OK, my bone stock 84 runs hot. No hotter than any other stock C$, though, so I'm ok with that. Generally, running around town, I see temps in the 198-205 range. With the AC on in hot weather, its more around the 213-220 range. When I get stuck sitting in traffic or something close to that I will see it climb into the 220's, eventually hitting 230 where the fan seems to come on and bring it back to the low 220's again. Occasionally it's gotten as high as 233...

All in all, I can live with that.
I thought about changing the thermostat to help it run a little cooler, but I was concerned of what the lower operating temperature will do when I have to pass an emissions test. Ultimately, I thought I'd Drop in a Hypertech Thermomaster chip and stat, not for the performance of the chip, more for the advantage of the chip allowing the fan to come on sooner and also I had heard about it helping to eliminate the dreaded 1-4 shift :rolleyes: But again, I was a little worried about emissions so I decided to leave it stock.

Anyway, something happened the other day, and it's made me change my mind, but I'm not sure I'm changing my mind for the right reasons. I wanted to get the input of some of you here on the forum.

My wife and I were out for a drive... The temperature was about 90+ with humidity over 84%. We had the top on and the AC cranked up. Now, personally, I feel like the motor is lugging when I drive on back roads because it seems to shift into 4th too rapidly. Therefore, when I'm on backroads, I keep it in 3rd and only shift up to OD when I hit the highways. Tis really does improve the ride.

AAAnyway, going down the highway, I look down at my gauge to see that it says 238 :eek: I'm thinking, man! Thats hot! So I'm wondering if I should turn off the AC when about 30 seconds later it goes to 239. :eek: :eek: 30 seconds after that, 240... 241... 242... About the time it hit 246, I got the AC off. ...247...248... So I'm thinking poopie! This things gonna boil over. I turned on the heat to try and help out a bit. At this point, I also noticed that I was still running in 3rd gear. I had forgotten to shift out when I hit the highway... no big deal... I was only doing 70 and it was turning around 2800... Yeah, thats running hard, but it shouldn't hurt it. Anyway, I also shift to over drive. ...249.... It sits there for a minute and then 248...247...246... and so on back to around 231 when I reach my exit and get off the highway. Back on the backroads, I leave the AC off and leave it in 4th. It eventually comes down to 222. At that point, I switched the AC back on MAX and let it blast.... The rest of the way home (about 8 miles) it never saw over 226.

Now, because of this, I'm thinking again about doing the stat and chip. A little background, my radiator is clean! It's been flushed and there is no debris clinging to the outside of it. Unless the thermostat stuck, I can't think of a reason for the stock system to really over heat.

I know running the motor hard on the highway probably caused some additional heat buildup, but I can;t understand teh buildup I got... that just doesn't seem right to me. It makes me wonder if something isn't wrong.

I'm thinking the stat and chip will keep the car with a lower initial temperature which should help coolong overall plus the fan coming on at a lower temp should help me from seeing the high temperatures overall. But if theres something else wrong int he system, am I barking up the wrong tree?

My other questions, honestly, how do you think it will effect emissions? And, the thermomaster chip is paired to a 160 degree stat. I live in Maryland. We get some hot weather (in the low 100s) in the summer, but fall and spring are usually nice 70's weather and pretty mild. I'm thinking a 160 is too cold and might prevent the motor from going into closed loop in the cooler months. Am I just worrying too much? I'm thinking a 180 would run better for my climate. Will the thermomaster chip work with a 180? If not, perhaps I should go 180 and put in a manual fan switch? Is there another option for the shift issue?

Really sorry fot the long post... just wanted to get all the information out on the table for more informed opinions.

 

I have the chip and 160 stat and my car runs 165 -185 with heat here in the 90's.
Did you read this recents post http://forums.corvetteforum.com/zerothread?id=628132
Good Luck
:cheers:

 

Driving in a lower gear causes higher engine rpm and higher friction so more heat. I can downshift (I have a 4+3) and my coolant starts rising so your experience is normal. During emmissions testing, only your fan is going to be moving air through your radiator so the engine isn't likely to operate at 160 with a 160 stat. A 160 stat in the summer is going to be wide open all the time because C4's have radiators sized for 180-195 operation and they cannot get rid of heat fast enough to maintain 160. In the winter you may likely be able to operate at 160 and I wouldn't operate my 87 at 160. I think a 180 stat might help some, but in the summer under 35 mph you are going to see the temps you posted because your 195 stat is wide open and so will a thermostat of a lower temperature. It does help to have the fan turned on at a lower temperature, but when your a/c is on, the main fan is also on.

 

I have a 1984 and went through the same scenario. I feel I've cured the problem by:
1) Clearing out any built up debris between the radiator and ac condensor. Mine had quite an array of leaves, cigarette butts, etc.
2) Replace the fan switch, passenger side, between cylinder #6 & #8 with one that swiches (grounds) at a lower temperature. I use on at 210/off at 198, available at Ecklers. Careful with the connector, it may be very brittle with age. A replacement connector is available thru GM or Ecklers.
3) Replace the termostat with a quality (not heavy duty) such as Mr. Gasket, 180. The reason I said not to use heavy duty is because in my experience these tend to open at a higher than listed temp. and do so more slowly.
4) Replace the stock radiator! This made the biggest difference! I bought a Modine, it's very reasonable, about $250, and it is nearly twice as thick!

 

Don't be concerned about lower temps and emissions; I run a 160deg stat & fan switch year around and passed emissions tests easily last Jan.

 

Can you give us more info on that modine radiator?

 

I bought mine at a radiator shop, here in Los Angeles. Their plant is in Kansas. They manufacture OEM and replacement radiators for most domestic cars. In the Corvette application (1984) theirs has a much thicker core.