All:

I need your opinions as to what this antifreeze leaks might be telling me about the state of my engine. This is a new leak that I found this morning after driving the truck about 30 miles yesterday. I had no issues driving it yesterday.
About the truck: I have a 1986 F-150 302 EFI engine, AOD transmission. 151K miles on the engine. In the past year I have added the following parts: New spark plugs and wires, MAP sensor, TFI module, distributor, starter solenoid, Throttle position sensor, oil sending unit, engine coolant sensor, EGR, and air filter.

From my last post some of you know that at present the engine is running rich and I am getting a new O2 sensor to put into it. I have it done that yet but that would not have anything to do with the present leak.

Oil - After finding the leak this morning I checked the oil dipstick. It is clear - no antifreeze in the oil (no milky color). The oil is dirty but even when I change the oil it does dirty up fairly quickly which I attribute to the age of the truck. It is holding the level and it is not dropping.

Antifreeze - There is antifreeze in the reservoir and it is full in the radiator. Both are bright green in color and I do not remember any drops in the levels in the radiator and reservoir. To my knowledge the truck has never overheated - at least not in any catastrophic way (steam, antifreeze everywhere, etc.), but the temperature gauge never goes far into the normal range - that is unless it is 85+ degrees out when I drive it.

Other observations - It appears that the seal around the oil pan is starting to fail. I am not getting drips or puddles of oil on the garage floor but the sheen of oil around the bolts leads me to believe this. Thanks to the previous home owner I have an oil change pit in my garage so I can look up under the truck and today I did see a little bit of oil coming from the driver's side back by the firewall - seemingly from under the air filter box (maybe near Cylinder #8?).
The truck does idle high when you first turn it on. It returns to normal after about a minute - but I do not think that contributes to the present problem.

I can't think of anything else to tell you about the truck and driving her that might help diagnosing what is wrong with her. I did look online and searched for symptoms for a cracked cylinder head and blown head gasket but this is like self-diagnosing personal health issues using the Web - you end up thinking that you have every disease on the planet but in reality you don't.

Any help is appreciated. Here are some photos.

This is a new leak.




This is under the truck near the back of the oil pan. Exhaust is in the foreground.

 

The photos did not come through fro some reason. Sorry.

Photo #1

 

See that large flat inset plug in the side of the engine block? That's what is commonly called a "freeze plug". There is coolant behind it. If the coolant was not taken care of in it's past life, these can get pin holes in them from rust, and start leaking.

 

I'll 2nd that! I had a pinhole leak in the plug right behind the motor mount after I did a coolant flush in a bottle. Wasn't able to find the leak until I put a pressure testing cap on the radiator so the system would pressurize and you start looking for leaks. I borrowed on from my neighbor who has a mechanic shop but you should be able to rent one from a parts store.


Something like this with the correct radiator cap attachment

 

I had a little v6 ranger a guy gave me. I went to drain the radiator, it would not even drain. I ended up pulling the lower hose, and a bunch of brown coolant came out. I then pulled the radiator and it had about 2 inches of rust sediment in the bottom of it. Cleaned that all out, flushed the block, put it all back together and it ran fine, but after awhile I didn't have any heat in the cab. Flushed the heater core, and bunch of gook came out. Put it back together and a month or two later, same thing happened again, the heater core was clogged.

This time I just filled it with water, ran it a week, drained and flushed it, filled it with water again, week later flushed it again, it kept getting better and better. Finally got it all cleaned out. Ran it for a few weeks, the freeze plugs started leaking, one on each side. Put those rubber type in there, one kept coming out on me. I finally pulled the engine and replaced all the gaskets and freeze plugs, good thing I did, there was a plug behind the bellhousing that was seeping. Been good after that, and it still has heat.

 

I have owned the truck for coming up on three years and have not done anything to the cooling system. Basically because there were other things that needed attention with the truck. But I will now look into the cooling system. Thanks guys! As always, I appreciate the help!

 

This leak is showing at the front of the crankshaft so will be gravitating down from the water pump or timing cover, thermostat housing, a hose, etc or possibly (but less likely), a leak at the intake manifold/head faces.......all of which are above the point the coolant is showing behind the crank balancer.
If you inspect with a mirror & the engine warmed up (but not running obviously), the built up pressure in the system should make any leaks more evident.