2013 tundra overheating

my truck runs fine , no overheating or anything but the moment i put a 21 foot bay boat on the hitch and drive the temp gauge starts to go up. running the heater helps. i am not losing coolant until i tow the boat then the motor gets hot and i lose coolant. this has happened twice. crazy thing is as soon as i stop the temp comes right back to normal. and the slower i drive the cooler it runs with the boat on . i got motor up to temp and turned it off, the fan stops immediately, like the clutch fan is engaged , it does not spin freely . what ya think is bad ???? also i've been dragging this boat for years no problem and my temp gauge on the transmission is not getting hot either . thanks

 

Thermostat would be my suggestion, but I'd look into your radiator cap 1st. if its missing the center piece, you may have a blockage with added coolant pressure.

 

I've chased this on my '19 with about 30k when it started. Thermostat fixed it despite no visible issues. Drained entire system and checked radiator and hose connections for blockages, all was good. All remains good with temps never higher than 197 while towing heavy, long distances, with a headwind.

 

Ok thank u

 

Ok so i looked at cap and center piece is gone. So what’s next ? How do I get this piece out ?

 

Remove radiator. Turn upside down and shake vigorously. Pieces like stuck in upper tank.

 

Remove the upper hose and check down that metal opening on the engine side... Someone has postex an image on what it looks like.. Also replace the cap or you'll be losing coolant out of there.

 

Here is a link to a thread with 2 possible places where it may be lodged at

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

 

Pull the upper rad hose and suck out some coolant. Then look and see if its stuck in one of the little coolant passages there. Pick it out. Thats where mine was and same for several other people.

 

Was just going to post this...

 

toyota can't figure why it's overheating. the new radiator cap didn't dod the trick. evrything else checked out ok. they think either radiator or water pump. gonna go with radiator first i gues