Interesting question:

Today I'm flushing my coolant -- my 84 T/A's 350 is a bit overdue for one. Anyway, I bought a jug of the Prestone Radiator Flush and am following the directions -- drained the radiator, but the bottle o' stuff in, filled with water and started running my car for the required 10 minutes after reaching normal temperature.

Upon reaching normal temperature, a minor amount of smoke began coming out of the muffler. Nothing -too- major, just a small wisp or two moving into a small cloud. I let it run for the 10 minutes while looking at the general area, then turned the car off.

WHAM. Two or three cycles of the engine after turning the car off, and then a minor backfire (it only sounded about as loud as me closing the car door or the hood closing).

Out of curiosity, could this be relevant to the coolant flush? Perhaps a heater core problem -- I've never needed to run the heater before since I bought it. I tried running the car again with it just in vent (though only for around 4 minutes) and no smoke nor backfire problems.

What the heck is this all about?

EDIT: It's a carbed 350, so no computer issues, thank heavens! It's definitely smoke, not just steam, and it doesn't really have that much of a smell to it. I'm operating under the assumption that it's exhaust.

 

probably just spilled some coolant on the exhaust, hence the steam. I wouldn't concern myself with the backfire, I really don't think a coolant flush could cause that. I would just continue on.

 

Oh, I'll definitely keep on' truckin' with it. I was just curious as to whether that'd cause the backfire -- I was having some vacuum hose issues earlier, too.

As the backfire was very minimal, I'm not freaking out too much about it. I'm just glad it wasn't a rifle crack -- those are always enjoyable and a half.

(Heh heh, in case it isn't too obvious I'm pretty new to 350 carbed engines)

 

You got some after run ? If so, maybe the flush wasnt cooling as well and you got hot spots, allowing some run-on. Was the rad cap on tight?

 

Fifty bucks says you're right, Toe. After removing the cap, flushing with just water, then re-driving it at normal temp for 10 minutes, the car's totally fine. I've got some steam coming out of the hood, though but that's expected when you're just running water.

I've got one of the Stant Lev-R-Vent caps on it, so I'm betting there wasn't a good seal or the lever wasn't down completely.