Steam in exhaust until engine warm

[stano]

Hi, I've had this truck (98 ranger4.0) for about a month. Has run well for the first 1500 miles and still does. The engine has 117,000 miles on it but I'm unsure how well it was maintained. Now when the truck is started the exhaust is clear for about 20 seconds and then the engine rpms drop a bit and quite a bit of steam comes out of the exhaust. This continues until the the engine warms completely to operating temperature.( between cold and hot on the gauge). The exhaust does smell a little sweet but not exactly like coolant. The level in the radiator and overflow tank haven't dropped noticably but judging by the amount of steam I am seeing I have to assume the water is coming from the cooling system. The exhaust forms a cloud around the truck when sitting. I am taking it in Monday to have a compression check and leak down if necessary but am just curious, does anyone have any ideas why the steam would start after 20 seconds if idling and coicide with a drop in rpm. Also, if the test don't show any cylinder or head problems, would the intake manifold be the next place to look? Thanks for any help!

 

[MAKG]

Is it massively cold there?

The engine is dropping off fast idle, which will cool it down some. It isn't completely warm yet. Almost every vehicle under these conditions will condense water vapor. It is normal to produce water (not coolant) with combustion. If the engine isn't completely warm, you can condense it, especially in cold and/or very humid weather.

It is also normal for condensation to form in the crankcase before a SOLID warm-up; this gets sucked through the engine by the PCV system. It will only produce water vapor this way after the oil gets above 100 deg C, but it will clear out when all the water boils out.

So, unless you start consuming coolant or find a lot of it in the crankcase, I don't think you have a problem at all.

 

[stano]

Thanks for the quick reply. The temp. here is ranging from 15 - 40 F. I took my wife for ride and she laughed non-stop until the thing warmed up and the smoke(steam) screen we were laying down dissipated. Much more than I see with my other ford vehicles. I haven't driven the truck much since I noticed the problem so I think I'll drive it a bunch this weekend and monitor the coolant level more closely. I know a little water can make bunch of steam but I would expect my coolant level to be dropping a bit more if it were involved.
I understand what you mean by the engine cooling down when it drops off fast idle but it is still puzzling to me that the exhaust goes from completely invisible to white instantly, as if someone flipped a switch.

 

[AllanD]

"steam" or "water Gas" is entirely normal...

Let's examine the chemistry a bit...the fuel you use is "Hydrocarbon"

Evenyone understands that when you burn Carbon you get Cabon Dioxide
and a smaller ammount of Carbon Monoxide...

But everyone forgets that the Hydrogen (remember that "hydro"?)
when burned produces WATER.

IT makes a startlingly small amount of water to make a
huge cloud of steam...

That is easily explained by noting that a given volume of water expands
by 1200times when it becomes steam.

When you first start the engine you don't get much steam, that's
because most of the water condenses very quickly inside the cold
exhaust piping.

you start to see that big white cloud only after the pipes become saturated then the heat starts to warm them up... so basically the exhaust "Saves" water for a short ammount of time before it starts blowing it out...

You oughta try driving a 4.0 Ranger with straight pipes (no cat)
around at 6,000 feet in winter (-15F) in Wyoming...

The white cloud of steam NEVER stops.

AD

 

[stano]

Thanks, So this is all just what I want to hear. I'll watch the coolant level but won't spend any money on this truck just yet.