Just got my mk 3 genesis back on the road. Everything fine but the temp gauge never gets above 70 even on a 15 mile run at 60mph.It starts on the peg and rises to just under 70 and the maximum I've seen it is just above 70.

I've checked the thermostat in a pan of water (didnt have a thermometer). It started to open at the point where water just begins to get those tiny bubbles on the bottom of the pan, just before boiling.

I replaced the thermostat and bled the system then drove home another 20 odd miles and it never got above 70 on the gauge.

I realise that the needle should be middle of the gauge ( 90) after 10 minutes of driving.

Could it be the "blue sensor" that I see a lot of posts about and if so is that just a device for sending a reading to the temp gauge or will it affect fuel mixture etc.

Cheers for any advice.

The blue sender is the ECU temp sender, the black one is the one that feeds the gauge.

The blue sender is the ECU temp sender, the black one is the one that feeds the gauge.

Cheers for reply

I thought that it might be a problem with the gauge sender. I could understand if the needle didnt move at all but it starts at its lowest point and rises to 70 where it just stops.

Can the black sensor be faulty and give off a reading like this cos I thought if the black sensor was knackered then it would'nt give any reading at all.

Cheers for any advice

I don't know, I'm in the same situation as you but I haven't actively tried to sort the problem out. I swapped my blue temp sender a while back mind, and it didn't make any difference. My car does go higher than 70 sometimes, normally when sitting in traffic for a while after a healthy rag.

Test the gauge by getting the engine up to temperature, (go for a drive to save time) and then let it idle or run it at an increased idle speed. Wait until the cooling fan kicks in and then see what temperature the gauge is reading. If the fan cuts in at something silly like 80C, then its probably the black sender. If, however, the temperature does rise to about 95C when the fan kicks in then its something in the cooling system is a amiss.

I don't know, I'm in the same situation as you but I haven't actively tried to sort the problem out. I swapped my blue temp sender a while back mind, and it didn't make any difference. My car does go higher than 70 sometimes, normally when sitting in traffic for a while after a healthy rag.

That's excatly my symptoms (forgot to post about the needle rising when in traffic after a run) so must be a thread on here somewhere that has the answer.

I'm gonna try to find a black sensor first from a scrapyard and replace that to see if it fixes it.

I hope its just the gauge giving an incorrect reading and nothing more serious.

Its wroth even going to the scrappy and finding a lowish mileage car and just pinching the sender off it. There so small and easy to take off you might as well just have'em :p