My 2002 Ford Ranger with a 2.3 engine overheated to the point of the engine shutting down. I fixed the broken hose, replaced the coolant and the engine fired up and appears to run fine. However, the thermostat wasn't opening, forcing coolant back into the overflow tank (and overflowing it). I got an error code that contact was lost to the thermostat heater. I replaced the thermostat (the electric one) and it's still not opening -- the upper radiator hose is hot but the lower one is cold. There are no leaks, the coolant is mixed properly, the fuse to the thermostat (#41 under the hood) is good, the radiator is about 4 years old and before the overheat the truck ran fine.

I can't figure out what's going on and I'm pulling out the few hairs I have left. Any help greatly appreciated.

Jon

 

There should be no circulation in the radiator when engine is started cold, so upper radiator hose should stay cold, but heater hoses should warm up, so test for that



What did you fix that caused the first over heating issue?
If a hose broke it could have been CAUSED by the overheating not the reason for the overheating

When coolant gets too hot the pressure in the system spikes very high and will split/break an older hose, so you may have fixed a symptom of the over heating not the source

You could have clogged radiator, might be time to test for that by pulling it out
Or you can drain the coolant and pull off upper and lower hoses
Run water thru radiator from upper inlet and see how well it flows out of lower outlet

 

The engine gets up to 235 degrees (as measured on my engine analyzer) and the lower hose remains cold.

There is a plastic tee fitting on the lower left (driver) side of the engine that connects three hoses together. It's known to fail and did on my truck. The assembly of three hoses and the fitting is over $100, but a replacement tee was found at O'Reillys and that fixed the leak. One of its hoses is the smaller hose that goes to the thermostat. The engine pumped itself dry through the broken tee fitting. There are no longer any coolant leaks.

The radiator is four years old and has been fed only with antifreeze out of the container and distilled water.

Jon

 

I would drain the coolant and test radiator flow, if its OK then take thermostat off again

You can test thermostat with boiling water, 212degF, to see if its opening, should start to open at 180degF so fully open at 195degF
You an just pour the hot water on to it, the wax end/spring end

If radiator is OK and thermostat is opening then water pump is the next stop


You can put a 2004-2011 thermostat in, much cheaper, and leave the electric one connected to the wires and tied up out of the way

Ford found they didn't need an electric/heated thermostat on the 2.3l but they used up the ones they had before installing the non-electric/heated model, and remove that software from the computer in 2004 and up, just FYI

 

Thanks. I'm thinking of using the later model thermostat. What I'm trying to grasp is if the engine overheating could have caused this problem. I meant it got VERY hot -- it shut off -- a couple of times. I had to limp the vehicle home to fix it and it ran five minutes and shut down. I let it cool, then got another five minutes out of it. I know overheating can crack heads and head gaskets, but there appears to be no problems with the engine.

Jon

 

The 2.3l Duratec uses a CHT(cylinder head temp) sensor not a coolant temp sensor and thats what shuts engine down, head temp, and with both an aluminum head and block its less likely to crack a head, or blow head gasket but certainly could happen

You can test for that by squeezing the upper rad hose before starting cold, should be 0psi so easy to squeeze
Then start the engine and squeeze it again, and again, it should be easy to squeeze until it starts to get warm, 2 + minutes

A crack head or bad head gasket leaks the 1,000+ PSI cylinder pressure into the cooling system, which displaces the coolant(the overheating part) and builds up pressure in the system as soon as engine is started so instant pressure in upper rad hose

 

Thanks for the info. Busy this weekend but will get back into on Monday and will check the upper radiator house per your suggestion.

Jon

 

Took another shot at the Ranger today. After trying a couple different things I still couldn't get coolant to flow through the engine -- the top radiator hose was hot and the bottom cold. I decided to go after the Autozone replacement thermostat I installed last week and removed it. It was stuck closed, even when the engine temp on my scan tool was 240 degrees.

I had saved the old one, which I knew was bad. I stripped out the thermostat and just installed the housing. And guess what, coolant flowed through the engine. Yeah, I know not to continually run it without a thermostat, but at least I've found the problem. I returned the thermostat to Autozone and ordered a new one (not from them).

Thanks for the help and suggestions.

Jon

 

Interesting, not to get a part that's bad out of the box that' become a regualar thing now-a-days, but for it to not open, the fail mode on a thermostat is stuck open

Thanks for posting the fix

 

Sad story continues. Replaced the thermostat with another from a different source. Same problem. Took the new thermostat out, put it in a pot of boiling water and it did not open. Removed the thermostat, reinstalled the housing and the water flows, though the engine remains below operating temperature. I've ordered a later model thermostat without the electrical heater in it. Don't know what else to do. And now the radio died!

 

Perhaps it's fixed! I installed a thermostat from a later model Ranger (2004-5) that did not have the electric heater. Same connections, same bolt-up pattern. Seems to be working. Operating temp around 225-230. That sound normal? I've left the old thermostat hooked up to keep the "check engine" light from coming on and reporting a lost connection to the heater. I believe you can put a resister inline to eliminate that issue. Anyone know the value?

Jon