Overheating checked thermostat in boiling water?

It sounds like the radiator is clogged either internally or externally, please go over this guide to see more.

https://www.2carpros.com/articles/engine-overheating-or-running-hot

Please go over this guide and get back to us.

Fire it up

'Listen to fan'

It is sort of freewheeling. Fan rpm is much slower than engine rpm.

Let it get to operating temperature.

'Continue to listen to fan'.

When the radiator gets to the right temperature it will activate the fan clutch (if it is working).

The fan will suddenly get a louder roar to it (it is easy to hear!).

When it cools the radiator back down, the roar will stop, and it is back to the freewheeling mode.

This cycle will continue over and over.

If you are doubting this, listen to someone else's vehicle that has a fan clutch.

If you never get the "strong roar", I would say the fan clutch is not working like it should.

Of course, the mechanical, part (not much or no resistance while turning by hand, floppy, wobble, locked up) would also deem a clutch as 'bad' too.

The Medic

Hi guys. As I was reading this, I was remembering this problem on my minivan. It was caused by corroded and rotted cooling fins on the radiator. Since you replaced the radiator, the next thought is HOW did you determine this is not due to a leaking cylinder head gasket? That isn't a common failure for this engine, but if combustion gases are getting into the cooling system, that can cause the thermostat to close. Thermostats have to be hit with hot liquid to open. Hot air won't do it. Once they open, air getting in SHOULD go to the reservoir, but when engine speed is a contributing factor, the volume of gas could overwhelm the thermostat.

The clue to this is a 200 degree radiator hose will be too hot to hold onto for very long. If the thermostat is closing, and the engine gets to 250 degrees, you'll still be able to hold onto the upper radiator hose. If that hose is much too hot to hold onto, feel the lower hose. If that one is also real hot, the heat is not being given up by the radiator. Possible causes of that are the fan shroud was removed, an excessively enthusiastic butterfly collection stuck in the AC condenser, the rubber seal along the front edge of the hood is missing, or there's unplugged holes in the core support. That's the sheet metal with the opening the radiator sits in. Any of those things can let the hot air from the radiator go around to the front and right back through the radiator again.

Removing the thermostat is not a valid test. Doing that can actually cause overheating because the hot coolant doesn't stay in the radiator long enough to give up its heat. If this happens, you won't have reached a valid conclusion.

You should also confirm the engine really is getting that hot. If you can still hold onto the radiator hose when the dash gauge says "250", it isn't. You need a scanner to view live data and see what the Engine Computer is seeing for coolant temperature. The computer uses a two-wire coolant temperature sensor. The dash gauge uses a different single-wire sensor. Both have an extremely low failure rate because there's just one component inside them, but if a sensor's readings suddenly shoot up faster than engine temperature can, I'd expect to find the sensor has a problem.

Hi,

Unfortunately, he never replied back. The idea that it only happens at 2,000 RPMs is odd. Does it happen if you are at higher RPMs? Also, when the temperature gauge increases, does the engine show signs of overheating? For example, is there any steam or coolant being forced out? Do you hear any boiling?

Do me a favor. I want you to check if the heater works when it is overheating. Actually, do it at both times, when overheating and when it isn't.

Let me know what you find,

Joe

Hi,

I like the idea that you want to get a thermometer. I would suggest an infrared one. Also, the idea that it could be inaccurate is very possible. So, the coolant temperature sensor is a good idea as well.

LP does cause it to run a bit hotter, but it shouldn't cause this. When you pick up a temperature sensor, if you haven't already, replace the radiator cap as well.

Let me know what you find.

Take care,

Joe