Yea, that can be a nerve wracking experience the first time you see. Once you realize it's perfectly normal, it's a big relief.

@@VetteSource- there's nothing "normal" about it! Chevy....

@@mhicks5008it’s normal….. relax

It is normal but i still dont like it

Exactly, it's the time sitting in traffic that can cause that stress and anxiety. That was what I was going for with this demonstration. Even with the cars sitting in the mid afternoon heat, they will perform as designed and keep from overheating as long as the cooling system is functioning as designed. Thanks for the comments👍

Michael, excellent writeup and information regarding the cooling systems for the C4's. Like you stated, bypassing is an option if an owner is uncomfortable with how hot their C4 is running, but beware of the unintended consequences of deviating from the factory settings. Thanks for taking the time to share your knowledge with everyone

@@VetteSource Thanks VS. The throttle body coolant passage is only there to prevent icing of the throttle body; it has no engine cooling effect. But I do take your general point, and I've previously given that a lot of thought. There is an air temperature sensor in the intake plenum, which helps the ECU choose the appropriate fuel/timing map. A cooler reading from that sensor equates to cooler ambient air. Since intake air temp is a fundamental and immutable factor in combustion characteristics, it's a prime determinant for the ECU, not to be ignored under any circumstances. The throttle body coolant passage does have significant control over TB temperature, but does NOT have absolute control over intake air temperature. Ambient air temp, TB temp, and plenum case temp combine to create a net actual air temp inside the plenum. I'll try to illustrate why bypassing the throttle body coolant passage is safe under most conditions, but not all possible ones. At one extreme, perhaps you're in Canada in January and the ambient temp is -40F. Combined with the warming effect of the TB coolant passage and plenum case temp, let's say net plenum air temp is +80F. The ECU has a map for that. At the other extreme, perhaps you're in Death Valley, the ambient temp is +120F, and the net intake air temp is +210F. The ECU has a map for that as well. Bypassing the TB coolant passage and reducing net plenum air temperature simply causes the ECU to select a different air temp factor for its calculations, which it is perfectly capable of doing over the widest expected range of net intake air temps. If TB temp dips below +32F, there is a very real risk of ice forming inside it, the severity of which is determined by incoming air temp, duration of exposure, airflow volume per unit of time, and the humidity level of the incoming air. This is why the factory incorporates the TB coolant passage. But, given that the TB is attached to a hot engine via the intake plenum, icing is unlikely under all but the most extreme conditions. While there is obviously a coolant temp sensor connected to the ECU as well, the expected range of normal operating temperature for mapping purposes is predicted to be between +195F, at which the thermostat opens or closes, and the fan-controlled max of +230F. Coolant temp is mostly a pass-fail factor based on whether the coolant and oil are above or below +195F. Below +195F, the engine is considered to be 'cold'. There are, of course, some 'gray areas' involved in all of this. Welcome to the realities of managing internal combustion engines over an extremely wide range of operating conditions. Contrary to popular belief, the factory really does have a clue about what that requires. Whew! OK, if all that doesn't cover it for someone, I guess they'll just have to attend automotive engineering school.

Very well said. I'm surprised you don't have an automotive channel yourself, you've got quite a bit of good knowledge to share👍

@@VetteSource Thanks again. I have thought about starting a channel, but I'm aware of how much time and effort that can require, and I already have a lot on my plate.

For sure, it's quite a handful to add to an already busy achedule. I appreciate you taking the time to contribute here👍.

Thanks Muhrad, glad you enjoyed it buddy👍

Great perspective, thanks for sharing👍.

Randall, thanks for sharing your personal insight from the field. That's the kind of valuable real world information that's gold for a new generation of Corvette owners working to keep these now classic Corvettes on the road. Considering how thorough GM likes to be in regards to the mechanical side of the cars, you would think they'd have done a better job communicating the normalcy of high engine temperatures to the new owners. However, I think the aftermarket Corvette suppliers are partially to blame with all the cooling fan bypass kits they were hawking during the 80's and 90's to make your car run cooler and more "efficient". Once they started advertising those, the urban legend of "your Corvette runs too hot" spread like wildfire. They should see how hot early 427 big block Corvettes like to run😁.

Excellent information the both of you. Understanding all of this, are there any advantages to "try" and run the system cooler if emissions are not a concern, say with no cats? Horsepower wise?

Mark, good point. Thanks for sharing with the group👍

No problem, glad to help👍

No problem, glad to do it👍. I found myself having to revisit the service manual to make sure I wasn't losing my mind when I noticed the gauges juat about being pegged out.

Hey David, glad you enjoyed it. I'll bet your enjoying cruising those scenic roads up there right now 👍.

Thanks, will do!

Oh yea, summertime in Houston. Good idea to get that straight water out of the system, that makes a mess with cars that were originally equipped with Dexcool. Thanks for the comments👍

@@VetteSource the two knock sensors and the bleeder valve were the "hoot" in corvette technology.

Yea, that bleeder valve sure is an interesting engineering solution to removing air from the system. If it wasn't spelled out whilst their purpose was, most people would miss them.

glad you enjoyed it. You're definitely not the only one. Quite a few C4 owners suffering the "temperature gauge" anxiety disorder

Can I drive to Georgia from I Illinois at temperature 200?

@@kennygibbs9627 It won't stay that high all the time. Usually on idle it goes up.

@Steve-xf4uv drive around town, it runs at 190 .

Sure, that's perfectly in the normal operating range.

Great, I'm glad to hear you found it helpful👍. Sounds like yours isn't very close to stock, so those mods to your cooling system would be called for.

Yep, good point. Thanks for sharing the information. The cooling systems do a great job at drawing in all that road debris and trash until it affects the operating temperature like you mentioned.

Great, glad to hear it👍

Thanks, Giorgio👍.

No problem👍

Glad it was helpful!

For sure, the closest you'll ever get to driving around inside a pizza oven during the summer🤣.

Yep, that's exactly in line per the specs in the service manual. Thanks for sharing, love the Admiral Blue cars👍.

I'm also in Texas...would love to do a video with you!

Sounds interesting, just drop me an email when you have time👍

No problem, I'm glad you enjoyed it. The deteriorating underhood plastic is a real issue on these cars of the 80's and 90's. It definitely makes it a bit harder to keep them on the road, but it's worth it with as much as they are to drive👍.

Thanks, man. I think it came well, just not as much fun to make it in the heat😁.

Glad to hear, it's one of those things to get nervous about when you don't have a frame of reference of the normal temperatures to work with.

@@VetteSource Having such a narrow normal range on the needle is strange for how hot these run. I watch my temp on the digital now knowing where it should be.

Yep, the analpg gauge is almost worthless in my opinion unless you just like to be stressing out over where it's sitting😁.

Glad to hear you enjoyed it👍. You know, I completely forgot about the auto transmission temp gauge on the later C4's. Normal cruising temperature should be around 180-200, higher in town. The temperature will come down a bit slower simply because the transmission cooler is only receiving indirect cooling from the fans due to its location in the radiator tanks.

Good information. Thanks for taking the time to share👍

Thanks for the feedback Bill, glad it was helpful for you.

Funny, that is the truth. Everywhere you look in Florida you're likely to spot a Corvette. There are quite a few of them here in Texas as well, but there's so many roads it's easy to miss them cruising around.

No problem, glad it was helpful👍.

Thanks Glen, appreciate the feedback. Whenever you have time you'll have to share with the audience your "secret sauce" method.

@@VetteSource here ya go..works like a champ. kzfaq.info/get/bejne/brFnnK2WtNDPcnk.html

Whats the secret ?

You must not live in Houston during the summertime😁.

Hey Chris, thanks for chiming in. The temperature urban legend is one that definitely will not go away. Glad to be getting some time to wrench on the Formula myself. It's time to put the red down for paint, so I need the yellow one to cruise around in.

@@VetteSource correct, I think as long as these cars are around that argument will be too 😄 Well no matter which one you pick you'll be cruising in style!

No problem, glad I could ease your mind👍.

Good morning Abel, Unfortunately the lack of the dual mass flywheels has created the problem you're describing with ZF equipped C4's once the original dual mass is replaced with the single mass. From what I understand, there really isn't much to do about the excessive noise, as part of the dual mass flywheels original purpose was to dampen clutch chatter. At the very least, I would double check tolerances between the flyweel and clutch disc to make sure everything was installed to spec. If you also have your original dual mass flywheel and its not damaged,, you could try having it resurfaced by hand. It's a tedious process, but some people have resorted to that so they could keep the dual mass setup.

Hey Rocky, thanks for the comments👍. I've seen quite a few of those conversions done and dismantled quite a few C4's that burned to the ground because of it. Unless it's absolutely necessary, I always advise people to stay away from grounding the relays. It's an accident waiting to happen.

That's correct. The temperature and fan on/off settings will be the same.

Hey Steve believe it or not the ZF was filled with 10W30 engine oil from the factory. Nowadays, there are several vendors making replacement oil for the ZFs including Amsoil and Castrol. These will be in the range of 10W60 and specifically designed for the ZF gearboxes and specify "synchromesh" fluid on the container.

Yep, the c4 front end doesn't lend itself much to cooling if anything gets in the way or there's a blockage. The cooling system was tough for Corvette with the introduction of the C3 in 1968 all the way through the C6's. It wasn't until the fish mouth debuted on the C7 that the cooling system received some extra help.

@@VetteSource yeah exactly! GM should of put more of a cold air induction system in it! And heat extraction system in place for at least the C4! But I thought like the C3 generation they had a better system but I don’t much about them…I’m not a fan of the C3 generation!! I have a buddy whose owned several C3’s(heck still has a ‘68 L88 427 4spd sitting in storage!) owns a 94 C4(owned a ‘84) Owned a’00 C5!! He can tell me everything he knows about them…I just keep forgetting to ask him!!🤣

Sounds like a nice collection your buddy had. I am a fan of the C3's myself. There seem to be a few of them laying around here at the shop😁.

Interesting, hadn't heard about that hack before. Thanks for sharing👍.

Sounds like somebody direct wired your fans so they would run all the time rather than address any problem that may be present with proper fan operation. This is a big no-no. The relays were not designed to be delivering constant current to the fans and can overheat and catch fire. I've dismantled many Corvettes over the years that had burned to the ground from this modification.

Yep, that analog gauge on the dash is as close to a modern day idiot light that you'll find. When these came off the assembly line, there was a sticker placed on the cluster explaining that the temp gauge was not linear, so in other words don't rely on it for any degree of accuracy. I should have had my MT2500 hooked in as well to show the readings from the ECM, but forgot to bring it out.

Great suggestion, thanks for sharing👍

¿Estás viendo 240 grados en el indicador del tablero o en el indicador electrónico ubicado debajo del velocímetro?

Hey James, that's great! Glad to hear the video was helpful. It is always nice to hear from another Cometition Yellow LT4 owner. You may be aware, but these were very low production, with around 140 Competeiton Yellow LT4s produced. Is yours a coupe or convertible? You can see my playlist with quite a few C4 trivia and how-to videos here - maps.app.goo.gl/mphDKMF6QsB4ovhp8 Let me know if you need anything else, and welcome to the club👍.

Interesting observation that's overlooked fairly often. Thanks for sharing👍

Sounds like somebody hot-wired your fans to run all the time with ignition on. Check the fan relays mounted on the driverside of the radiator/cooling pod, directly above the frame rail. I'll bet you'll find an extra 12V wire jumpered in there to force the relays to run the fans all the time.

You can just reach in and pull them off. It's a tight squeeze, but there should be just enough room to get your arm up there.

Yep, that's my normal cocktail since we don't get too many hard freezing events this far down in South East Texas.

I'm not so sure I'd call it a bad design, but they definitely left room for owners to upgrade to their personal tastes. Thanks for sharing the info with the group.

That is pretty warm. I'd check that radiator inlet to make sure no trash is blocking the airflow.

Nope, these cars are both completely factory original. I also have a 1993 40th Anniversary with 27K miles on it, and it follows the exact same temperature pattern.

Yep, I've mentioned that they aren't linear in a few of my videos. With that being said, the analog gauge really isn't your best indicator for actual temps. Using the "gauges" button on the DIC switch to select " Coolant Temp" displayed under the speedometer is the most accurate indicator, as it uses a different temperature sensor than the analog gauge for its reading.

That seems to be a bit on the cool side, unless you're in a cooler part of the world with mild summers. Do you know if any previous owners made some modifications to the cooling system?

@VetteSource I don't know, but like I said I run antifreeze and drive 90 minutes at a time in 80 degrees temperature always temp gage rarely goes past 1st line which I'm calling 140 unless I'm in heavy traffic which is almost never I drive at either 10am or 6pm Midwest state. This car is just for fun and it wouldn't be fun if it was always running hot or if I'm worried about it running hot while I'm driving it.

Ok, 80 degrees ambient is a cooler temperature for sure than what we see down this way. One thing to consider as well, is that the needle garage on the dash is fairly inaccurate, as pointed out by GM when describing it as a non-linear gauge😁. The best read of your actual temperature will be the electronic reading that can be accessed by pressing the "gauges" button on the DIC

@VetteSource I used the numerical temp gage that you mentioned and I didn't know I had lol and my readings are 179 t0 183 while cruising and 194 while sitting in traffic but this is in 80 degree temperature in Midwest while driving about 75 to 90 minutes almost everytime thanks for the info.

It's controlled by the ECM internally, so there's no real way to adjust the setting.

@@VetteSource is there any kind of aftermarket relay that can turn the fan on if the engine gets over 200?

Not that I'm aware of, but somebody may offer one that will interchange with the factory relay that will kick the fans on earlier.

@@VetteSource that would be good. I hate running so hot.

Hey Michel. Do you mean it would reach over 262 degrees and boil over? Sounds like you may have had a cooling system or electric fan issue.

@@VetteSource The needle would go all the way to real hot though there was no boil over. However, I got rid of it because it started to leak oil then finding out Chevy used silicone as a sealant around the water pump, distributor and bottom pan which dried out over time. The car was 3 years and 2 months old. Chevy knowing this was a problem didn't stand behind it. I sold the car and swore I would never buy a GM product again of which I haven't though I do miss the Corvette.

I understand, Corvettes of all generations are somewhat high maintenance. If you're trying to use as a daily, it's hard to ignore all the little annoyance items like leaking targa tops, squeaks and rattles, computer problems, paint issues, and random component failures that sometimes force you to leave it parked in the garage for weeks on end. However, when your behind the wheel and it's running well, you'll easily forget everything that annoyed you about it in the first place😊.

Yep, the YT algorithm works in strange ways for sure. Maybe you're destined to have a Corvette in the future😁. Thanks for the comments👍

@@VetteSource I see a lot of them at work, maybe I'll impress someone with this new found knowledge someday

There you go. Nothing like having a ready made conversation starter👍.

Hey Rocket, that's a common bypass, but one you need to be careful about. I can't tell you how many C4s I've dismantled that burned to the ground due to this type of bypass. Usually, it ends up overheating the relay or the associated wiring and catching on fire.

@@VetteSource Sense I wrote that Ive replaced both temp sensors with 185 switches(sensors) and have it wired back the way it was factory so now everything works like it should

Yep, that sounds like it should work👍

Definitely more accurate. There's even an information label on the cluster when the cars are delivered new that points out how the analog gauge is not a linear device. You can see it in this video here - kzfaq.info/get/bejne/m5d7grFny8y8oIE.htmlsi=JS38G4b-B4Z3AY44

It sounds like you may have more than one issue going on there. It would definitely be worth your time to hook the car up to a scan tool to see what it's doing on the first start up and after it goes closed loop. It may give you a starting point to work from.

Yes that's the electronic digital gage in the center of the dash. That analog gage is junk even though it works like it's supposed to. Just like your car's mine is 100% stock. Nothing but the oil and battery has been changed.

Yea, 243 is a bit too high. Was that the temperature indicated on the electronic display under the speedometer?

I would look underneath the car in front of the radiator to make sure you haven't sucked up a plastic bag or other debris that is blocking the airflow. I would look at the coolant reservoir level also to make sure you're not experiencing a small leak somewhere.

Excellent, that's good information for other owners. Thanks for sharing👍

I would probably disagree. The computer controlled stock fuel injection system from this generation is designed to burn as much fuel as possible during the combustion process, with the excess being recycled back to the tank through the return line. When you lower the operating temperature of the engine, you may feel more "seat of the pants" power, but it's not as clean or efficient of a burn and tends to foul up the associated fuel injection components and sensors which over time just leads to more maintenance and $$$ spent fixing it. Figure that the GM engineers spent literally thousands of man hours getting the system perfectly balanced between power, fuel economy, and emissions output and you can see why they specified the operating temperature that it runs at. Thanks for the comments👍

@@VetteSource I'm ok with disagreeing on this point. I do appreciate the videos.

No problem at all. I'm always appreciative that you guys enjoy the videos and take the time to comment. Just to clarify, I don't think it's always bad to adjust the coolant temperature to what your comfortable with, but I usually aim these type of informational videos to my viewers that may be more driver orientated Corvette owners than gearheads. I know my fellow gearheads will always find a way to make their car faster, it just gives us an excuse to wrench on them more😁 Have a great week👍.

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Good one😁

237 is a tad high. 230 should be your maximum upper limit if the system is operating correctly.

Have you looked into the optispark or coil?

@@VetteSource brand new optispark and coil and plugs. The problem seems to be intermittent. And i noticed the car runs rough when i turn the AC on.

Sounds like you will need to hook it up to a diagnostic scan tool that will provide real-time data streaming. Something is obviously happening once you put a load on the system, and in the absence of a "service engine" lamp you're chasing shadows without hard data.

@@VetteSource that’s the hard part i have no engine light on i have a guy looking at the car now I’ll mention the data stream too him and the car isn’t acting up when he drives it.

Good info, thanks for sharing👍

Yep, that second cooling fan helps quite a bit. Thanks for the comments👍.

@@VetteSource I also have a 96 and I leave the AC on year-round and the car runs much cooler, The first time I took the top off and shut the AC off I thought it was overheating and stopped the car and started looking for the problem. I didn't find anything and continued to drive back home. I then got on the computer and read about the reverse cooling system and how it always shows hotter than most cars because of this. I did replace the left side fan because it was always running slow and that fixed the problem of not speeding up when it should have. I noticed that when driving with the climate control (CC) on the car runs a lot cooler down around 180-200 so for peace of mind and I live in California I can run the CC year around. The right fan seems to be always running with it on. Good info for those who are not used to the LT engine reverse cooling system.

Yep, that sounds about right. You may have noticed, but when I first jumped in the yellow car towards the beginning of the video, it was running around 200 degrees with the AC engaged. It only got to the higher temps once I shut the AC off. Thanks for sharing your experience, that's good information for everybody to have👍

The boiling point is raised in a closed system. Thanks for taking the time to comment.

That just means you've well.on your way to becoming a subject matter expert😁.

Yep. I believe the F bodies were designed to run a few degrees cooler. In addition, they have both electric cooling fans wired in parallel, so they both run at the same time either low speed or high speed with AC on. Thanks for the comments👍

Perfect, good for at least another 35 years with that low of mileage👍.