I have a 1992 and I would like some advice. All mentions of temp will refer to the digital gauge. Using a Snap-on scanner my digital gauge reads 2 degrees low.

How can I make this car run cooler?

First I have flushed the system, replaced with a mixture of 50/50. New radiator, water pump, all hoses, and new 180 stat, and new AC condenser, and new Opti. On the highway on a 65 degree night at 70 mph the car runs 220 to 225. This is with air on or air off. The car is completely stock except it has a big mouth air dam.
If left sitting after highway drive the temp will range from 220 to 225, with air on or off.
What conditions must be met to turn on the primary fan?
What conditions must be met to turn on the aux fan?

 

The main fan comes on at 228F and the aux fan at 238F. It will be easier for you to become comfortable with the 220 F temperature than it will to lower the operating temp. NOTHING in the engine can be harmed by this temperature. 50/50 coolant at 15 PSI boils at 265 F and GM says to shut the engine off at 260F and let the engine cool down. Coolant boiling forces coolant out the overflow and lowers the coolant in the heads and the head temp can rise to where head damage occurs. Your temp numbers are correct for a 92 and are safe and it was designed this way. The only way to lower your temps would be to install a larger radiator. You see 220F because of where the digital gauge sensor is located. Since you don't see even 228F, you don't have thing to worry about.
The radiators job is to get rid of heat and its ability to do this is primarily determined by the difference in temperature between the outside air and the coolant temp. The larger this difference, the higher the heat flow out of the coolant. To run lower coolant temps requires a larger radiator and there is inadequite room to do this. C4 vettes do not have the reputation of short engine life from higher than past vette coolant temps. I have been driving my 87 every day since 1989 and it has 233k miles with the original engine which is still in good condition and I have always had the stock 195 thermostat in it and is what the coolant temp runs when I am under way. I think most modern cars run at higher temps than older cars, this allows for lower exhaust emmissions and better fuel mileage.
Instead of spending a lot of money to shoe horn a larger radiator into your 92, do as Bugs Bunny says, "Unlax Doc"!

 

You do not need a larger radiator (remember the radiator is a heat exchanger..it will exchange about the same heat energy at 100 or 300F). You need a lower thermostat for lower highway temps (the thermostat sets the 'floor' on the operating temperature). And the fan on/off temps must be set lower for a lower city driving (fans increase air flow during idle or city driving).

However, your temperatures at 220 are not excessive on these LT1's

I put a 160 thermostat in my 95 LT1 (same as your 92) and I run 185 at road speeds. MAKE SURE YOU GET a LT1 thermostat $20 from Ecklers, etc... a generic thermostat will NOT function properly in the reverse flow LT1 set-up.

For city driving you must lower the fan on/off temperature. On my 95 I can program the fan temp with programmer, I am not sure about your 92. My fans come on at 195 and my city temp in traffic is 200-210.

When your A/C is on the fans run high speed all the time. So, if you just install a 160 thermostat and keep the A/C you will have city temps of 200-210.

Joe

 

Check in front of the radiator

http://forums.corvetteforum.com/c4-g...post1570992791

 

You clearly don't know anything about heat transfer or thermodynamics. One of the factors that determine the heat transfer rate of radiators that I have already explained is the difference temperature between the outside air and the coolant. From 100 to 300 degrees, a radiator, all other factors equal, can transfer 5.23 times more heat than at 100 F. Furthermore, if your coolant is running 185, your 160 thermostat is wide open and has NOTHING to do with controlling your coolant temperature. If a 160 stat was of any good to the cooling system, GM would have installed them at the factory.

 

^^ thanks, you saved me from having to type all that out.

A Lower Temp Thermostat is not the answer.

 

Why not put a 32 F thermostat in, you could make ice while you are driving down the highway!

 

JFB & John, well, I do not know all I would like to know about heat transfer, but I have some experience.

1.I agree with your original comment CVETTE04's temps are normal. He has done all the clean-up of the system and should be good just to leave it as is.

2.CVETTE04's question was how to lower the temps. I was telling him how I did my 95 LT1 which is quite similar to his 92 LT1. I did on my 95 because it is high mileage and I feel better if tranny fluid and oil temps are a bit cooler. On my other Corvettes I run as GM designed.

3.Yes, you are correct that LT1 radiator will exchange more heat at 300 F vs 100 F operating, but we are talking a very narrow 170-240 F operating range on his LT1. (I work with -100 to +600 F process exchangers so 70 degree changes are small to me)

4.Again, with a 160 F thermostat in my stock 95 LT 1, I typically have 185 F temps at highway speeds @90 F ambient. Minimum temp is 175F @ ambient less than 80F. Both the front digital and rear analogue run the same temps.

5.In city driving I would have the typical LT 1 temps of 220F; however, I reprogramed my fans to come on at lower temp which yields city stop and go temps of 200-210F (rather than 220-240)

JFB you are correct, GM designed these to operate at higher temps for emissions, etc. I pass the Texas inspection with my lower operating temps., may be a question in CA.

If I did have an emissions problem, I can quickly reprogram my fans temp back to factory settings and operate at 220F.

6. On LT 1's the two fans run in tandem at low speed and then step up to high speed at a higher temp. I believe your older C4 fans run one speed in series as second fan is activated at higher temp. On the LT 1's the fans are on high speed whenever the A/C is on. (I had a couple of new early C4's, but do not remember the fan operation).

I also have a manual switch on the #2 fan (ground the blue-purple wire) to emulate the A/C high fan activation. So if I should want I can go to high speed fans without the A/C engaged.

7. I run about a 5% glycol coolant fluid (to avoid corrosion), I never will be in freezing temps and water has higher heat exchange capacity than 50/50 mix.

So, to answer CVETTE04 question how to lower cooling system operating temperature on his 92 LT 1 use a lower temp thermostat and lower the ON fans temp for city driving. If he can not have his fans ON temp programmed lower as I did, there are some after market thermal switches kits (made for C4's) that can be installed to activate the fans at a lower temp. Four of my Corvette buddies have these.

A bigger radiator is not needed. I did not need it and these four other C4's did not change radiators. My one buddy has owned 6-8 C4's and he always adds this C4 fan kit ($70?).

CVETTE04, John, JFB
come visit anytime and you are welcome to go drive this old tired 95 LT1 and see what happens to the temps. You can dive the other Corvettes as well. My old 61 which is all original (had it 42 years) has 180 F thermostat and indicates 185, never varies more than 10 degrees even while sitting in 98F ambient.

One should have a cold beer or iced margarita when discussing thermodynamics, especially the third law.

Joe

 

JFB,
I do have that problem! I do not think the cooling system on an LT 1 could do that (I am not going to be in those conditions).

But, I do have some big engines North of the Arctic Circle in Russia (Yamal) that will do this. These are huge 20,000hp compressors. In the winter when temps can drop to below -40 for days with high winds the coolant freezes.

Even though the engines run and coolant circulates, it will freeze. We have to put insulated shutters on the heat exchanges to keep them above -20. Fans in summer...shutters in winter.

Have similar concern on two of my airplanes at high altitude, the oil coolers will (not freeze) congeal the oil if not monitored

Joe

 

God help you if the coolant ever does freeze!

 

Something doesn't make much sense here - 40 degrees above the thermostat at cruise? Sounds like a pretty crummy heat exchange to me - either the Big Mouth Air Dam ain't doin' it, or the shroud is broken - assuming everything is clean. Come to think of it, if you're running the a/c, just what is the High Side doing (check/log the Pressure Sensor signal with your scannner which will you give you volts and pressure)? 100 to 140 degrees is about max for the gas in the Condensor - well below any thermostat which is why you need one - what's yours got? You don't usually see the gas at that temp/pressure with these coolant temps; in fact the a/c doesn't work very well when it's this hot.

 

I had the same issue, replaced the radiador, all hoses and tstat, and cap. freeway I am at 190 and in traffic it starts going up. Make sure you bleed the system, and maybe add some water wetter. Maybe the stat is no good? I used an autozone duralast stat. Maybe get an AC delco one? Heater core? do a flush? My automatic trans was getting hot, and was down a qt, check that too. Since it can heat up the radiador as well.

 

When I had my 92 vert, I would see temps of 195 to 215 in stop and go city traffic with ambient air temps in the high 70's. When air temps rose to 85 and higher, the coolant temps would be 210-225. I could see a drop in coolant temp as the secondary fan kicked on.

I never did see any coolant temp reading much past 230 and when that did occur on really hot days (100 degrees plus), it was just before the secondary fan kicked in.

The bottom line is that the temp readings you see are normal or maybe just 2-5 degrees warmer than normal for the LT1 cars.

When you flushed the system, did you drain the block by removing the knock sensors? It's possible that the block has a buildup of mineral deposits that could be causing some heat transfer problems around the cylinder bores or the combustion chambers in the heads. Did you use any sort of flush chemical (although the FSM does not recommend using chemicals) to clean out the system?

Maybe the later LT1 cars work this way, but the secondary fan on the 92 does not run until either the proper temp is detected and a signal is sent by the ECM to the fan relay or the A/C is running. The 92 FSM does not show or discuss any 2-speed (high/low) fan operation. The secondary fan either runs or doesn't.

 

I thought the Poster was talking Cruise - not idle or low speed? Seeing 230 at cruise (on a 70 degree day?) with the a/c on or off is usually air flow and assuming everything else is as it left the factory you might expect that the Condensor fins are clogged up with stone chips/bugs and assorted trash or they're just beat up. It'll show up at the vent or just slap some gages on it to see what it's doing. I'd guess the pressure is going to be too high and with a new radiator, it isn't getting enough air through the Condensor to let either system work the way it was designed - a/c on or off. If it is a plugged up Condensor, backflush it with water and get a 2 Buck fin comb at Harbor Freight Tools to straighten things up.

 

You da man, Cr!

 

I would like to say thanks to all of you for taking time to answer my questions.
I know these temps are not extreme. It is just that I have had other Vettes and none of them ran this hot except an 84 I had. I currently also have an 04 that never runs over 202 in traffic and runs 198 on highway.
The 92 has 110,000 miles on it and the 04 only has 12,648.
Today on highway car ran 220 but when I got home and sat in driveway with AC on, both fans running temp held at 194.
I think one problem is the air dam on the highway. But I would like the first fan to come on before 228 without the AC on. I do not know how it will do in winter. Only time will tell.

devildog
I do not think it is possible to reprogram my fans. I know however another chip could be installed. I think they are a little pricey. I think I will order the thermal switch kit from Ecklers, 200 degree kit with the stock 180 degree stat. Where are you located. I am in north west TN.

SunCr
I do not think the Big Mouth is installed correctly. I did not do the install. I have only owned the car for about 2 months. Tomorrow I am going to remove it a reinstall it. I do not know what the high side is doing but I will check it.

dolbnyc
I got the stat at Autozone, maybe it is not working properly. I flushed the heater core, engine, and radiator 3 times.

c4cruiser
I did not remove the knock sensors but I will do so when I install the thermal fan switch. My secondary fan only runs when the AC is on or temp is at 238. The 238 is what I have read do not know for sure, car has not reached that temp. I have bleed the system 6 times.

Again a big thanks to all

 

Sounds more like the air dam from what you noted in your Driveway.

With the a/c runnning, Fans are programmed to keep the gas at around 200 psi (idle to about 40 mph) - so something near that number should get them cranking. The guys who design these things really don't care about coolant temps (or emissions, a/c is exempt) so the radiator and everything else is from another engineering dept. Assuming the a/c has the right charge, one if not both fans will be turning the minute you start it; even if it's sat overnight and they'll keep running or cycling a lot less than when it's off (meaning the Coolant Temps should stay 10 to 15 degrees lower with the a/c on - low speed/idle).

 

cvette04,

Whereas I might too have suggested it was a bad thermostat, your driveway test with the AC on and it staying at 194 (which is exactly where our 94 stays at too) proves thermostat is fine.

FYI, some after market stats' lower plate are not the correct depth and can cause problems -- most noticeble as a large difference between digital and analog gauge readings due to the analog gauge's sensor being more towards the rear of the engine.

ALSO, your driveway test also proves radiator and rest of cooling system is fine.

Your idea of a problem with the big-mouth install makes sense as it does sound like an air-flow problem.

However, if that does not correct the problem, there are two other possibilities:

1. Might the fans be running at highway speed (via some chip change by prior owner)? If so, they can actually block air flow through the radiator (as they are normally programmed to turn off above a certain mph -- maybe around 35 mph). You could rig a test-light to the fan motor plug to see if it goes off at highway speeds.

2. Might the engine be running too lean and is actually generating too much heat (btu's) for the radiator to handle at cruising speed in closed-loop operation.

Check the FSM, as there is a way to tell if the engine is running in closed-loop (might be to drive it while the paper clip is in to tell diagnostic codes).

Next, are there any bad plugs or wires which might be causing one or more cylinders to dump unburnt fuel, causing the o2 sensors to read rich, thereby causing the PCM to lean out the other cylinder mixtures to compensate and causing an overall lean engine which will run much hotter than normal?

You could pull the plugs to check them and at night check for any spark jumps from the wires. ALso, first check the plugs to assure they are properly torqued (I found 2 plugs just finger tight from a previous owner's dealer's 'mechanic').

Or might there be a exhaust leak which can also fool the o2 sensors and might cause a lean burn and associated heat?

Best of luck,

 

I had never thought to check the gas pressure, but I will do so. I will also check the running of the fans at speed.

This may seem like a dumb question but here goes, do the fans blow air onto the radiator or pull air through the radiator? What is the correct rotation of the fans?
At highway speed with AC on, should any of the fans be on?

I installed new plugs and wires when I changed the Opti.

 

I, too, have a 92 and had the same problem when I bought it way back in 1998. I had a small oil leak and my clutch was slipping because of the oil leak. It also ran, what I thought was, too hot (220 - 230) and got hotter in traffic with the air off. I started my major fix by first working on the oil leak and replacing the clutch and flywheel (stayed OEM). Now for the oil leak fix, I had to pull the intake and also pulled the oil pan and timing cover. Because I pulled the water pump, I found it was leaking through the weep hole onto my opti. Both had to be replaced. Here's what I'm trying to get to, I replaced the water pump with a Meziere HD electric pump. This pump keeps the water flow at a more constant flow even at idle. While I was in there, I really cleaned the condensor and radiator fins to ensure a unrstricted air flow through the radiator. I replaced the t-stat with a 180 degree. One more mod, I installed two switches that bypass the ECM and turns on the fans. Now at idle (like in traffic) I can turn on one or both fans and bring down the temps. I just need to turn the fans off and let the ECM control them when I get the speed back up. Otherwise, I may get a check engine light. The results, my normal operating temp stays between 195 and 210. In traffic, when the temp is in the 90's, if the temps reach 210 I can flip on the fans and the temps drop back to 190 nicely. Why not use the A/C to turn the fans on? I have a vert and like the top down. Up to now, this has worked flawlessy, even at the track, I can cool it down between runs using the electric pump and fans with the engine off. Just something to thing about.