My 1995 X300 4.0 has started running cool. The gauge never reaches normal and at best gets to the first mark below normal. Often it reaches about a quarter and sometimes moves even lower towards the blue mark. Even on a long run, it never reaches normal, not even when ticking over in traffic.
The obvious solution would be to replace the thermostat - correct? But I see that there may also be a temperature sender and I'm wondering if my symptoms point to the thermostat or the sender.
Is the only solution, to simply replace the thermostat and see if this solves the problem?
Thanks.

 

I'd change thermostat - a cheap easy option that doesn't involve messing with elderly electrics, and it probably is the problem.
You burn no bridges replacing thermostat; if you have trouble with wiring/sensor, which may be OK anyway, it may be creating a new problem

 

Thanks a lot for the prompt response. Nothing really lost I suppose replacing the thermostat. That's what I'll try then.
Thanks again.

 

I had the same issue (as have others) and a change of thermostat cured it for me. Points to consider, when removing the old stat, take note of the orientation to avoid replacing it "upside down". I also got a rubber O ring with mine, which caused the housing cover to sit a bit high. Having read several reports of covers being broken when tightening down, I left the O ring out and had no problems whatsoever. Warms up in a few minutes to 12 O Clock and stays there. So, take care when tightening the nuts on the cover! You can also test the old stat by lowering it into boiling water, and see it opening, or not, as the case may be.
A suspect sensor might send a suspect signal, but shouldn't affect the actual heat/ running cool etc.

 

Once again, a big thanks for the advice. Much appreciated.

 

There are two temperature senders, one for the dash and one for the ECU. If you can borrow an OBD-II "Scan Gauge" or similar, you can read the temperature value from the ECU. If it agrees with the dash, it's quite likely the stat. If it reads OK, it's the dash temp sender.

When my stat failed I couldn't get the car about about 80 deg C.

 

Unfortunately I don't have access to such a device. Got the thermostat on order, so I will fit that and hope for the best.
Thanks for the advice, which if the thermostat replacement fails to solve the problem, might point me towards the senders.
I presume though that if it's 'only' the senders that are causing the low dash reading then that's less of a problem than a failed thermostat as the car will in fact be warming up properly although I can't see it on the dash instrument.
We'll see though what the new thermostat does!
Once again a big thanks for the advice.