next step in checking bad headgasket

[Kings911]

Have only had this 86 for 50 miles or so, never noticed smoke before today.

Details on the car that probably don't matter. It has a header and gutted cat.

Details that do matter. Oil and anti freeze are not mixing. Both completely clean. The car runs at mid to slightly bellow mid temps and fans work great.

So I drove the car today about 30 miles. Just having to stop for 10 seconds or so at stop signs. Till I finally had to stop a few minutes for construction. Upon take off a bunch of white smoke came out. Now even at idle a little bit of white smoke comes out of the tail pipe.

The car doesn't seem to lose much antifreeze at all. We used a combustion leak tester and it showed no issues.

With the overflow cap off it did have coolant come out of it? So we put the cap back on and bleed the system and that was fine. Again the car runs great temp wise.

I am assuming there are no chances its not a head gasket. So what should be my next test.

[IdahoDoug]

Describe what you mean here:

"With the overflow cap off it did have coolant come out of it? So we put the cap back on and bleed the system and that was fine. Again the car runs great temp wise."

You say this like a question, plus don't specify what condition the engine was in. Running? Hot? Cold? Just shut off? All of that matters.

So what specifically did you do with the combustion leak tester and specifically what kind was it? A sniffing device? A fluid that changes color in the presence of combustion gases?

[Kings911]

Originally Posted by IdahoDoug

Describe what you mean here:

"With the overflow cap off it did have coolant come out of it? So we put the cap back on and bleed the system and that was fine. Again the car runs great temp wise."

You say this like a question, plus don't specify what condition the engine was in. Running? Hot? Cold? Just shut off? All of that matters.

So what specifically did you do with the combustion leak tester and specifically what kind was it? A sniffing device? A fluid that changes color in the presence of combustion gases?

The combustion leak tester was the kind where the blue fluid should turn yellow if gases are getting into coolant. I followed the directions which was to squeeze the plunger slowly 5-10 times [I think that was the number] and the blue fluid never changed color.

As to the first part the coolant came out of the overflow while the engine was warm and running.

So we shut the car off let it cool a bit and topped off the fluid. Then started the car and bleed the system and it was fine.

Let it idle for a bit and just like when I drove it 30 miles earlier the fans kicked on and the temp gauge stayed at about half

[IdahoDoug]

OK - thanks on the tester. Thats fine.

On fluid coming out the overflow - also fine assuming you had the system full. With the engine warm and running it would be expected to overflow with the cap off.

So if you have a head gasket leak, it is not at a location where its getting combustion pressure. I don't know the 944's coolant system esoteric details yet but if for instance there is a coolant line in the intake manifold/throttle body that would be a suspect location. Or a cracked head at the exhaust valve seat.

You should pull the spark plugs and look for one that's notably cleaner than the others. If so, the intake/throttle body is not indicated but a cracked head at the exhaust valve would be in play.

Doug

Doug

[Kings911]

so 3 spark plugs were blackish and 1 was whitish but still dirty. All of them looked fairly new..

[IdahoDoug]

So, if I were you, I would put the suspect cylinder at a point where both valves are open and use a rented cooling system pressurizer from a local auto parts store. Pressurize at 13 or 15. Expect pressure to drop as fluid goes somewhere. Spark plugs out. You are pushing a bit of coolant into the cylinder. Have someone crank starter w fuel pump disabled n look for coolant mist. Video is wise as it happens fast n you can doubt yourself.