Ok, so I have been thinking my 79 has been running a little warm. Normal cruising around 45-55 she stays decently cool, when it is about 70 degrees out side, the temp gauge is reading around the 160 mark (between the 100 and 220 degree marks), but if I get into it a little, it likes to warm up. Today, it was around 80 outside, and with a mix of highway (60-70mph) and light (cruising 40-55mph) My car would seem to get a deal warmer, and would be about half way between the 160 and 220 marks, and at one point, got up to the 220 mark when cruising at about 70. When I say cruising, I mean light acceleration, not really getting into it. I have a bigger than stock Champion radiator in it, and there are some small gaps around the edges, but I have sealed off the top which was the biggest gap. I have tried "water wetter" stuff that is supposed to help, but it is not looking like it is. Now, I know 220 is warm, but at what temp would you start to worry about the engine running hot? Somewhere, I heard that you can run the risk of warping your heads if you get to be over 200 degrees.

I have contemplated taking out the thermostat and running it with out one and see if that helps at all, but I am wondering if there are any risks involved with that. A guy I work with has a 32 Ford with a Chevy 350 and says he has no problems at all running with out a thermostat.

I have also read the thread about the spring in the lower hose. As I inherited my 79 this summer, I don't know if that spring is in there or not. Is there an easy way to check with out taking the hose off and draining the cooling system?

So, to break down this novel, my questions are:

-At what temp should I be concerned?
-What are the risks of running with no thermostat?
-Is there an easy way to check if the spring is in the lower radiator hose?

Thanks in advance everyone.

 

My 79 usually runs at just under 220 on a 90 degree day here in Florida. I put in a new thermostat, and a new fan clutch a month ago and it didn't change the running temp at all. I'm no expert on this subject, but from what I've learned doing some research is that our emission heads on the 79 usually run hotter than some older model motors. Hopefully someone else with more experience will chime in.

 

The first and most important thing to know is how accurate your gauge is. Borrow or buy an IR thermometer and shoot your thermostat housing with your engine at operating temp. You may find you have less (or more) of a problem than you think.

To answer your questions, IMHO 220 deg is no problem. Again, you may find 220 on your gauge is really 210...nothing to worry about. As far as ruining cylinder heads, if you're not boiling at shutdown or running at redline temps for long periods, you should be fine.

There's no reason to run without a thermostat. What I was taught is that your engine is designed to work best at operating temperature (180 deg+). All of the different parts, with all of their different cross sections and materials, are sized to work together at those temps--including your oil--and the purpose of the thermostat is to get them to those temps as soon as possible, then open to allow the radiator to remove excess heat.

You will be able to feel the spring by squeezing the lower hose with your hand.

Based on your comment that she heats up on the highway, I would also fill the gaps in your radiator support or cowl, and check/set your engine timing according to the article in the tech FAQ sticky.

 

Ok, I will check for the spring tomorrow and take a drive and see if there is an IR thermometer at one of the local parts store that I can barrow.

One thing that stands out with this is that the footwell gets pretty darn warm when it gets about 180+ on the gauge. Is there a way to help on that? Tired of my feet sweating...

 

You want 180+ for minimum wear. The stock thermostat may not start to open until 195 & then fully open at about 220.

If you live in a hot area you can run w/o a thermostat though you may need one in the winter. A better solution is a 180 thermostat or adding hole(s) to thermostat. Note that if stock is 195, running lower thermostat or none then carb heating, EFE may not go off.

Hot foot well
You can make sure the heater shut off is working. Note blower runs full time on Low speed. I changed Low to Off.

 

if you run NO Tstat you may have trouble cooling at prolonged high speed highway driving. some say this is untrue but my old 65 mustang would run hot on the highway without one (because the coolant was circulating too fast to cool off in the rad) JMO

 

IF you are running a 50/50 mixture of water and ethylene glycol, 220 degrees is NOT hot. If that is the highest you see, you are fine. My car ('70 454 with ac) will run all day long at 180 even on a hot day if I am moving consistently. If I have the ac on, and do a lot of sitting like in traffic, the temp will slowly rise to 220 and stay there. This is normal and is nothing to worry about. When I get consistently moving again, it will slowly drop. It takes a while, but it will go back to 180 even on a hot day, this is an indication the system is working as designed.

Generally speaking, a temp of 240 is cause for concern, and the system should be checked. Much above that and you will probably start to have problems.

 

The cooling system will seek its own operating temperature...regardless of what thermostat you install. The stat only establishes the lowest temp you can expect to get; it is there only to get the engine up to normal operating temps quickly...for less engine wear and better performance, and for heating the interior of the car in cold weather.

The fact that your engine temps go up when you ask it to do more work is not a surprise. However, the fact that it raises 20-30 degrees just from running at highway speeds is not normal.

It would not hurt anything to change the T-stat. It could have a mechanical problem that is restricting flow (not fully opening). That would cause the engine to heat up with more work being done. Also, the radiator could be limed-up inside, which will reduce cooling efficiency considerably. If you haven't had the radiator cleaned (not "flushed") in some time, you might consider doing that with some Prestone [or other brand] 'radiator cleaner'. If you follow directions, it will clear and build-up from the inside of the fins.

There are other 'cooling efficiency' type of problems as well: foam seals around the radiator deteriorating or missing--this will cause cooling air to bypass the radiator instead of going through it; missing shroud housing or missing shroud extension--reduces the ability of the fan to draw air; collapsing lower radiator hose--usually found when a "hi volume" water pump is added to the system; missing front spoiler under the nose--air is not deflected UP into the radiator airpath; improperly functioning thermostatic clutch on the fan; wrong fan for the system; etc.

Look for the 'cooling efficiency' type problems first. Fix any of those and change the T-stat, then see how it behaves. If you still have problems, use the radiator cleaner.

P.S. If your engine timing is retarded from where it should be at highway speeds (2500 rpm and higher), your engine will run hotter, also. You could have a distributor problem with the mechanical advance system, such that it doesn't advance properly with increased rpm. Put a timing light on the engine and raise rpm up to about 3000 or so. The timing mark should smoothly increase throughout that range. It it stops increasing at 2000 rpm [or isn't working at all], that could cause your problem, too.

 

Thanks for the input. Maybe I am just being overly concerned with the 220 mark. It has only gone over that once, and that was doing over 70 on the highway on a 90+ day. When it is around 80 out (like yesterday) it will run around the 180-190 when cruising at 40-55, but will get close to that 220 mark when doing 70. The engine has had work done to it. I am still trying to figure out exactly what all has been done. I got it when my dad passed away in July, and he said it was over heating, so I assumed that 220 was running hot on the highway. I know it has had cams, and torque converter done. Bored .030 over, an Eddlbroc carb, (I believe a 750cfm) and some other stuff done to it. My dad told me before he passed away it was about 435HP at the crank. I am gonna check and see if that hose has that spring in it soon as I get off here, because I remember him saying he put in a high flow water pump. The radiator is less than 2 years old with less than 3000 miles on it. It is a Champion 4 core radiator I believe, bigger than stock, but leaves a little big of a gap around the edges. I have been working on closing those off. I will keep you guys updated.

 

Ok, does anyone have a picture of the lower radiator hose spring? I am curious to know exactly how far apart the coils on it are spaced and exactly how close in diamiter it is to the diamiter of the hose. I went out there and squeezed the lower radiator hose where I could reach it (its a tight fit down there) and I was not able to feel anything. So I am thinking that may very well be my problem. So if you have a pic, please post it up!

Thanks!

 

Now w/ more info. you can see you are close & just that rad. gap, missing or damaged front black dam under bumper or a lower hose could help.

 

I dont know if you can really feel it. I replaced my radiator last month and was ready to dumpster the lower hose because I couldnt feel anything but much to my suprise, there it was. Took it out and put it in the new hose.

I looked at the vendors here and thought they would sell them and I knew years ago Dewitts did but can find anything now. Google lower radiator hose spring and you can view a pic.

In another post I took this
"The best material to construct a spring out of is a length of thin diameter Bronze Welding wire, and coiling it around a pipe or rod for size."

Don't forget to bend the ends a bit more, so that the sharp ends cannot piece the hose from the inside.

Doesnt have to be pretty, just in there.

I have higher temps at highway speed also and am working to seal around the radiator. It will go up 20 degrees when I'm at 65mph.

 

also, overheating at highway speeds only could possibly be an old rad that needs to be professionally cleaned,,,,

 

Maybe, but now I am not so sure.

If your cooling system is working properly, it will tend to run hotter when you are going slowly, or in stop-and-go traffic because there is less airflow over the radiator. Steady highway-speed driving should result in lower operating temperatures (assuming your normal operating termperature is above your thermostat rating).

This sounds unusual. On an 80 degree day, my car will run at 180 cruising at 40, 50 or 70. It was 90+ degrees last year on my way home from Carlisle, 160 mile straight run on the highway. The needle did go up a needle width above the 180 degree mark, but not much.

It doesn't sound like you have a big problem here, so like the others said, I would address the gap you mention here and see where you are. I wouldn't be surprised if you're fine after that.

 

No mention of the engine type-L-82 or L-48 or something else. Normal operating temperature for the 78/79 L-82's was 225 degrees from the factory due to emissions standards. The 78 gauge reads 200 at the 12 O'Clock position of the gauge and was changed to 225 (you mention 220, I thought it was 225) at the same position in 1979 due to the customer complaints about the engines running hot in 78. When my car was totally stock it routinely ran 235 with the A/C on very hot days. My friends 79 bought new in 79 (L-82) ran 225 all day long. Yes, the heads are the real culprit here and these years the engines (L-82) get HOTTER with speed on the highway like you describe. Finally totally cured the issue a few years ago with a Dewitts aluminum radiator and a Stewart Stage 2 aluminum water pump with a 180 degree thermostat-never goes over 175-180 now even on 100 degree days which was never true in the past. BTW-my gauge is dead accurate-verified with an infrared thermometer recently. Hope that helps!

 

There are many good suggestions in this thread. All I can say is I live in FL and on a 90* day my 79 runs hot. On a club cruise driving 120 miles, there were mostly C-5-6 Corvettes participating. They cruise comfortably at 80 MPH and a challenge for my 79 with a 3.73 gear to keep cool. It ran 230*-240* most of the way. If I keep it 65 MPH or below, it will stay around 220*. For this reason most C-3 owners doing upgrades add a better cooling system and an OD transmission. I doubt your lower radiator hose is an issue, as there have been many threads on overheating issues with C-3 cars posted here. Squeeze your lower radiator hose and you should be able to feel the spring. When replacing a lower hose, it is a good idea to keep it, just in case you need to use the spring. Good luck, you are not alone with the running hot engine.

 

Could a front license plate be blocking air flow to the radiator?

 

It has a bra on the front to cover up some of the paint that rubbed off over the years. A new paintjob is in the future. Bit as far as i can tell it isnt blocking any air flow to the rad. Lower air dam is there and intact. I may remove the bra and see if it makes a difference. But i cant see how.

 

Not on a '79 no, there is no grill behind the license plate. In any case the corvette is mostly a chin feeder anyway.