My truck is acting like it has a bad thermostat.

The Water pump is circulating coolant, I can see it in the reservoir, and the heat is working perfectly.

I've drained it a few times while putting in a new thermostat, but I just boiled the old 180, and it opened up right at 180.

I drained the coolant from the bottom of the radiator and was able to pull air through the radiator with a vacuum.

I have the tube out of the thermostat that is vertical going up to the coolant elbow and the radiator, the smaller 45 degree tube to the water pump.

I am not sure how to proceed aside from drain it again, and put the tested thermostat back on.

Can anyone think of anything I am missing? It's like there is something obvious, but I am just not seeing it. The Engine temp sensor is new, radiator relatively new, and the thermostat should be working.

All I can think of is obstruction in the lower radiator hose.

 

Welcome to my hell

 

You could be getting air sucked in through a bad coolant reservoir cap, bad throttle body heater/connections, or bad bleed screw.

Air in the system is going to make everything funky.

Consider the inline thermostat mod, plugging (just temporarily!) the coolant overflow tube, and duct taping or otherwise double-sealing the bleed screw.

Remove and plug the throttle body heater+tubes for a test, too.

Also, check your oil level just in case you are super low.

Add in Water Wetter to pure distilled water as a coolant temp test.

Check fan speed/connections for radiator.

Consider adding a $5 heat sink around your oil filter.

Test your coolant for exhaust fumes (just in case).

Check your air flow through radiator. Discos have some interesting air shrouds next to the headlights, and verify upper+lower main fan shroud is all intact and properly directing airflow.

Maybe consider removing the belly pan tray?

 

 

 

 

You've done a **** ton of work on this engine, hate to see these issues. Hang in there. You've had the cooling system open a bunch it looks like. Tighten all hose clamps again, inspect all hoses, double check belt routing. When u do the bleeds, front of truck raised and res bottle raised too. Something somebody says is gonna get this thing right...

 

fwiw- did the inline mod a couple years ago and have had zero cooling issues since then. It's pretty straightforward and makes the system a bit simpler and more stable.

 

Thanks. I am going to tighten everything up, step away, tomorrow go to Autozone get coolant test strips, and the pressure tester. No sense is continuing to dump coolant everywhere.

If the pressure tests is good, there are no exhaust gases in the coolant I may do the thermostat mod, because at that point it is that or the water pump, and I can see the water pump is working.

 

Thermostat still not opening. Everything is tight. I got the top hose onto the current thermostat really really far down, thought maybe it was not bleeding.