Noticed last week my 02 seems to be running hotter than normal, mostly at idle. Thought it might be the fan motor but they both run with the a/c on. Nothing blocking the radiator, was the first thing I checked. Had a tune done about 2 yrs ago and put in the 160 stat. Never really noticed before but does anyone with a 160 stat know at what temp the fan should come on? Not throwing any codes which I thought it should do if it was a fan switch acting up. Any ideas?

 

The fans will come on at whatever temp they are programmed for. Some tuners reset the fan temps, so you may want to check that.

The fans have no clue what thermostat you have installed, they are driven by command from the PCM, which also has no clue what thermostat you're running.

 

Thanks for the info. Your right, the tuner did reset the fans during the process along with a few other things since I went to 342's from 273's on my A4. I'm under the extended so if the dealer does anything I'm not sure they'll be able to do much unless its something simple like changing a switch.

 

Before going to the dealer ... what temp, at idle, are you getting ?? It is normal for the LSx engines to reach 230 degrees at idle. If your tuner lowered your fan temp settings, but you had dealer work done recently (like the column lock recall) it is possible the dealer updated the PCM and the fan temps are now back to factory settings.

 

Haven't had anything done at the dealer recently so I know they didn't do anything. I let it sit idling and it did get to around 226 and I got scared and shut it off. Did notice some gurgling sound coming from the recovery and I never noticed that before. Did send an e-mail to the tuner since I'm unsure whether to go see him first.

 

Here's what I would do ...

1) With the engine STONE COLD check the coolant level in the overflow (recovery) tank and make certain that the coolant level is at least at the MINIMUM level (duhhhh ... sorry to be so obvious )

2) If the level is good, and you heard gurgling at 226, I'd be tempted to think the radiator cap may be going bad. With the engine still cold remove the radiator cap and check to see if the coolant level is at the top of the radiator. If there is air in there, then the cap isn't functioning properly.

3) If you decide to replace the cap, be certain to get the right type. I believe our caps are 16 PSI, but more important the cap has to be the type that works with the overflow (recovery) system. Obviously the dealer should have one, but a good parts store like NAPA should also carry the right part.

Other than the gurgling (which may well have been normal if the coolant system hasn't got really hot in a while), the engine getting to 226 is nothing to worry about. Sitting in traffic on a hot California day I will see the coolant hit 230 to 235 and then drop to about 220 as the fans kick into HIGH speed mode. If I continue to sit in traffic the coolant temp will cycle back and forth as the fans kick in and out of high speed mode.

Finally, you really can't overheat your engine .... read the section in your owner's manual (look in the index under ENGINE, it is listed as "Overheated Engine Protection Operating Mode") .... pretty (sorry for the pun) COOL technology.

HTH

 

Thanks, I'll do all that. Learned something though. Didn't know they're 2 speed fans. Is your t-stat stock or did you go with a lower temp as well?

 

My thermostat is stock (195 degree I believe).

In my opinion a colder thermostat only does two things ...

1) Makes the engine take longer to come up to "normal" operating temperature. This wastes fuel, and a cold engine is less powerful than a hot one since the heat (energy) being used to warm the engine is less energy available to power the car

2) If you live somewhere like, say, Cleveland, and take the car out when it is 20 below zero (OK unlikely a Corvette owner will do this ... but bear with me) with a 160 thermostat you'll get a warning message that the engine is actually running too COLD ... the PCM wants to see the engine temp in the 190+ range, and a 160 thermostat on a REALLY cold day may not let the engine get warm enough. (DTC P0128)

HTH

 

All that makes sense though it hasn't really gotten that cold here to give me any problems like that.

 

Actually, neither of those is true. The heat used to heat the engine is just "throwaway" heat that the radiator would have had to expel. The engine isn't using any more fuel to turn the crank or propel the car.

I have run my 160 since new in 2000 and have NEVER gotten a too cold code, even when driving in the 20's. Consider: the PCM commands the car to go closed loop (normal operating characteristics) based on several inputs. The minimum temp for it to go closed loop is in the 120's, WAY below what you will see with a properly operating 160 thermostat.

The checks you suggested are good, I would add when it is started stone cold, monitor the temp gauge and keep a hand on the upper radiator hose. When the thermostat starts to open you will feel the warm water starting to flow. It it gets above 160ish and the hose is still cold your thermostat isn't opening properly and could be your problem.

 

Thanks. Lots of good ideas. God I love this forum! Just got back from a cruise and the temp stayed in the mid 170's which is fine with me. The problem is while sitting it starts getting up there. Guess I'l just have to let it sit to see just when if at all the fans kick on.

 

Neither one of these is true ??

1) "Lower coolant thermostats are reported to INCREASE Hydrocarbon emmisions by as much as 30 percent, at 160 degrees, as indicated in SAE paper #950163" (Quote is from Corvette Fuel Injection - by Charles O. Probst - Bentley Publishers ISBN 0-8376-0861-9)

If you're getting increased HC ... you're not efficiently burning the fuel.

From The Design and Tuning of Competition Engines - by Philip H. Smith - Bentley Publishers ISBN 0-8376-0138-X

"For the engine to be efficient, in every meaning of the word, it must burn its fuel to the utmost possible advantage from the point of view of power production. If as big a percentage as possible of the heat energy is converted to work on the pistons, good design will take care of the disposal of the remainder which is unavoidably wasted." (page 47 - section entitled "Water Temperature")

Note that heat that is disposed is "wasted". If your engine is running at a lower temperature than mine, you are "wasting" more heat - which is power. The limiting factor to engine temperature is fuel pre-ignition caused by hot engine surfaces. The ideal engine temperature (and hence coolant temperature) is as high as you can get it without pre-igniting the fuel. The engineers that designed the LSx engines knew what they were doing when they specified a 195 degree thermostat. Don't you thing they'd have specified a 160 if they thought it would make the engine run better ????

2) While you may not have gotten a P0125 or P0128, you also may have and not realized it, as the first time either of those DTC's set they do not turn on the Check Engine Light. The fact is the PCM checks the rate at which the coolant temperature is rising and it WANTS to see a rapid rise. Just 'cause you may have dodged that "bullet" doesn't mean that the PCM isn't looking for a fast rise in coolant temp. Running a 160 degree thermostat slows the ENGINE's coolant jacket temperature rise. With a 195 thrermostat the ENGINE coolant quickly rises to 195 before the engine now has to "heat" the water in the radiator. With a 160 degree thermostat the engine only reaches 160 before it has to start heating the coolant in the radiator, and therefore spends much longer at a lower temp than a car with a 195 thermostat.

HTH

 

Actually, a 160 thermostat only STARTS to open at 160. Most folks find, like I do, that the engine will operate at/about 180 with a 160 stat. And mine has never had excessive HC counts when it was smog sniffed. The only way the HC count could be that much higher would be if the cats hadn't lit off yet, everything else being equal.

I agree that the best coolant temp is the highest you can run without preignition. However, that temp is really about 180, not 195. At 180 you can retune to run more timing, or at least reduce KR that you would have been getting at 195 plus (just opening there, not steady state).

I have been involved in many dyno tunes on LS1/6 Vettes and all made more power at/about 180, not 200 degrees.

When I say I haven't had any too cold codes that's from checking for them through the DIC and through a Predator data checking device, not by "dodging the bullet" and not seeing a CEL.

GM picked the running temps for very good power and lowest NOx emissions, not the best power.

 

I run the stock thermostate, 192 or so.

What does a 160 degree thermo. do that a 192 doesn't do ??
It only opens sooner, nothing else, when both are open they both allow the same amount of flow.
The idea is to get the engine up to temp. fairly quickly and keep it there, most of your engines wear occurs at cooler temps. Normal operating temp. is around 195 or so, say 200.

Never warm up your engine by letting it idle, get in start it up and then as soon as it "cleans up" (only a few seconds) drive it away slowly, being very gentle with it, it warms up faster when you drive it.

If your car is running warm, start checking things. Change the coolant AND flush the engine, get those lime deposits out of there. (Use distilled water)
Clean the radiator by spraying it with a hose backwards, from the fan side to the front of the car, take it out if you have to.
Install a radiator grill of some type, not too fine of a screen.

Change the radiator cap, I think the new ones are 18 PSI.

I do not know what the C5 water pump looks like, but on other engines ... One thing I found most people miss is the water pump body to impellor clearence, too much clearance and it will not pump the proper amount of fluid, so if your've changed the water pump and then it starts running warm, this may be the reason. I'm not sure what the clearence should be but I bet it says in the service manual.

Oh yea, check your thermostate, make sure it does open at the right temp. Use a candy thermometer and a pot of boiling water on the stove, the wife and kids love when I do that.

 

Have you cleaned out the Radiator and AC condesor?? lots of grass, sand and dirt get stuck up there.