Overheating Issue - 1.6L Engine
I have a 1991 Toyota Celica ST with a 1.6L engine. I recently replaced the water pump (because it failed) as well as the radiator (it leaked). However, after that I have had nothing but issues with overheating since then, and I need help in figure it out. Trying to find manuals online is far harder than I thought it would be. Here are the symptoms:
Each morning I have a commute of about 30 miles. For the first 3 miles, I drive 35-45. Then for the next 5 miles I drive 60 to 65 until I reach time. Temperature during this time is normal. I slow down to 25 mph through a town for about 5 miles, then speed back up to 60-70 mph for another 18 miles. During this time, the temperature gauge slowly creeps up.. even with the heater on and settles at about 80% max temp. The temperature drops dramatically if I slow down to 50 mphs, and then goes back down to normal in 25-35 mph driving. On the way home, the same cycle repeats, but much quicker.
Here is what I have done so far, not in order:
Replaced the radiator three times:
- First Radiator had a major coolant leak right out of the box.
- Second radiator appeared to be working, then considering the previous radiator, the ongoing overheating issue made me think it had a blockage.
- Third replacement radiator acts like the second.
Replaced the thermostat three times:
- All three appeared to be fine, but I replaced them anyways because it could have been it.
Replaced the original water pump.
Flushed out coolant at least a dozen times, and there are no leaks currently.
Hosed down the air conditioner radiator.