Running cooler than the thermostat...

[bszopi]

Ok, so on the trip back from the meet, I noticed something I thought was kind of strange. I was going around 78mph and for long, open distances (ie, not many cars around). I looked at the temp gauge and noticed the coolant was around 180º. Now, I have a stock 195º thermostat in there, and it usually stays right around 200º for normal driving. I just thought it seemed wierd that the coolant could be running over 15º cooler (lowest I saw it go was 177º) than what the thermostat was at. I figured with the speed and air that it would run cool, but not that cool. Any input?

[RednBlack]

That does sound strange. Especially on a sealed system. Fan relay didn't freeze up did it? Even with a 195 stat, you should be up to at least 210 at highway speed. BTW Was there a meet somewhere?

[robby1870]

My 92 always ran below the thermo temp on the highway. Like 180-185 on a stock 195 stat. I didnt think anything of it. Id see the temp go up to the 195 every 15-20 min, then come back down to 180-185. My STE will run at 195 steady on the highway.

[bszopi]

This never popped up. It ran at around 180º for over an hour. After talking to Ben, it might be because the gauge is hooked up prior to the thermostat. But that means that the engine was staying cool without going through the radiator. And this was at the end of a 10hr trip, so the engine has alot of heat built up in it. And it was about 93º outside....

[Manitcor]

I dunno, Ive seen the same thing on mine since I swapped and fixed all my leaks, ran 6 hours to a meet never going above 190 after getting on it HARD. Same thing on the way back. Only time I got the temp to even read 200 was when I was doing donuts.

[jmgtp]

I put the sender for my gauge in the thermostat housing in place of the bleeder screw that should be there and it reads accurate to the best of my knowledge (I bleed the system just the same by loosening the sender). The only time it seems off is before the thermostat opens the temp climbs slowly to around 140* and then the stat opens up and the temp rockets to 180 degrees - after that it never dips below 178 but I've seen it as high as 215* at stop lights. In regards to the comment that at highway speed it should be at 210* with a 195* stat: I think that is false. With a 180* stat, at freeway speeds my gauge fluctuates between 178-184* even on the hottest of days (this is a digital readout), why would a 195* stat run so much hotter than its rated temperature? If the fan was 'stuck' on that would probably mean higher temperatures, not lower, at highway speeds because it would be inhibiting air flow. Does it still do it or was it a one time happening?

[dbtk2]

You do have to remember that the factory thermostats are usually drilled. So maybe coolant is flowing enough to keep the engine cool at highway speeds (although it doesn't seem like that little hole would let enough coolant through, but it is possible). Also, the thermostats aren't EXACTLY the temperature they are rated for, afterall they are mechanical not computer controlled. My dads GTP is usually at about 155 on the freeway with his 160 t-stat...but his t-stat is drilled and his electric water pump is always running full speed so it moves a lot of water.

Shawn

[Gemmer]

even if the stat is closed, the coolant from the engine is still connected to the radiator. Itll convect slow, but itll still convect.

Anyho, Ive never had a car that was over stst temp while driving hwy

[bszopi]

Well, its actually a stuck open thermostat. On Friday, I made the trip to Topeka again (~60 miles) and the temp never made it above 160º. And now, driving to work (4 miles) it doesn't get above 180º, even in the worst stop and go traffic I can encounter...

[pocket-rocket]

I would rather have a stuck open then stuck closed to say the least.