# Vapor under the hood!



## Bigplanz (Apr 10, 2009)

Mercury Villager, 1995. Yesterday, I left work and at a stoplight white vapor was pouring out from under the hood. I stopped, opened the hood and white vapor billows out. Temp gauge was normal. I turned off the heater, and drove home, watching temp gauge. It stayed normal. After I had gone about 4 miles, I pulled over and opened the hood. No vapor. I checked the coolant recovery tank and it was empty. Drove home and today drove the five miles to work with no vapor. Temp gauge did go up to higher in the normal range but the fan kicked on and the temp went down. No overheating has occurred. 

Today I put some antifreeze (a quart, maybe) in the recovery tank, and the vapor returned. Turned off the heater and the vapor went away. Temp gauge goes up a little but fan brings it back down. 

This is puzzling. I'm going to replace the radiator cap because it's cheap but I doubt that is the issue. No coolant leak detected. No coolant on the ground, no hissing from the engine compartment. 

Any ideas on what may be causing this? Thanks.


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## Bondo (Dec 8, 2007)

Ayuh,... Sounds like ya got a Leak, in the heater circuit...


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## Bigplanz (Apr 10, 2009)

That occurs to me as well. No puddles or evidence of wetness anywhere, and no smells of antifreeze. I will trouble shoot this weekend to find where the vapor is coming from. Seems to be sourced back on the firewall.


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## ukrkoz (Dec 31, 2010)

Hey, Bondo, what's with all the Ayuh-s? Is this some sort of a clan call?

Anyhow. So you fill the expansion canister and vapor shows, and if it's low in expansion canister, no vapor? How about crack IN THAT CANISTER throwing some coolant, not much, onto something hot? Pinhole leaks are very hard to spot. Maybe do a dye test?


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## joecaption (Nov 30, 2011)

Take it to any garage and have them do a simple pressure test. If it's going to leak it will leak at a much higher pressure.


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## Bigplanz (Apr 10, 2009)

I replaced the radiator cap, filled the recovery tank to "max" and drove it around town. No vapor, no fluctuation in temp on the gauge. Hmmmmm.


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## paintdrying (Jul 13, 2012)

Stant radiator cap? Stant is the best! You may have gotten a new crappy cap that will not hold pressure. Ylaps will rent a pressure tester for the radiator, get the dye and light and glasses kit and look for leaks. Should be easy to find that leak if it is making vapor. Cap may have been the problem....


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## Bigplanz (Apr 10, 2009)

Got it at autozone. Cheap generic. The van still had the original cap which was pretty crudy. So far, so good.


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## paintdrying (Jul 13, 2012)

Their is a chance that that generic cap is not holding the proper pressure. With a lower pressure that leak will not show itself.


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## Bigplanz (Apr 10, 2009)

Drove the van this weekend all around town, plus 20 miles on the interstate. No vapor, temp gauge normal, no fluctuation at all. 

Drove to work Monday, no issues. Left work, vapor at the first stoplight. Vapor gone when car fully warms up, heater off. Turn on heater with engine hot, no vapor. No sign of overheating. 

This vapor condition occurrs when I leave work. I park on the 6th floor of a parking garage. Can't think of why that would matter, but going down seems correlated with vapor. 

Pressurized systems with leaks will leak whenever the system is pressurized, not every now and then. Very odd situation!


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## paintdrying (Jul 13, 2012)

take a few days off work- see if condition improves


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## Bigplanz (Apr 10, 2009)

Hey! Great idea! Maybe even retire!!:thumbup:


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## Bigplanz (Apr 10, 2009)

About six days ago, I took off the radiator cap and filled up the radiator. Put the cap back on and haven't had any vapor since. Heat is strong, no vapor, temp gauge reads normal. Oh well. Not gonna argue with, uh, success.


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## r0ckstarr (Jan 8, 2013)

Can't beat a cheap fix.


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## noquacks (Jun 5, 2010)

Glad you got it, finally. Yup, cheap caps, made in Mexico.....If it was indeed anti freeze (looks klike it was) it wasnt vapor, but fumes or smoke. Bigplanz, youve been smokin, not sniffin.


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