Cockpit Heat
Thread Starter
Racer
Joined: Jun 2009
Posts: 365
Likes: 37
From: Soddy Daisy Tn.
Cockpit Heat
I took my new to me 70 Convertible out for our maiden voyage yesterday and it nearly cooked mine and the wife's legs! The faster I drove the more heat was felt around our legs and right up into our faces. Any ideas on what to check? The air cond. and vents along with the blower fan were all off during the drive. the car is a 350 auto if that matters.
Instructor
Joined: Oct 2010
Posts: 112
Likes: 0
Sounds like you have heat flowing through the heater core, Its normal. The vacuum shut off leaves a lot to be desired. Had the same issue on my 77, I replaced it with a manual shut off and it makes a world of difference. Used a 3/4inch ball valve and replaced the vacuum switch. I tried to put a new switch in and it still didn't help. The only thing you have to remember is to open the valve to allow antifreeze to flow to the heater core once in a while.
Hope this helps.
Ron
Hope this helps.
Ron
Advanced
Joined: May 2011
Posts: 61
Likes: 4
From: Paragould Arkansas
Had the same issue with my 80 model. Found that the vacuum line from the actuator that shut the water off from the heater core had a crack in it. Replaced the vacuum line and everything worked better. I leave the air conditioner or vent on all the time to keep any air from coming in the floor vents.
I also wrapped my exhaust pipes under the cockpit which cut down some additional heat.
I also wrapped my exhaust pipes under the cockpit which cut down some additional heat.
Last edited by Triple M; Aug 28, 2011 at 01:22 PM.
Racer
Joined: Jul 2011
Posts: 292
Likes: 4
From: LI NY
Same problem here with my 82. I have no vacum at the shut off valve and its stuck open. I feel it more with the tops off I believe due to aerodynamic suction pulling the heat out of the vents. Seems like the problem is in the consol since the vacum line is fine untill it goes through the fire wall.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
Cherolet put some insulation in the tunnel over the transmission at the factory, and a sort of a horse collar affair is supposed to fit over the bellhousing. Look at Zip Products ZM-317 and ZM-2548. Check those as well as the heater core shutoff valve.
In '76, I believe, Chevrolet changed the floorpans over to steel to address that problem directly.
In '76, I believe, Chevrolet changed the floorpans over to steel to address that problem directly.
Cruising
Joined: Aug 2011
Posts: 14
Likes: 0
From: Austin TX
Sounds like you have heat flowing through the heater core, Its normal. The vacuum shut off leaves a lot to be desired. Had the same issue on my 77, I replaced it with a manual shut off and it makes a world of difference. Used a 3/4inch ball valve and replaced the vacuum switch. I tried to put a new switch in and it still didn't help. The only thing you have to remember is to open the valve to allow antifreeze to flow to the heater core once in a while.
Hope this helps.
Ron
Hope this helps.
Ron
Instructor
Joined: Oct 2010
Posts: 112
Likes: 0
I open it up to prevent rust from building up in the heater core and plugging it up. Up here in South Dakota its nice to have a heater to take the chill out of the air when we go on the "Cruise to the woods" cruise that we do in early October. Some say that the heater core will rot out but haven't experienced this. My wife said it makes a difference. I carry the handle to the ball valve with me in case we stay out late and the temp drops.
Ron
Ron
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Burning Brakes
Joined: Dec 2010
Posts: 945
Likes: 10
From: Winston Salem NC
The Chevy 350 radiates lots of heat as it runs. This is waste heat that gets absorbed by anything close to it, like firewalls, floorpans, ac boxes...legs, ankles.
Shutting off the flow of heat to the core is a first step. The fan runs all the time so you could get heat even during the summer! A second step is to insulate the cabin from the engine heat. It can come thru firewall holes and floor pan holes and also radiate thru them. As an example, my speedo cable grommet was missing so I had a 1" diameter hole just behind the drivers side exhaust manifold. Plus the aroma of old engine!
Check the tranny collar mentioned above. There is also supposed to be a blanket. Mine is gone. I have the collar. I also filled the firewall holes and put down hushmat (for noise) and reflextix (for heat) on the floor and firewall. I yanked out the old firewall insulation. It was not doing much.
That did the trick for me.
In summary:
1. shut off coolant flow to heater core
2. fill/fix holes in firewall/floorpan
3. replace/repair tranny collar and or tranny blanket
4. put down heat barrier and optional sound deadener.
bonus: get AC working to make the cabin even more comfy.
Good luck.
Shutting off the flow of heat to the core is a first step. The fan runs all the time so you could get heat even during the summer! A second step is to insulate the cabin from the engine heat. It can come thru firewall holes and floor pan holes and also radiate thru them. As an example, my speedo cable grommet was missing so I had a 1" diameter hole just behind the drivers side exhaust manifold. Plus the aroma of old engine!
Check the tranny collar mentioned above. There is also supposed to be a blanket. Mine is gone. I have the collar. I also filled the firewall holes and put down hushmat (for noise) and reflextix (for heat) on the floor and firewall. I yanked out the old firewall insulation. It was not doing much.
That did the trick for me.
In summary:
1. shut off coolant flow to heater core
2. fill/fix holes in firewall/floorpan
3. replace/repair tranny collar and or tranny blanket
4. put down heat barrier and optional sound deadener.
bonus: get AC working to make the cabin even more comfy.
Good luck.
Instructor
Joined: Jun 2010
Posts: 165
Likes: 0
From: concord ohio
this one works perfect and is very indiscreet. http://www.petazon.com/price/product...lve-34-in.html
Cruising
Joined: Aug 2011
Posts: 14
Likes: 0
From: Austin TX
Finally got around to looking into this today. The previous owner apparently disabled the ac and diconnected the heater hoses from the engine, so no water is going through the heater that I can see, unless I missed something. Still, with no hot water running through the heater, the cockpit is hot as a 2 dollar pistol in a gun fight. I was hoping for the easy fix. The good news is, after the hottest year ever on record for Texas, there's a cold front coming and the temps are supposed to drop into the mid-90's on Monday.
Melting Slicks
Joined: May 2009
Posts: 3,079
Likes: 315
2024 C3 of the Year Finalist - Unmodified
Check your firewall grommets, steering column seal, interior firewall insulation, upper and lower shifter boots (especially the lower), underbody insulation, transmission tunnel insulation, foam collar between bellhousing and tunnel.
Racer
Joined: Oct 2006
Posts: 255
Likes: 3
Not sure how much work you want to do to cure this problem but I have been thru this as well in my 74. The first year I got it my wife and I went to a show and it was over 100 degrees that day. Our feet were toasted till we got there and back. I shut the water off to the heater core but still had to much heat. So I read about a product called Lizard skin. Bought a gallon and removed my seats and carpet. Then sprayed the lizard skin onto the floorboards. While it was apart I went to home depot and purchased their insulation that has the the thin bubble wrap covered with foil. I cut and fit it to the floor boards and the heat was gone. Took a few nights but I am very satisfied. I am doing a 72 convertible now and I have done the same with the inner floor and I am also doing the underside of the caar since I have the tranny out. The bad thing is that you have to buy a special gun to spray the lizard skin. Should you decide to go this route, shoot me a pm and I can let you use my gun. Good luck
Rodney
Rodney
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
Lots of places for heat to sneak in. A/C evaporator drain tube missing if so that is a opening right next to the exhaust. Is the weather strip alone the back of the hood worn. If so heat comes out of the engine bay into the cowl then to the vent. Usually its not just one thing but several.
Cruising
Joined: Aug 2011
Posts: 14
Likes: 0
From: Austin TX
It's an aluminum flex fan with a 2" spacer replacing the fan clutch so it turns with the engine speed. Part of the problem is being an AC car (with non working ac), it only has a passenger side air vent in the kick panel. The driver's side "vent" is non functional from the factory so there's a lot of trapped hot air around the floor. The car also has headers - more heat, and it's possible the previous owner removed some insulation for some reason and didn't replace it. You can put your hand on the side of the console and it feels real hot. One thing's for sure, Chevrolet would have never produced a car that was this hot inside. Something's not right.
Racer
Joined: Jul 2011
Posts: 292
Likes: 4
From: LI NY
It seems like there are several different heat issues being discussed here. I was able to fix mine today and this may help others with the same issue. I had no vacum going to the heat shutoff valve, causing the heater core to heat up and when the tops are off your feet would get hot. There is a vacum relay behind the glove compartment that has a button that is pushed in when your temp control is on cold, sending vacum to the heat shutoff valve causing it to close. This relay was out of position and the temp control cable needed adjustment and it now works perfectly. No more hot feet! 
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
It seems like there are several different heat issues being discussed here. I was able to fix mine today and this may help others with the same issue. I had no vacum going to the heat shutoff valve, causing the heater core to heat up and when the tops are off your feet would get hot. There is a vacum relay behind the glove compartment that has a button that is pushed in when your temp control is on cold, sending vacum to the heat shutoff valve causing it to close. This relay was out of position and the temp control cable needed adjustment and it now works perfectly. No more hot feet!
Is the cable holding in the cold position (keeping the vacuum flowing to the heater valve) ?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
It's an aluminum flex fan with a 2" spacer replacing the fan clutch so it turns with the engine speed. Part of the problem is being an AC car (with non working ac), it only has a passenger side air vent in the kick panel. The driver's side "vent" is non functional from the factory so there's a lot of trapped hot air around the floor. The car also has headers - more heat, and it's possible the previous owner removed some insulation for some reason and didn't replace it. You can put your hand on the side of the console and it feels real hot. One thing's for sure, Chevrolet would have never produced a car that was this hot inside. Something's not right.