Driving around the city with stop and go traffic and hot miami 100 degrees or more weather I usually average around 210-220 and thats with the new 160 thermostat. Before it would stay around 230-240. On the highway it stays around 180-190. And at idle it will stay between 225-235 thats all with the air on. If I have the air off the second fan will not come on no matter what temp. If I leave the car idling with the air off the temperature will continue to climb all the way to the top of the guage near the max. And while driving around the city it will go up to around 240. Any suggestions to what I can do to improve the temps and what could possibly be wrong with the fan. (If I need to change the relays or etc.) Thanks.

 

From what I understand the logic to turn on the second fan does not include the engine overheating, strange right. Here is what works for me. I have a 180F thermostat, a TSU that turns on the fan at lower temp then stock, i got it from mid-america, I can did up the part # for you if you need. I upgraded to the CS144 alternator to support the fans runner more, you need to do this anyway if you have not already great mod. I run the A/C most of the time, so the 2nd fan is on most of the time. This is a good ballance, I run 180 to 210 all the time even in the Houston summers. I never get hoter then 220. I had the same issue before.

Keep cool...

 

On my stock 86 L98 I installed the 160 degree stat with a manual switch that turns on both fans any time I want. I got the switch from Corvette Central about $15. I am old school and when the temp gets up around 190 I just turn on the fans. This combination works for me.

 

darkstallion_69,

Presume your talking about your 1994 LT1...

Are you quoting digital gauge or analog gauge temps?

If analog, what are the digital temps (as often the analog temps are higher due to analog sensor wire connector corrosion, non-acdelco thermostats (don't open the internal passage way enough), or old anti-freeze)...

1994's fans are activated by the ECM by grounding the associated fan relay. The ECM primarily uses the coolant temps (from the ECT) and AC pressures (from the high-pressure ac line sensor) to determine when to turn on the fans, and the MPH for when to turn off.

Does the secondary fan (passenger side) cycle on/off when the AC is on -- if not, then either:
1. your freon level is low (which could keep the secondary fan from coming on.
2. bad relay -- there are 2 on the driver side of the radiator cover, one for each fan, grounded by the ECM to activate the associated fan
3. broken wire(s) somewhere between ECM and relay
4. fuse blown, there are 2 fuses, one for each fan
5. fan motor is shot
6. ECT (engine coolant temperature -- mounted to lower driver side of water pump) sensor is not working or damaged or its wires are damaged

Suggested tests/solutions based on above are:
1. have the AC system pressures checked and add freon if needed
2. try switching relays and see if the other fan now doesn't come on, if so, replace the relay
3. since the ECM is grounding the circuit, trace/probe wire looking for a good ground and then repair
4. replace fuse
5. replace fan
6. replace sensor (drain coolant first to save the OPTI) or wire or connector as needed.

If the secondary fan DOES cycle on/off when AC is turned on, but DOES not run with AC off when temps exceed 238 F (digital), then perhaps the ECM was reflashed/modified and was not done correctly so the secondary fan's 'on' temps are incorrect.

Considering you have a 160 F thermostat, was the ECM 'on' temps altered to accomodate the change.

Also, fyi, having a cooler thermostat doesn't do much to control the max temps, only to control the min temps -- remember that the block and heads are designed to run at a certain temp, so likely the heads/block are not getting to designed temps (190-200) until the temps exceed the ability of the radiator to cool the coolant (which increased engine wear and likely engine oil loss -- so suggest being very easy on the engine until temps get to 190+ or replace the thermostat with a warmer version (e.g. OEM 180 F or maybe a 170 F).

 

yeah i was thinking about doung the fan switch to manually turn them on. Its so hot here that I always put the air on so that second fan is on regardless but i would like to take the top off and not have the air on. thanks guys.

 

all the temps I put are read from the digital guage. The system had been flushed and new coolant was put in before I bought the car. I then after buying the car put in the 160 themostat. I went outside right now and turned on the car for the first time today.I let the car warm up without the air on. The primary fan stayed on till like 150 and then shut off. The primary fan didnt come on again until 230 in which the temp went down to 215 and stayed there. I turned on the air (secondary fan came on) and it went down to 210. I then turned off the air (which turned off the secondary fan) and closed the hood to see when it would come back on. It went up to 234 and I heard the secondary fan click on and the temp go down.

With the air on the secondary fan stays on. It doesnt go on and off.

 

Sounds like all is working well. I would leave it alone.

 

I had a similar issue with my 93, and I just posted on a similar post. There is a 30 amp maxi fuse that powers the relays for the fans. Thats was blown on my car, causing the second cooling fan not to turn, and as a result I was running in the 240-255 zone while driving. No good. The fuse is located in the fuse box just below the ECM on the drivers side, it was $.35, replaced and solved my problem. Sometimes it's the simplest of repairs that fix the most annoying issues.

 

really? Unless the 86 L98 is very different, my fan comes on at 215 and goes off at 200; when it's working anyway, which is why i'm reading this thread! Sounds like its running hot to me.

 

The LT1 is very different.

Temps in the 230 range while sitting in stop and go traffic are normal.
The cooling fans don't come on until the 228 range (depending on year).

230 - 240 is not hot in a modern cooling system. With the correct antifreeze mix and under pressure, the coolant won't even boil until close to 260.

 

 

I would rewire it so you get both fans at once like the 95-96. If you have a schematic for the fan wiring I can show you how.

The fans are more efficient when both are running.

Or a simple toggle switch

Or a PCM reprogram.

Or an aftermarket switch that goes in the head.

 

OMFG

Dark Stallion, Instead of "Rigging" the car with Wires, switches, gadgets, snake oils, Water wetter....

I gottsa a idea......How about addressing the problem?

Some of this advice is like the Doctor that ignores the disease and gives you a Tylenol to bring down your Fever.

First off, what is the service record concerning your cooling system? Are we to assume you've pulled the top of the shroud off and checked for debris in between the Radiator and the Condenser?

When was the last time you pulled the radiator out and had that 16 year old radiator boiled out?? If the answer is never.....THERE IS SEDIMENT in the bottom....how much cooling ability has been lost do to that sediment?

How many miles on the Water Pump? It is 16 years old as well. It may not be bad....but I can promise you it is not working as well as a new one.

perform or have these service items performed for you.....put the stock thermostat BACK in there.....once you've done this....let's see if you have heat issues.

Until you have these 16 year old components serviced or replaced, why would you consider going through the trouble rewiring and adding switches?

Understand, I had issues like you did with heat....the day mine got to 249° was the day I went after the cooling system prior to killing the motor by over heating it...And since I replaced worn parts, I've not seen any temps above 219° and rarely does the car go near 210° to begin with.

City Driving on a 90° day with a completely stock system.


4-5 miles down the road on the freeway



Sorry to be so Harsh, its just that it seems that there is a new thread like this every 3rd day......

To sum it up, if you never saw temps above 220° in extreme conditions, would you still be interested in adding a switch or making other Modifications???

 

FYI - I recall that mineral motor oil starts to lose is lubricity properties around 250F. Not sure for Moble 1. That is why I never let any of my engines come close to that temp, modern or not. From what I understand, the higher temp are for emissions. For prefomance I have found 180F to be optimal.

 

Yeah, that day....when it hit 249° I pulled over....it was stop and go traffic due to a wreck up ahead.....I went to a convenience store and waited for about 30 minutes. CentralCoaster wouldn't answer his phone that day either so I had to panic all by myself.

The Higher temp thing is a misnomer, NO ONE designs IN heat. The only thing that needs heat for emissions is the Cat. If they needed it hotter they merely needed to move it closer to the headers. They could also add pre-Cats.

The C4 is just susceptible to picking up trash....it's a sports car. If one wanted miles of trouble free no maintenance free driving, you can get that.....in a Honda.....

And yup, you can feel how peppy the car is when it is 180° versus 210° maybe the A/C compressor pulling....I dunno for sure.

 

Not true. The system and not to mention engine on your car is completely different than the 92-96 LT1/4 versions.

Lets begin w/ cats. Yours has 3 of them. 2 pre-cats and than the main cat underneath. The LTx had only the two in front. The design was for a higher flowing exhaust as the LT1/4 had 10.5/10.8 to 1 compression ratios. They wanted a 300 hp engine that could pass emission tests. That is why they reverse cooled the engine. Letting coolant flow to the heads first keeping the valve train cooler. By adding more heat to the combustion chamber, more of the co2 gases are burned, thus meeting EPA requirements w/o having to add the third cat or reducing exhaust flow. This is why the factory fan settings on my car are primary at 228 and secondary at 230. NO ONE designs their cooling fans to come on AFTER the engine overheats.

Yes, we all could benefit from a complete cooling system overhaul, but there is no reason for Darkstallion to throw a penny at his cooling system right now unless he wants to.

 

I was listening until we got to this point.

So you are maintaining that the temps should be 230-240?

OBTW, My car has One single Cat.

 

I was thinking about wiring up the secondary/AC fan to the 1st fan.That way they both come on and off togethor.Just to keep more air flowing under that fiberglass oven of a hood.
Is there any downfalls to this ?

 

As has been stated, it is perfectly normal for an LT1/LT4 car to run in the 220-235 range while sitting still for any length of time.

Without cooling fans running a C4 will overheat rather easily, as I am sure you will agree.
Well, right from the factory those fans don't come on until the 228 range (might vary slightly, depending on year).

So yes, a brand new LT1/LT4 Corvette rolling right off the assembly line would reach 228-230 while sitting at a traffic light.
Note: Turning on the A/C system will also cause the electric fans to come on, will will lower temps down around the 200 - 205 range while stopped.

Now of course, if it is running those temps while moving down the road at anything over 20 MPH, then something is wrong.
Once moving the temps should settle back down to the 190-195 range.

 

Turning the A/C on does force the fan/s to come on, but also, the condenser which is ahead of the radiator heats up the incoming air and the cooling system radiator receives hotter air and this causes the coolant temp to rise. I also agree with jhammons01 about looking into the space between the condenser and the radiator, you will absolutely see a lot of debris jammed into the radiator which reduces greatly its ability to get rid of heat. GET RID OF THIS DEBRIS and you will see lower temps.
One fan comes on at 228F and the second fan is programmed to come on at 238 F and GM says to shut the engine off at 260 F and let the engine cool down. I believe this is because this is about 5 F from the coolant boiling.
From my experience with my 87 and a stock 195 stat, the cooling sytem will hold 195 when underway up to an OAT (outside air temp) of 92 F, then the coolant temp will follow the OAT, that is, at 100 F OAT, the coolant temp will be 195 + (temp over 92, or 8 F) = 203 F. This is due to the heat ridding capacity of the radiator. Also, for the life of me I cannot understand why anyone puts a 160 stat in their car, it doesn't help cooling once the stat opens fully. The cooling system stabilizes in temperature where the radiator gets rid of heat as fast as the engine makes it.
Clean your radiator, take the top off, don't turn on the A/C and sitting at stoplights or lower than 25 mph in 100 F OAT, expect coolant temps of 210-228 and above 35 mph, expect 203 F.