True or False
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
It is quite hot inside of the engine once combustion starts happening. It does not take long for the pistons to start warming up.
We also froze parts in the shop I used to work at. We used liquid nitrogen to drop a part roughly 0.002" so it fit in a machine bore. If your temps are on par with the temperature of liquid nitrogen then I think you have a bigger issue and should consider moving away from your -320 degreeish environment.
For future reference you can expect the common metal to change size something like 0.000006" per degree of change. It is some ridiculous tiny amount. Ill have to look in my old text book for the actual number.
We also froze parts in the shop I used to work at. We used liquid nitrogen to drop a part roughly 0.002" so it fit in a machine bore. If your temps are on par with the temperature of liquid nitrogen then I think you have a bigger issue and should consider moving away from your -320 degreeish environment.
For future reference you can expect the common metal to change size something like 0.000006" per degree of change. It is some ridiculous tiny amount. Ill have to look in my old text book for the actual number.
CF Veteran
Joined: Feb 2013
Posts: 1,267
Likes: 1
From: Franksville, Wi
Year: 1995
Model: Cherokee
Engine: 4.0
you've obviously never worked in a machine shop and dealt with tolerances.
Piston slap has nothing to do with the tolerences of a given engine when it is built and has nothing to do with a cold engine since cold compresses metal which would make the bores smaller.
Anything else?
Piston slap has nothing to do with the tolerences of a given engine when it is built and has nothing to do with a cold engine since cold compresses metal which would make the bores smaller.
Anything else?
CF Veteran
Joined: Feb 2013
Posts: 1,267
Likes: 1
From: Franksville, Wi
Year: 1995
Model: Cherokee
Engine: 4.0
There's also the factor of your pistons heating up quicker than your block which would make your pistons expand quicker than your block does leading to a tighter seal and less slop.
Perhaps youre confusing piston slap on a cold engine with lifter noise? Idk.
Perhaps youre confusing piston slap on a cold engine with lifter noise? Idk.
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
You're kidding, right?
A lot of older 4.0Ls have excessive piston slap until they warm up. This is because of wear over time as well the cast iron block and aluminum alloy hypereutectic pistons do not warm up at the same rate. The youngest 4.0L on this site was built 13 years ago... original design tolerances in this context have nothing to do with anything.
A lot of older 4.0Ls have excessive piston slap until they warm up. This is because of wear over time as well the cast iron block and aluminum alloy hypereutectic pistons do not warm up at the same rate. The youngest 4.0L on this site was built 13 years ago... original design tolerances in this context have nothing to do with anything.
CF Veteran
Joined: Feb 2013
Posts: 1,267
Likes: 1
From: Franksville, Wi
Year: 1995
Model: Cherokee
Engine: 4.0
Right. Wear and tear is an obvious cause of piston slap. Has nothing to do with the weather thus has nothing to do with this conversation of driving while the engine is cold. If youre experiencing piston slap then there's a reason for it and it should be fixed. Again, nothing to do with this conversation. Lol.
Not quite sure where youre trying to go with that.
Not quite sure where youre trying to go with that.
CF Veteran
Joined: Nov 2010
Posts: 5,151
Likes: 0
From: glen burnie md
Year: 2000
Model: Cherokee
Thread Starter
Seasoned Member
Joined: Aug 2013
Posts: 358
Likes: 1
From: Kentucky
Model: Grand Cherokee
Engine: 4.0
Thread Starter
Seasoned Member
Joined: Aug 2013
Posts: 358
Likes: 1
From: Kentucky
Model: Grand Cherokee
Engine: 4.0
Neither. The only window that fogs over in mine is the driver side window. If you don't have air blowing on the front window and aren't breathing like a cave man then you should be fine. That's where the 'turn off your heat for a couple minutes' comes in to play. Once the Jeep is warmed up you can blast the heat and not have to worry about fogging up the front window.
But to each their own. I'm not a millionaire and I don't have money to just give away so im all about saving money where I can.
But to each their own. I'm not a millionaire and I don't have money to just give away so im all about saving money where I can.
CF Veteran
Joined: Feb 2013
Posts: 1,267
Likes: 1
From: Franksville, Wi
Year: 1995
Model: Cherokee
Engine: 4.0
Lol. Wind chill isn't a temperature and can't freeze anything. It is how cold the wind feels.
" For inanimate objects, the effect of wind chill is to reduce any warmer objects to the ambient temperature more quickly. It cannot, however, reduce the temperature of these objects below the ambient temperature, no matter how great the wind velocity."
So if the temp is 0 and the wind chill is -30 the lowest that youll go is 0 but you'll just get there much quicker. It will feel colder but it isn't.
http://www.nws.noaa.gov/os/windchill/index.shtml
" For inanimate objects, the effect of wind chill is to reduce any warmer objects to the ambient temperature more quickly. It cannot, however, reduce the temperature of these objects below the ambient temperature, no matter how great the wind velocity."
So if the temp is 0 and the wind chill is -30 the lowest that youll go is 0 but you'll just get there much quicker. It will feel colder but it isn't.
http://www.nws.noaa.gov/os/windchill/index.shtml
CF Veteran
Joined: Nov 2010
Posts: 5,151
Likes: 0
From: glen burnie md
Year: 2000
Model: Cherokee
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Right. Wear and tear is an obvious cause of piston slap. Has nothing to do with the weather thus has nothing to do with this conversation of driving while the engine is cold. If youre experiencing piston slap then there's a reason for it and it should be fixed. Again, nothing to do with this conversation. Lol.
Not quite sure where youre trying to go with that.
Not quite sure where youre trying to go with that.
Thread Starter
Seasoned Member
Joined: Aug 2013
Posts: 358
Likes: 1
From: Kentucky
Model: Grand Cherokee
Engine: 4.0
This thread is regarding about safety and very cold weather, not 30 degrees more like 15 and lower. Plus i live right off the highway. So i can't do 0 to 60 in 45 seconds without getting ran over. But i do respect everbody's opinion on the matter, so if i seem rude, i'm not trying to be. Just trying to understand why it would cause harm to my jeep.
Last edited by SHELBYGT NSM; Jan 8, 2014 at 11:19 AM.