White smoke under hood after stopping

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mako_Five.56

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Hey all, I'm sure this has been covered before. If so I apologize. So here goes:

I was driving the other day (hot, sunny day) for about an hour. When I reached my destination and parked, I noticed steam or possibly a semi-whitish smoke coming from the front grill area for about 10 seconds before it stopped. Temperature gauge was normal. I can't remember if it rained the prior day.

Any ideas? Is this normal for a hot day? Again I can't remember it rained the day before or not. I know these engines can cook off some water during/after it rains which is normal but should I be concerned?

2005 Jeep TJ Rubicon 4.0, stock

148,000 miles
 
rasband said:
Did you notice any scent you can describe?
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Yep there is no mistaking oil burn smell with coolant steam smell non pressurised water steam smell or even an (over rich smell at the tail pipe) If OP was driving for an hour there would be no water vapor from rain left to steam!
 
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Check that your radiator cap is fully screwed down and that it has the proper 18 lb. pressure rating. The symptom you describe makes me think the radiator cap is venting pressure when it should not be.
 
Thanks for all who replied. I did smell something; possibly coolant or oil. I have always smelled it on hot days since Ive had the Jeep (coming on 6 years now). I do have the notorious rear main seal leak as well (I just keep an eye on oil level and add when need be) so yeah, she does leak oil via small drips. I typically add about 1 qt of oil after/between changing oil (7k miles with synthetic). And yes I did pop hood but the steam went away in seconds so I couldn't locate. Possibly need new radiator cap? Am unsure how to check the pressure on a radiator.
 
Something else to check while you are under the hood; look for signs of seepage around where the valve cover mates with the head. Your engine may require installing a new valve cover gasket.
 
If you're using an aftermarket radiator, it's possible the cap doesn't screw down tight enough on the plastic threads. Happened on my WJ a few months ago. When I'd come to a stop I'd occasionally see white smoke. I had to get a new cap and bend the feet in a bit so it screwed down tighter. The proper fix would be to get a better radiator, of course.
 
bromel said:
If you're using an aftermarket radiator, it's possible the cap doesn't screw down tight enough on the plastic threads. Happened on my WJ a few months ago. When I'd come to a stop I'd occasionally see white smoke. I had to get a new cap and bend the feet in a bit so it screwed down tighter. The proper fix would be to get a better radiator, of course.
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Thanks for your reply Bromel. It is a stock radiator to my knowledge. I have had it for the past 53k miles (has 148k on it).
 
mako_Five.56 said:
Thanks for your reply Jerry. Any idea how I pressurize the system?
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The cooling system self-pressurizes itself. You can buy a pump-up pressure-testing device that replaces the radiator cap to pressurize the system for a leak test but you needn't worry about pressurizing it for other than that.
 
My 2005, 4.0, overheated without warning a few days ago on a very rough cobblestone residential street.

The "check gauges" dash light suddenly came on, my stock dash water temperature gauge was moving into the red area and my Autometer water temperature gauge (mounted above the dash) was moving into the 250 F degree area. Of course I instantly stopped. There was no cloud of steam or any smell.

When I opened the hood I saw what appeared to be water/coolant stains (dry and white in color) on the driver's side of the engine compartment. I noticed the small hose between the radiator cap area and the overflow/burp bottle had popped off at the radiator cap end. I put it back on and noted the fluid in the burp bottle was being sucked into the radiator.

I don't know how long the little hose had been off but it seemed to me the coolant had been spraying across the engine bay as the radiator cap vented pressure.

I was surprised the engine cooled to 120 F degrees in about 20 minutes. I covered the radiator cap with an old towel and popped it off without a problem. I put about 1.5 gallons of water in the radiator and drove it home where I put a clamp on the small hose.

Perhaps you have a pinhole leak in the small hose?
 
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Hey Matt. Sounds like you got your problem figured out. Did you replace the rad? And thanks for the reply. I may have a leak somewhere or like Jerry said, maybe I need a new rad cap.
 
Thanks to all who replied. All very good insight. I will buy the pressurizer and perhaps a new rad cap. Or - Think I might as well go ahead and just replace the whole rad while Im at it? Pretty sure it has never been replaced. Sitting at 148k miles.
 
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