Do Corvettes always run hot? Long story...
 

Hello everyone,

First a big thank you for your advice while I got a new motor installed in January. So to catch you up, here is what has happened in the meantime.

About a couple of days and 100 miles after the new motor was installed, the radiator had to be replaced because it was "plugged". I complained that it was fine before so it must have been something that happened while they were installing the motor and they ate the labor and not only installed a new radiator, but fixed several other things they found wrong like vacuum hoses, fan clutch, heater hose, some fuses and added freon for the A/C. They said everything should be fine now (reminder, this is a GM dealership). So during the next 100 miles, I notice that it still runs pretty hot, more than 220 degreese most of the time. Finally the other day it went into the orange on the temp gauge and again, just like before the radiator was replaced, boiled over out of the reservoir and the cap was whistling. However, I was running the A/C, just to make sure THAT worked. (It did work, by the way, nice and chilly, perfect for our 80 degrees we have had lately.)

Anyways, now I am begging the question, as I am taking it back for them to fix tomorrow, why is it running so hot? Is this normal for Corvettes? Could it be related to running the A/C?

It does get very hot under the hood even only after half an hour or so of driving and I know the space in that compartment is very densely packed.

I have to add I am so disappointed, I was going to take it on a road trip (about 4 hours) to a gathering at a friend's house this Friday.

In addition to that being said, will I ever be able to do that? Are they not "road trip" vehicles? Am I grounded to within 100 miles of my home?

Any suggestions, advice, comments appreciated. Please send to my email address (robiniqua@yahoo.com) since I am firewalled at work and can't check your responses while I am not at home.

OH and one more thing: I am taking it back to where I had the radiator installed only because I need to give them a chance to fix their work before I can sue them, which believe me, is on my to-do list if this doesn't get fixed this time. If nothing comes of this trip, I have a Corvette specialty shop I just discovered in my area that I can take it to.

Thanks again everyone,
Robin in Silicon Valley

i have no idea whats going on with your car, but i can tell you that that isnt right.

these cars get hot, very hot actually, but it shouldnt be doing what yours is. mine normaly sits around 180 during normal conditions, and ive had it go a little over 200 when im really pushing it over a period of time. ive never had it over heat on me though.

as for cross country trips, not my first choice of a car to do it in, but it is most definatly doable.

My guess is that you have a 195 thermostat and it most likely is defective. I bought one for my Z71 GMC at the dealer and it was defective. I bought one at Napa and when I got home, put both in a pan of water on the kitchen stove. The Napa one opened at 195 all the way. the one from GM only opened a fraction. Easy fix if that is your problem. Might I also add, put a 180 in your Vette. That is what Im running and I have NO overheating problems with my new crate 350.
It NEVER gets to the 200 mark, even sitting in traffic. :thumbs:
I always ran a 180 in my stock 305 and never had any overheating issues in 27 years and the original radiator.

Just my 2.3 cents worth on the issue;)

Didn't see that the motor was new

Wow, I just read your complete post.. It looks like your dealer is bending over backwards to make you happy. I surely wouldnt take it out on the radiator shop if your car is still overheating. Like I said in the above post, my bet is the thermostat is defective and that is where the problem is. Also, you could have an air pocket in the cooling system if it is a fresh install. Give everyone a chance before you mention the sue comment. I would think after making that comment, all the freebies that you have received from the dealer will stop and any future relationship will be gone forever. Dont burn your bridges.

You might also check the radiator cap. Could be defective and that will also cause an overheating problem. As I see it, you most likely don't have a real problem that can't be fixed rather easy. And also, yes, these are very "cruise" able cars. I take mine to the Oregon coast in the summer months just for lunch with the wife. That is a 200 mile round trip. Never a problem. Good luck and keep your cool. Its not like you are dealing with Hecklers! Then I would understand your problem.

Is a 180 a thermostat? If so, can I request one be put in? Also, I was kinda hurrying when I typed it--the dealership has done all the work on the car, including the radiator.

Heh heh, so far I am much cooler than my corvette is. I'll try not to blow a gasket when I go in tomorrow. :)

Robin, I have virtually the same car with the same motor in the same locale.
I have a 195* thermostat, and the car never gets above 200* even when driven hard.

If they changed the motor and radiator, they left out the foam seals that direct the air flow thru the radiator, or it's not tuned properly.

You shoul be able to drive cross country if you want.

It's a Chevy, not a Ferrari.

:iagree: :iagree:
I agree with the rubber seals, yet my Vette has had a new crate and no issues with the problems mentioned. I still like my 180 degree stat. This summer I plan to drive my Vette on my monthly commute to Chico Ca to visit my Grandkids. It is a beautiful drive down I-5 and its even better in a Vette with the tops off!:D :thumbs: :cool:
Best of luck with the dealer. Im still betting on a defective GM thermostat.

NOt much doubt in MY mind either about the t stat being bad, hell, I would pull the thing out, cut the guts out, leaving a restrictor plate, and run it that way.....make damn sure the clutch fan is plenty snug and not wobbley, also check coolent levels after a say 1/2 hours trip.....

those 3 things should fix it....is the water pump new?? if not, change it....

You had a crate motor installed and repairs done at a GM dealer?! They would seem the least knowledgable mechs to take it too this day and time.

If you change the stat, make sure that it is one that when and if it fails, it will fail open, not closed. Jeg's has a Mr. Gasket stat that you need.

Make sure that all open areas around the shroud are sealed 100 Per cent.

I could never understand why stats failed closed.

gm73vette

The key I see here is that a new motor was put in. I would be suspect something in the cooling system may be plugged due to some type of "crud" or residue from the motor swap. I don't care what thermostat you have, if the coolant can't flow properly it won't cool. IF you have a 195 degree thermostat that is where your temprature should be during normal driving. With the air on, on a hot day it will rise some. If you are standing still idling with the air on, it will rise, as a matter of fact I have learned that if you stop and are idling on a hot summer day, you better trun of the air....all Vettes, new or old exhibit this. Vettes do all run hot, but the bottom line is that if the temprature is above 195, then the thermostat should open, allowing the coolant to flow through the radiator and maintain that temprature. As the temparature drops, the thermostat will close, and allow the engine to warm the coolant unitl it again hits 195 and opens. This allows the engine to operate optimally. In your situation I do not believe putting in a 180 degree thermostat will do anything for you. Most folks put a 180 in a Vette to help keep the interior temperature a bit cooler. This is because the fan on your heater motor always runs at low speed and even though the temp on the heater panel is set to cool, some coolant still tends to flow through the heater core. On C3s you can put a shut off valve on the heater core hose to help this further. Now, back to your issue. All that will happen if you put in a 180 is that the thermostat will open 15 degress sooner. That may help you a few degrees, but if the thermostat is opening at 195 and your cooling system can't bring it down at that temp, it won't at 180 either.

Part 2.....lost keyboard.

If I were troubleshooting this problem I would back up and check and rechecked everything involved in the engine swap. It just makes logical sense. The cooling system was fine prior to the engine swap. So what has changed is that someone has gotten their hands in there. I would disconnect all hoses, etc. Can they do a pressure or flow test throught the block? Is it possible a plug or the like was left in? Whenever someone has had their hands in something, that is where you start the troublshooting process.

e.g. I once had my console guages apart. A couple of weeks later we are on a club road trip when my oil pressure appears to be dropping off. Looking under the oil filler cap I can see that oil is getting up to the valves properly. For grins I change the oil pressure sender. After I get home I decide to pull the guage panel again and lo and behold, I found a lose nut on the oil pressure guage. The point is, start where the human hands were. most likely they will find it is something the mechanic did. I spent years supporting computer repair people from a high level, and I learned that if someone was troubleshooting and the problem got worse, there was an original problem and typically one or more problems introduced byt the technician. The tech/mechanic will always tell you the did everything right, because they believe they did. The experienced mechanic knwos to back up a check everything previosuly done.

Here in Bangkok the average temp year round is 95. I am still running my original radiator. Now I have changed everything else in the past two years including the engine but I never had over heating problem with my 180 thermostat. I do have problems when I run the AC in the city especially at the famous Bangkok traffic lights. Everything in my AC system is new but I had to add two extra fans in front of the Radiator making three electric and one engine flex fan, all to try to cool the cars AC. But with all this the engine temps never go over 190.

Our cars are called bottom feeders since they draw most of the cooling air from below the front end and to do this the air flow must perfect or you have over heating.

You could still have a mechanical problem of thermostate however you must start the car up cold from overnight or risk burning yourself. In the morning with a cold motor you remove the rad cap. Start the car and wathc the temp gauge. As it reaches 180 to 195 you should see water begin to flow through the radiator via the cap hole in the rad. Flow should be significant and you can also check flow by squeezing the upper hose to make sure your feel the water flow and it's hot. Oh and water will run out the cap hole while doing this test but you refill when it cools off and then put cap back on. Do not attempt to put cap back on when engine is hot. Also make sure animals do not have access to water/anti freeze from rad becuase they will drink it and die.

Now as Big2Bird mentions there must be foam seals between rad a fan shroud. This gets back to the car being a bottom feeder. If the shroud is not fully sealed to the rad or rad is not seald to cor support it will pull considerable air around the rad instead of through it. You'll be amazed how much a small air leak will cause temps to rise.

I found out after chasing over heating with AC on that it was the shroud not sealed to the radiator. When the AC is on the air coming into the rad is much hotter so it requires more air flow. Unless the shroud and rad is sealed completely you will not get the need air flow through the rad. Most none Corvette specialists do not know about this.

To install the required seals you have to lossen the shroud and rad (tilt them back). Even with the factory eals installed I still added compressible foam in every hole the shroud had. This made my car drop 20 degrees with the AC on. It was amazing.

One other thing, while we know the car is over heating where did they put the temp sensor? In the head or intake because if in the intake it'll be a bit delayed in getting up to temp vs. the head. This however is not causing your problem.

:iagree: I have a 195 T-stat in mine and other than it is not the most comfy car to ride in, I would not be afraid to go 1000 miles today and it won't overheat (Griffin radiator from DeWitts and dual C4 electric fans). It has never gone over 210-215 with a/c on on a 100 degree day in traffic.

I would make sure that all the foam seals are there and in good shape. See Dr Rebuilds catalog for good descriptions/requirements on foam seals. They have to seal the front of the car so ALL the air goes through the radiator. I would make sure the fan shroud is there and that the fan clutch is good. Make sure you have a front spoiler and that it is all there. If all that is good, I would look at engine tune. Is the timing right? Is the air/fuel ratio right? Lastly, how big a HP jump is this engine? Do you have enough radiator? I have done engine swaps to more powerful (same displacement) engines that stock radiator just couldn't handle.

One other thought comes to mind as I'm reading this. The location of the fan blades within the fan shroud is very important to effective cooling. It should not be completely inside the shroud. The blades should be about half way in the shroud. It should not be totally outside the shroud either. Use of a water pump with the wrong length shaft will cause the fan to be in the wrong location.

cc

:iagree: Excellent observation. That crate motor could have come with a different length water pump/shaft. I'm pretty sure most "everyday" mechanics would not have caught that. And, yes, if the fan is completely inside of the shroud, it will probably not pull a lot of air [deadheading]. Also, I don't recall your car's model year, but up until 1974, C3s had 180 deg. thermostats. The 195s do nothing but reduce emissions [somewhat] and use up your engine life from excessive heat. If Zora Duntov thought that a 195 deg. thermostat would be better for his engines, what do you think he would have put in them?

I have had serious issues with overheating as well...note my car is still undergoing much mechanical and cosmetic work as i get money.

Here is what I did. 1) Get a lower degree thermostat...they are saying 180 degree, i went way below that and went to 160 degree (i know it seems low, but thats what mine took it had a 180 before)...helped my problem. 2) Im not familiar with the 79, does it have an electric fan? if so, make sure it works. New engine doesnt always mean its working. If you dont have one, id consider getting one if the thermostat doesn't fix it. My car heats up when my electric fan isnt working. 3) If none of those work and you see the temp climbing, turn off A/C and open the vents to HOT and have it looked at again. i know it sucks, but it may save your engine by releasing all that hot air which is trapped in the engine compartment. These are all things I have done and have seemed to work for the time being.

Is the cars chin spoiler in place and is it in one piece and not broken? This spoiler is a very important part of your cooling system and most people don't pay much attention to it. They usually pull into parking spaces and catch it on the cement pile on and break it and think nothing of it. Get a 180 degree Robert Shaw t-stat for your car and make sure the system is burped so you don't get any air trapped in it and make sure all your support and shroud seals are in place.