Bostech

I have 2002 RL with 208K miles and during mechanic checkup found water pump was seeping little bit and make bit of noise.So drove it for while (mostly to store) then one week as replacement for my 2006 until one day did not want to start so replaced main relay and worked for 30 minutes then started doing it again.
I scanned for codes and found temperature sensor bad P0118 and P1486 EGRA malfunction.Its also low on coolant.Its been leaking oil for years from rear main seal and sometime will be low on oil but like I said my family did not drive it much except to store.
So trying to figure out how to tell if engine is ruined as I would like to refurbish car since I found good mechanic for good price.

Is it possible car overheated without showing any signs since temperature sensor is bad (did not have that code 2 weeks earlier when I scanned it) and coolant is low.I did not see needle move past half in that time and no smoke from under hood.I did have elevated engine temperature needle few times during idle 3 months ago but only saw it 2 times.
Currently car is parked,it would start ok when sitting for while but might have trouble starting when it heated (I assume has to do with temperature sensor).Engine sounds same as before,I dont notice anything unusual.
Is there any good way to tell if there is any engine damage and if it overheated without obvious signs.

1186KA9

Fix the sensor and bleed the cooling system. Then test with a combustion gases detector. I think there are 2 chambers in a cylinder that you attach to the radiator? Been a while since I've seen one. Either way, you put fluid in it and if it changes color, new HG or engine. The coolant temp sensor absolutely affects how the car starts. It help determines A/F ratios when in closed loop (warm engine).

1186KA9

Make sure that you bleed it properly, I'll post the procedure if needed.

Bostech

Well I might take it to mechanic to do it since I have no proper place.
Ill try to replace sensor but leave it to him for test.I just wanted to know how I can also be on lookout for signs of bad engine.Engine sounds same as before but I am worried due to bad sensor that it might overheat without knowing it.

Would car still show overheated engine even with faulty sensor? Is there backup or another one?

1186KA9

There is another sensor for the cooling fans. Dunno if they warn of overheating though. If the cooling fans are working ok then no real damage should be done. Just make sure to do the combustion gases test anyways.

1186KA9

Think there are 3 sensors. The gauges have their own sensor, the engine has its own sensor, and the cooling fans have their own sensor.