# Overheating



## Trainman (Oct 27, 2016)

Need some advice. Got an 8n recently. Had lots of oil in the antifreeze. Suspected head gasket or cracked head. Flushed the cooling system for two days. Then I had radiator cleaned and repaired. Installed new water pump. Installed two new radiator hoses. Installed thermostat (correctly). Put on new 5 psi radiator cap. Filled radiator just to the top of the core (not top of the filler neck). Have performed 3 compression checks with gauge. All three times both wet and dry the readings have been identical. Two cylinders at 100 psi, two cylinders at 105. Have performed two Combustion Leak test (the one with the turkey baster and blue fluid) both tests negative for carbon monoxide in the radiator. Absolutely no water in the oil, no foam on the crank case breather. The problem is every time I accelerate or put the engine under any stress, the antifreeze boils over. At quarter throttle cruising down the road in 3rd or 4th, it will run all day. But put it under stress and the radiator explodes. ANY SUGGESTIONS at what to try next.


----------



## sixbales (May 18, 2011)

Howdy trainman, welcome back!

When you see the temperature rising, and it will rise quickly with a head gasket leak, look for miniscule bubbles in the coolant, and also check for combustion gas in coolant at the time. 

It's hard to get an 8N to overheat, so I feel certain that you have a head gasket leak or cracked head.


----------



## Trainman (Oct 27, 2016)

Thanks sixbales. I keep thinking its the head gasket or head that is why i keep doing compression tests and combustion gas testing all of which are OK. But my next step is to pull the head and see what's going on. While there, I about as well do a valve job. It smokes a lot, compression tests good so am thinking bad valve guides as well. I will also check both block and head with a straight edge. Your comment put me over the edge. I need to pull the head regardless of the compression tests. Thanks again.


----------



## dozer966 (Dec 30, 2014)

Also you might consider having the head magnaflux for hair line cracks.


----------



## pYLON1357 (Dec 2, 2016)

Head gasket leaks can be a fickle thing to detect. If you have ruled out everything else, take the time and pull the head. 

I was involved in the 3.8 liter Ford gas engine head gasket concerns back in the late 90s. We would run every test under the sun and the damn things passed. Pulling the head in desperation was the only way to determine the concern.


----------



## Trainman (Oct 27, 2016)

Thanks for the advice. I have pulled the head and am taking it to the machine shop today for cleanup and magnaflux. I don't see anything obvious but the combustion chambers and piston tops are coated with carbon. I am going to clean block up, look for cracks there and if none, I will replace the valves also. The problem remains a mystery to this point, but something is wrong.


----------

