How long do you have to wait after driving in order for your engine to be cold? i want to do the idle procedure but dunno how long i have to rest my car. thanks

 

It'll vary.

How long you were running it, how hot it got, how hot it is outside...

Might take an hour or two to completely cool down

 

i drive about 30 minutes to get home..
so 3-4 hours should be plenty for it to be considered cold right?

 

Definitely should be. If you can trust your neighbors, lifting the hood when you get home, may help things cool down, quicker.

 

also you can run a hose over it... shouldn't hurt anything

 

or, if you want it cold-cold, then let it sit overnight and wake up earlyer in the morning and do what you need to do.

 

bad idea... hot parts from just being driven + cold water= possible cracked parts.

To answer the original question, I let the car sit for at least a couple of hours. If when you start the car and the "cold" indicator comes on in the dash, you know you've waited long enough.

 

I wouldn't recommending putting water on it either. But I doubt it'd be that drastic. It seems about as bad as turning off the engine after parking your vehicle in the rain?

 

Believe what you want, but a hot engine doused with cold water can easily crack cast parts. it can be that drastic.

 

This is right on the money. When you have extreme temperature changes, just like any other substance, metals will warp and sometimes break. They need time to slowly cool down so they can change shape without too much stress.

If you want to experiment, do a half-dozen panic stops from 60 and then flood you front rotors with water - instant warping...

 

I should've worded myself better. I'm not saying nothing will crack.
I'm just observing that the conditions can be similar to what happens naturally. Say when you're running the engine got and it starts raining. Or you just parked your car and it starts raining. Or it's been raining and you just parked your car.
And I left it as a question because I am not sure if these natural occurrences are really similar to the scenario we're considering. So I'm half expecting people to tell me why the natural scenarios I described are actually very different.

Hmm... maybe we're thinking different things. I'm thinking putting water on the closed hood (which cannot be good in any case). Are you thinking opening up the hood and putting water on the engine?

 

yes, that must be it.

I was assuming iwu was talking about running water over the engine to cool it down faster as I don't see how running water over the hood would cool the engine down any faster. I agree the hood would be cooled down faster, though.

 

Seems like theres a misunderstanding going on here. Running water over the closed hood will not cool the engine faster. And running cool water on something hot will cause it to crack. Whether it be engine parts or brakes. But the best way to cool it down quicker would be to prop the hood up and put a fan in front of it.

 

i would recomend letting it sit over night, i remember when i helped coupe de tat swap his intake, you have to do it when the motor is cold, we let the motor cool down for over an hour in low 60 degree weather, motor had hardly cooled, judging from the coolant i got on my hand the motor was still around 160 degrees... normal operating temp according to my scangauge, 173 degrees... so 13 degrees in the first hour. also using my scangauge i have noticed 3 hours later, my car is still around 125... if you want it cold, let it sit over night that is your best bet!