looking to reduce under hood temps: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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July 30, 2011 1:49 p.m. ThePhranc New Reader

1995 Mazda MX-6

It gets really hot under the hood to the point of the car running poorly after heat soak fully sets in. I know part of it is my fans dont work anymore and I have headers. Wrapping the headers isn't an option because they have weak welds thats come apart under increased heat from the wrap. I have replacement fans and an adjustable thermo switch to put in along with a flush and new coolant. While all this helps cool the engine the laws of thermal dynamics dictates that heat has to go somewhere and it seems to get trapped in a bubble under the hood. While I don't cringe at the thought of chopping a hole in my hood and adding a scoop I'd like to avoid it if possible. It would be a lot of work to determine where and how to mount it to work correctly.

So my question is what kind of tips and tricks do you folks have that might be of help to me?
July 30, 2011 2:17 p.m. stan_d Dork

Shim up back side of the hood really helped with my v8 swapped 240
July 30, 2011 2:20 p.m. Aeromoto New Reader

Back in the old days they would put some spacers/washers between the hinges and the hood, so the hood was kicked up about 1/2 inch at the rear to let the heat out. On certain cars, you can also space the bottom of the front fenders out at the door. Maybe also try an oil cooler?
July 30, 2011 2:38 p.m. M2Pilot Reader

Used to see beer cans proping up the rear of the hood on 67 big block corvettes when they were being driven around town.
July 30, 2011 3:04 p.m. ThePhranc New Reader

I'll give the propping up the rear of the hood a try and see what kind of effect I get out o fit.

Thanks fellas and/or ladies.
July 30, 2011 4:47 p.m. novaderrik Dork

propping up the hood may help at low speeds, but once the car gets moving it might actually make it worse due to the air pressure build up at the base of the windshield.

get the fans working- they built hundreds of thousands- if not millions- of cars exactly like yours and i'd bet that most of them don't have a heat soak problem. they design the cars to let the air out under the car and thru the wheelwells.
July 30, 2011 8:47 p.m. corytate Reader

more heat exchangers, as said above
the fans should definitely help a lot
July 31, 2011 7:46 a.m. Curmudgeon SuperDork

On the Abomination (rotary Spitfire), I had to add a 4" x 10" vent on either side of the flip up bonnet so hot air could get out. You might investigate whether you can add vents inside the fenders on each side so the hot air can escape.
July 31, 2011 8:20 a.m. ncjay Reader

First step is to get an electric fan working. Do what you need to do to fix the headers and wrap them or have them coated. If it's getting so hot it affects the way it runs, you're headed for lots more trouble in the future. If the fan isn't working, are you sure the engine isn't running too hot?