I have been hunting down a cooling "issue" that keeps making me scratch my head.

When I first bought the '82 C3 back in August and drove it 3 hours home in the summer heat, I noticed that the temp gage was redlining after an hour to hour and a half of driving. In my initial research I found that it may have been a bad sender. I swapped the sender only to find that the new one was worse than the old one. I decided to leave the sender alone and focus on making sure it wasn't actually overheating so I swapped the thermostat. It had a 195 and now has a 180.

After swapping the thermostat and topping off the coolant I continued to drive it and noticed after 30 minutes or so that there would be coolant outside of the radiator. Once cool I opened the radiator to find that it was half full. at which point I assumed it was being boiled off due to getting so hot. I did more research and found that the clutch fan was bad. It would continue to spin well after the engine stopped running. So I swapped that out. I then decided to swap out the sender again (previous replacement was with an AC Delco and the second is Standard from O'Reilly's if I remember correctly). Now the coolant gauge seems to be reading correctly (or as best as I can tell). While replacing the clutch I also gave the water pump a wiggle but it was solid, of course I know that it's not a fool proof test if the pump is good or bad but from what I can tell at least the pump seems to be good.

Shortly after swapping the clutch and sender, I took the car for another 30 minute drive. What I noticed is that the coolant would get to temp pretty quickly and stay there. Great, right? Well then after 20 minutes of driving the temperature kept creeping up. Never hit redline but still was closer to it than I would prefer. I did more research and came across someone's post where they were listing off what they've tried and what not. What dawned on me was that I was filling the radiator with pure coolant and not 50/50. The other day I drained the coolant and filled it back up with 50/50.

Just last night I drove it for about 30 minutes to a destination that was 90% highway around 6:30 PM in Texas. Again around 15-20 minutes the temp started creeping up again. I'm cruising around 65-75 MPH. By the time I reach my destination the needle is past the halfway mark. Later that evening I take the same route home and its now 10pm or so, I make it all the way home and the needle never went past the halfway mark.

Hoses look fine, no signs of collapsing. Heater works perfectly.

At this point, I am wondering if I am being overly concerned or if there is something that I'm missing here. If I'm missing something, what are some recommendations I can look at?

 

I would change the WP.If its OEM the impeller is probably coroded to nothing meaning its not moving fluid.Youve got to eliminate that piece of the puzzle

 

Your correct, there have been a lot of threads on here about C3's running hot.
you have an 82, is it all factory stock as per the injection and ignition system?
Running hot on the highway is usually a lack of air flow through the radiator OR, improper ign. Timing.
You do have a overflow tank on the car and it is hooked up correctly?.
I ask because you said your rad was half full at one point. This shouldn't happen. When the coolant gets hot, it expands. When it expands it gets pushed into the overflow bottle. As it cools down it slowly gets drawn back into the rad. Thus keeping the rad completely full at all times and eliminating any air in the system.
A half empty rad with a properly installed overflow tank is a HUGE red flag.
That's the first thing to check. Testing the coolant for signs of leaking head gasket would be the second thing to test. Any shop can pressure test your system. Or perhaps you can borrow a tester from a auto parts store. Your fan and clutch shouldn't be needed on the highway, that's not it. Are ALL the seals correctly placed around the rad? This is important. Is your front spoiler in good condition? You need it to direct air through the rad. Is the rad plugged up internally?
Is your ignition Timing correct?

 

I had a 300zx once that ran fine around town but on a long drive the temps started to creep up. After a good number of “WAS NOT THE PROBLEM” episodes I figures out it was the radiator itself. Over time the lower part of the radiator had gotten plugged and the flow wasn’t what it should have been. It was flowing but not enough to keep things cool on a long drive. Swapped it out and never had another problem. Just another thought for you. Good luck.

 

At any time, did you measure the temperature with an independent thermometer? An IR temp gun ($25- at Harbor Freight or Amazon), is a must for diagnosing things like this. Shoot it at your upper radiator hose, so you don't get false readings from reflections.

 

First question is what are you calling hot? Your 82 was designed to run at 210, and the normal operating range for an 82 is 210-240.

You said you replaced the sender, I assume you mean the temp sender for the gauge, but what about the sender (actually switch) in the right (passenger side) head that controls the electric fans. The switch turns the fans on around 235-240. Have you checked to see if your electric fans are coming on when they should, or that they're coming on at all?

Are you aware that 68-82 Corvettes are bottom breathers? Very little air reaches the radiator through the grills, especially when the headlights are closed, most cooling air is directed to the radiator by the spoiler from under the front bumper. Does your 82 have the black rubber two piece front spoiler in place and the large valance panel that the spoilers mount to, and if the spoilers and valance panel are there are they in the right position? Many 80-82 Corvettes have had their front spoilers/valance panel bent up out of place on concrete parking blocks, steep driveways, etc, limiting their ability to direct air to the radiator. There's more than a few 80-82's that have had the spoiler and valance panel knocked off completely.

Next are all the foam seals that seal the spaces between the radiator and core support in place, and also the one between the radiator and the hood? Air is like water, it's going to take the path of least resistance, without the seals in place much of the air coming to the radiator will go around the it, instead of through it.

Finally have you checked if you have air in the radiator, especially after refilling it when it was halfway down. Also have you checked between the radiator and the AC condenser for debris, etc? It seems to be a place that mice like to make a nest, and leaves and stuff like to find their way into, blocking air flow to the radiator and driving people nuts because it's not easily noticed or thought about.

 

You lost half the fluid in your radiator? have your radiator cap pressure tested!

 

Replace the Radiator cap and verify that the overflow hose is still one piece. When the radiator cap fails it can release the coolant at a lower temperature. After it spits out coolant while cooling down the radiator cap will pull air in to replace the coolant that was lost. Air is fairly useless when it is inside your radiator.

Check your vacuum advance mechanism to be sure it is working like it is supposed to be. A faulty non/functional vacuum advance will leave your engine running hot because it is holding the timing back and not advancing the timing properly.

The cooling system on your engine should more than handle the heat from your engine, what is not the way it was when GM made it? It could be something so simple like a missing spring in the lower radiator hose allowing the hose to collapse under the vacuum created by the water pump. I change hoses and thermostat every 10 years, coolant and radiator cap every 5 years and I verify that they cooling system is working prefect. When I change the coolant I will also add a bottle of REDLINE's Water Wetter as it helps remove the heat. Being in the South East I only use 30% anti-freeze and 70% distilled water because this mixture works well for me.

 

gbvette62, Where did you get the information for the 82's operating range? I've never seen mine go above 195 even with A/C on in traffic and/or long highway trips here in FL. Mine's been completely restored with new radiator, cap, heater core, thermostat, foam seals, and pump.

 

This is not an entirely true statement for an 82 Gen1 block. At 240* I would be shutting down the motor ASAP! (Your C3 is NOT a LS motor which runs hotter by design.) Your heads can/will wrap if it goes off scale high rather quickly. Roughly speaking on temps a relatively good cooling system in an 82 should be around 205* or less, 195* being optimal. GM put a 195* stat in it for a reason. At 195* the stat is wide open and max coolant is flowing around the motor. If you have an issue of it heating up at cruise, you have an issue with your cooling system like mentioned above or ignition issue. Base timing on a stock 82 is 6* BTDC with the EST wire pulled, check it.

Also like mentioned, the 82 like others are bottom breathers, so it is critical that you have your lower valance is installed along with the foam pieces around the top of the radiator installed correctly to funnel the air through the radiator and not round it, thus poor cooling. By you putting a 180* stat in there, the system is merely opening 15* sooner and is still wide open at that point, max cooling. It's the rest of your system that is question here. If you are losing coolant, you have an issue for sure. If you don't have that coolant in the overflow, you have an issue. Could it be the pump? ...Maybe? I would pull the radiator out if original and just replace it vs having gone through, but that's just me. @ctmccloskey As far as..."vacuum advance goes...THERE IS NONE ON AN 82". It is completely computer controlled on everything, including the advance. This is why you MUST pull the EST wire when checking or setting the base timing to disable computer control of the timing.

Your sending unit on an 82 can be problematic and sometimes frustrating to find a good one, ask me how I know. A guy that had a corvette parts business on here (vendor) that is no longer with us, did some videos on this very subject and issue a while back. I would get a laser temp gun also like suggested and see what your temps really are and go from there. There is potentially a lot of things that can cause your issue, it's a matter of troubleshooting correctly to narrow down the issue. Also, if you do not have a GM service manual for your 82, PLEASE get one, it's worth its weight is gold. GL and hope this helps a bit. You can PM if you like as well.

 

I must apologize, I had not received notifications that there were replies so I did not bother to check the post until today.

I have yet to pull the water pump to check the impeller. If I had to guess I would say that it's likely stock but unable to tell just yet.

I have checked my timing several times. Letting the engine get up to temp, pulling the EST wire and using a timing gun. Its bang on 6* BTDC per the sticker. Also, the foam seals appear to be in place and intact. I will more thoroughly check later today but I do recall at least seeing the foam seals at the top of the radiator. Cannot confirm about around the sides, etc.

I did read at some point that the C3's are bottom breathers. I never really thought anything of it as I could see that from the bottom the radiator has unrestricted air flow. However, what I did not realize was how important the valance and air dam are to the overall cooling. The valance appears to be properly secured and intact. No holes or cracks or anything that would indicate that it's not working properly. The only thing I will say is that the middle "seems" to be a little higher up than the rest. It's where the hook meets the valance. I'll try and get a picture of it in a little bit.

As for the air dam, one side has a decent chunk missing from it and the other side seems to be bent backwards to a degree. If I had to hazard a guess, I'd say that the air dam isn't properly doing it's job.

What I can say is that since I have swapped out the fan clutch I have not had any coolant coming out of radiator cap. The overflow tank is properly set up and I have seen coolant has been added and removed by way of radiator with me topping off as necessary. I will say that I do think the lower radiator hose needs to be replaced before I do any major driving. It has GM stamped on it and where it connects to the water pump has a pretty decent bulge. That's next on my priority list as I definitely don't want to have that hose burst on me while at speed.

I think at this point, I am definitely replacing the hose, the air dams, and going to likely replace the water pump as well but want to take a look to see if I can determine it's age. Though with as cheap as the pumps are I figure I might be better off replacing it. I'll keep everyone posted but also welcome any other ideas to check in the meantime!

 

The 82 Owners Manual says: "During normal operation, gage will indicate between 190F and 260F (88C and 127C) (start of red zone)". The Owners Manual does go on to say that 260F is overheating. With a stock 195 thermostat it's always been my experience that they seem to run more in the 200-210 range? Note that "gage" above is GM's spelling, not mine.

I don't have an 82 Shop Manual and a friend has my 81 Manual. I just called him and he looked it up for me and said according to the 81 Shop Manual the switch for the electric fans is set to turn them on at 238F and off at 201F. I was a little high on the 210, but I was working from memory on what was in the Shop Manual and I guess I reversed 201 and 210 in my 70 year old memory. Still the Manual leads me to believe Chevrolet considered 200-240 normal for the 81 Corvette, and the temperature range for the 82 should be the same as the 81 (the 81 and 82 Owners Manuals have the identical wording for "normal range" 190F and 260F).

I bought my 81 new and as I said above I've always found that it normally runs in the (gauge indicated) 200-210 range. There have been a couple occasions, maybe stuck in traffic, where I've watched the temp get into the 230 range and heard the fans come on and the temps go back down.

 

Not starting a debate on this subject...but I could care less what the owners manual says. The 82 GM service manual is actually the bible, since the GM service department did not work on these cars new by using the owners manual, jus sayin'. Anyway, the 238* is too high and too close to over heat at that point. Bad things start to happen at those temps rather quickly. If the OP has issues at cruise, there are problems for sure. I would bet on one thing that is bad for sure by him anyway are the foam pieces around the radiator which NEED to be in place correctly for cooling at idle especially. The other that is probably an issue is the radiator itself. The third item that the OP mentioned is more than likely the hoses, especially the bottom hose. If it is bulging, it IS bad no question and may be collapsing at some point. A way to see, is to nail it at cruise and see if the gaskets on the pump blow out, which would mean that the pressure is too high behind the hose and blowing out the gaskets at the pump, the weakest point. Chances are high that this may happen. OK, I'm not really asking for the OP to do that, because if that is an issue, it will be a huge mess and maybe prang a motor as well. I would just replace the hoses with good quality hoses like Gates hoses and be done with it.

Like I mentioned above, the temps would normally be in the 205 or less area on a good running cooling system, under normal conditions. I replaced my temp switch to have the aux fan come ON earlier and turn OFF at a lower temp, later. This works a lot better for me and I live in Arizona.IMO, the OP DOES have some issues to sort out before I would take that car on ANY trips anywhere. GL on your repairs.

 

I am about halfway through the repair. Water pump is definitely stock so I'm glad I'm getting it replaced. I can only imagine how many more miles I would have got out of it. I dug the spring out of the old lower hose and re-installed it on the new lower hose (Gates) to help prevent collapsing.

Shown in the images below, the first two show the foam seals that are currently installed (If I had to guess, I'd say that they're not 100% properly installed, thoughts?) the next three pics show the air dam and the valance. Valance looks good to me, other than how at the nose it seems to point a little too far upwards in my opinion. Meanwhile the air dams are not in good shape, currently waiting for new air dams to be delivered.


Passenger side radiator foam

Driver side radiator foam

Drivers side valance

Driver side air dam

Passenger side air dam

 

Not to knock fixing things that are broken, and the air dam is certainly a critical component of the system, but before you throw more parts at the problem...

Have you independently confirmed the actual operating temperature with an IR temp gun?

Good news on an intact lower radiator hose spring! I don't know where to find those for sale, other than ordering from McMaster-Carr.

 

Any chance to get pic of inside radiator holes, you might just be marginal on that.
seals to me look good. Spoiler wont hurt
pressure check cooling system?

 

I just replaced my Water Pump, Clutch Fan and lower radiator hose with the higher quality Gates Hose. Installed a HD Dayco Water Pump and a new HD Clutch Fan along with a GM 180-degree thermostat. Since my repair on my 78 L82, what an improvement, living in Palm Desert CA, my temp has not climbed over 205 degrees. Make sure you examine your Clutch Fan, that is another component that would help to keep your temperature down. My original clutch fan was not working probably and I know for sure it made a big difference in helping keep the temperate down. If you are not sure if it is working probably just replace it with a new HD clutch fan while you are replacing components - my suggestion. You can purchase a HD clutch fan for around $75.00.

Also, keep your parts if they are original to the car. If you ever sell your vette buyers love the original parts, the vehicle came with.

 

get a test kit for exhaust gases in cooling system.

 

I have not been able to verify with an IR temp gun. Once I get these new parts installed and running again I'll get one of those temp guns and give it a try.

 

OK, you show the top radiator foam pieces, but what about the sides? You MUST have the side pieces in place correctly as well, which is actually more important than the top. Are those all the way down the sides with a snug fit?