First, I would like to apologize for requesting advice/guidance on a problem that has been discussed to death. Iím not car smart.
At this point I have read a few hundred threads here and in other forums and right now Iím overloaded with information and donít know what to do, therefore I ask for your advice.
My car is a Honda Accord EXR 2000, 4 cyl, 112,000 miles; I have owned the car for the past 6 years.
4 months ago the thermostat was replaced (OEM, direct from Honda).
Timing belt and water pump were replaced at 70K miles.
A few days ago when driving back home from work I got in a huge traffic jam and after 25 minutes of very slow traffic I saw the temp gauge slowly rising above normal. Outside temp was 92F and I had the AC on max.
I turned off the AC and opened the windows, the temperature kept rising, then I put the heater on full blast and the temp gauge instantly dropped. I then managed to get back to the office and tried to replicate the problem, but couldnít.
I left the car idle for 30 minutes with AC on max, both fans engaged normally and the temp gauge never rose above normal. When the traffic went down, I drove to my house and the temperature stayed normal for the entire trip (8 miles).
On the next morning I opened the hood and saw that the reservoir tank was full, way above the max line, I checked the coolant level in the radiator and it was low. (my guess is overheating the day before was because coolant in radiator was low).
I put some water in it, took about 16 oz (500 ml) to fill the radiator.
The coolant in excess in the reservoir was about the same amount missing from the radiator.
The next day I took the car to the mechanic for a scheduled tune up (spark plugs, oil change, filters..) and told him about the overheating problem I had. When I picked up the car in the afternoon, the guy say he didnít find anything wrong with the car, he could not replicate the problem, I specifically asked about coolant in the oil or something weird in the spark plugs and he said everything was normal, according to him, there are no coolant leaks.
The next 2 days I went to the office and back (8 miles each way) with no problems, traffic was very light those days. On each trip I checked coolant in the reservoir tank and radiator (when cold) and radiator stayed full, as well as the reservoir (when I say full reservoir I mean really FULL).
Then 2 days ago the radiator was missing some coolant again (about 3 oz, 100 ml) and the reservoir was still full.
Since the reservoir was full, I couldnít tell if the missing coolant leaked or overflowed from the reservoir tank.
Yesterday I put on a new radiator cap (1.1 bar, 16 psi) and took some coolant out of the reservoir with the tools I had at hand (around 7 oz), so I could see if it is going up and down, then took the car for 3 test drives, checking the coolant level in the reservoir with the engine hot after each drive, then allowing the engine to cool down to check the coolant level on the radiator before the next drive.
1st test drive, 8 mi, AC off, 15 minutes, light traffic, no change in reservoir, rad full, temp normal.
2nd test drive, 11 mi, AC off, 25 minutes, light traffic, no change in reservoir, rad full, temp normal.
3rd test drive, 11 mi, AC on, 45 minutes, heavy rain, light traffic but slow moving, no change in reservoir, rad full, temp normal.
Today I drove to work, 8 miles, 20 minutes, light traffic (city), no change in reservoir, rad full, temp normal. Reservoir tank was cold to the touch.
When is coolant supposed to go to the reservoir tank? Im almost sure there is no flow from the reservoir tank to the radiator when the car cools down, how can I tell for sure?
I canīt find any leaks.
No coolant in oil.
No oil in coolant.
No white smoke in the morning.
Any suggestions? What should I look for? What should I check now? Am I crazy for thinking something is wrong?
Thank you for reading this far.