Paul L

Had an outcome that was entirely predictable. And some of you predicted it. Sometimes I feel like a real dolt!

To recap, last Sunday was very hot and humid. About 91F. With my factory recommended 195 thermostat the heat gauge pegged at 220 at about 70mph on the highway. That is well short of the red line but does seem hot. And that has been the case for a number of years with no problems. But I cooked up an experiment :rolleyes: . I dropped in a 180 t-stat hoping to lower the temperature :bb . Some of you made the point that, be it 180 or 195, the t-stat would be wide open at 220! Nevertheless, away I went.

Today was my first drive since the 180 install. It is less humid than last Sunday and about 85F. So not an apples/apples comparison, but close. And here is the result at 70mph. The temp gauge is just shy of 220, hardly an appreciable difference. What the heck, it is always fun to turn a wrench and try out new ideas, however silly they may be!
http://temp.corvetteforum.net/c3/pau...mostat_026.jpg

So back to stock I go with a new Stant SuperStat. And I do wonder if my car is just operating normally. But I will do a Prestone SuperFlush this afternoon as I have not done one for several years. Can't hurt. Longer term (winter) I will go with a new rad as mine is the original.



Lastly for my American friends, wouldn't you love to see a sign like this on your highways;) ?




[Modified by paul79, 2:16 PM 8/17/2002]


[Modified by paul79, 2:18 PM 8/17/2002]


[Modified by paul79, 2:19 PM 8/17/2002]


[Modified by paul79, 2:20 PM 8/17/2002]

page62

>>Lastly for my American friends, wouldn't you love to see a sign like this on your highways <http://www.corvetteforum.cc/zeroimg/smilies/wink.gif> ?


Yeah...but we know better than that. Out in west Texas that same sign would say 120!

kenincanada

Paul, It seems to me that you spend more time wrenching your car than driving it :D :cheers:

Ryan77

page62-- is there really a sign that reads 120 :eek: , if you're not joking then texas here I come!

Paul L

Ken,
I do fool about mechanically. But I do drive about once a week. And I love to take pics as is obvious. One more for today coming up when the darn camera batteries recharge. I believe I have solved the mystery of that mark between 100 and 220 ;) .

SteveG75

The problem is not the thermostat but the cooling system. Heat transfer rate is dependent on the temperature differential between the hot and cold sides. As the radiator gets hotter, it gets better at transferring heat until you reach the point where heat in equals heat out then it will stabilize. For your car, this seams to be 220. If it is cooler outside, there is a greater temperature differential, so the equilibrium point is lower.

In order for the lower thermostat to be really effective, you need a radiator fan combination that can cool more efficiently. With my BeCool Spal fan combo, it will hold a constant 180 on the highway and cycles between 185 and 195 in town when the electric fans are coming on as necessary to provide airflow. This is with a 180 thermostat. With a 160 stat, I would run 160 on the highway when I had a lot of airflow and 185-195 in town when the fans where doing the work.

If I ever went to a 195 stat, I would probably run 195 all the time and the fans would run constantly.

What you really need to cool down is a more efficient radiator so it will transfer more heat at lower temperature differentials (say 95 outside and 195 coolant).

This info bought to you courtesy of Thermodynamics 101 circa 1988. :yesnod:


[Modified by SteveG75, 5:36 PM 8/17/2002]

jerryp58

I appreciate the experiment; It's what I would have expected. But, I would also think no thermostat (or one of the hi-flow thermostats) might run just a bit cooler because of improved flow.

I'm just about to do maintenance on my cooling system.
If I remember correctly, I believe that I have a 180 degree thermostat in there now.

I'm planning on changing the thermostat. I'll stay with 180 degree, but was hoping someone could recommend a brand/model that flowed well and had the fail-in-the-open-position feature.

I'm also thinking of doing a Water Wetter experiment after I do the maintenance and run it a bit to see if the Water Wetter has any impact. I expect without it I'll go back to my 195 degrees that I had when I did this drill two years ago (versus the 205 now). The question is, will I go below 195?

And yes, I'd love to see a 100 MPH sign :yesnod:

Paul L

Steve,
I accept that argument. But the 1979 ran just fine in that year without the bells-and-whistles. Why do we need them now?

Paul L

Just a comment on that mystery mark between 100 and 220. What temp is it? Well with the Stant 180 t-stat at hot idle this morning it was 180. With my new 195 Stant this afternoon the temp gauge shows just above the mark. So my conclusion is that that mark is 180F. Perhaps that mystery is solved? Did the Prestone Super Flush job this afternoon. I will let you know if it has any effect after driving in the coming days.

Here is a pic of the Stant SuperStat install. That emission plumbing is a real pain!

Markm10431

you need to go to Montana. speed limit UNLIM during the day

jerryp58

SteveG75,

I'm just curious here: "If I ever went to a 195 stat, I would probably run 195 all the time and the fans would run constantly."

Is there any reason the fans should be running when the thermostat is closed? They would have no effect on engine temp with a closed thermostat, would they? Do cars equipped from the factory let the fans run if the thermostat is closed?

Paul L

Really? I did not know that! So you can go as fast as you wish?


[Modified by paul79, 9:43 PM 8/17/2002]

SLICKMAN

Jus my two cents.. My 78 L82 had a 195 in it and around town it ran at 192 - 205 on days around 85, on the highway it ran at 205 to 215.. I don't like to see temps that high soooo, in went a 165.. Now, around town (at about the same outside temps) it runs at 170 to 180 all day. At highway speeds it will get up to 195 with a max of 205. In the future, I plan on taking out the clutch fan and setting up a flex.. That should drop the highway temps down, maybe even the around town stuff..


[Modified by SLICKMAN, 11:31 PM 8/17/2002]

Paul L

Steve,
I have been thinking about your reply. There was an optional electric fan in 1979. I imagine I could find one at a salvage yard. And I know the sensor is already in place on the passenger side block. But that fan was controlled in some way by the A/C system which I do not have. If I purchased one, how could it be controlled?

Note that the fan does not come on until 238F?? Which leads me to believe - but not necessarily conclude - that 220F might be a normal operating temperature....
http://temp.corvetteforum.net/c3/pau...ricfan_001.jpg


[Modified by paul79, 8:52 AM 8/18/2002]


[Modified by paul79, 8:53 AM 8/18/2002]

mrvette

the biggest change in t-stats has been the size of the opening in the middle...
used to be the hole was larger in diameter...and now it's about 1/8 inch smaller across the board...restricting the flow...hard to fina a stat with larger hole diameters these days...would take a bunch of holes drilled in the plate to make up for the differance....and then actually prove the thing opens at whatever rating it is for...say 180f.....I find that gutting the stat, snipping off the controll valve and leaving it as a restrictor plate is the most effective summertime solution.....I didn't bother this summer, so the vette runs a bit warm...but still less than 200f the fan stays on though...
it's set for something like 190f turn on...but then again, i'm running a/c most of the time anyway...so it stays on of course for that reason...

point is, the mfgrs have played with the stat design to get engine to run hotter, it's an epa thing....gutting the valve will increast flow a good bit....
but somehow leaving it out entirely does not seem so good of an idea either...
probably because the pressure of the pump capacity is not working against that restrictor plate, increasing water pressure in the cyl heads...and making boiling harder....with much less water pressure in the heads due to NO stat/plate in place....I would think it's easier to boil off the water in the heads and actually cause overheating because of it....

GENE

JB

Yes and no. There's no speed limit, but the rule is no speed that's unsafe for the conditions. They interviewed a state trooper who was working those highways with a speed gun and he said, "there is no condition under which 140 miles per hour is safe."

JB


[Modified by JB, 8:42 AM 8/18/2002]

SteveG75

Jerry,

You are right. Just when the car was warmed up, the electric fans would turn on at 195 and since the thermostat would never let the coolant get cooler, it would never get down to 185 allowing them to turn off.

While the car was warming up, the fans would not be running.

Steve

tboltkc

I don't believe removing it is a good idea, because more flow isn't necessarily a good thing. The coolant needs to stay in the rad. for awhile to get cooled. Too much flow, and it doesn't stay there long enough to cool. Gutting the old one sounds like a good idea, though. Seems like flathead v-8 F**d guys use big washers instead of thermostats cause those things always run hot, but you need some restriction or the rad does no good.

Paul L

Just to add a few last observations. I did the Prestone Flush yesterday and installed the Stant 195 SuperStat.

So what, if anything, did that change? Today was a mirror image of yesterday: sunny and about 85F. I followed the same route, same speeds at the same time of day. I must say that I am perplexed, and pleased, with the results. The temp gauge runs about 195-200 in the city and 210 on the highway. It fluctuates only within this narrow band. It never touched 220 or beyond; the source of my original concern. I do not know if it was the flush or the Stant t-stat but I am finished fooling about. The result is more than satisfactory to me :) .