160 runs at 170-175 and oil bang on 200

 

Update: I cleaned the condenser and now my temps are 201-203 on the highway and sometimes 205 (uphill). I still think I should be in the 190s.
Coolant, hoses, and thermostat (OEM) are all new and air bled from system.

 

When I initially replaced my thermostat with a factory spec, my running temperatures went up 10° from the initial thermostat from the factory

 

The radiator can look clean from the outside but may have an accumulation of sand tiny bugs and dirt in it. Maybe take a hose from the inside of the radiator and /or blow it out but make sure the pressure is not too strong. Good luck!

 

I did reprogram my fan with my tuner. I will have to double check but I am pretty sure it was set to come on sooner than that. Not sure the exact number.

Having a lower temp stat couldn't hurt things in that regard, I would think. People put them in for a reason, yeah?

 

There have been reported issues with fans that run for a long time - in particular the plug that plugs into the fan assembly can melt.
M...

 

The reported coolant temperature depends on a number of things, but the laws of physics apply. The radiator's purpose is to transfer heat from the coolant to the air flowing through it. The rate of heat transfer depends on the air flow, and temperature differential. The bigger the differential, the faster the rate of transfer for the same air flow rate assuming that the amount of coolant presented to the rad is the same. The purpose of the thermostat is to stop hot coolant from entering the rad until the 'stat set point is reached. This allows the engine to reach operating temperature faster. If the heat exchange can keep up with the amount of heat presented to the rad, then the thermostat cycles a bit - it may open and close, or reach a point where it is partly open. At some point depending on how much heat is being generated, the 'stat is fully open, and the resulting coolant temps are purely dependent on air flow. If the best that the rad and airflow can do is to keep temperatures at say 200, then it doesn't matter if you have a 160 stat except that you might reach 200 a bit slower. The 160 stat won't keep the temps at 160 if the best that the rad and airflow can achieve is 200.

Things that effect reported operating temperatures:

Ambient air temps: The warmer the air flow entering the rad, the less able the rad is to dump heat because the temperature differential is less. Hot air from the AC heat exchanger sitting in front the rad makes the heat transfer less efficient.
Reduced air flow though the rad: The slower you are driving, the less air is passing through the rad. Any obstruction to the rad, such as dirt, bugs, leaves, bags etc will reduce air flow. Fan operation and programming. At some lower speed, insufficient air will flow pass the rad, so the fan needs to operate to generate air flow. There is a table in the computer that can be programmed which dictates % operation vs. coolant temps.
Obstructions in the rad itself: The tubes can corrode - kind of like hardening of the arteries. Foreign material in the coolant: dirt, stop-leak, etc
Coolant flow: any obstructions in the water passages, hoses, etc. A 'stat that fails in the closed position, or partly open. Air bubbles in the system. Defective water pump. Serpentine belt breaks or flips off.
Amount of heat being generated: Biggest factor is engine load, so long uphill stretches, high speeds, towing something, etc. Also, if there are other exchangers in the rad, like the xmission cooler, engine oil cooler will add to the heat load.
Type of coolant: Some coolants are better able to exchange heat than others, so having the correct coolant at the correct mix ratio is important.
Amount of coolant: If coolant levels are too low, there isn't enough coolant to transfer all of the generated heat to the rad.
Sensor accuracy: Nothing lasts forever, so the Hail Mary for high reported temps is that the sensor is defective. Unlikely but not impossible.

So if you think you are running hotter than you should be, keep the above in mind.

 

[QUOTE=Cherokee Nation;1599340758]Thanks! I figured that was probably the case, but didn't realize they ran the trans oil lines all the way from the back to the front. Guess they have to.

That being said, I still don't see how running a lower stat would negatively impact the transmission performance. If anything, I would think it would benefit it especially in the middle of the summer when in traffic. I know it is a ways to go here before the dead of summer hits and would think a 10-15 cooler stat would be a good thing to put in.

I do need to do a radiator flush and fill. Anyone know, how big of a container is needed to capture all of the fluid from the radiator?

 

[QUOTE=SPSandman;1599352996]As I tried to explain above, a lower temperature stat won't help if you are truly stuck in traffic. It has everything to do with air flow. Unless you change the fan table, you are going to see coolant temps in the 221 - 223 range. All the lower temp stat might do is give you an extra few minutes before you reach that because you are starting from a lower set point temperature. These engines heat up really quick. I've got an A6 with a DeWitts rad, and I still saw 221 - 223F when stuck in traffic on a hot day (108F). AFAIK, the engine is designed to handle those temps, otherwise the engineers would have put more put in more aggressive cooling.

 

[QUOTE=FatsWaller;1599353515]You are correct: The shop that installed my cam and headers put in a 180 stat that is what they use...A160 is not recommended and then the tuner takes over and tunes the car and he set my fan to come on at 30% at 195 degrees and 70% at 203 degrees and in this HOT Texas heat the highest temp i see in my DIC is 205 and cursing at 45 mph or less or maybe 50 mph down the blvd it will drop into the high 190s and while I'm moving i check my tranny and oil temp and my engine oil temp will be around 215 and i have never seen my tranny temp over 200 degrees.My setup seems to work great and I'm happy with it for the past 7 years.

 

About 1.75 gallons comes out of the rad drain ****. You have to ensure that the system cap is open.

M...

 

An 07 with the automatic runs right at 203, highway driving in the summer time. Manual will run a bit cooler. Any spirited driving or traffic can easily get it to 220+.

 

[QUOTE=FatsWaller;1599353515]I understand that and as I stated I have adjusted the fan tables with my tuner. I also understand the engineers knew what they were doing and the engine can handle the temps. However, if I can get a lower stat in it can't hurt matters and if I adjust my fan table a bit more it should help as well.

 

When stock on the highway my 2008 temps were 192*F - 198*F depending on the ambient air temps and grade. On incline, temps rose a few degrees. Also, I have a manual, Z51 which I believe has the larger Z06 radiator.

BTW: A lower T-stat with adjusted fan settings work together in lowering the average coolant temps in both city and highway driving. At highway speeds the fan is off because air flow is sufficient. A lower T-stat with fan adjustment starts the cooling process earlier. However, once the T-stat is fully opened and radiator fan at max (90%), then cooling becomes dependent on air flow thru the radiator. If at low speeds, the fan is insufficient at pulling air through the radiator, then engine coolant temps will rise no matter what T-stat you have.

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[QUOTE=SPSandman;1599357539]My belief is that the faster the oil can reach optimum operating temperature, the better it is for your engine. Ideally, an oil temp of 220F is sufficient to boil off water vapor, and retard the formation of deposits and the production of sulfuric acid. So, the faster your oil can reach that temperature, the better. That's why I went the DeWitts route, and kept the stock t-stat. Oil temps come up as fast as they can, and the extra cooling capacity allows a lower duty cycle on the fan, thus extending the life of the fan motor and connector. I don't ever worry now about overheating even in pretty extreme situations. I'm thinking that a lower temp t-stat would make it such that the oil would take longer to reach temps. Maybe it doesn't matter all that much. This is an interesting article concerning oil temps: https://www.hotrod.com/articles/engine-oil-temperature/

 

[QUOTE=FatsWaller;1599359508]Thanks! That is one thing I didn't think of with regard to the boiling off the water vapor. That makes great sense. Though, I would think the temps would still get up there in a similar amount of time, with a 10 degree cooler stat I will have to check what my oil temps are at the times the coolant is at 220. I think it was closer to 230-240, but I could be wrong will check that more closely the next time I am stuck in traffic when it is hot out.

Thanks for the article too will definitely keep that in mind when looking at all of the temps.


Edit: LoL I guess things got confused with the quoting at some point in the conversation. funny.