Weirdest thing I have ever seen!!

[ubtripn]

Today I was driving my truck and I floored it just to see the response, it accelerated BUT white smoke started billowing out of the back and I instantly let off. I figured I blew a head gasket. But it went away like it never happened. I drove another 15 minutes. No smoke, no temp change, idles fine and drives fine. What happened??

Don't know if its related but I have had a coolant leak at the back of the engine which may be the intake manifold gasket but I replaced that last summer.

[Stocker]

Are you sure it was smoke and not water vapor? I have seen that happen (vapor) in cold damp weather before the truck gets fully warmed up, when there's a lot of moisture in the exhaust system.

If it was smoke....

[ubtripn]

Oh yea, white smoke. It turned on like a switch and was all over the place, diss-appeared when I let off the gas.

[mr48chev]

Most likely you heated up an blew out the condensation in the exhaust system all at once rather than a bit at a time as normally happens. If your weather is like ours here in the Yakima Valley the last couple of weeks there is a lot of moisture in the air to be drawn into the hot exhaust system after you shut the truck off after driving it. If you have made a number of short trips in it but didn't get it out on the road and warmed up good to dry things out the moisture will build up until you do heat the exhaust up and turn that moisture to steam. One reason those "granny" cars that only go to church, the hair dresser, doctor and store and never leave the city limits always need exhaust work.

[TBONE1964]

I have a couple of questions for you,

Did you notice if the white smoke was coming from the tail pipe or just out of the rear of the truck?

Does your truck have a vacumn operated heater control valve? If yes, it is possible for it to leak when enough vacumn is applied such as when you floored it. It will allow coolant to spray out of it and when that gets on the exhaust, there you go. I am not saying it is your problem. My 72 with factory AC has a vacumn operated heater control valve and it took a while to diagnose it but I had the same syptoms that you are describing.

Exhaust condinsation has to be really hot to make smoke or steam. I may wrong but i dont think your smoke/steam is a result of condensation.

[HotRod C/10]

check the oil and make sure it doesnt look milky.

[ubtripn]

Oil looks great. It mt is vacuum operated so that must be it. I have never heard of a head gasket failing then healing. I did have it warmed up each day so I am not sure if there was any build up but the heater thing sounds like it to me. It was just billows of smoke behind me for a short time. White smoke.

[white 67]

Is your truck an automatic? Mine something like this before when my transmission modulator was going bad. It has a vacuum line that goes to it and it would suck in trans fluid and make alot of smoke.

[ubtripn]

yeah, she's got a 700R4

[71swb4x4]

My wife is always telling me to quit blowing smoke out my a**, maybe you have the same problem???

[72 K20]

If yes, it is possible for it to leak when enough vacumn is applied such as when you floored it.

The vacuum would be strongest at idle or cruise,, weakest at WOT or under acceleration.
If it's a coolant leak, and only leaks at WOT or acceleration, I would say that you have a bad head gasket that is causing high pressure in the cooling system.

Don't know if its related but I have had a coolant leak at the back of the engine which may be the intake manifold gasket but I replaced that last summer.

It might have sprayed coolant from this leak onto your exhaust.

[rico7769]

be nice if the smoke came from the tires. Explains why it stops when you let off. lol

[ubtripn]

lol-all true

[kenbob87]

if coolant is pooling up in your intake valley when you stomped on it could have ran down your engine to your exhaust causing white "smoke" and it could have been just coincidince that it stopped when you let off

[VetteVet]

Originally Posted by ubtripn

yeah, she's got a 700R4

That rules out the automatic transmission fluid. 700r4s don't have a vacuum modulator.

I sure hope the coolant leak at the back of the engine isn't a bad freeze plug.

[deadof_knight]

if its a freeze plug you can be sure itll be the one farther to the back .......

[deadof_knight]

you should try to duplicate the problem when warm and when cold ....

If you do the same thing after you have been highway driving ...... and it doesnt happen
probably the condensate... in exhaust ...... if it does happen again then I would start thinking coolant leak not ahead gasket ..... once blown always blown !

[ubtripn]

I will do so. I am getting to the point of just buying the crate engine and then working on this one as a back up.

[mattfranklin]

When it the engine is cool pull the spark plugs and look for green coolant (or whatever color yours is) in the combustion chamber. It might be as simple as a headgasket (or cracked head if you're not as lucky).

[ubtripn]

Ok, will do. A headgasket can fail while still n ot mixing coolant with oil right?

[Stocker]

Yes it can, it depends on exactly where it failed.

[mattfranklin]

Exactly as Stocker says. Lots of places for a head gasket to fail; your symptoms depends on which part of the gasket failed. Re-reading your original post, I'm wondering if it's a flaky gasket that hasn't fully failed. It can only get worse. One big risk is that you might hydro-lock it. The coolant isn't compressible and you might bend a connecting rod or break a piston if you get a cylinder partially full of coolant then the piston comes up.

[ubtripn]

So it sounds like new gaskets fast are in order. Thanks info the info all.

[Bierkan]

I had a F**d 302 head gasket fail that didn't mix oil and coolant. How I found it bad was standing behind the car, with true duals, and one side was blowing a hint of white smoke while the other wasn't. The gasket was *just* starting to fail.

[ubtripn]

I have true dual. I will have to check it out.