Hi all!

Trying to diagnose my son's truck, a 2002 Ranger with a 3.0 V6. He started noticing it was running hot on freeway drives to school. Not really overheating, but definitely running hotter than normal - between the temp icon and "H". Before he told me about it, he took it into a garage near the university and they put in a new thermostat (unsure of the temp rating or whether OEM or not) and a new lower hose, but the problem remained.

So this morning, I wanted to see for myself. But before hitting the road, I hosed all the bugs and whatnot off the front of the radiator, made sure the belts were tight and the fan could be turned smoothly and had no play. I opened the cap (16-lb/decent shape) and the radiator was full of 50/50 with no obvious leaks. I did the glove test to see if there was reason to suspect a head gasket, but that was negative. So far so good. It got up to normal operating temperature (just under middle of icon) but the water in the radiator seemed still, suggesting water pump, but maybe it just hadn't kicked the thermostat to open. I also checked the upper hose, which was flexible and hot, but the lower was way cooler.

After the running it on the highway for an hour, it did get hot, but didn't overheat. Both upper and lower were hot, and the temp gauge had come down significantly just during the two miles from the exit to home. Then it sat at idle for an hour after and never even get to the middle of the icon. I looked in the overflow, and it was a definitely a bit more...but not even a few ounces. I could hear fluid gurgling back through the upper hose, after shutdown.

I'm leaning toward a radiator problem. I may phone the shop my boy took it to and get the details of the thermostat they installed and whether they pressure tested the radiator. Auto Zone has a lifetime guarantee for $155 and Motorcraft is $320. Anyone seeing something I'm not...? Thanks in advance!

 

Welcome to the forum

Very good testing

Yes, I think radiator is most likely the issue

One more test you can do is to get it up to operating temp or a 10min drive
Then shut it off and pull fan shroud back, just the two top bolts
Then run you hand over rad fins
Should be warmer towards the upper hose and then get cooler towards the lower hose
Should be nice even heat
You can feel cold spots where tubes are blocked, this would confirm radiator is the issue

But I think you are spot on in anycase

Aftermarket(3rd party) are fine to use, radiator is not that much trouble to replace if there is a problem

Fuel Pumps on the other hand are a pain to replace, so I would go with Motorcraft for those, lol

Also always swap heater hoses around at the firewall when doing any cooling system work, or every 2 years
Heater cores don't have a set IN or OUT
Swapping around the hoses back flushes the heater core while driving, it can help it last longer
i.e. if radiator was getting clogged up then heater core may be as well, and very hard to change those on 1995 and up Rangers

 

(I could hear fluid gurgling back through the upper hose, after shutdown) could be air in system or as Ron said... i remember years ago i had a Datsun 510 ..temp gage getting hot on the freeway ..turning on the heater/ high fan speed windows open lol.. brought the engine temp down.... blocked radiator?

 

Yes, gurgling after shut down means there were/are hot spots in the heads
When water pump stops circulating, the coolant next to those hot spots flash into a vapor, so gurgling

If engine is running warmer than it should its good to let it idle for a minute or so to cool down before shutting it off
Like if you pull a long grade or a larger load so temp is running above 1/2 then when you do stop let it idle to cool down a bit before shutting off the engine

 

Could be head gaskets. Mine acted similer To yours but I could not pinpoint that it was head Gasket. Finally tore it down anyway and found that the water passages were weeping through the head gasket in small amounts into the cylinder. I’m replacing them now.