bighank

2005 V6 Mustang with about 120K miles. Was running fine.
Car had a blown lower thermostat housing and leaked coolant all over top of engine. Replaced that and put in new Motorcraft plugs and new lower thermostat housing. That was several months ago. Now it is loosing coolant as seen on reservior with no apparent coolant coming out of thermostat housing and throwing misfire codes on plug #5. Replaced plug which looked OK and still getting MIL and misfire code. Also now overheating.
Just replaced thermostat with Motorcraft part. Old thermostat seemed to have the stem go down about 1/4" to 3/8" further at the bottom part which faces the engine. Same part number for new one. Put in new Motorcraft plug wires and cleaned off coil.
Started car and did not see any leaks on engine.
Went behind car and saw thick white smoke coming from exhaust which lasted for about 2 minutes at idle. Car had not been run overnight so engine was cold.

See on here that cause could be warped plastic intake manifold or blown head gasket.

How do I determine the cause?

Intake manifold would be easier to tackle as I just did the UIM and LIM gaskets on a Ford Duratec. Not sure what it is like on this engine.

How can I pinpoint the cause of the white smoke (steam)?

kevinmalec

A buddy and I replaced out my thermostat housing (upper & lower), sensor and the coolant cap.
I didn't experience any thick white smoke.
Did you make sure all of the hoses are secure with no cracks?
I haven't experienced any issues.

jimkaray

White smoke is water vapor, i.e. steam so that would be a head gasket. Intake manifold leak would make it run lean or possibly suck oil into the combustion chamber. Oil burning would be blue smoke. That could have happened first and caused the head gasket issue but probably not. My guess is you drove too long after the coolant leaked out and overheated it causing the head gasket to fail.

Nuke

Certainly does sound like a head gasket...

Bitter

The best way to check is this way. Sears sells the kit for $57.

bighank

Saw the coolant test kit which is available from NAPA. Looks like it only has a grommet that fits a standard radiator neck and cap. The 2005 4.0 V6 has a degas bottle with a wide neck screw on pressure cap. What do you do with that? They sell the fluid for about $6 minus the plastic tube and grommet. If I get the bottle of fluid and jury rig my degas bottle top will this still work. Is there enough gas going to the degas bottle to turn the fluid from blue to green or yellow?

jimkaray

It should fit fine, just use a rag if you need it to seal better. The fluid is real sensitive it will change if any hydrocarbons are detected. You can also use it to help ID/confirm the bad gasket. After you confirm the head gasket is bad I would pull that plug 5 first and see if it stays blue.

Mr.Ski

Yep. Blown head gasket.