2001 Discovery, non-secondary air

Radiator, water pump, temp sensor, and multiple cooling hoses have been replaced. Fan clutch seems to be fine, system has been pressure tested, no signs of leaks, no water in the oil, no water out the tail pipe. IR thermostat reads at normal temp while sitting (hard to test with IR thermostat while driving).

At idle it runs at operating temp. When moving, below 40 mph, the temp gauge goes up and little red light comes on. According to the autologic it is running between 218.5 and 227.5 while moving, but at idle it runs at about 190. If the Disco has been driven (get hot) and I stop with it still running the temp goes back down to 190. If I let it sit at idle for over 30 min. the gauge goes up, but the IR t-stat still shows it at 190.

Please help.

 

Did have someone else look at the fan clutch and they said it had a little wobble.

 

1. So you have "normal" operation at idle, and overheat indicated while moving (gauge and light), but a scanner attached to OBDII port shows temps 218 - 227? Following lists ideas, but read all first and do free ones first.

2. IR thermometer read of thermostat housing was a number. What do you see with IR of the discharge pipe that comes out of the intake manifold? That's #8 on attached drawing from the RAVE.

3. There are two coolant temp sensors on a D2. The top one drives the ECU and is used to compute the needle position on the gauge. But your gauge is reading way different than normal for 218 F. And red light normally comes on at a much higher temp (284 F). At 212 F your electric fan should come on, does it?

4. The second coolant temp sensor is on the bottom of the radiator, back side, passenger side. It detects a stuck thermostat, if your truck has it. It can turn on a code, but does not make the way2hot light come on.

5. I would compare best IR readings of that outlet pipe, and the scanner reading from the sensor. You may be able to duplicate conditions by revving up at idle. Sensor could be bad, sensor could have slight short or ground on wiring, could have corroded connector. But if sensor is telling ECU it is not hot, and ECU is making hot light come on, who do you believe? The sensor is the cheaper to replace for sure. And you might want to have a second opinion on the scanner, stop at auto parts store and see what coolant temp they show (free read).

6. You could have a large accumulation of mud, leaves, etc. between the AC condensor, tranny radiator (and engine oil cooler, for certain VIN), and main radiator.

7. Fan blades - cupped side goes toward block. Test at idle and above - hold wimpy plastic grocery bag at grille, it should be sucked toward engine, not blown away from truck.

8. Belt route - see attached - very common to have wrong if multiple things replaced under hood.

9. Thermostat - sampling holes could be obstructed on top fitting.

 

1. Only has one sensor
2. in front of the radiator was cleaned out yesterday when the new radiator was installed
3. the temps taken with the IR were from multiple places and those places you suggested were one of the many that were checked, but I have checked them again and everything is normal
4. fan blades are going the correct direction, sucking not blowing
5. the belt pdf does not show the non-ACE routing (I have Rave and factory workshop manuals)
6. did check and the water pump is rotating the correct direction
7. when checking the belt routing I moved the upper radiator hose and it leaked onto the serpentine belt. I think I am having a problem with the belt slipping because of the leak.
8. I have an upper radiator hose assm., fan clutch, and belt on the way. Delivery is awesome! Don't know if I will actually need to replace the fan clutch, I want to look at it a little closer.

 

OK. So if we are to accept the reading of 217+, is the electric fan coming on? I would think that your digital scanner reading does not equal conditions shown on the gauge. Hope that IR can help resolve that (bad coolant temp sensor or unusual scanner reading). If fan is not coming on, perhaps it is the scanner. If fan is coming on, ECU thinks it really is 217 F.

Now for the RAVE, I saw this under engine management for the ECT:


the signal from the inlet air temperature sensor. When the strategy default value reaches 60
Short circuit to earth.
Incorrect mechanical fitting.
Signal fixed above 40 °C (140 °F) will not be detected.
Signal fixed below 40 °C (140 °F) will be detected.



MIL illuminated.
Instrument cluster temperature warning lamp illuminated.
Temperature gauge reads excessively hot.
Temperature gauge reads excessively cold.
Cooling fan will not run.

 

Fan clutch - when engine is warmed up and switched off, a spin and release of the fan should rotate, but not more than one revolution after release. I had one that freewheeled, it was empty of fluid. I could see that at certain low speeds, with clutch not working, coolant temp would rise. But not to 260F +, and then return to normal at idle. It is normal at idle to increase temps over a period of minutes. Usually aq bad clutch shows up first at idle.

 

The electric fan is coming on, it was the first thing I checked when it started doing this. The Autologic is specific for Land Rovers and shows all of the computers and readings. The readings it gives are the same as the gauge, but the IR are different.
Have a few guys taking it out to see if it is actually getting hot or not while driving. It is thought that it is a sensor problem.
I have had no MIL on, until the upper radiator hose clamp was replaced (hose and t were fine, clamp was bad). Then the light came on and it was a misfire on cyl. 8. Did check oil and tail pipe again and no coolant.
Going to test the wiring and connector.

Do you know the temps for the thermostat should be at each of the inlet/outlets?

 

Don't know the temps, my D1 is different. Thermostat spec is start to open at 180, full open at 204. So if we can believe, by scanner and IR thermostat, that we are not over heating, we are not venting coolant thru overflow cap, hoses are not rock hard, etc. that leaves a bad gauge, or one that is getting extra power applied to it via a multi-pin connector with goop on it.

The gauge circuit starts as +12 hot coming out of fuse 13 inside the truck. That runs lots of lights and gauges. The "center" wire on the gauge is connected to the ECM, on pin C0636 # 44. The other side of the gauge goes to earth (frame). So extra gunk on the gauge to ECM connection, to ground, or a skinned wire shorting, would increase the current in the gauge circuit, make it read whatever, and even turn on the red light. Even if ECU thinks everything is OK. Would not bother ECU, as it is switching ground on/off at the ECU end of the cable, so an extra ground means nothing to the ECU. Could be connector in cluster, wire in between, or connector at ECU. Could be at header C0223, pin 18. Pix attached.

 

Well, after repairing the leaks in the system and replacing the radiator, thermostat, temp sensor, water pump (was changed in May), and a few cooling hoses, the truck officially overheats. The gauge, the autologic, and the IR all say that it is overheating now.

 

Arrgh. So frustrated. I let it cool down and restarted it. While idling and checked the gauge and the temp with the IR, and the IR read cool, but the gauge was pinged to the top and the light was on. I am going to walk away from it tonight and maybe think about it over the weekend. I tested the connector and sensor and they are fine. I still have to test the other wiring from the sensor to the gauge, but being frustrated is not going to get any results.
If you have any other thoughts over the weekend please post them.
Thank you for the help you have already given Savannah Buzz, it does help to have another person's thoughts on the situation.