More "The cockpit is too hot!!"

[Tom L.]

I am quite aware that one of the joys of owning a Big block C-3 is all that extra heat in the car. While preparing to go to Carlisle this past summer I decided that I needed to do something to try and make the trip more comfortable.

I bypased the heater core and plugged the discharge ducts under the dash with rags. It made a significant improvement so I planned to put a shutoff valve (no valve in '72) in the system and removed the plugs in the ducts. I figured things would be better.

Yesterday was a beutiful 65 degrees and sunny here in NY so naturally off we went for a ride. The thing I found was that it was hotter in the car yesterday than in august! The heater core was still bypassed but the ducts were unplugged. It was noticeable that heat was flowing from the ducts and it was not radiant heat.

What in the system would allow hot air though without a functioning heater core?

[James W.]

Re: More "The cockpit is too hot!!"

I am quite aware that one of the joys of owning a Big block C-3 is all that extra heat in the car. While preparing to go to Carlisle this past summer I decided that I needed to do something to try and make the trip more comfortable.

I bypased the heater core and plugged the discharge ducts under the dash with rags. It made a significant improvement so I planned to put a shutoff valve (no valve in '72) in the system and removed the plugs in the ducts. I figured things would be better.

Yesterday was a beutiful 65 degrees and sunny here in NY so naturally off we went for a ride. The thing I found was that it was hotter in the car yesterday than in august! The heater core was still bypassed but the ducts were unplugged. It was noticeable that heat was flowing from the ducts and it was not radiant heat.

What in the system would allow hot air though without a functioning heater core?

Based on my experience with my LS5 71, look to the transmission tunnel. Mine would blow heat up through a torn boot and any place else that it could. If you don't have the foam transmission collar that seals that area off, it's egg-cooking time. I would take towels and wrap it all around the shifter and plate area and that seemed to help a lot. Of course, you could judt fix it, but that takes all the challange out of it

Jim

[Roger O.]

Re: More "The cockpit is too hot!!"

If the hood seal is leaking the hot air from the engine can get into the wiper area and be drawn in by the fan.

[Bill C.]

Re: More "The cockpit is too hot!!"

1. Check the upper plenum door inside the wiper door bay to be sure it is closed when in AC mode.
2. This door will be open when vent is selected but closed when no position is selected on the wheel.

3. Need to look for areas that are not sealed correctly that make up the plenum area on the left and right side. If there are spaces between the fiberglass parts super heated air will find its way in from the engine compartment.

4. Be sure the WS on the hood ledge is sealing and not cracked.

5. Be sure the boot between the wiper door actuator and the mounting bracket is sealing on both side.

6. Be sure the gasket that fits in the lower outer heater core - on the bottom where the tubes extend down - is not missing. Air will fly into the evaporater core and leak in the car.

7. If you have a 4spd, look to see if the clutch rod boot is torn or missing.

8. Any carpet plugs missing can cause an isue.

9. The WS wedges that go in the lower birdcage need to be in place.

10. WS that sits over the frame rail, just aft of BDY MNT # 1 and #2 (front two) has to be inplace.

11. Be sure all gasket in the outer evaporator core box are sealing and not cracked or missing.

12. As mentioned above - shifter boot (under the leather boot) and the tranny tunnel insulation.

13. Check all gromets on the firewall, ie: speedo cable, tach cable, wire harness etc..


list still goes on from here.....

[Terry M.]

Re: More "The cockpit is too hot!!"

1. Check the upper plenum door inside the wiper door bay to be sure it is closed when in AC mode.
2. This door will be open when vent is selected but closed when no position is selected on the wheel.

3. Need to look for areas that are not sealed correctly that make up the plenum area on the left and right side. If there are spaces between the fiberglass parts super heated air will find its way in from the engine compartment.

4. Be sure the WS on the hood ledge is sealing and not cracked.

5. Be sure the boot between the wiper door actuator and the mounting bracket is sealing on both side.

6. Be sure the gasket that fits in the lower outer heater core - on the bottom where the tubes extend down - is not missing. Air will fly into the evaporater core and leak in the car.

7. If you have a 4spd, look to see if the clutch rod boot is torn or missing.

8. Any carpet plugs missing can cause an isue.

9. The WS wedges that go in the lower birdcage need to be in place.

10. WS that sits over the frame rail, just aft of BDY MNT # 1 and #2 (front two) has to be inplace.

11. Be sure all gasket in the outer evaporator core box are sealing and not cracked or missing.

12. As mentioned above - shifter boot (under the leather boot) and the tranny tunnel insulation.

13. Check all gromets on the firewall, ie: speedo cable, tach cable, wire harness etc..


list still goes on from here.....

Nice list Bill. You did a good job with it. Very thorough.

One point about the firewall grommets: I can't tell you how many "restored" Corvettes I have judged that no longer have the sealant on the grommets -- probably most of them. Not only do the grommets have to be in place (which is also a common issue), but there was a sealant poured onto them to create the final seal. Look in the AIM for the sealant note, but I think it might be the same sealant that was used in the base of the windshield wiper compartment. It looks like the same stuff.

“Restorers” commonly clean this sealant off and then don’t re-apply it. It doesn’t look very pretty, but was there for a very good reason. I would bet that even on unrestored cars it has now gotten hard enough that with body flex it has cracked and opened fissures. Nothing (except stainless steel) lasts forever.

Also the sealing foam in the heater box (You touched on that in #3) just turns to much over time. This leaves all the heater control doors leaking air.

Lyn:
You have to shut off the flow of water to the heater core. A shut-off valve on just one side of the heater core will only stop the flow of coolant. Given enough drive time the heat will conduct throughthe fluid in the other side of the heater circuit. A system that actually by-passes the heater core, and leaves it empty of coolant, would work the best. Failinfg that complex a system a shut-off on both sides of the heater core is next best.

[Bill C.]

Re: More "The cockpit is too hot!!"

Terry == thanks
been up and down that list way too many times in the last 15 years.... LOL


I do have another observation to report on ...

The cars which have factory AC have the worst ventilation system going.
Since the rear plenum (under the rear deck) is sealed up, when you roll down the side windows it seems to pull hot air in from the engine compartment even worse. My steering column will get hot as all hell after 1-2 hours of highway driving. If I roll up the window then I can actually feel the hot air subside (entering from the steering column). I don't think the "astro-ventilation" works at all!!!

Take out the rear window, side glass down or up, and no hot air comes in the car. The steering column is warm only to the touch. It pulls cool air from the rear area of the car into the drivers compartment.

I wish they would have put the doors in the back on AC cars.....

[Terry M.]

[Roger S.]

Re: More "The cockpit is too hot!!"

My 73 too does not cool well. The AC system will drop the temperature 20 - 25 degrees F from the outside air temperature, but never any lower. I checked everything I knew to check and never could get a recirculation temperature any lower. I finially used an infrared camera and found heat at over 150 F at the steering column and flange. When touching the column flange I was not able to keep my hand on it but just a few seconds. Also most of the upper firewall did not have the insulation blanket and the uninsulated areas had a surface temperature of 120F.

My winter project will be to insulate the hidden part of the firewall and the steering column and it mounting flange. May try to insulate the column in the engine compartment area also.

Roger

[Roger P.]

Re: More "The cockpit is too hot!!"

Lynn,
Although I own a '65, I agree with everything listed by James, Roger, Bill, and Terry. The issues are similar with C2's - and living in the South Florida heat, I have gone through "the list" a few times. After doing all that was possible on the list, I decided to get creative in an effort to provide a more comfortable driving experience for me and my passenger. Take a look at my recent thread titled "Poor Man's Air Conditioning" and see if my personal cooling "invention" might improve your driving experience, too.
https://www.forums.ncrs.org/showthre...73699&uid=9813

Good luck,
Roger (50141)

[Roger O.]

Re: More "The cockpit is too hot!!"

For those of you that want the benefits of shutting off the flow of hot coolant through the heater core but don't want to alter the cars originality these hose pinch clamps might be for you. Put it on before driving and remove it when the hood comes up.

Here is another picture of a slightly larger set that has been painted to match engine color.

[Warren F.]

Re: More "The cockpit is too hot!!"

I've had a few '70 to '72 big block 'vettes equipped with the C60 option, never again way too hot in the cockpit. I only buy non A/C optioned cars, the center console fresh air levers venting system is a god-send. On a warm day just open the vents, makes a huge difference. In conjunction with rear window removal or side windows down or roof tops removed you have a variety scenarios to keep comfortable while driving.

[Tom L.]

Re: More "The cockpit is too hot!!"

Thanks to all for posting. Many of your suggestions either have been explored or need checking when I am able to get some time in the garage, work really gets in the way of the things we like to do!
However, I do have a few questions for some of your well thought out suggestions, so here goes... (BTW, it is an A/C car)

Bill, very thorough, thanks.

For #1, after my trip I did repair the plenum door under the wiper door it was stuck open because the vacuum line came off. What I did notice was that it doesn't seal very well, is there a gasket for it? I didn't see one in any of the vendors cataloges.

#3, You mention the plenum area, which Terry referred to as the heater box, where are we talking about. Under the pass. side dash or under the hood around the evaporator.

#6, Since you brought it up I don't recall seeing the seal by the heater core inlets, I'll have to check. If it is missing can it be put in without removing the core itself?

#8, Are the carpet plug locations shown in the AIM? I'm not at home.

Terry, The heater core is still bypassed so that is not a problem. I am curious about the grommet sealant. Does anyone have a picture or source to see how it is supposed to be applied. Several of my grommets are loose, I know that.

Roger O., The hood seal is new (about a year old), any reason I should check for misalignment?

Roger S., Is there supposed to be a seal around the column or are you madifying it for your own prefrence?

Roger P., Your "poor man's A/C" is neat. Fortunately we don't have the unbearable heat for as long as you do, a small benifit of the north. I'll probably deal with it.

Again, thanks to all.

Tom & Lynn

[Jack H.]

Re: More "The cockpit is too hot!!"

For #1, after my trip I did repair the plenum door under the wiper door it was stuck open because the vacuum line came off. What I did notice was that it doesn't seal very well, is there a gasket for it? I didn't see one in any of the vendors cataloges.

Add-on's...

I've seen quite a few A/C cars with deteriorated foam seals around the refrigerant lines going in/out of the air box on the firewall. If the open space surrounding the refrigerant lines servicing the evaporator core isn't closed off, there's a direct path from the engine compartment into the heater-A/C plenum and you can expect underhood hot air to inflitrate ESPECIALLY when the cabin is open (soft top down, T-Tops removed, and/or side windows lowered) with the car at cruising speed as you've created a low pressure center in the cockpit...

Next, the make-up air baffles in the RH plenum (outside air vs. recirculate) operate in 'flip-flop' mode (one open the other closed). These seal via overlapping rubber sandwiched between their stamped steel door panels. FEW bother to remove the vacuum operated air baffles and restore the rubber gasket material!

If I rememember correctly, Dr. Rebuild sells overhaul kits for these baffle doors. Getting to the cabin baffle is pretty easy (behind RH kick panel), but getting to the outer cowl baffle is a (*&^ of a job!

If one or both of these baffles isn't sealing properly (typically due to rubber deterioration), then you've got outside air, ram driven, invading the cowl and testing the integrity of these baffles AS WELL AS their counterparts in the inside heater-A/C air plenum. Again, with a low pressure center in the cockpit, you'll be testing the sealing integrity of the entire system and few bother to overhaul each/every baffle seal on their car...

[Joe L.]

Re: More "The cockpit is too hot!!"

All------


I realize that none of the cars here are likely equipped with headers. However, this is one of the MAJOR reasons that I ALWAYS advise against the installation of headers for a street-driven Corvette. This applies to BOTH small blocks and big blocks, but it's ULTRA-important for the latter. If you think that cockpit heat problems are tough with cast-iron manifolds, wait until you see what it's like with headers. Forget them. No matter what they do for performance. Period.

[Tom L.]

Re: More "The cockpit is too hot!!"

Jack, It is sounding ore to me that my problem is primarily a seal issue. I have not gotten into repairing all the seals on the various dampers and pipe inlets but it seems that this is in my near future. Your description of leaking air as "ram driven" makes the seal issue make sense.

You also mention that the make-up baffles are stamped steel. When repairing the outer plenum door under the cowel, and you are right, it is a "(*&^ of a job!", I saw that the door was made of plastic and showed no evidence of a seal or adhesive residue. Is that door supposed to be stamped steel and have a seal?