I'm new here....take it easy on me :) I picked up a 1999 Ford Ranger 3.0 Flex 219,000 miles for a 4x4.. I drive a 2006 C6 Corvette that has to be parked for the Winter here in southern WV. Replaced front grill and bumper, rear bumper, and tailgate because of rust. Replaced rear shocks and dropped $450 on having the front end replaced (ball joints and tie rods). The guy that sold it said that his son had kept putting water in it instead of replacing the water pump that was leaking out of the weep hole. He put a new water pump on it ( with too much RTV if you ask me). He had Preston's radiator flush in it when I picked it up to flush the system because they had used the red antifreeze for equipment instead of the green. He also had the thermostat out of it. I put in a new Stant thermostat and noticed some bubbles in the coolant reservoir, however the truck ran great temp wise, right in normal range on the gauge. The coolant still had what looked like rust or possibly the flush or red coolant remnants in it. Pulled the radiator and it wouldn't even drain out of the drain plug because of what resembled wet clay in it. Replaced the radiator with a new one from Advanced Auto. The truck had good heat, no bubbles when idling, no white smoke. After I would drive it I would have bubbles in the reservoir again with more coolant in the reservoir than before.I have tried to burp the cooling system to get the air out, parked on a hill with rad cap off, heat on high, and still get bubbles after I drive it. So this evening I tried again, on hill, rad cap off, heat on high, air bubbles came out rad neck, no bubbles in reservoir, but no heat really, just warm. Let it cool off, topped it back off and took out the road. Came back and those damn bubbles are back in the reservoir. So I'm planning on replacing the head gaskets this weekend and checking the heads out to see if they would be warped but doubt it with no "bad" signs of a head gasket leak. Oh yeah, no,oil in the coolant, no coolant in the oil. Haven't done compression test but narrowing down by elimination. Here's my question, could the heater core be clogged up from the junk that was in it? No leak in floor board, no smell of coolant, no fogging up of windshield like if it was leaking. One of the heater core hoses are hot (the one closest to the engine) and the other is barely warm. This along with the no heat all of the sudden is what makes me question the heater core as well. Could all of this be heater core related? I know it could all relate to the head gasket, but searching for a second opinion. The system has been flushed several times with 50/50 coolant added after. Any advice you could give me I would GREATLY appreciate.

 

Hook a garden hose to the heater core and blow the junk out of it.
And the sludge in your radiator I'm 99% sure is oil so you may be right on the headgasket being blown.

 

Thanks for the garden hose tip, I'm gonna start tearing it down tomorrow and I will try that. I didn't even consider the sludge being oil, thanks for that too.

 

Well got it all tore down and took the heads to the machine shop and they are trash. New ones will be here next week. What I thought looked liked wet clay turned out to be some kind of a stop leak that they must have put in it trying to hide the heads. That stuff is junk!!! I'm treating the problem not the symptom. Gonna replace the heater core this weekend so that nothing but what I can't get out of the block will have that stop leak trash in it. They should make that crap illegal to sell lol