I recently purchased a 2001 Cavalier base with 48k miles & has a 2.2L OHV engine. This was my first Cavalier and I'm pleasantly surprised with it. One thing that I've noticed about this engine is the water temp creeps up a little higher than I'd like. Looking on my scanner, the water temp will typically modulate between 200-206 degrees f. Besides the higher than expected coolant temperature, the car runs quite well. The following is what I've done so far...⏎
- Replaced the OEM 180 deg thermostat with a 180 replacement (I was surprised to see these call for a 180 but it does). I compared the new thermostat to the original (in a pan of water on the stove with an accurate thermometer) and while both operated in approx. the same temperature range, the new one seemed to open a little further.⏎
- I went into the PCM program and set the cooling fan to switch on @ 198 deg f & off at 194 deg f.⏎

Its still doing about the same after trying the above. Yesterday, I noticed something interesting. It 'appears' the replacement water pumps 'may' have a more efficient water pump impeller design. I borrowed the image (below) from a You Tube video by Raw Customz where the gentleman is pointing out the difference that he noticed between the OEM & replacement WP impeller. The thought being that 'perhaps' GM improved the impeller design to help the water flow at lower RPMs (which seems to be where the temperature is more prone to creep higher).

My question is does any of the Cavalier gurus have any thoughts to offer? Either with the new water pump impeller designs or does anyone have any ideas or thoughts to offer.⏎

Thank you for your input

Try this: After it has warmed up all the way and doing what you are talking about, turn on the air conditioning full blast (but not on recirc or max) with all of the windows wide open. Does the behavior improve?

The test here is to keep the fans on as much as possible (because of the AC) and see if it is able to reject that heat from the radiator that it otherwise doesn't.

GM is notorious for "accurate" gauges. By "accurate" I mean that they move around a lot to reflect the changes in whatever they are reading, but they may not necessarily point at the actual values they think they are pointing at. This as opposed to, let'* say, Ford that has a lot of gauges that don't move at all unless they are warming up or have crossed over to the far side of whatever dead bands they have programmed into the gauge telemetry.

When I bought my Roadmaster used, it was a few states away. Went out and test drove it. Drove great and did everything well. Ice cold AC which was great for the desert area that I bought it, and lived in at the time. The next day, took it for a drive through a nearby national park in the morning. Where the temperature gauge would stay at 1/4 (no real numbers on it, just marks) the day before, it was now creeping up to 3/4 then back down nearly to half . . . unless I kept it above about 30MPH for a bit. After checking under the hood a couple of times and watching its behavior, all the while dreading that I bought someone else'* problem, it started to warm up outside. Since it seemed to control its temperature kind of, I turned on the AC and rolled up the windows. It immediately wandered back down to 1/4 and stayed there no matter what I did. I turned the AC back off for a bit, and the needle started moving around like before. Turned the AC back on and 1/4. Then I had an epiphany: The electric fans run whenever the compressor clutch engages regardless of coolant temperature. The thermostat opens like it probably should, but they count on natural airflow to keep fan usage under control until it can't, and then it will spin the fans to control coolant temperature. It would all have been transparent to me if they programmed a dead band in the coolant temperature gauge like Ford does.

120,000 miles later and after replacing the radiator, hoses, cap, and thermostat (the radiator failed and the rest for age), same behavior until the ambient temperature gets into the 30s or lower. Same water pump the whole time. This is the cam-driven unit and the cooling system is reverse-flow like they did for a few years of LT1.

I bet you're seeing the same thing.

If it bothers you, you could work your way down on the fan thresholds until the gauge doesn't move much but the fans do shut off from time to time. Personally, I might do that a bit more, but the car has survived this long the way it was so it'* really not that necessary. If you have a 180 thermostat, I bet 198/194 wouldn't get you much. I'd try 188/184 and see if that strikes a good balance.

Regarding the impeller blades, I like the idea of the wicked cool cast impeller on the left in your picture. It seems like that'* a more intentional design where a stamped unit like the picture on the right is compromised by the limitations of stamping it from a single piece of metal in a press. I don't know which one is technically more efficient, but I've seen the stamped version on all kinds of cars that work just fine until the shaft seal leaks and/or the bearing fails. I've seen a few where the "blades" are rotted away, but that was always on a heavily neglected cooling system. That could never happen to the cast aluminum impeller.

Thanks for the response, as usual, you raise some excellent points to ponder. To borrow from Shakespeare, it may be much a do about nothing. Or as my grandmother often tried to teach me "Don't trouble with trouble until trouble troubles you."

LOL good way to put it!

I came up with a modification to me 2001 Chevy Cavalier to address the higher than desired cooling system temperatures which has worked well and is described in the attached 3 page Power Point slide show. I thought I would share the details in case this might be helpful to other 2.2L engines (Chevy Cavalier, Pontiac Sunfire, some S10 pickup models).

Typo corrected.
I came up with a modification to my 2001 Chevy Cavalier to address the higher than desired cooling system temperatures which has worked well and is described in the attached 3 page Power Point slide show. I thought I would share the details in case this might be helpful to other 2.2L engines (Chevy Cavalier, Pontiac Sunfire, some S10 pickup models).Attached Files

With all due respect, I don't buy it . . . and that inline thermostat business might melt your engine. I'm not surprised that the guy that sells this product suggests it. Not saying it is bad in all situations, but in your situation it would likely create overheat issues.

I can't speak for the evidence presented by the .PPT presentation. I'd have to thoroughly test that in person to believe it.

An engine makes a certain amount of waste heat while doing a certain amount of work. If a supposedly-over-restrictive thermostat caused less heat to appear at the radiator coils, that waste heat would build and build and build until something melted.

The part about the extra cool coolant suddenly cooling the thermostat so much that it instantly closes also doesn't jive. If the cooler coolant gets through the engine to the thermostat and isn't above the thermostat'* open temperature, it will close. This is what happens when you drive your car in Alaska in January . . . and you will approach the other end of the spectrum driving your car in Brazil in August.

And yes, an engine will always run cooler with no thermostat. In this condition, there is less restriction on coolant flow and any coolant that is above ambient is immediately cooled by the radiator.

So let'* talk about the inline thermostat: How hot will the coolant be at the head when the inline thermostat, that is now all the way over by the radiator, sees coolant warm enough to open it? Yes, water conducts heat, but until the thermostat opens, the coolant at the head will get hotter and hotter and hotter. Eventually the coolant at the thermostat gets warm enough to open, and when this allows flow, the super-hot coolant that just came from the head will have the thermostat open up a lot more. Now all of the cool coolant from the radiator rushes in and eventually makes it to the inline thermostat and closes it, then start the process again. This would happen over and over and over until some accidental balance of flow and temperature is found, if that ever happens. Every variation of engine load would undo the trend toward balance. Stop, idle, go, shift gears, fast, slow, etc. In the meantime the head and head gasket are getting a lot more hot and cold over and over.

Then also, oil reaches its designed warm viscosity at the engine'* proper operating temperature. What viscosity is the oil at when it is 30 degrees warmer than normal? Or 30 degrees colder? I've actually done some research on this and nobody seems to give a straight answer publicly.

Then also also, when the head gets hotter, the combustion chamber gets hotter. When the combustion chamber gets hotter, detonation is more prevalent. When detonation is more prevalent, the PCM will back the timing off to avoid detonation. Now the engine is running less efficiently off and on, and producing less power off and on.

Thinking hard about this as I've been typing, I can't think of one engine that I've seen on 120 years of cars, buses, trucks, tractors, motorcycles, boats, or generators that has its thermostat at the far end of a hose. The whole point is to have it close to, or on, the head(*) to allow the proper head temperature to be reached and maintained. Maybe there is one? I've love to see it.

I'm not sure what the coolant pressure is on the back side of the thermostat, but it is more than the cap pressure. Not sure how much more, but a couple of PSI at least. Can the hose handle this on the upstream side? Probably. Why take the chance? If the hose has a defect or damage, the coolant will escape that much faster with a thermostat blocking downstream.

I could probably go on for a bit.

Anyways, I suggest that this is not a good idea. I'd have to see some really good thorough evidence in-person to be convinced otherwise, and even then, I don't see a real gain.

If you do it, I'd be really curious about how it works over time. You'd be the first that I've heard of.

I'll provide occasional updates.

Cool, I'm definitely interested to see how this goes!

Be sure to get all the air out of that hose, or you'll blow a head gasket because the thermostat will never get warm enough to open, even sitting at idle.

The inline thermostat is still working well, I drive the car every day. The temp never exceeds 196 deg f. The range is 186f - 196f.(cooling fan still set to 196f on & 192f off).
I added a check valve to prevent a vacuum from forming when the engine cools (updated file attached).