My 92 SC400(230,000 miles) is about to have major surgery...water pump...timing chain, etc. The car was suddenly overheating fairly quickly after about 10 minutes or so. I tried several minor, inexpensive fixes(cap, coolant flush) and did not work. Mechanic checked cooling system...no leaks, put in new thermostat...while checking system the water was being pushed out when hose was off(which I thought a sign that water pump was working) but he thought the water pump not working correctly. After reading about overheating problems on forum I am wondering and hoping that the sensors...coolant and temp sensors might be the root problem...I know nothing about these sensors, so can someone give me a brief explanation about their function and tell me if either one of these could cause the overheating problem...otherwise I am facing a rather LARGE bill for all the planned work.
Thank you, greatly.

 

Have you considered a headgasket issue? Have your mechanic test for gases before you start throwing parts at it... although it may be time for tb/wp anyway...