That day has come and gone!

Just the opposite, actually. The only way to vent them is by rolling the windows down. We can always close the sunroof slider and basically have a hardtop. Remember, my 168° @ 81° OAT reading was with the slider closed all day. As evidenced by the 53° reduction with my stationary aero foil, the issue is more a matter of letting heat out than it is keeping it from getting in.

 

I followed up on that test today @ 91° OAT 3:15pm (direct sun):

Hood: 173°, Trunk: 168°, Roof: 185°

A couple interesting things there: 1) The % temperature differential between hood and roof actually went down, not up, and 2) the trunk is painted BBQ Black now, apparently resulting in less surface heat.

So much for the theory that darker colors will absorb more heat... Unless it's something specific to the high heat paint that allows it to dissipate heat? I know black paint is supposed to be able to pull heat out of engines and better cool them off, i.e., it's a two-way door for heat, but my understanding was that that would be vastly outweighed by the effect of direct sunlight. I'm thinking a lighter color version of the same paint would be even cooler relative to the hood.

I've actually given some thought to BBQ Hunter Green for the rest of the car, assuming the BBQ Black holds up well on the trunk/spoiler and b-pillar test sprays. It would accomplish having a paint job that is super easy to touch up, would be close enough to Royal Jade Pearl to look just fine without re-doing the door jambs and engine bay, and now may have the unexpected bonus of keeping the car 5+ degrees cooler.

 

As it turns out, there's no space above the headliner. Or insulation, for that matter. The headliner attaches directly to the sunroof tray, which in turn is right up against the sheet metal with what feels like foam gasket tape. You might be able to squeeze a space blanket in there, but I'm not sure it would help enough to be worth the trouble.

I was surprised to discover that the front sunroof drain hoses are only ~2" long and connect up to metal hard lines that run down the A-pillar. So, any leakage along the pillar or down near dash level must be coming from the hose-metal connection and running down. I had assumed there's another hose junction halfway down, based on people's reports of where leaks occur.

 

I got my windows tinted (Llumar) yesterday and have another encouraging data point to report:

5/09/15: 167.8° @ 81° OAT - 3pm
7/30/15: 100.9° @ 83° OAT - noon, 35% window tint
7/30/15: 137.4° @ 99° OAT - 3pm

All of the readings were with the roof visor closed & window sun shade up all day, in direct sunlight. I chose noon today because it's headed for a high of 105° and that wouldn't make for a very useful comparison point to 5/09. However, today's reading was with the car spending less time sitting in the sun despite a very similar temperature, so I'll check again in a couple hours.

(Edit: The weather site said 88° at noon but my computer and thermometer (in the shade) both said 82-83°, but half an hour later my computer reports the same 88°. Depending on where and when the readings were taken, my cabin temp may have only been 13° above OAT.)

I thought about doing a clear tint on the front windshield but held off on that for now. Too much hazing of the inner surface and pitting of the outer surface... But, my driveway is situated such that the back window gets clobbered all day while the front windshield only takes a glancing blow from the sun.

Today's noon reading is 14° cooler than at the same OAT two months ago (also 3pm) with the sunroof open and shielded from the sun. That gives me hope that the combination of tinted windows and my stationary aero foil can keep the cabin temps very close to that of OAT when parked at home.

Edit: Added in today's second reading. That's uncomfortably warm in the cabin now, but still 30° cooler than the literally lethal 5/09 reading in significantly cooler weather.

 

I just picked up an SC400 with manual swap and I too have noticed that the cabin gets extremely hot, particularly within the center glove console, and around the shifter including all the plastic above the transmission tunnel.

I'm considering putting in some of that thermal guard as linked in this thread a few posts back, but wasn't sure if I should get the double sided thermal, or if the single side would do just fine. I'd be installing it inside the cabin under the plastic console pieces.

Also, the cat heat shield would be considered too, but I haven't got under the car yet to see if it came with one already.

 

That seems to be an extremely common sentiment. Do factory manuals come with extra insulation? It seems like everyone with a manual swap complains of transmission tunnel heat, but I don't recall hearing of any such issues with stock trannys. (Or engine swaps, but that usually goes hand in hand with a tranny swap.)

 

My black on tan SC300 gets insanely hot in the sun. I have a mix of 5% and 2.5% ceramic tint all the way around, along with 30% on the whole front windshield and it still gets really hot. I sometimes bring a sun shade and it helps a bit too.

My black on black LS430 doesn't get anywhere near this hot nor does my other black cars.

 

Kira the problem is the SC is just a way hotter looking car!! DUH!

 

I didn't even know they make 2.5% tint. With that dark of tint, plus the windshield at 30%, you would think it would be staying pretty cool unless the glass isn't the only significant source of heat buildup. Mine is much, much better now with 35% tint on the sides and back, but even so, that makes it comparable to an un-tinted regular sedan.

 

Anyone considering clear tint on your windshield please be advised of the risk of cracking your windshield. I had clear tint installed on my OEM windshield. It did help in reducing heat buildup but the price that I paid was having to buy a new windshield when I got a very small rock chip. The glass cracked the very same day while the car was parked. The tint changes the way that the glass dissipates heat and makes it prone to cracking ( as explained to me by windshield repair tech). He said further that even if the glass hadn't cracked he could not have repaired the chip in the glass because the resin that is used requires heating from the inside of the glass.

Just something to think about before tinting your windshield.

 

Thanks for pointing that out, I hadn't considered that aspect. I held off on doing the windshield because I've got enough rock pitting that it may need replacing before long, and the clear tint costs nearly as much as new glass. Now you've got me glad I passed!

 

t2d2, I haven't done any measurements but I also noticed a very significant drop in my average cabin temperatures after getting Llumar CTX 35% put on all side glass and Llumar Air Blue on my windshield. In my case my windshield is not original (due to a crack a couple of years ago I had a new PPG windshield installed) but I am going to assume that what lev00221 mentioned is the case no matter the age or spec of your glass. My rear windscreen I held off on at the time but I intend to get that done soon.

For what it's worth, I am very happy with the AirBlue on the front. No issues. To me it's a night and day difference before and after with the Llumar.

As for the transmission tunnel heat, I do think that's a real thing but with factory manual cars there is a lot of rubber gasket shielding between the opening of the transmission shift mechanism and the underside of the center console. At least on the early 5-speeds. When a manual swaps is done while leaving that area exposed it probably does allow in some additional heat to the cabin beyond what is normal.

And I also use sunshades in the front on hot days. Sometimes also in the rear.

 

Kahn, that's the same setup (Llumar 35%) I went with. I would definitely recommend getting the back window done. It's at such a steep slope, it seems to be the most significant entry point of direct sunlight (based on visual observation). That or some old school louvers. I know how you like your muscle cars.

Good to have the confirmation about factory vs swapped manual's insulation and their respective tranny tunnel heat. We can leave swaps out of the equation now. We know the glass lets in a huge amount of sunlight, but we haven't quite pinpointed if there's something else about the cabin shape or metalwork that produces a significant amount of heat build-up, or if it's a lack of ventilation. I assume the vents under the front seats are the return air for the HVAC? (I keep forgetting to run a simple direction-of-air test on them with the car running.) I've never had reason to search for its location in any other car... Is that a typical spot for return air? Obviously, it's doing very little to allow heat to escape being down that low when parked, even if air could somehow circulate with the HVAC off.

 

Some classic and retro styled cars look great with louvers. The SC isn't one of them

Now a Lamborghini Espada or 69-70 or 71-73 Mustang...

The trans tunnel heat I think is just a characteristic of the car's design but taking out whatever factory seals and dust boots keep the shifting mechanisms isolated from the cabin has to make the quirk more apparent. On cool nights on the highway though I don't really notice any excess heat in my car (factory shifter dust seals/boots retained). It might possibly be heat soaking in stop and go traffic that makes people notice this? Hard to say.

Yes, I think it is the windows of the car that are the most likely culprit and a fairly sealed cabin. Also, how many of us have black cars and how many have cars with lighter colors?

100% agree about the rear windscreen-- it's time to get that done soon.

I have wondered what those under-seat vents are for...

 

Did this today hopefully it helps with the heat from the transmission tunnel

before


after