The A/C could operate better w/ it open.
Any benefits to lifting hood in hot weather?
- Thread starter tripleM
- Start date
- Status
I use to do this on drives over 4 hours but in the end it made no difference. On 18 wheel heavy trucks, some OOs have the fan clutch programmed for a "manual on" setting and they trigger it 5 minutes before arriving at destination to assist in cooldown. I think its one of those things that seems like a good idea but really doesn't do anything ??? Perhaps a little Taoism (can I say that word ?)would be good here - "do by not doing".
After towing; after trying to back in a heavy load; after a long hard 70 mph run, it is a good idea to open the hood for a few minutes. Under any of these scenarios -- where I haven't driven a mile or so -- a few minutes of idling with the hood up keeps temperature spikes to a minimum. This advice goes back to the advent of motoring as there is no real airflow through the radiator (fans are an aid, not much of a replacement for travel at 25 mph), and gaskets, seals, fasteners, bearings, etc take it on the chin.
It can be one of the reasons one car has a like-new engine at 150,000 miles and another does not.
High heat, high load, no/low airflow is especially hard on auto trans and power steering.
It can be one of the reasons one car has a like-new engine at 150,000 miles and another does not.
High heat, high load, no/low airflow is especially hard on auto trans and power steering.
LOL, sorry, but I found the comment about a "hard" 70 mph run. I don't consider 70 mph driving to be very strenuous for modern vehicles.
Perhaps after a 110 mph dash from Kingman, AZ to Las Vegas on Route 93, in 100 degree heat with the A/C on full blast...then maybe I could see opening the hood. Except I didn't, I parked the car in a parking garage with the hood closed; still works fine.
Perhaps after a 110 mph dash from Kingman, AZ to Las Vegas on Route 93, in 100 degree heat with the A/C on full blast...then maybe I could see opening the hood. Except I didn't, I parked the car in a parking garage with the hood closed; still works fine.
mstrjon32 - I've been that Route 93 NUMEROUS times in the desert heat; I honestly don't call that as harsh of a route as say I-70 corridor, running 65-70mph with the A/C on at 10-12,000 feet elevations.
Kingman, AZ - Vegas, NV is flatland country with the exception of the Hoover ____ area which only extends 3-4 miles.
Kingman, AZ - Vegas, NV is flatland country with the exception of the Hoover ____ area which only extends 3-4 miles.
I've only driven I-70 all the way across once, and it was probably about 50 degrees in Colorado when I was at those high elevations. I suppose if the temperature were the same as the desert heat maybe it would have been tougher, but, IMO, the high speed/high heat/AC on gave the car more of a workout than the 70 mph/no AC I did over the rockies.
Yeah, we're averaging high 90's right now. Big difference in running a/c versus not, I'll agree for sure.
I should say from my experience, I didn't notice any of my vehicles having too much of a work out on the flatlands of the desert, even with a/c and towing a boat, as long as our cooling systems were on par, but then again, I wouldn't dare drive any of them at 110mph either.
Had a blowout one time, in a 3/4 ton chevy truck hauling a heavy camper and towing a boat, doing about 65mph on a Wyoming highway dead of summer; let's just say we were white knuckled and quaking in our shoes. All I can say, is thank goodness it was a rear tire that blew, had it been the front we would've rolled it for sure.
I won't EVER travel faster then 65-70mph for that very reason - we were very lucky. And yes, they were brand-new tires on that p/up.
I should say from my experience, I didn't notice any of my vehicles having too much of a work out on the flatlands of the desert, even with a/c and towing a boat, as long as our cooling systems were on par, but then again, I wouldn't dare drive any of them at 110mph either.
Had a blowout one time, in a 3/4 ton chevy truck hauling a heavy camper and towing a boat, doing about 65mph on a Wyoming highway dead of summer; let's just say we were white knuckled and quaking in our shoes. All I can say, is thank goodness it was a rear tire that blew, had it been the front we would've rolled it for sure.
I won't EVER travel faster then 65-70mph for that very reason - we were very lucky. And yes, they were brand-new tires on that p/up.
Tires surely need to be watched closer in hot days. Last week I saw a car that blew a rear tire at the highway. Luckily maintained a stability but rear quarter panel was in miserable shape.
Recently we saw ~105°F (38-41°C) and at sustained high speed (160kph) engine tended to run cooler (as always). Stop and go worries me more. If cooling capacity is enough it is just a matter of how often the thermostat kicks close. I can observe this if I watch the temp needle carefully, and at high speeds it still *tries* to keep engine hot.
On mountains after a climb when there is a big and speedy decline I worry to cool the engine just too fast. One can see the needle moving, .stat could be too slow for that couple minutes.
Recently we saw ~105°F (38-41°C) and at sustained high speed (160kph) engine tended to run cooler (as always). Stop and go worries me more. If cooling capacity is enough it is just a matter of how often the thermostat kicks close. I can observe this if I watch the temp needle carefully, and at high speeds it still *tries* to keep engine hot.
On mountains after a climb when there is a big and speedy decline I worry to cool the engine just too fast. One can see the needle moving, .stat could be too slow for that couple minutes.
I know this an old thread, but rather than start a new topic, I decide to revive this, like lazarus was revived.
The logic to this is not to cool the oil or fluids faster, but for the rest of the components, like power steering pump, rubber hoses, wires, battery, distributor, ac compressor, harmonic balancer yada yada.
Temps over here can reach nearly 40 celcius during the afternoons, and our batteries rarely last beyond 3 years, unlike you guys in the US of A.
Of course, I cant do this all the time especially when parking in a public lot( I could say I can do this almost every trip), but lets see if the battery life increases noticably. There is a great amount of heat trapped under the hood in equatorial countries.
Pic of my car's open hood this afternoon.
The logic to this is not to cool the oil or fluids faster, but for the rest of the components, like power steering pump, rubber hoses, wires, battery, distributor, ac compressor, harmonic balancer yada yada.
Temps over here can reach nearly 40 celcius during the afternoons, and our batteries rarely last beyond 3 years, unlike you guys in the US of A.
Of course, I cant do this all the time especially when parking in a public lot( I could say I can do this almost every trip), but lets see if the battery life increases noticably. There is a great amount of heat trapped under the hood in equatorial countries.
Pic of my car's open hood this afternoon.
Last edited:
When we were in Iraq, we idled our armored Suburbans a lot, even in 122* temps. We often idled for 2-6 hours a day while our VIPs were in meetings so we would open the hood. You could definitely feel a difference in the AC system as well as see the temp gauges go down with them open.
Nick1994
$100 site donor 2024
I read this thread title and thought “Merk used to do that”, sure enough, there was his comment 
Yup, standard practice over here if the engine's going to be idling for some time; especially if it's a K-9 unit.
That being said, idling with an open hood won't do much to extend battery life.
4WD
$50 site donor 2025
Folks used to do this on south Texas construction sites while doing computer/paperwork etc …
or having a lunchtime siesta …
or having a lunchtime siesta …
I've put insulation around and over my battery to keep it from heating up much with the radiator air flying past it. I don't typically lift the hood but maybe I should, it's insulated well enough not to feel warmed up from engine heat.
When I first took my new DD on an extended trip to Florida, I would check the oil level at every fuel stop. I would just leave it open until I was ready to leave, some breaks would be longer, for fuel and lunch. I figured it's already open so why not leave it up; it can't hurt.
The C4 Corvette is known for running hotter than other vehicles, by design. This is fine while driving since coolant and oil are circulating. But I am not comfortable shutting the engine off with the digital gauge reading above 225F due to heat soak. So if it's reading this hot when getting close to my destination, I try to remember to turn on the A/C for the last 1-2 minutes which triggers the radiator fans and quickly brings the temp down to around 200F. Or if I forget to do this, I might hit the A/C and drive around the block to let it cool down. If I don't feel like driving around the block, I'll park it in the garage and turn on a pedestal fan to blow air into the front and underneath the car. 20 minutes later, the garage air temperature is at least 10 degrees higher, probably closer to 15 degrees. This garage heating happens more slowly if I do not start the fan. Not sure if any of this makes a real difference, but I tell you what, that engine bay is packed full and it gets very hot under the hood. About the original OP question, I do not pop the hood when it's hot because the hood cables on these cars are known to break, they are over 26 years old after all. While I do have emergency loops on the latches, I'd rather not deal with a broken cable.
Every car I have in storage with gas hood lift supports I leave the hood or trunk open.I do when I park my Regal GS 2.0T in the garage after driving on 100deg days.
Only if you have a 280ZX Turbo with vapor lock issues caused by a bad check valve.
I opened my 300ZX hood open after I parked my car in the garage. Very tight space in the engine bay (after I found out that the rubber parts were getting brittle).
- Status
