Evening all

Did a 440km round trip today from Gibraltar to Seville. Not been doing my usual motorway journeys for 4-5 weeks now since I have been occupied on some things closer to home meaning the car has mainly been sitting in traffic or done 4-5km journeys only.

Checked oil/coolant etc. before I set off. Oil fine. 200ml of coolant brought it to the correct level. So all good.

I noticed as we got up to speed - 130-140kmph that the temperature gauge was reading either zero just above. Stayed like this for the whole journey until we got into Seville and into traffic. It then went to its normal position just shy of the N centre mark. Journey back exactly the same, when I got back I noticed sitting in traffic the temperature back to normal reading again.

I am guessing somethings not right here - any suggestions? Seems to me some kind of false reading rather than an actual issue (like the typical issue with oil pressure sensor ...)

Many thanks in advance.

 

How is the heat from the climate control system? Do you get normal cabin heat??
Do you have an OBDII socket? Can you read data from the DATA Link Connector?

The engine coolant temp can be accessed from the ECM to see what the control module is seeing. You could monitor that.

The INSTPK might not be very accurate.

bob

 

Hi Bob

Thanks for your reply. Cabin heat is fine. The car is 1994 but does have an OBDII socket. I have an Autel Maxisys Pro tablet scanner but from memory it didn't give me a lot of data - I'll try that again tomorrow to see if live data gives me engine temp - whats the acceptable range do you know?

Many thanks
Sam.

 

As Bob says, first check should be with OBD Live data to see if you actually have a temperature issue or a gauge issue.

If the actual temperature of the engine is OK then a couple of things to look at;

- the temp reported by the ecu is from a different sensor to the gauge. You will see two sensors at the thermostat housing. The 2 wire sensor is for the ECU and the 1 wire sensor is for the gauge. So check/clean the connector.
- A poor engine earth can cause the temp gauge to fluctuate. But that normally results in erratic behaviour. Your behaviour sounds consistent. But worth a check.

 

Thanks - presumably the ECU sensor is a two wire with signal and ground whereas the other one has a single signal wire with sensor ground to the block (or stat housing)

I'll try my scanner tomorrow

New sensor seems to be about 7 euros so maybe just replace it if scanner doesn't show anything solid?

Do you know what temps I should see on scanner for normal idle?

 

Sounds like thermostat stuck open to me. Too much cooling in open road conditions, when the thermostat should be restricting flow around the radiator, but isn’t because it is stuck open. When in traffic, the full cooling capability of the radiator is required, so the thermostat being stuck open doesn’t matter.

 

Thanks - yes that would be logical. For the sake of a 7 euro sensor and 11 euro thermostat I will change both.