Vapor coming out one tailpipe

dodge
pickup

#1

Guys- I’m going to look at a older Motorhome to buy. It’s been well cared for-but a while back when the guy started it to move it to mow the grass-he said there was "vapor coming out the left tail pipe:. A buddy of his said it had a head gasket leak. The motorhome was last used a year ago-took on a 200 mile trip-no probs-the guy said he checked the antifreeze after seeing the “Vapor” , it was not low. Also he reports no antifreeze in the oil. Is there any way I can get a better idea, when I look at it, if this has a headgasket leak or just moisture in the tailpipe from sitting? I would have to drive it 90 miles home. Thanks-Al


#2

take along a mechanically inclined buddy, and have him do a compression test and a bleed down test. Also take a vacume gauge and have it hooked up while running the engine. These two diagnostic tools will tell you more about the shape of the engine than all the computers in the world.


#3

When you get to the Motorhome, check to see if the engine is a V design, four cylinders forward and four rear. It would also have to have two independent exhaust systems, each including a catalytic converter. In other words, the exhaust from the front cylinders would not coexist in any chamber or pipe with the exhaust from the rear cylinders. If these two conditions exist, it could be a blown head gasket.
To find out, check the oil for yourself to see if it is a clear amber colored(or even dark brown, which is not good either, but not fatal), or gray and milky. Next run the engine until it warms and look for yourself to see if vapor is coming out of one of the tailpipes. Look under the engine for leaking fluid. Remove the air filter and see if it is wet (turn the engine off first).

Head gasket failure presents in several ways; outright leaking, mixture of oil and coolant, a soaked air filter, overheating, and fluid loss come to mind. Also, if the coolant is being vaporized and leaving the vehicle via the exhaust, it is doing it by way of the cylinders. The engine would run very rough immediately after starting and soon fail.

Ask if the radiator fluid was recently changed, and if it has overheated since or prior to the coolant change. If so, don’t buy it.
This could be as simple as condensation, maybe even an automatic sprinkler or something that sprayed water into a tailpipe, but you need to careful here. Unless the price is low enough to justify replacing the engine, skip this purchase.


#4

I agree with Ignoramus that you should get this checked out as per his recommendation.

But be aware that the vapor he saw dripping out of the tailpipe may be normal. Your engine actually produces water vapor. When the gas explodes, the hydrogen and the carbon in the hydrocarbon molecules (the gas) seperate and the hydrogen bonds to oxygen to form H2O…water vapor. That water vapor in the exhaust of a not-yet warmed up engine can condense on the insides of a cool exhaust system and drip as water.

Gas is 1/2 hydrogen. Since it bonds as H2O, that means that every gallon of gas you burn has the potential to produce about 3/4 of a gallon of water. Normall the hot exhaust gasses carry it out the tailpipe and you never see it.


#5

It’s a good price-so if I decide to try nursing this thing home-would it help to run engine with radiator cap loosened one click (no pressure)?


#6

Definitely NOT.
The radiator cap allows the coolant to pressurize, increasing the boiling temperature. This is something you want to happen.

Keep the cap on. As I said before, while you should get this checked the water dripping from the tailpipe just may be normal. You do not want to allow to overheat an engine that might not have a problem at all.


#7

So how did this turn out?


#8

Thanks everyone for your replies-this vehicle was on Craigslist-Boy did I learn something about human nature-got there-didn’t hardly smoke at all-but the brakes were so bad it wasn’t driveable-Thanks-Al


#9

You’re welcome.

Sincere thanks for the update. We seldom hear how the stories end.

Happy motoring.