Hi all, Happy Presidents' Day weekend! Hoping the gurus on this group can help me with another issue on my '89 Corolla SR5. It has 147k miles, carbureted 2AF, and 4-speed automatic with overdrive. It runs fine, gets 36mpg on the highway. It's on its original radiator and I do get the coolant flushed about every 2 years/
10k miles. The coolant level looks good and the coolant level looks right. The exterior of the radiator looks clean and looks good. The grille, which is quite small to begin with in a Corolla SR5, is unobstructed. The water pump is original from 1989. The car normally "likes" to run at 40% of max temp, which is what I notice with other cars too. When I'm on the highway at 60-70mph though, when it's between 2400-2800 rpm, the temp often creeps to about 75% of max temp, and then either the cooling fan will kick in or I'll get to a downhill area and the temp will fall. After it goes back to 40% of max temp, it may reach 75% of max temp in about 5 minutes. Between 60-70 mph, the car doesn't have a lot of power, understandably (2500 rpm in a 1.6-liter engine) but it doesn't feel like it's lugging or struggling either. On purely level ground it probably is usually at 50% of max temp. NOW, if I turn overdrive off, say at 65 mph, then the RPMs rise by 1000 and the temp immediately falls to 40% of max operating temp within 5 seconds. Likewise, if I drive at 75-80 mph, the car is at 3500-4000 RPMs and also will run at 40% of max operating temp. If I floor the car for quick acceleration, it'll also downshift, accelerate, and the engine temp drops quickly.The thermostat and fan switch were all replaced in the past few years, and the car operates at 40% of max temp under low-strain conditions like local driving, so I don't believe either of these is faulty.
Unfortunately I didn't pay very close attention to engine temp before so can't remember how long this has been happening. I don't remember it was happening when I bought the car back in '99. It may have been this way for a year or more, I just don't know.
Questions:
- is it bad that the engine temp is reaching 75% of max temp if I drive between 60-70mph in overdrive? Or is this normal? I worry that the engine isn't supposed to be above 40% of max temp for too much time. Also, I worry that cooling fans aren't meant to be kicking in every 5-10 minutes, and that the fan could easily fail if it needs to do so.
- given that the engine temp is cooler when the engine's revving higher, I'd have to conclude this is because the water pump is spinning faster and therefore circulating more fluid when the engine's RPMs are faster. When you see this situation, where the temp's high in overdrive, does this mean: a. don't worry about it? b. get a new water pump? ($$$) c. get the radiator "power flushed"? (don't object but am always a little leery of places that want to sell "power flushes") d. get a new radiator? ($$$) e. add more coolant though the coolant level looks ok?
Please let me know what you think, John