Hey there.

My 04 disco ii seems to have the fans on a lot even thou ac is off. Just had head gasket replaced, water pump, grey tstat, belt done.

I swapped the grey tstat out for a oem one just to see if it was the tstat but now it comes on even more frequent. Temp gage inside the truck is in the middle. But the fans are always on. But not when turned off.

I bleeded the cooling system but still comes on after driving

Any ideas?

 

you need to know what temperature your truck is really running at, the gauge on the dash is useless.
Find yourself an OBDII scanner that gives you real time information and see what temp. it is really running at.
You condenser fans a set to come on a 210 degrees +/- your truck will easily run over 210 without the gauge moving at all, I think Savanha show a picture of a truck running at 240 degrees and the dash gauge it still dead center.

 

1. Using the dash gauge to measure temp is a waste of time. It is programmed to show 50% from about 130 - 240F. And the red warning light turns on at 284 F, long after engine damage has been done. Note the pic below, two different trucks, two different temps, same gauge reading. You need a scanner, Ultra Gauge, or blue tooth adapter plus smarty phone app to read temps from OBDII port.

2. The AC condenser fan is controlled by a relay in the fuse box under the hood. The relay could be fried and stuck closed, or the signal wire that operates the relay could be grounded by a wire in the engine harness being crushed. Look on attached diagram, and unplug the cooling fan relay (R4). Fan should stop. Swap relay with another, like head lamp washer (R3).

If still acts up, then relay is being switched on by a wire that leaves the socket it plugs into being shorted to ground. That wire is green with white, and runs all the way to the ECU connector C0636 pin 31. Of course, outside chance ECU could be damaged.

3. Put the gray thermostat back in and run 10 - 15 F cooler.

4. Consider that But the fans are always on and seems to have the fans on a lot even thou ac is off are two very different conditions. "Always" would indicate fans start as soon as truck is cranked, as with relay problems mentioned above. Running a lot or more frequently indicates coolant is above 212F, which it should not be. You will want to review belt route (if water pump running bassackward cooling will be bad), and test radiator for blockage. Feel or use an IR thermometer, measure heat on fins top to bottom, same vertical line, engine warmed up, engine switched off. Should be no more than 10F spread. If sludged up, rad will be cooler on bottom. Half a rad could make truck not able to stay under 212.

5. Coolant sensor could be bad or wiring disturbed.... if you are lucky.

 

I put the grey Tstat back and bleed the system using discomikes method. The coolant sensor has already been changed. It could be a clogged radiator. Cuz it only comes on when it's warmed up. I'll see if it comes on again after it cools for a bit. It didn't come on this am after I bleed it and warmed it up. If it does I may have to bring it to a shop to have them check out the radiator since I don't have access to an IR or ultragage.

 

You can also test by Mark I Palm Reader, warm up truck until gauge first hits center, turn off, and feel the fins top to bottom, much colder on bottom would be suspect. Swing by a parts store for a free code scan, and let them demo one of their live data scanners, check coolant temp.

 

My bet is that you are running over 212 all the time. Ultragauge FTW

 

The fan doesn't come on as much now. After I changed the tstat and bleed it. I also changed the coolant cap.

I did notice that the fan spins when in park and I raise the rpm. Is that normal?

 

Yes, as you increase feet per minute of air flow, the electric fan which is just sitting there, will have the blades begin to spin by the force of the air. So that is a good thing, in that the fan is not siezed.

 

Replace:

T-stat with 180 degree

Fan clutch with heavy duty hayden

Radiator $225 from Rockauto.com


Bleed - using Discovery I method.
Raise coolant bottle. Take off the cap on the coolant bottle.
Run engine for 8 to 10 mins at 1,500 to 1,800 rpm.
Now go to idle.
Put in more antifreeze to fill line.
Put cap back on.
Put bottle back in clips.
DONE.

 

What is this Hayden heavy duty clutch of which you speak. Been off for a few days...