Hi all, need some input on an overheating issue on mom's 99 OBW 2.5L w 115K.
The car overheated the other day while driving. No visible leaks and when I spoke to her she said she had heat from the heater. I checked the car when I got home from work, needed about 1/2 gallon of coolant to fill the rad and overflow tank. I started it and let it idle for a bit. No leaks or smell of coolant. At operating temp there was no heat, then the cooling fans kicked on and continued to run as the temp gauge kept rising. The gauge continued to rise but there was still no heat. No visible leaks, no appearance of coolant in the oil, no sweet smell from the tailpipe, no steam like I've seen on other cracked heads/blocks.
So..... No heat tells me that there is either a blockage or air bubble in the system. How can I check for either of these? The thermostat, if stuck closed, would force boiling coolant into the overflow, correct? This did not happen so I'm assuming the t-stat is OK or stuck open. Maybe I'll replace it anyway. What happened to the 1/2 gallon of coolant that I had to replace?
The car is going to the shop Tuesday but what else should I check first? It's snowing right now (Northeast MA) so I'll have to look tomorrow.
All ideas and input greatly appreciated,