I recently bought a 98 Dodge Dakota with a 3.9 V6.

The engine runs around 170 degrees and no more. I put in a new 195 degree thermostat, checked the coolant level and condition and NO change in the engine temperature.

I drove it around about (30) miles today and when I go home checked under the hood.

The top radiator hose was warm (not hot) and strangely, the bottom radiator hose was COLD. Not even warm..... ?

The fan clutch doesn't appear to be locked up as it moves (with resistance as it should).

I would think it the radiator was clogged or water pump not pumping correctly, it would be running HOT. Right ?

What the heck is going on with this truck ?

 

take a piece of cardboard and cover half the radiator to act as a "winter front". Being in ohio, the windchill at 40 MPH at 50 degree ambient is about 40 degrees acting on the radiator...it's just doing it's job.

 

How are you measuring the temperature? The sending unit/gauge may not be accurate either.

Do you have heat?

 

The dash gauge actually. It's reading 1/2 way between the 130 and 210 marks.

Yes, I realize it "could" be a gauge/sensor issue, BUT, I have very low heat out put from the heater core and the bottom radiator hose is COLD to the touch as well. This is what leads me to believe it's not related to them.

I'm hoping it's not the new T-stat I just installed.... those bolts were a MAJOR (and I mean MAJOR!) PITA! I'd go replace it with another new one in a heartbeat if it weren't for getting those (2) damn bolts back in place. TIPS ??

 

Don't rely on the dash gauge.

The engine burns fuel and is going to produce heat. The thermostat is what controls how much water goes through the radiator to cool the engine down. The water goes in the top of the radiator and out the bottom. The bottom being colder is normal, the radiator is working.

Thermostats can be defective. What brand did you use?

There is also the possibility that the heater core is partially blocked. It's very common as a vehicle gets older. How hot are the hoses? Again, the inlet should be hot and the outlet cooler.

 

The top hose is supposed to be much hotter than the bottom. It's the intake coming from the engine and the cooled coolant flows back out via bottom hose. That said, it shouldn't be hot/cold... more like hot/ very warm.

I'd run a prestone radiator flush through it. If that doesn't help, the radiator or heater core could be clogged.



Edit: Yeah, get that flush in there asap. It does sound like radiator or heater core. Try back flushing heater core too. You never know if someone used some stop leak crap to clog the system.

http://www.wikihow.com/Diagnose-a-Co...System-Problem

"If you are having heater problems, then you may have a problem with the heater core, which can become blocked and need to be replaced. Find the two hoses that are smaller than the engine hoses, they run to the back of the engine compartment (bulkhead). One of these hoses should feel slightly warmer than the other when the engine reaches operating temperature and heater turned is on. If one is significantly cooler than the other, the heater core is closed off and may need to be replaced"

 

My input:

Don't fix what isn't broken. If the gauge isn't showing overheating, then water is flowing. If the output hose is cold, then the radiator is working, especially being in ohio where it's cold if not frigid already. Like i said, most trucks use winter fronts up north to cover up half the radiator.

 

Duralast. Mid-grade quality one.

I started to redo replacing the new thermostat this afternoon, this time I took the alternator off. I did NOT give me any better access to the thermostat housing bolts. At that point I said "screw it". I'm not going thru the aggravation of trying to get the bolts back in.

I did check the temperatures (by touch) of the heater hoses. There was a significant difference in between them. I am highly suspecting the heater core is partially clogged as well.

A clogged heater core shouldn't make the engine run cold.

The truck will be getting the cooling system flushed tomorrow AM. Hopefully, that will remove any crud that may be blocking up the heater core and keeping the thermostat stuck open.

 

I also had a 'custom' piece of card board to cover part of the radiator for a few trucks and cars, back in Illinois.
Take note not to cover your trans. cooler if you have that in a tow package.

 

Right.

We (Yankees) don't typically block of radiators until the temps drop into the teens and below. When I owned a diesels, I would block them off when temps went into the 20s. .......Man I miss my bad azz Cummins!