F-150, 1997, V8 4.6L. 130.000 miles. Very well maintained. Original owner.

Symptom: After only 3 miles , temp gauge goes into RED and oil can light comes on at same time. Coolant spews out of reservoir and almost empties it.
Last time it happened I was next to my Mechanic's shop who measured temp to be only 115F , way below operating temp 210F
Since coolant was not boiling, it appears that somehow pressure is built up and comes out through reservoir. This is the 3rd time it happened in the last 4 weeks. Mechanic replaced thermostat first with an after market and then with a Ford product, however, it seems not to be a stat issue.
During these 3 incidents, engine felt like it was tight and going to lock up.
Prior to the overheating/over pressure problem, the Mechanic had replaced the manifold intake gasket because I had reported lack of power going up hill and during towing. It made no change.
Another mystery is that Oxygen Sensor 1 bank 1 keeps turning Check-engine light on. Sensor has been replaced twice in last 2 weeks.
Mechanic has 40 years experience and says he has never seen anything like it as far as being unable to identify the actual problem.
Any kind of direction on this matter would be so greatly appreciated.
Thank you in advance.
Michael

 

Sounds like a blown head gasket to me. Compression is getting into the cooling system causing an air pocket.

 

Thank you for the reply. Ill have mechanic do pressure/leak test.

 

Thank you for the reply. I'll have a pressure/leak test done.

 

If you're interested in what's involved, I just did a head gasket in my '03. Here's the thread: https://www.ford-trucks.com/forums/1...g-coolant.html

 

read my similar problem on the #8 post down on this link.
https://www.ford-trucks.com/forums/8...lant-blow.html

 

That's quite amazing since the symptoms point to a blown head gasket or a water pump with a broken impeller. Either one is quite simple to verify.

 

Thats what I was thinking.
Puking coolant is a dead giveaway of a head gasket problem.
Sounds like you need a new mechanic.