hi guys
got a 2002 disco
replaced head gaskets, thermostat, coolant temp sensor, the whole nine yards
Now i run it and the gauge says its overheating, but the car does not overheat.
it does not boil water it does not force pressure out, it stays on for 30 min. infra red temp tester say about 190 f but the gueage says its overheating.
Could the new coolant temp sensor be bad??????
please help
thanks

 

Did you check for any hoses leaking Coolant?

 

1. Have you checked and double checked serpantine belt route?

2. ECT is located between alternator and AC compressor on top of the manifold. Wires OK to sensor? No gunk in wire connector?

3. Any water rushing sounds under dash, from air or exhaust in coolant? A pocket of steam could make sensor do strange things.

4. Do you have a scanner that can display live data, or can you have it read at a parts store? In a D2, the coolant sensor is read by the ECU, and a special signal sent to the instrument cluster and the gauge. Normally the gauge reads 9:00, even though temp may vary. If ECU can't see the sensor it may make the gauge read low and the warning light come on.

5. If you don't have a data reading scanner, a volt meter can be used to confirm the output of the sensor. With sensor attached to cable, you will have to use pins to reach the wire, and meter should read DC volts, 212 F is very close to 1 volt, 185 F is about 1.4 volts. There is a chart in the RAVE.

6. Sensor could be telling the truth, where are you reading with the IR thermometer? Seems like to me the curved pipe that brings water out of the block would be a good place.

7. There have been posts about defective stats not opening, but truck really overheats.

 

If you want to get to the bottom of this, PM me your number and I'll be glad to call and walk you thru what to do.

 

thanks for your responses
yes all hoses are connected
@Buzz
wires are clean, no sound in the heater core makes me think there is no air in the system,
connected it to a LAUNCH (EXPENSIVE) code reader and it read the temp at 129*C, but my if thermometer say about 190*F at the pipe exiting engine, witch is a lot lower, thermostat is new.
i just ran if or 1 hr the guage says is overheated but the truck looked great, didnt spill water didnt seem hot (i kind of think i know what an overheated engine feels like ) )
next im gonna try that with the multy meter see what i can come up with
MAN I AM PISSED OFF
but thanks again

 

129 C would be 264 F, which would be hot. So gauge tells you overheat, expensive scanner tells you overheat, IR thermometer tells you around 190.

At 264 F you are very close to boiling with 50-50 coolant mix and 15 psi in the cooling system. So upper hose should be very firm.

At 212 F the Disco is supposed to turn on the electric fan. Of course, this may not be working for un-related issue.

The coolant reserve container gets returned hot water from the throttle body. How warm is it?

How about your thermometer - milk in the fridge should be like 40 -42, your palm should be about 96 - 97..

From what you have said, the truck should be capable of idling with the coolant cap off. Don't open it until it feels cool by touch.

I'm not sure that running a truck that says over heating, confirmed by an expensive scanner, which probably cost a lot more then the ir thermometer, is a good idea. On the other hand, the Launch system is pretty complex and it might be possible you were looking at some other value, in F, like the IAT (incoming air temp) which would be around 129.

I hope you err on the side of caution. If it is 264F, you do indeed have some other problems.

 

thanks Buzz
but tell me this
what if the new coolant temperature sensor from CarQuest for about $20 is bad
what if it sends the wrong info
wouldnt the launch scanner be getting that wrong info as well

it just seems like if the truck was running THAT hot would the container cap not let the pressure out
pretty confused
thanks

 

All correct, and would explain a lot. But if sensor is correct you risk much. If IR thermometer is incorrect, you are also at risk. But if your IR device reads something else with known temp, that adds to you case. The idea of a 50 - 70 degree difference in a metal pipe less than a foot from the sensor is unlikely.

In any lab experiment, the researcher has to have faith in the instruments, or a way to compare them to a standard. If engine was cold, and you pulled sensor, there will be minimal coolant loss, if any. If cable has enough slack, you could connect sensor, and dip it into a coffe cup with warm water. You would have water you could read with IR. Turn ignition (don't start) and see where gauge goes on a known water temp.

Of course at this point you could have changed the sender. And you'll find posts about aftermarket sensors being problems.

 

so i get another IF temp reader.
i live in seattle and today was about 40 F started the disco and the guage come to the middle in about 5 min, i think that a bit to quick.
when the guage started telling me that the engine is overheating the IF temp reader said it was about 204 F or so at the metal tube leading from the engine to the heater matrix
so im thinking that the engine is not really overheating, now the reason i havent replaced the CTS yet is because i have it on back order at the dealer.
what do you guys think about all this
@ disco mike
i tried everything you told me to do, and this still happens

thanks in advance guys

2002 disco

 

While you are reading 204F on the coolant tube, what does your scanner indicate as the coolant temp? Truck would normally get up to middle of gauge in 5 minutes. Because the 9:00 position is really for a wide range of numbers, which you will see when comparing your scanner readings.