Overheating engine.

Well here is a head scratcher for you all. I have a 2012 crewmax limited. Has 360,000 miles on it and runs like a dream, most of the time. I have replaced the radiator, coolant and thermostat in the past 8 months. Zero leaks, head gaskets arnt blown, no sign of leaks anywhere, but keeps getting hot, overflow keeps filling up and seams to be boiling. It look like the water pump is pumping but it may be going out. The water pump itself has no leaks, no noises or any signs of damage or going out whatsoever.

WHAT AM I MISSING? So extremely lost.

 

Pull the radiator cap off run the engine. When the thermostat opens you should see coolant flowing. It’s possible your water pump is bad or maybe a bad thermostat even though it’s new? I’d go with an OEM thermostat if you didn’t already?

 

So I took off the new thermostat and put it in a pot of water and brought it to the temp it will open too. It opened. So it’s not the thermostat. I had the cap off but the coolant started to over flow a bit.

 

You need to confirm it is flowing. That overflow is fluid heating up before the tstat open, which then drops the fluid level a bit.

Be careful with scalding as this is all dangerous with hot fluids.

If that proves to show a good water pump, try putting the cap on and look for compressed hoses (they get soft over time). You can also check that the fan is turning, as that clutch could be bad. The cap itself could be, too, and there are ways to tear that also.

 

I had this issue with my Tacoma,
fan clutch was the problem

 

So I lifted the cap. The fluid swelled and was overflowing into the overflow tank. Was bubbling and looked like there was some air in the lines. Once the thermostat opened it kept doing the same thing. Upper radiator hose was extremely hot and the lower hose was Luke warm. I think the fan clutch is ok. Stops on a dime when truck is turned off and the fan doesn’t spin freely.

 

Is your radiator cap ok? I see it reported to happen a lot that part of the radiator cap breaks off and gets lodged in the cooling system and restricts flow causing overheating.

 

The lower rad hose being lukewarm means there isn’t flow through the rad. The coolant bypass to the thermostat housing being plugged by a piece of a broken rad cap is one possibility, as is a water pump impeller that is damaged or slipping on the shaft.

Once it’s hot, crank the heater to hot and the fan to high, what do you get for temp from the heater ducts?

 

Thermostat installed upside down?? Or what @landphil said - could be some debris blocking things. I also wouldn’t rule out a bad water pump. I’ve seen some come out that exhibited zero signs of failure, but had half or more of the fins worn off…

 

We are working on a 5.7L here, right?

 

Well, looks like bad news. What are my next steps? The radiator and hoses are all less than a year old. Radiator is under life time warranty. But I don’t see how the broken pieces could fit into the port hole.

 

I’m going to drain the radiator in the morning, pull the bottom hose out and attach a hose and see if I can flush out the debris. I don’t think it got thru the thermostat into the pump thou.

 

There is an air bleed on the thermostat. It should be in the 12 o clock position. It's a small brass pin that wiggles, it's located radially offset on the thermostat.

Why did you replace the components that you did? Did you have the problem before?

At 360,000 miles, I'd probably just remove the thermostat entirely to take it out of the equation.

 

Last summer on the 4th of July it over heated and blew coolant all over. The upper port that the hose attached to deteriorated and broke. Had to replace the radiator. So I just replaced the hoses and thermostat since I already had it apart. Has been fine ever since.

 

If you do have a 5.7L, look down in here where several others have found the cap pieces.

https://www.tundras.com/threads/2008-tundra-5-7-temp-issue.59514/page-4#post-1933713

 

Yep, smaller gasket is missing. I had a pic of mine but can't seem to find it right now. You probably know what it should look like though. You'll probably need to remove the radiator and run a hose through it to see if you can flush it out. You may need to also remove all the coolant hoses (not the heater hoses though) to check them to see if there are part there too, especially the T-stat. I doubt that it made it into the block though.

Whenever I've needed to drain and refill the coolant, I will fill the radiator and then squeeze both the upper and lower hoses to push out any air. Then with the radiator cap still off, I will start the engine and as it warms up, give the hoses another squeeze or two. At some point, with the cap still off, the T-stat should open and you'll see the coolant flow. If you try to remove the cap after the engine has warmed to a certain point, that won't work.