Disco help please

[MoGas]

Got a call from a buddy.

2004 Disco.

Wouldn't start. Killed battery trying. Got it jumped and it finally started after several attempts.

Check Engine light on.
No temperature indication, but high temp light on.
No heat from vents.

Started driving home and all of a sudden, the high temp light goes off, temp indicator jumps to normal position, heat starts to blow out of the vents.

Turned into driveway and the vehicle returns to the previous condition of no temp indication, high temp light on and no heat from vents.

Any ideas?

Thanks,
Dave

 

[Disco0311]

Maybe he has to check the cooling system, from the reservoir to all the lines going to the radiator.

 

[Brian McVickers]

If there is coolant in the system it could be a sensor issue.
The scenario of symptoms sounds familiar, I think I have heard of it somewhere before on Dweb or LRR. If the sensor, cant remember which, is bad or shorting it will not allow the engine to start and affect the other things mentioned.

Brian

 

[MoGas]

I haven't seen the vehicle personally to assess exactly what is going on. I know on some vehicles, the way the temp sender is located, it is possible to not get a high temp reading on the indicator if there is no coolant at all in it because it needs to be immersed to read. I will swing by his place tomorrow and get a full assessment to you.

Thanks,
Dave

 

[david despain]

I haven't seen the vehicle personally to assess exactly what is going on. I know on some vehicles, the way the temp sender is located, it is possible to not get a high temp reading on the indicator if there is no coolant at all in it because it needs to be immersed to read. I will swing by his place tomorrow and get a full assessment to you.

Thanks,
Dave

need to pull the codes.

the temp sensor does'nt drive the needle. it tells the engine ecu what the temp is. then if its within a certian range the ecu puts the needle in the middle of the band so that you dont really ever know the temp of the eng as long as the temp is "acceptable". appearantly people dont like to see the needle moving around.
need to use an OBDII scan tool that shows sensor data in real time to see what the real temp of the coolant is, this will be the temp that the eng ecu is seeing from the sensor.

does this truck have SAI? if so then i think it has at least one other temp sensor. i know the pn for the radiators is different and i think its to mount another temp sensor to tell you if the thermostat is opening or not.

edit: i just read that system (SAI and thermostat sensor) and it should have nothing to do with this problem.

but i bet its got blown head gaskets and thats why no heat and no start

 

[cruiser guy]

the temp sensor does'nt drive the needle. it tells the engine ecu what the temp is. then if its within a certian range the ecu puts the needle in the middle of the band so that you dont really ever know the temp of the eng as long as the temp is "acceptable". appearantly people dont like to see the needle moving around.

You've GOT to be B.S.ing us? Are you serious? The sensor doesn't drive the needle, but the ECU simply sticks it in the middle of the range?!?!? It's just a glorified idiot light then!

 

[david despain]

glorified idiot light, yeah thats a good way to put it. it will tell you once its on its way out of the safe range, and it will tell you before its warmed up. but yeah. i have no conclusive or even circumstantial evidence but i bet there are LOTS of new cars that operate this same way. people like to see the needle in the same place. it makes them feel safe. they think something is wrong if its wiggling around.

here it is straight from rave:

The engine coolant temperature gauge is an analogue gauge with three sections: cold temperature; normal operating
temperature; high temperature. Under normal engine operating temperatures the engine coolant temperature gauge
will display in the centre of the gauge. When the engine is cold e.g. from first start-up, the coolant temperature gauge
will display in the cold band. When the engine is over heating the temperature gauge will display in the high
temperature band. If the engine coolant temperature gauge receives no input or the input is out of range the
temperature gauge will read cold and the high coolant temperature warning lamp will be illuminated.
The input signal is a PWM signal from the engine coolant temperature sensor via the ECM.

 

[david despain]

The ECT sensor is located at the front of the engine adjacent to the coolant outlet pipe. The ECT sensor forms a vital
part of the ECM operating strategy, and therefore the optimum control of the running of the engine. Richer air/ fuel
ratio is required at lower coolant temperatures such as cold starting. Coolant temperature information from the ECT
sensor is also vital to enable the ECM to weaken the air/ fuel mixture as temperature rises to maintain low emissions
and optimum performance.
In the event of an ECT sensor signal failure any of the following symptoms may be observed:
l Difficult cold start.
l Difficult hot start.
l Driveability concern.
l MIL illuminated.
l Instrument cluster temperature warning lamp illuminated.
l Temperature gauge reads excessively hot.
l Temperature gauge reads excessively cold.
l Cooling fan will not run.

P0116 Engine coolant temperature circuit/range
performance problem
Signal differs too much from temperature model for
longer than 2.53s
P0117 Engine coolant temperature circuit low input Open circuit or short circuit to battery supply
P0118 Engine coolant temperature circuit high input Short circuit to earth




this is the system description from the rave cd. sounds like your culprit is the sensor. at least thats where i would start. easy and cheap, realitivly speaking.
on a side note. i had 95 f-150 back when the expo was still brandy new. it had a bad temp sensor and it was always hard to start when warm. from cold, no problem but once it warmed up for about 5-10 min. it was hard and took a lot of cranking. swaped sensors and no problems anymore.

 

[david despain]

a little more info

The high engine coolant temperature warning lamp within the instrument pack utilises a red LED and a clear legend.
The ECM illuminates the LED when it detects the engine coolant has exceeded a temperature of 121 °C (250 °F) and
switches it off when the coolant temperature drops below 118 °C (244 °F). The ECM also illuminates the high engine
coolant temperature warning lamp when it detects the PWM duty cycle to the temperature gauge is out of range. If it
is greater than 94% duty cycle when the engine is hot, or less than 8% duty cycle when the engine is cold, the engine
coolant temperature gauge pointer will indicate cold, thus alerting the driver with an additional visible warning.
When the ignition is switched on, the ECM illuminates the LED to provide a self-check, providing there is no fault it
will remain illuminated for 3 seconds or until the ignition is switched off.
The response of the engine high temperature warning lamp varies according to engine type and market, there are
three conditions:
l V8 - Gulf.
l V8 - all markets except Gulf.
l Diesel - all markets.
The vehicle configuration determines which condition is set.
The PWM duty cycle thresholds for illuminating and extinguishing the warning lamp are given in the table below.
The power input for the LED is supplied by the instrument pack via fuse 27. The ECM controls the earth path to
illuminate the warning lamp.
Market Lamp on Lamp off
V8 - Gulf 79.8 ± 2% 77.8 ± 2%
V8 - all markets except Gulf 77.8 ± 2% 75.7 ± 2%
Diesel - all markets 78.8 ± 2% 76.8 ± 2%



so according to this if the sensor is out of range you will get the same symptoms you have described. further strengthening our sensor as the culprit