya don't need the valve and GM should have never complicated a simple situation by putting one in there.
Are you confident there is a complete shut-off of the air flow thru the heater core when the temp. lever is in the "Cool" position? Is the heater duct work in the pre-'88 the same as the post-'88? GM could have saved quite a few nickles by eliminating that heater shut-off valve. I found that the Four-Seasons 74800 heater shut-off valve is an excellent, and cheap alternative to the original octopus!
(The heater core will be "wet" regardless of whether coolant is flowing thru it or not.)
St. Jude '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-‘19-'20-'21-'22-'23-'24
IMHO the best thing you can do is eliminate this valve.
The cabin temperature benefits are minimal.
But the longevity of the heater core is secured by the continuous flow of water.
The biggest problem with getting "hot" vent air, is the fact that the entire heater/blower box (and 1/2 the intake plenum) is sitting inside the engine compartment....which is HOT. In fact, one huge aspect of the heater box is facing and right next to the exhaust manifold. So you blow ambient air through a box that's probably 150˚, and it's going to warm the air up...whether coolant is flowing into a radiator in an adjacent compartment of that box, or not.
In my experience, if your blend air door is adjusted to close all the way, it won't make any diff to your vent temps if water is moving through your heater core or not.
Are you confident there is a complete shut-off of the air flow thru the heater core when the temp. lever is in the "Cool" position? Is the heater duct work in the pre-'88 the same as the post-'88? GM could have saved quite a few nickles by eliminating that heater shut-off valve. I found that the Four-Seasons 74800 heater shut-off valve is an excellent, and cheap alternative to the original octopus!
(The heater core will be "wet" regardless of whether coolant is flowing thru it or not.)
Ha! Yeah, of course, but I meant when not in use, during the summer let's say, with the valve closed, the core just sits there static, damp, waiting for the blessed flow of coolant. That's a cause for corrsion, sure thing. I used to work on small gas engine equipment for Sears. People with generators mostly, but other stuff, snow blowers, another one, who never ran them periodically... moisture would develop in the float bowls, and wallah! Corrosion set in. Owners would say, "how could this thing be broken, I never use it!" Ha!
About the duct work and all that.... tested things... like others, valve not necessary. That's Good, because mine is toast!
Oh! Test: Turned on Heat. Moved lever to full hot.. Good. Moved lever to cold. Good. Moved lever to middle. Good. Turned on A/C with lever in cold position. I wanted to see if there was any effect on the cold air temp. None.
IMHO the best thing you can do is eliminate this valve.
The cabin temperature benefits are minimal.
But the longevity of the heater core is secured by the continuous flow of water.
Exactly! What I'm Sayin'! If you don't move it etc...
When my '86 heater control valve began leaking several years ago, on advice i found right here on this forum i eliminated it.
I put a plug in the vacuum line and have not missed it at all. I used straight hose.
I just re-did my entire cooling system, T-Stat, All Hoses (Cool Blue! from Continental/GoodYear), Sensors, relay, cap... everything but the water pump... oh... and the only hose I didn't replace yet, the 3/4" hose from pipe to pump. I'll get that whenever, if ever,I do the pump. Never know! Pump might last forever... When I flush the system,or whenever whatever, I'll get rid of the pipe.
08-27-2018, 07:33 PM
Do I need a heater control valve?
The biggest problem with getting "hot" vent air, is the fact that the entire heater/blower box (and 1/2 the intake plenum) is sitting inside the engine compartment....which is HOT. In fact, one huge aspect of the heater box is facing and right next to the exhaust manifold. So you blow ambient air through a box that's probably 150˚, and it's going to warm the air up...whether coolant is flowing into a radiator in an adjacent compartment of that box, or not.