New parts, water pump, 2 thermostats, 2 radiators, 2 heater cores, top radiator hose and I am losing my bloody patience.

For the past year I have been screwing about with this stupid cooling system in my truck. I've replaced all of the above parts and I am still having problems. My heater blows, but only cold air, which would lead me to believe that I have not been able to fill the radiator and block with coolant.

I've never felt like I've been able to bleed the system properly which may be part of my problem. I now have my temperature gauge moving up to halfway and every time I give the truck some gas it tends to drop down to about a quarter. It's almost as if the truck is not circulating the coolant unless it is under some serious load and even at that I don't feel like it is much getting through. When I changed the radiator this weekend I filled it with coolant, when I couldn't get anymore in I filled the block side with water. When I changed the thermostat today, I took off the bottom radiator hose and almost pure coolant poured out as if it hadn't been mixing through the engine, because the block side was a very faint green. Which would support my claim that not much but a little is getting through when I am giving it some heavy gas.

My next theory is that I must have a blockage somewhere in the engine block.

Any other suggestions are very much appreciated.

Like I said, this is really testing my patience, to say the least.

 

Is the top rad hose hot and pressurized? Same for the bottom?

That right there would should coolant circulation which means no blockages.

 

The top hose was hot and pressurized. I didn't check the bottom. My whole radiator was hot to touch on both sides if that makes a difference.

I am not getting any hot air now through my vents, even when I am giving it gas.

 

Your heater core might be clogged but it sounds like the coolant system is fine

 

May be the heater core is plugged.

Is the truck overheating?

The temp guage going down when you get on it, isn't out of the ordinary.

If the T-stat opens right then, the water pump pushes the hot coolant out of the block, and the cooler coolant from the rad into the block, causing the temp guage to drop.

If the engine itself is not overheating, I would suspect the heater core.

Check the hoses running to the heater, see if either/both get hot.

 

He replaced heater core twice. What engine? You can have a block test done to see if you have a blown head gasket.

 

This. ^
Depending on what you feel from the heater hoses will help direct where to check next. If both heater hoses are hot, your problem is probably in the cab. Maybe even a broken blend door or bad actuator.

 

D'oh! My bad. Reading comprehension is bad this morning.


I concur, especially if not getting hot air in the cab is the only problem (no overheating/loss of coolant)

 

Just in case you have not made any progress and are still thinking blockage, remove the thermostat and flush the system. That should clear up any question of a blockage.

 

Craft a small campfire in the passenger seat for warmth.