I would always see Police cars in Florida with their hoods propped up at wrecks, traffic detours, etc... I always thought it was for a alternate switch to another set of batteries to run the lights or something to do with the car being able to charge at a idle with the lights on for a extended amount of time. I finally asked a cop, why was his hood propped open with a soda can. Much to my surprise he said, it was because the cars overheat and its so the engine can cool better while they are sitting with the engine running. I personally don't think this would make a difference. I work in Florida, on construction sites, where there is no shade, its all been cleared and I will let my F-150 idle with the air on for hours, I ve never had a issue. I would think a police car, with the enhanced performance package, would have even better cooling. I would also think on a covered water cooled engine, raising the hood, 6" isn't going to do too much, in the way of cooling on a 90+ day. I didn't argue with the cop, just a Hmmm. What's your thoughts? I say it doesn't make a difference. Air has to come in at the radiator, driving it would cool it, but the hood, up? Heat rises, but I still don't think its a difference maker.
Police Technique in Florida?
- Thread starter Panzerman
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I'm a retired cop who used to work many 90+ degree traffic details. I popped the hood on the Crown Vic to decrease the under hood air temps. It let most of the hot air escape from the engine compartment when running with the AC on for hours at a time.
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I think it's plausible.
Nick1994
$100 site donor 2024
Here in Phoenix if say about close to 99% of cop cars and highway patrol cars are the new Impalas and Tahoes. They retired the Crown Vic fleet and I see the hoods raised on the Impalas a lot, but don't really remember them being raised on the Crown Vics.
It worked on an old car I had in the 70s. If you did not open the hood, the car would die after about 10-15 minutes.
I see diesel Ford ambulances do that a few times.
Now that you mention that, I only really started seeing the hoods propped on the new Impalas. I never see the Chargers with hoods propped. Never see the Crown Vic's anymore.
Originally Posted By: Nick1994
Here in Phoenix if say about close to 99% of cop cars and highway patrol cars are the new Impalas and Tahoes. They retired the Crown Vic fleet and I see the hoods raised on the Impalas a lot, but don't really remember them being raised on the Crown Vics.
I think you mean the Caprice, not Impala, although Impalas could be easily used I guess. Interesting subject. Thinking.... I once worked with a Mechanical Engineer who was modelling underhood air flow for Mercedes SUVs to see if any thermal hot spots for idling in summer weather appeared. I remember he said that if you keep the hood closed the air path is usually designed to stay close to the engine block and exit under the car. Conclusion: Better to keep the hood closed so the fan air makes velocity-contact with the metal surfaces on the engine block and accesories. If you open the hood, the fan air exits without swiping up against the metal parts for good heat transfer.
Here in Phoenix if say about close to 99% of cop cars and highway patrol cars are the new Impalas and Tahoes. They retired the Crown Vic fleet and I see the hoods raised on the Impalas a lot, but don't really remember them being raised on the Crown Vics.
I think you mean the Caprice, not Impala, although Impalas could be easily used I guess. Interesting subject. Thinking.... I once worked with a Mechanical Engineer who was modelling underhood air flow for Mercedes SUVs to see if any thermal hot spots for idling in summer weather appeared. I remember he said that if you keep the hood closed the air path is usually designed to stay close to the engine block and exit under the car. Conclusion: Better to keep the hood closed so the fan air makes velocity-contact with the metal surfaces on the engine block and accesories. If you open the hood, the fan air exits without swiping up against the metal parts for good heat transfer.
From reading the posts, it totally depends on whether the car maker designed the fan air flow to evacuate properly under the car after breezing over the metal parts. Some makes/models might not have gotten this right. If you think about it, its negligence for a car maker not to optimize the air flow.
31 year old native Floridian and I have never seen/noticed this. If this is a legitimate problem they should consider a different car.
Not coolant overheating but electrical.
leftlanenews.com: Dodge recalls 9,688 Charger police cars for overheating issues
The should do the ricer trick.
http://www.gtplanet.net/forum/threads/hood-spacers.308096/
Not coolant overheating but electrical.
leftlanenews.com: Dodge recalls 9,688 Charger police cars for overheating issues
The should do the ricer trick.
http://www.gtplanet.net/forum/threads/hood-spacers.308096/
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many years ago i was working at a trencher mfg. in the experimental shop. one trencher model was having over heating under the hood. the hydraulic system was over heating. while holding my hand i was trying to find the air flow. we thought the air was smashing in to the oil tank. so we opened the wall next to the oil tank, to let the air out. oil temp went UP. the open wall let the hot air run down the side of the oil tank. so i think finding what is REALLY happening with air flow is NOT easy.
I have seen this all my life, and have officer friends who said it was for heat issues. I never really understood it as my own cars could always idle all day with the AC on, but who knows.
I do know that on my wife's BMW the air path underhood is clearly designed. There are rubber gaskets that seal the hood perimeter and it it very obvious how the air flows through the engine compartment and out at various locations.
I do know that on my wife's BMW the air path underhood is clearly designed. There are rubber gaskets that seal the hood perimeter and it it very obvious how the air flows through the engine compartment and out at various locations.
Nick1994
$100 site donor 2024
Originally Posted By: boundarylayer
Originally Posted By: Nick1994
Here in Phoenix if say about close to 99% of cop cars and highway patrol cars are the new Impalas and Tahoes. They retired the Crown Vic fleet and I see the hoods raised on the Impalas a lot, but don't really remember them being raised on the Crown Vics.
I think you mean the Caprice, not Impala, although Impalas could be easily used I guess. Interesting subject. Thinking.... I once worked with a Mechanical Engineer who was modelling underhood air flow for Mercedes SUVs to see if any thermal hot spots for idling in summer weather appeared. I remember he said that if you keep the hood closed the air path is usually designed to stay close to the engine block and exit under the car. Conclusion: Better to keep the hood closed so the fan air makes velocity-contact with the metal surfaces on the engine block and accesories. If you open the hood, the fan air exits without swiping up against the metal parts for good heat transfer.
Nope, they use the Impalas here. I have seen the new Caprice twice though.
Originally Posted By: Nick1994
Here in Phoenix if say about close to 99% of cop cars and highway patrol cars are the new Impalas and Tahoes. They retired the Crown Vic fleet and I see the hoods raised on the Impalas a lot, but don't really remember them being raised on the Crown Vics.
I think you mean the Caprice, not Impala, although Impalas could be easily used I guess. Interesting subject. Thinking.... I once worked with a Mechanical Engineer who was modelling underhood air flow for Mercedes SUVs to see if any thermal hot spots for idling in summer weather appeared. I remember he said that if you keep the hood closed the air path is usually designed to stay close to the engine block and exit under the car. Conclusion: Better to keep the hood closed so the fan air makes velocity-contact with the metal surfaces on the engine block and accesories. If you open the hood, the fan air exits without swiping up against the metal parts for good heat transfer.
Nope, they use the Impalas here. I have seen the new Caprice twice though.
Originally Posted By: Nick1994
Here in Phoenix if say about close to 99% of cop cars and highway patrol cars are the new Impalas and Tahoes.
Those aren't the new Impalas, those are the old Impalas, the 3rd Generation W-body, the new ones are the 2014 Impala with the Epsilon II platform, completely different and actually new.
Here in Phoenix if say about close to 99% of cop cars and highway patrol cars are the new Impalas and Tahoes.
Those aren't the new Impalas, those are the old Impalas, the 3rd Generation W-body, the new ones are the 2014 Impala with the Epsilon II platform, completely different and actually new.
Originally Posted By: Panzerman
Much to my surprise he said, it was because the cars overheat and its so the engine can cool better while they are sitting with the engine running. I personally don't think this would make a difference.
Exactly. Taxis (i.e. former CVPIs and the like) often used to run with their hoods open the first notch during the hottest days of summer, claiming the same thing.
If the vehicle overheats in the summer, it's a design issue or something in the cooling system is amiss. I can't remember the last vehicle I saw overheat that didn't do so because of poor maintenance or some serious part failure, not because the hood wasn't up.
Much to my surprise he said, it was because the cars overheat and its so the engine can cool better while they are sitting with the engine running. I personally don't think this would make a difference.
Exactly. Taxis (i.e. former CVPIs and the like) often used to run with their hoods open the first notch during the hottest days of summer, claiming the same thing.
If the vehicle overheats in the summer, it's a design issue or something in the cooling system is amiss. I can't remember the last vehicle I saw overheat that didn't do so because of poor maintenance or some serious part failure, not because the hood wasn't up.
Could GM deny a police car warranty engine failure claim if they found out they idled it in hot weather for 3 hours? I say just let the engines fail and let GM pay for the warranty repairs, and then you'll see bigger cooling fans and/or fins suddenly get added.
The fan(s) of non moving cars at idle have to work harder to pull air through the radiator and a/c condenser, then push the heated air around the engine and out the bottom of the car. With the hood open, hot air has a path of less resistance, as hot air wants to rise. More efficient cooling requires less energy, as electric fans will run less, and mechanical fans will pull less power from the engine.
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