I recently purchased a 1998 Legacy Outback with a 2.5 & automatic. I got the car very cheap. The car had no heat and would only get to 1/4 on tempature gage. I was sure there was no Thermostat, and it was obvious that the car had overheated in the past, due to looks of engine compartment.
I was correct there was no thermostat. I put in a new thermostat and had system flushed. I could let the car idle for 45 minutes and it would not overheat, and had great heat. When I took the car for a test run (after 5 minutes of driving) it would completely lose the heat at low RPM and the gage would show engine was starting to overheat. If I revved the engine to 3000-4000 RPM the heat would come back and the temerature gage would quickly show a drop back to 1/2 point.
I then replaced the waterpump and timing belt. This time the heat was even better and car ran at 1/2 point on temp gage. After about ten minutes of driving the heat was gone and engine was overheating. Revving the engine would have no effect as it did with old pump. I have tried three new thermostats with the same results.
Here's the confusing part: If I put in a thermostat with a 3/8" inch hole in it, the car will run for days at several hours at a time and never overheat. The bad thing is that it then takes 3 times as long to warm up and has luke warm heat. The temp gage will then only reach 1/8 and less. I tried the thermostat with the hole in it many times during the above senarios and it would always give these results.
Thermostat is in the correct direction. Upon refilling coolant after working on, I warm engine and shut off. Wait for a back suction (Thermostat Opens?) and quickly fill when this happens. Am I not doing something correctly? Any ideas? I've been working on this for over a month.
I have never used a forum before, I hope I am doing this correctly. If not, I apologize for my ignorance.
To further elaborate: the coolant markings in the engine compartment appear to have come from the radiator cap area.
One more item I forgot to mention; when I first got the car and inspected the cooling system, I found the fans did not work and immediately fixed the issue. I assumed this was the reason for overheating in the past, but I guess I was wrong.
I think the first thing I am going to try is replacing the radiator and the cap. I will post the outcome of this.
After this I will look into replacing the head gaskets. I realize head gaskets could be the issue, but am stumped as to why a thermostat with a 3/8" hole drilled in it will cause the car to never run hot and the oil looks good, the overflow never bubbles, and the exhaust shows no burning coolant.
Also, what is the trick to not getting air trapped in the coolant system when refilling? This seems to be a pain in the butt. If you have the knowledge please explain in detail? All the literature states that these cars are known for trapped air, but does not explain how to remove. Maybe it's common knowledge, but I have never heard it explained.
Why is the thermostat placed at such a low level?