Help me figure this out. 1995 stock LT1, 180 degree thermostat.. Car runs between 201 and 205 on the highway. Sitting at stop light temp climbs up to let's say 220.. Light turns green get up to speed about 50 mph side roads and the temp starts to drop off all the way down to 194. Then it will gradually return to its normal range of 201-205. My question is why such a drop off after reaching above normal temp?

 

My guess is that the fluid in the radiator cools off a little extra when you are sitting at the stoplight since the engine is idling and there's not so much flow... which also causes the engine temps to climb a little (220) as you describe. Then when you get back up to speed, the engine is revving more and there's more flow, bringing the cooler stuff back from the radiator, so your temp drops back down to 194. Then the whole system stabilizes around 201-205. Just a guess.

FWIW I just got a smog check and they idled the engine for about 10 minutes during. The engine temp (digital) showed 230 which is much higher than I've ever seen during any highway or city driving, or even sitting at lights... probably because I don't ever spend 10 straight minutes idling at a stoplight LOL. These engines run hot though and I would not be concerned unless it got up above 250. The fans kick on late, by design.

 

Sitting at a stop light, there is no air flowing across the radiator fins until the electric cooling fans come on.

The fans will come on in the 228°F range (depends on year), or if you turn on the A/C.
When the fans come on, the temps will drop until it reaches the fan turn off temp, and then begin to climb again. That cycle will repeat as long as you remain stopped with no airflow going through the radiator.

Once you get moving at a speed above 30-45 mph, you will have enough air flowing across the radiator fins and your temps will equalize to whatever your cooling system can function at.

What your describing is completely normal for these cars.

 

My guess, with the thermostat closed coolant doesn't flow to the radiator, temps rise, stat opens, coolant flows to radiator, cooler coolant from radiator flows from radiator to engine, temp. drops and slowly equilibrates to normal operating temps. N'est pas?

Sorry, I typed too slow see #2 &#3 above....

 

This is completely normal for your 95 and for mine

 

I purchased a Hypertech Tuner, @ $100. Tuned my fans to come on sooner on my 95, now sitting in traffic It does not go above 205, the downside is that my fans pretty much run all the time. I feel better it running a little cooler. Here in Mobile, the summer heat and humidity makes it tough for it to cool down once it gets up to 228○

 

 

Nothing to figure out, running perfectly.
Cars always cool better when moving forward and driving (as said).

You can do this. Fans will run all the time and you have lost control of them. I just personally like control of them. And when it get hot, it is harder to bring down the temp, I agree.
Or for $5 you can wire up the fan relays to run wherever you like. (As I did)

 

I ran into the same situation in my '89. Changed out the temperature sensor on the drivers side of the blocke with a sensor from Jags. Gave you 2 choices. 190 and 205. $20.00. yes it does turn on the radiator and pusher fans right on the money and they do both run down to about 184 on mine, but I found that not as scary as lokking at that gague going to 220 and above.

 

I have a 96 LT-4 and used to freak out when the temperature would climb up into the 220 range. On the 96 fans come on is series at 228 ( half speed ) and in parallel ( full speed ) at 230. To help with this I went to one of the corvette suppliers and put in a 160/5 degree thermostat. This seems to help a lot when driving around town. But on those hot days it going to climb up in the 200 + range. Just keep an eye on your hoses and water level. I drain the whole system every other year in the winter. Pull out the two knock sensors, thermostat and rinse out the system. Then add in the right amount of antifreeze and top it off with distilled water. hope this helps

 

The fans automatically shut off about 55 mph. If the vehicle is running hotter than the opening temp of the thermostat @ 55 mph & above it needs a new radiator.

 

nothing really out of the norm one thing that sticks out to me is you have a 180 deg stat and you are running 201 to 205. on the highway, You should be running right at your stat setting. really one of three things could cause this, Temp sensor is off, thermostat is messed up or rad cluged up or air flow is restricted

 

The thermostat sets the MINIMUM temperature that the system will run.

The maximum temperature is determined by a bunch of factors, mainly the ability of the radiator to get rid of the heat. Another big factor is engine load. The temperature will go WAY up on a dyno (or while racing)...

 

I agree that there are other facters involved but the fact is if you have a 180 stat your temps running down the rd should be close to 180. Contray to popular beliefe on here a stat flucates to mantaine the engins temp. From day one that has been the purrpose of a stat.
Perhaps the most common example of purely mechanical thermostat technology in use today is the internal combustion engine cooling system thermostat, used to maintain the engine near its optimum operating temperature by regulating the flow of coolant to an air-cooled radiator. This type of thermostat operates using a sealed chamber containing a wax pellet that melts and expands at a set temperature. The expansion of the chamber operates a rod which opens a valve when the operating temperature is exceeded. The operating temperature is determined by the composition of the wax. Once the operating temperature is reached, the thermostat progressively increases or decreases its opening in response to temperature changes, dynamically balancing the coolant recirculation flow and coolant flow to the radiator to maintain the engine temperature in the optimum range.

I agree that a engine should not go below the stats setting but the stat does a lot more then open once tep is reached. Go to any good Tech school and they should be able to show you a stat in work on a running stand. I agree your temp will go up while on a dyno or raceing but this is not the problem of a stat not doing its job it is the problem of the rad the fans the waterpump not being able to do their job in these conditions. And the op was not talking about these conditions he has talking about normal conditions and with the conditions he was talking about his highway numbers were high.

 

With your thinking installing a 140 stat would cause the engine to run at 140. Of course that wouldn't happen.
A stat does not keep an engine from running too hot, just minimum temp

 

So all the information that GM ford and all the other manfactures mput out is wrong. Tell you what go to Stant fui section you may be inlightened. Of ask some of the top like Rad manfactures. And yes if you have the cooling comp. you cold indead run at 140. If any one wants to belive what you say why do they have stats. Why are they different temp rateings. Whe does every car made run on the highway at the temp the stat is set? investigate your self with the manfactures not somelame guy on here of youtube

 

The function of a stat that was in my post came form the liticture that GM and Ford has been handing out for year in their beging of cooling classes. I said I agree it is the min temp that it lets the egine gets to but it also works it *** off to keep the engine at the set tep as long as the rad and other things are working right

 

a C4 will not run that low. Try it

 

I really have no need to try it. If yuo do not trust in what I say take your stst out of your car you will not be able to controll then temps they will ba all over the place esp with weather changes. Ill be you a whole lot of money you put a stat in the same car the temp will stableize to the stats settings. Did you go to stans site and look at the guesting information? Email dewitts ask them one simple question does a stat flucate to maintain engine temp. If you do not belive me like I said email them check on stants site or probley most thermosts sites

 

Hmm, mine runs at the same temps as many have said, but the temps rise pretty high when it idles for a while. Should I be worried if the fans aren't kicking on until 230s?