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Old 11-29-2012, 11:35 AM   #61
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Originally Posted by Jeeperz Creeperz View Post
it is another myth like running higher than 87 octane (owner's manual recomendation) and 3,000 mile oil changes (normal use).
...and that it's harmful to run the tank to E all the time.

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Old 11-29-2012, 12:23 PM   #62
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If your Jeep has a manual choke, yes.

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Old 11-29-2012, 12:28 PM   #63
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While I didn't bother to read every post in this thread, this may have already been brought up, but...

...while that's all well and good we should or shouldn't drive off in hasty fashion on a cold engine, you can sit there and idle all day long or until the engine has reached normal operating temperature, but what about everything else? You're going to be moving right along but what about that transmission fluid or gear oil that's still chilled gum?

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Old 11-29-2012, 01:47 PM   #64
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While I didn't bother to read every post in this thread, this may have already been brought up, but...

...while that's all well and good we should or shouldn't drive off in hasty fashion on a cold engine, you can sit there and idle all day long or until the engine has reached normal operating temperature, but what about everything else? You're going to be moving right along but what about that transmission fluid or gear oil that's still chilled gum?

You should drive gently for the first few miles, regardless of whether you warmed the engine up by idling or not.
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Old 11-29-2012, 05:39 PM   #65
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The internal engine components (pistons, rings, journals, crankshaft, rods and their accompanying bearings) were designed to fit best at operating temperatures; they all need to heat up and expand for best economy and performance and minimal wear. And, the hotter an engine can run, to a limit, the more efficient it is. The limit is the integrity of the materials and lubricants and a function of thermodynamics of the intake/exhaust/cooling system capacity.

BManz, you are right that the engine is engineered to fit BEST at a specific temp, and therefore be most efficient at that temp.

HOWEVER, the bit about the hotter the better is completely false. We can't prevent heat from transfering to components, so we engineer them to fit best at a temp they will inevitably heat to. Any heat transferred to a component is heat that is not used for work. Only heat used to create work contributes to efficiency in a positive fashion. Period.
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Old 11-29-2012, 05:52 PM   #66
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I let mine warm up when its bellow zero. Just enough to heat up the steering wheel. I'm wierd like that....
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Old 11-29-2012, 05:59 PM   #67
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I let mine warm up when its bellow zero. Just enough to heat up the steering wheel. I'm wierd like that....
-----

I imagine that many (that park outside)have to let them idle to get the defroster warm to clear the windshield.

I was always amazed at the drivers that would scrape a peep hole in the windshield leaving the side & rear windows covered in ice/snow and drive that way. They would also leave their brake & tail lights covered as well.

Crazy!
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Old 11-30-2012, 10:55 AM   #68
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My first post

OK, here's my first "newbie" post: My wife's boss has a 2008 Unlimited, and says he has shattered three windshields having the defroster on while it's warming up (we live in Iowa). Anybody else experienced this?
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Old 11-30-2012, 10:56 AM   #69
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OK, here's my first "newbie" post: My wife's boss has a 2008 Unlimited, and says he has shattered three windshields having the defroster on while it's warming up (we live in Iowa). Anybody else experienced this?
I guess I'll find out this winter, but that shouldn't be happening (obviously...). I've never experienced this in any of my vehicles.

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Old 11-30-2012, 11:03 AM   #70
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OK, here's my first "newbie" post: My wife's boss has a 2008 Unlimited, and says he has shattered three windshields having the defroster on while it's warming up (we live in Iowa). Anybody else experienced this?
Jeez. Making me rethink my heated windshield washer fluid modification.
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Old 11-30-2012, 04:20 PM   #71
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Jeez. Making me rethink my heated windshield washer fluid modification.
They come from the factory with washer fluid heaters, so I don't think you'll have any issues.
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Old 11-30-2012, 04:39 PM   #72
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Originally Posted by MikeK46

They come from the factory with washer fluid heaters, so I don't think you'll have any issues.
I didn't know that. I'll have to check that out
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Old 11-30-2012, 06:41 PM   #73
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New engines do not require warming up but I start mine and wait 20 seconds or so for the idle to come down and then drive easy out of my subdivision and onto the main roads where I continue to drive with a soft foot until engine warms up a bit. Not necessary but just cant thrash on a cold engine.
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Old 11-30-2012, 07:00 PM   #74
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Originally Posted by Boppa
OK, here's my first "newbie" post: My wife's boss has a 2008 Unlimited, and says he has shattered three windshields having the defroster on while it's warming up (we live in Iowa). Anybody else experienced this?
This brings back memories. A lazy Marine in my old unit had a junior Marine start up her car to let it warm up. The heat and defroster was on high. The windshield cracked all the way across the bottom. From seeing that I never put the defroster and heat on high. I slowly increase fan speed and heat to defrost the window.
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Old 11-30-2012, 07:07 PM   #75
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It was in the 60's last week! Freezing! I warmed it up before I ventured out.
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Old 11-30-2012, 09:39 PM   #76
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The answer to the original question is NO.
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Old 11-05-2013, 01:39 AM   #77
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Quote:
Originally Posted by Boppa View Post
OK, here's my first "newbie" post: My wife's boss has a 2008 Unlimited, and says he has shattered three windshields having the defroster on while it's warming up (we live in Iowa). Anybody else experienced this?
Shattered no - but if you have the tiniest chip that's been ok all summer you'll find out where it is when it runs across the windshield. I've had that happen twice now, once in the TJ, and once in the JKU.

I thought I got away with the JKU, it's happened last November a few weeks after I bought it. I heard two small rocks hit the windshield when on the highway and a semi crossed into my lane. I cursed the minutes I heard them hit, but I didn't see anything on the windshield. I checked with the flashlight when we got out and couldn't find anything that night. It was about 40 degrees out.

I parked at home outside, with the windshield facing east, and when I got up the next day it had warmed up nicely to about 70 by the time I left the house. I was greated by a crack about 2 inches long, running straight up form under the middle of the driver's side wiper coming up into my line of sight. I got the defrost going on it set to cold, rolled the windows down (pressure does make a big difference) and I got it over to a glass shop as fast as I could. Unfortunately, the sun warmed it up enough that is was 4 inches by the time I got there. The kid said he would do it for free because they had little hope it would hold. He worked on it for awhile, mainly on the end where it was running.

The crack became stable after that for awhile, until I ran the defrost over winter. Apparently we missed a hairline split lower in the crack. The end he worked on is still stable, but about an inch below the end ran one day I used defrost. It took off towards the rear view mirror so I quickly turned the defrost to cold and ran it on high. This stopped it dead in it's tracks and turned it towards the passenger side. I tapped the glass with my pan a few times and sent it running across the windshield and into the bottom passenger corner.

At least it's stable again this way, all the ends are taken care of now and nothing is in my line of vision. I debated replacing it, we get so much debris here it's almost not worth doing. It's odd too, once I get a crack in the windshield, it repels more cracks. So I have grown to the conclusion that having a good crack is much better than risking a bad crack. So far since spring I have kept a tally in my head - we ave had at least 6 rocks hit it, all in the size they could have cracked it, none did. I had a 2x4 scrap fall off a truck in front of me that was about 6 inches long, it hit the windshield on the largest surface area, perfectly flat, and it made a horrible sound! Both of us saw it coming and I was squinting my eyes in preparation it was coming through the glass. It didn't leave a mark! That one hit on the upper passenger corner. After that hit I swore off replacing the glass for a bit longer, I know if that had been a new windshield it would have broken. I had similar things occur with the TJ windshield. I replaced it once, but left it after the second windshield cracked. I traded it with a crack that was vertical from top to bottom right down the middle. I always wondered if Jeep windshields could be converted to split panes after that, I think it would be a nice nostalgic look.
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Old 11-05-2013, 11:41 AM   #78
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If you dump your vehicle every 50K miles like most people, fire it up and give it full throttle while cold. You won't notice anything

If you keep your vehicles over 200K miles like I do, let it warm up for at least 30 seconds before you move, and make sure the temp needle has at least begun to move before you go highway speeds.

BTW, cold start is the reason synthetic oil will pay for itself over the life of a vehicle. Synthetics flow better, and leave more on the cylinder walls after the vehicle sits for 10-12 hours. Most people don't realize that the majority of ring and cylinder wall wear occurs in the 30 seconds after startup.

I have owned four vehicles that have gone over 200K, and several others that I drove 150-200K, including three with turbos, and I've never had an internal engine repair. I use synthetic oil, I change it every 3000 miles, I never let it get low, and I let my vehicles warm up before thrashing them. One of my vehicles is a 2000 Chevy Silverado with the 5.3 V8 that had terrible issues with piston slap. Many people startied experiencing this issue within 40,000 miles. I've flogged the bejesus out of that truck for 220,000 miles, and I just started hearing the pistons at startup in the last 5K miles or so. It is a good illustration of why you want your vehicle to warm up. If I start that truck when it is cold, you can hear the pistons 100 feet away. It sounds like a bucket of bolts rattling. After 30-60 seconds of idle, depending on the temp, the noise will suddenly just fade away as the pistons heat up. If I just cranked it into gear and roared off every time, the engine would have been ruined years ago.

It ain't that hard, people.
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Old 11-05-2013, 12:22 PM   #79
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Old 11-05-2013, 12:30 PM   #80
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As a retired professional engine builder/machinist, Ive seen a lot of progress in the last 50 years. I would say that there are some pretty good answers here. The place that I saw most of the cold start problems was in the piston skirts. The piston is the most thermally active part in the engine right after the exhaust valve. It not only expands but it radically changes shape as it heats up. During the bottom dead center direction change you encounter the most piston rock. This is due to the piston skirt being pulled partially out of the bore as the connecting rod thrust is transferred from one side to the other. This is where you get piston slap from. When the engine is cold the piston has a lot more clearance and the skirt lateral acceleration has farther to go. This can lead to cracks in the skirt. When the piston and bore come up to temp the operating clearance might be cut from .003 to .0015. Not a lot to us but a huge amount to a piston slapping back and forth 16 times a second at 1000 rpm. I let mine warm up for about 30 seconds and then drive under 3000 rpm till it gets to operating temp. Just my opinion.
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Old 11-05-2013, 12:34 PM   #81
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You don't have to but you should if you live in cold areas. Our winters can get to -30 Celcius. When it's that cold my jeep is always plugged in with the block heater. But regardless I let it warm up for 15 minutes minimum. I've heard the pentastar knock for the first couple seconds on starts that cold until the oil gets to wear it needs to be. Not only do I do this for my jeep but I do it for myself I hate getting in a cold vehicle and freezing for 20 minutes till everything warms up. A lot of people don't live in places this cold so it may not be as detrimental.
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Old 11-05-2013, 01:42 PM   #82
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The OP is is southern Cali...not Alaska...

When it is really cold out, I basically warm my vehicles up for 2 to 4 minutes. Open door, turn on engine, close door, scrape windows, get back in, drive away.
Ha, I didn't notice where he was from! Yeah, in socal, you won't need to do much scraping or "warming up".
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Old 11-05-2013, 02:19 PM   #83
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i think warming up a vehicle is only necessary in living in cold climates... i will however agree though. whenever i start any vehicle i drive, i wait for the tach to reach below 1K RPM. then i procede to throw it into reverse and start driving.
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Old 11-05-2013, 02:48 PM   #84
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I do the R Kelly (stick my key in the ignition) and mash the throttle as hard as I can pretending I have VTEC.
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Old 11-05-2013, 03:01 PM   #85
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I use my oil pan heater anytime the temp gets below 50F. Plug it in for half an hour and the oil temp is between 60F and 75F. I let the high idle settle down then try to keep it at/under 1500 till the water temp is normal. When the oil temp reached 150F I can relax. When the oil temp is 180+ I drive normally.

I'm running 5-30 synthetic. When I start up even in summer the oil pressure is 90psi. In winter with a pan heater and oil temp around 60F the oil pressure is 90psi. If not using the pan heater in winter the oil pressure can reach 120+ Just a few stats for anyone interested. Yes I have a oil pressure/temp gauge in my 13'
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Old 11-05-2013, 03:05 PM   #86
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I noticed that on mine it doesn't want to fire up right away when it's cold. Not sure if it's a dirty fuel filter, plugs, or what.
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Old 11-05-2013, 03:24 PM   #87
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My mechanic told me not to let it idle. Just get in and go...
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Old 11-05-2013, 03:41 PM   #88
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I will say I do like my block heater ($35 option at the time) during the cold Michigan winters...the temp gage will move up a bit within seconds after start-up when plugged in overnight.
I still let it run for a few min before driving off.
The backside warmers are worth every penny also...keeps the wife happy too.

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