308 Footwell Temperature Measurements - Where the Heat Comes From

I purchased a infrared thermometer today for other purposes but used it first to measure interior temperatures in my 308 QV. See photo.

I drove with the top on, windows closed, heater/ac off and driver's floor carpeting removed. The car was fully warmed. Ambient air temperature was 65°F.

I have Dynamat on my floorpan but not on my front bulkhead (the wall behind the pedals). When I Dynamatted the interior, I confirmed there were minimal air leaks. The accelerator pedal opening is about the only point where there may be air entry.

My conclusion is that somehow, interior or exterior side, the front bulkhead merits insulation.
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Since you have the interior out, it would great if you could post a few photos showing where the air leaks are. It would be great to plug them. Based on what I saw in my car though, it looked to me like the problem is mostly radiant heat. Is the accelerator pedal box area open at all to the front of the car?

Great recommendation. Dynamat is not really a heat insulation; it is a sound damping material. It works great for the latter, but not so good for the former. There is enough room ahead of the pedals to put down a thick layer of insulation.

 

For sure, many words have been written, although there is not much explanation of what the fundamental problem is in the first place; mostly verbiage is about various attempts at treating the symptoms. The latter, of course, is what we're really after, eventually.

My belief is that it is virtually all radiant heat rather than air flow. There are a few others who believe that it might be unintended air leakage into the cabin. Hopefully HotShoe's photos / analysis add clarity. I can measure some more with my new IR thermometer too if it helps.

A photo of the baffle would be great too. It makes sense that this would reduce the temperature of the front side of the footwell bulkhead addressing either radiant or air flow heat.

Insulation on the bulkhead itself would be very good. Dynamat makes stuff called Dynaliner which is 1/2" thick and designed as a heat insulator.

I've never taken off the panel under the front of the car. Is there room against the front side of the bulkhead for insulation? In one of the other threads, I know someone put louvers in that lower panel and claimed significant heat reduction of the bulkhead. Interesting.

 

Anthony,

These photos are excellent. Very helpful. Thank you. (They are like those exotic National Geographic photos of some weird prehistoric relic.)

Now I see what you’re saying about places for air flow into the cabin. Wow. It is looking like a combination of carefully plugging holes and insulating is necessary. Louvers and deflectors would also help, but to a lesser degree.

The shots of the bottom panels are very informative. I want to measure now the temperature distribution across the floor board. I had measured 107°F just under the pedals, I measured 104°F down the accelerator pedal hole but "only" 87°F near the front of the driver’s seat. The 87°F measurement makes no sense seeing your floorboard photos.

Insulating the underside of the floorboard is definitely the best way to reduce heat from the coolant pipes. It’s a hard fix for most of us though, since most of us (me!) don’t want to cut off that undertray. The ½” Dynalayer is only 0.2 lbs/sq ft, so you won’t be adding a bunch of weight even if you do the entire floorboard underside which is about 20 sq ft (20 x 0.2 = 4 lbs).

I realize now that the accelerator pedal opening is an open port to the space between the two floor layers. A nice place for heat to seep upward. A gasket is warranted.

The front bulkhead is the point of main interest since I measured 115°F around the steering shaft. Do you have a photo of the front side of the front bulkhead above and below the place where the steering shaft passes through the bulkhead? Can insulation be placed there? Is this area is assessable through the removable lower panels? What does the passenger side look like?

It looks like good stuff by probably would only provide reflective protection, heat would "soak" through fairly quickly. The best insulation would be that Space Shuttle ceramic stuff with negligible weight and huge R factor. (R factor on ½” Dynaliner is only 1.7, so nothing spectacular either.)

Wowzer! That is one serious baffle. I bet you're getting a fairly good heat reduction. ...unless floorboard heat dominates. Humm.

 

Holy Cow! Your footwell is glowing white hot!!! ... oh, wait a minute, ... it's a thermal image.

Very interesting. Your floorboard look lower temperature than mine. It might be too much work to do the radiator pipes for the amount of floorboard temperature reduction you would get, although your floorboard readings of high 80°Fs are not exactly "cool".

Your front bulkhead is really hot (like mine). It is interesting that the passenger side bulkhead looks a little bit cooler. All evidence is leading toward insulating/sealing that front bulkhead as a first priority but thereafter, there is heat everywhere; surprised to see the top of the dash and the instrument cluster are glowing as brightly as they are. Also interesting is how warm the center heater pipe looks; suggesting airflow. Removal of heat source (baffle) is looking more compelling too.