Ah1313

I have posted twice in the last few months about this issue and want one last opinion. For the last year I have had a random overhead condition in my 2000 f150 4.2 l. I could always turn the key off, turn it right back on and drive for hours with no issue when it would overheat. I replaced thermostat and water pump and assumed the issue was fixed as I have been driving it about 160 miles a day with no issue and even towing a duck boat all the time with no problems. I recently made a trip from Oklahoma to Austin and about 6 hours into the trip my temp gauge rose up to about 3/4 so pulled off turned it off and on and it was fine. 10 minutes later the temp gauge would rise and fall constantly between 3/4 and normal so I pulled off checked everything and got back on the road and drove the final 80 miles going 55 mph with no fluctuation in the temp gauge at all. Once home I looked closely at my coolant tank and realized I had lost about half an inch of coolant from the tank. Also when looking at the oil cap there is white sludge on it. The sludge has been common over the past month but I assumed it was because the truck has not been driven but 300 miles over the last year until the past few weeks and it was condensation in the oil. Now I'm not so sure. I have not checked compression or any other tests but I am assuming at this point it's a leaky head gasket or something of that nature. Does this sound like a head gasket issue? I have dealt with them before but never like this. In all other cases I've seen I've been able to see water on the dipstick which I can't with this truck or oil in the water which I can't in this truck. The only sign of water and oil mixing is on the oil cap.

Manuellabour247

The dipstick has always been my verification for coolant in the oil. The cap will condensate too much at any given time. The 4.2's have had problems with overheating and head gaskets, but that's not always the problem. There's more to check before that. Have you checked your fan? If it's not pulling enough volume, it can overheat easier. That would be my first suspect if I were you.

Ah1313

I considered the fan but assumed it to be okay due to the overheating only occurring at speeds of 60+ mph. I didn't mention that before e but it has only ever happened while going 60+

Manuellabour247

Manual or Auto?

Ah1313

5 speed manual, 175k miles. We have two other of the exact truck both with 250k and never had any cooling issues

Manuellabour247

What's the condition of the radiator? Has it been cleaned recently? Are the fins bent over in a lot of places? Has it ever been flushed?

Has the block ever been flushed with new fluid or a cleaning agent?