Do you open your engine comparment to cool?
 

Curious if anyone else opens the engine compartment to cool after you get home from a long drive?

I have been doing this for years, always felt since the car doesnt have any cooling fans, it would let the engine cool down much quicker, which is better for the car/engine?

Just curious.........


Later,

Rod

I don't on my '86 3.2L. On air-cooled airplane engines we also rather have the engines cool down slow to prevent shock cooling. This means even descending from altitude as slow as possible with partial power. The faster metal warms and cools (extends and retracts) the more stress it gets. There is no real benefit of cooling the engine as quick as possible unless you have a vapor lock issue in your fuel system.

I've done that at DE events...between secessions it makes sense to cool it down faster, at least that is what I thought.

Engine cool-down.
 

Yup, when I park I my garage, every litttle bit helps.

110K miles-Dry motor....

I do, particularly on a hot day. Shock cooling is a concern for airplanes leaving altitude on a rapid descent but there is no way you're going to cool down an air cooled car to the same degree.

I do this occasionally with my BMW on a very not day (here in Phoenix). On BMW forums many mention that when changing their valve cover gaskets that the rubber gasket is crispy hard and crumbles on removal. I changed mine not long ago (70,000 miles on it) and the rubber gasket was soft and pliable.

I only open the lid if I need it to cool so I can work on it. If I'm in a big hurry I break out the fan and try to accelerate the process.

At the track... Always. All of us guys racing with air cooled cars do.

Street driving should never require this unless it is apocalyptically hot outside.

Nope, never. I normally need to get to where I'm going and I don't have to stand there with the lid open. Besides I never get past 8:00 on the temp dial around here anyway.

Mine has a big gaping hole in the lid, so no reason. With a front engined car which has been driven hard, I have seen this done a lot at the track. With P-cars, not really.

How many times can you open your engine compartment before the pull wire breaks?? After reading the work-around to open the hoods when the cable snaps - I think any possible gains of routine cooling are nixed by the risk of loosing access all together!

100 mile cruzes at 120+ mph on 100-110 degree days never gave us need to be concerned in the Arabian Gulf area.

Diverdan.

I definitely do.

I also keep the key in the auxillary position, one notch towards starting position for a few minutes to help cool the system and to prevent vapor lock.

I only open it when I decide I am going to do some work on her. Most of the time I end up just closing it and taking it out for some fun. Me= slack :) It can be opened in the winter;)

I used to pop it open all the time at the track. That's about it.

Good point. With the vents on the lid, you can certainly feel the heat escaping easily. So I never bothered opening the lid, even at the track, unless I am checking the oil level.

I open it at the track, cooling seems like a good idea but better is simply to take a look at all between runs. Better to see anything leaking or hanging loose vs. happening without warning.

As previously stated I also open the engine cover after a track session (DE or race). Leave the engine running for a few minutes too. Track temps are usually higher than even hard running on the street.
Never have during street driving though. Might if temps were say upper 1/3 of gage.

I never have but we don't normally get the conditions here to cause unduly warm engines. However, last summer, I visited a buddy for a long weekend and took my 911. He had me park in his back yard on the lawn so I wouldn't have to be on the street. When I left, there was a nice gift of a four foot across area of dead, brown grass from the engine heat.

Every time I come home, and pull into the garage. No sense oven-baking.

Vapor lock on an 80s Carerra? The whole system is pressurized from the pump up in the front. There isn't any vapor lock issues on these cars.

As far as leaving the key on... What is that supposed to do? It doesn't run the fuel pump. That is controlled by the DME and it only turns on the fuel pump when it sees the engine is spinning. There aren't any fans in the engine compartment that run when in accessory position. The only thing it will really do is allow you to operate the windows and listen to the stereo. And it gives you the opportunity to forget it and run the battery down.

Hi All,

Anytime you can SLOW the temperature change of metal - the longer it lasts. Flexing metal via repeated bends or repeated cooling and heating cycles causes fatigue - so - I don't get it - why would you want to more rapidly cool the engine - what is the purpose??? I am not saying you are "wrong" I just don't understand why you would do that....

I don't, on my 3.2
I don't want to introduce thermal shock.
At 95 degrees, after a 50 miles drive home, its not all that hot in there anyways. Most of the heat is underneath the car.

Trying to rapdily cool the motor is worse than slow cooling.

Not an engineer, but I know this as fact from being around jet engines.

Ideally, the motor will have it's longest life if it never cooled from it's operating temps. That would produce the longerst material life from I've been told.

Those more cautious could mount a low-profile fan under the grill and controlled by a temp.-sensitive relay (ala Japanese radiator fans). Orient the fan so it helps increase the normal flow of heat up and out of the engine compartment.

The more ambitious might use a reversible fan to help the cooling system in low-speed, stop-and-go driving.

Sherwood

I only pop the deck-lid to cool down the engine if I'm going to work on it. Or if I am working in the garage and need some heat :)

If everything is nearly too hot, (inter coolers, seals, turbos, etc.) and the oil is no longer moving, just sitting in the hottest areas...then wouldn't an open deck lid be a good thing? Not really to cool the engine metal faster, just to allow the heat out.

The water cooled 911s have a fan that blows air on the engine (downward I believe) after shutdown. While it will cool down differently than an air cooled engine, Porsche must have had a reason for drawing in relatively cool outside air and blowing it on a hot engine.

The fans in the newer water cooled cars (Porsche and non-Porsche) do not blow on the engine - they blow through the radiator. In the end, the air contacting the engine is hot after ambient air is blown through the radiator. The purpose of fans continuing to blow after engine shutdown is to cool the hot water that is now sitting without movement in the radiator, thus reducing thermal wear on the cooling system - it has nothing whatsoever to do with cooling the engine itself.

The water cooled models have a small fan attached to the deck lid to draw in air and blow on the engine as well as the radiator fans.

when driving my 356 to california during the summer months over the mountains during the day, i will open the rear decklid and in addition try to follow/stay next to a tractor trailer in its shadow - don't laugh it actually works and keeps my small hot engine just below the red on the temp guage.

Never, but mine is a daily driver, no track for me. yet.....

I've had a 996 and know what you mean.

It was probably for heat soak reduction more than anything else after shut down.

Every time. But mostly to make sure nothing is on fire.

;)

Tippy,

That would be my guess as well. Some here pop the engine lid after shutdown to reduce heat soak - Porsche installs a fan on the newer models to accomplish the same thing.

Those with fuel injection, not likely to make a difference. Those with carbs can benefit from keeping the topside of the engine relatively cool because heat soaking the carbs can boil the fuel in them.

Almost always after each track session : have a little look everywhere on the engine ... and refresh the compartment ...

And when we arrive at home...

It's always a pleasure to have a look there :-)

I only really do it at Track or DE events without the e-Brake pulled up to keep the rear brake rotors from warping/deforming or after a extreme hot day of driving L.A. traffic then in the garage lid open.

Plus I like to give the lid struts a break from being compressed all the time.

Sometimes I wonder about the cooking time for salmon in aluminum foil under the hood or seared next to a heat exchanger.

Sherwood

I've heard people suggest when stopping for pits stops that opening up the engine lid after a long drive on a hot day keeps the A/C condenser from building up heat. So when you drive off from a stop your A/C comes up to temp faster.

In the dead of Southern summer, after a long drive with sweltering heat and humidity about, I'll whip in the driveway,...power down,...then open the rear deck.....head inside, to probably get something to drink,.."whatever",.....then head back out to kneel at the rear and LOOK around,..probably touching a few things here and there,...checking to make sure all looks well.

I would presume this would help with the cooldown rate,..but am not quite sure that I've induced a thermal shock.....

I think about (too) the things Sherwood is mentioning....!!!!!!!

Best!

Doyle