Could leaking thermostat cause coolant bubbles?

[Mumbler57028]

Ok so i found a leak at the bottom of my thermostat housing, while in the middle of a tear down to replace head gaskets.

I was getting bubbles coming through the cooling reservoir. not boiling bubbles, I got them regardless of temperature of the water. cool to the touch, or operating temperature.

I would think that a leak in the system could not because consistent bubbling, being that it is a pressurized system and the thermostat housing is at the discharge of the water pump and there would be no suction at that point in the coolant system.. but then again if there was a leak loss of pressure could allow air to be drawn in.

could the leaking thermostat housing cause the elusive bubbles or do I have a leak in my head gasket, and its drawing air from the compression in the cylinder? I want to say that it smells like exhaust in my reservoir. but no water in oil and no signs off coolant on plugs.

My gut tells me i gotta bite the bullet on this and pull the heads.

 

[Mumbler57028]

1999 explorer 4.0L v6 sohc

 

[koda2000]

i've never heard of a leaking thermostat housing causing bubbles in the coolant, however a bad head gasket will. you do not necessarily get oil in the coolant or noticeable coolant in the oil with a bad head gasket.

pulling the heads on a SOHC is no simple matter. are you up for this job?

 

[Mumbler57028]

Oh yeah! Ive got it covered. I hear its crazy but im taking all the proper precautions to allow a smooth experience. Lable the crap out of everything and lots of photographs all the way. Proper tools and manuals for correct torque specs. No short cuts on this one.

Im actually excited for the experience. Im a habitual " hows this work" type person.

Anyways atleast i might have found what caused the headgasket failure.

I spoke to soon on the plugs. The last one i pulled out after my last post had coolant and lots of rust on it.. Its the one on the left with another on the right for reference.