My Ranger is Cold

[Zergt]

Hey Guys,

Got a 1990 Ford Ranger in a trade. I decided that i'm going to chase every issue and rebuild this thing because its a cool little truck. First thing were chasing is no heat in the cab and the temp gauge is always dead on C on the gauge. The coolant was rusty water and disgusting. Yesterday we pulled the thermostat and ran 6 gallons of water through it till it was pretty clear. We replaced the radiator, upper rad hose and put a new 190 degree thermostat in it and actual coolant. The truck is working as it was before, lift tick louder than the exhaust, but nothing changed. Still no heat in the cab and the gauge still stays buried in cold.

Today I am going remove the heater core and try to clean it but the fact the gauge doesn't go up at all is confusing. I know the gauge is mildly working because when I am driving and I let off the gas or coast in OD the gauge will go up a little bit and drop back to dead cold. After driving for 5 minutes the upper rad hose is warm at best but not hot. Same with the radiator. We will take the gauge out and clean the rust off the reading side but how could the engine be staying under normal operating temperature. Anyone have any idea of whats going on??

Thanks!

 

[Ranger850]

I am far from a mechanic, but it sounds like the thermostat is not working correctly or you have the wrong one and it is opening too soon and not letting the motor build any heat....Now, time for the pros to chime in.

 

[telsar]

Might try replacing the engine temperature sender unit. You can try cleaning the heater core. Here is a video of a method that I used successfully on my 93 ranger XLT:

My 93 has no valve on it the control coolant running through the heater core, it flows all the time. When I move the temp control to hot it moves the blend door.

Good luck.

 

[85_Ranger4x4]

You might put a real gauge on it and see exactly what it is doing. The gauge in the dash is electronic and a ground issue can mess up how it reads.

Also might remove the thermostat and put it in a pot of water with a thermometer and see exactly when it opens.

Also what engine/rad do you have? A 2.3 with a HD two row radiator might be kind of funky to get up to temp too.

 

[Zergt]

Thanks for the replies guys. The thermostat in there now is a new OEM one. I have the 2.9 v6 with a cheap radiator I bought to replace. Its the one that's only about 1 inch thick.

I see what you mean though, the gauge is right on top so I could just plug an aftermarket gauge in. The truck has no electrical issues at the moment but it could still be a possibility.

 

[alwaysFlOoReD]

If the sender unit has one wire then the threads are used as ground. If using teflon tape then make sure some threads are bare so there is a ground.

 

[85_Ranger4x4]

We have had brand new thermostats that are bad right of the box, anymore we always check them before we put them in. When you have things that can take up to four thermostats it sucks to change a bad one you just put in.

 

[RonD]

After running/driving the engine for 10 minutes feel upper radiator hose, if its hot then temp is up and Gauge is wrong

Feel both heater hoses if one is hot and the other barely warm the heater core is plugged

There are TWO temperature devices on the engine, near thermostat housing
ECT(engine coolant temp) sensor, it always has 2 wire, used only by the computer
ECT Sender, 1 wire, used only for dash board temp gauge

If you unplug the 1 wire connector on sender and Ground that wire, with key on temp gauge should go to HOT, if that happens the wire and gauge are OK, replace Sender
And make sure you get a SENDER, parts guys will give to a sensor 9 times out of 10
Sender uses 12volts
Sensor uses 5volts, so while the look the same they are not interchangeable

 

[DannyG]

I concur with RonD on making sure to get the sender. Just replaced the one on my '92 4.0 and the auto store and mechanic told me I needed the sensor.

Where abouts in MN are you located?

 

[8thTon]

Yeah on my Cougar at AZ the sensor listing was easy to find, but I really had to look to find the sender unit. I forget what it was called but it was obscure.

 

[Zergt]

I concur with RonD on making sure to get the sender. Just replaced the one on my '92 4.0 and the auto store and mechanic told me I needed the sensor.

Where abouts in MN are you located?

Im up in Cloud. The truck has been surprising me with other little issues too. The 4x4 has been staying engaged after disengaging and I have to pull the fuse to release the front diff. The engine was also 2.5 quarts low on oil the other day and I had checked it a couple days before. The engine in this is pretty weak. Im trying to figure out if I rebuild it how deep I have to go.