I just got a 94 Corvette as a weekend driver. I notice at low speeds or idling my engine (coolant temp) starts to run hot. Is this normal? If not, how can I fix it or diagnose it correctly on the first try-I don't wana spend several hundred dollars if I don't have to. I have never let it get over about 225 by turning the engine off-so it may continue to get hotter if I keep letting it idle longer. When I am driving on the hwy, it runs between 180 and 195.

The digital and analog gauges also do not seem to be exactly in sync. I know the analog isn't linear-I am going by the chart in the owners manual. Usually , but not always, the digital gauge reads 5-20 degrees lower when the engine starts getting hot. When the engine temperature is normal (180-195*), the analog and digital gauges are a lot closer; it's only when the engine starts to get hot in slow traffic/driving that the analog gauage tends to get hotter much faster than the digital. Which gauge do I go by?

Bottom line, I have never had a car of any kind where the engine starts running hot in slow speeds-my temp gauges on all the other cars I own get to the correct temp and stay exactly there. I want mine to run at 200 or less at all times if possible.

I have heard you can do the 160* thermostat and the manual fan swtiches-how much do those cost? Can you do it yourself? Where is the thermostat located anyway?

Also, please reply with layman terms-I don't know crap about LT1s (I am new to this) and what all the acronyms stand for, where stuff is located, etc stand for. Like I don't even know where the thermostat is on this car. Dummy it down. Thanks.

 

Those temps are normal for a stock LT1. Your primary cooling fan doesn't come on until 228*, and the secondary fan at 237*.

Hopefully this doesn't start a big debate. But, I'm running a 160* stat and have changed my fans settings to come on at 186* and 194*. My car never sees over 200* in the Midwest heat and traffic. Also runs around 178* on the highway.

 

 

The thermostat housing is located on top of the waterpump, under the intake bellows.

 

I've done the same thing only I am running a 180* stat. Additionally, I pulled the radiator to clean out all the crap that was sucked up in between the radiator then installed a screen lower down in the air duct channel so that no more leaves and crap can get suck back up in there. Mine like yours never sees much over 200*, a few times while stuck in traffic jambs during the summer heat it climbed to 209* but stopped at that point.

 

As long as it does not go over 245 (by digital gauge) your fine.
At that time, the analog gauge will look like it's almost pegged. But look close, the needle will be just shy of the shaded area.

Sitting at a stop light, there is no airflow through going through the radiator. It takes the fans running or for the car to be moving to keep them under 220 degrees.

GM says shut it down at 260.
If your cooling system is in good shape, it shouldn't get over about 230.

 

I had the same problem when I first purchased my 96 LT1. For emissions purposes these cars are designed to run hot, but not past the 228 protocol. I flushed my coolant system and back washed the radiator, added fresh DEX-COOL anti-freeze. The C4 is designed to suck all of the air from the bottom front part of the car. This means it is a huge vacume on wheels. Most road debris and leaves will get sucked up in between the radiator and A/C condenser. You might want to remove the radiator cover and clean this out. Mine was full of leaves and crap, and even a plastic bag! They sell a wire screen for this problem that is easy to install. Good luck!

 

BTW, the digital gage reads the water sensor at the water pump (water returning from the radiator), and the analog gage reads the water jacket right head temperature, that's why the analog gage is always hotter

 

I just drove around, but this time I turned on the ac/heater (I turned the temp way up since it's cold outsite) and my engine did seem to run cooler. I drove it around the block in my neighborhood after the engine was warmed up and I let it idle for about 5-10 minutes and the engine never got over 207 digital gauge and about halfway between the 210 and 235 marks on the analog (~225 degrees). Earlier in the day when I drove with the AC/Heater off, it got warmer much quicker in slow driving (I cut the engine off when the digital read like 226 and the analog read almost 240). However, if things are working right, both fans should have kicked in about that time-I guess had I let it keep going it would have worked.

 

The digital temp gauge determines when the cooling fans are engaged, 228* before the cooling begins. Also, on your 94 only one fan will kick on at 228*, the other at 237*.

 

On your car the second fan will come on when you turn on the A/C.
You change the stat to a 160 which I have in my car,then you are only putting in a 160 stat.Changing temp settings with a programmer is do able but that will only give you piece of mind.I have the orange coolent in my car and I add no water what so ever.The engine runs about 185 to 195 most of the time.My weather where I live is always in the 80's or above.
My car has never got above 225 even when sitting in traffic.You should do a presure test of the radiator and see if the tank is leaking on the pass side.Mine had a leak that you could not see or smell.I changed the radiator with a alum from e-bay with a company that has corvette radiators for 175.00,the tanks are not plastic.I dropped the temp by 10 degrees.This was my 2nd radiator in 3 years.The plastic tanks crack over here because of the acid and sulfer in the air.You can spend big bucks for the bigger radiator that is sold on the form ,but all that does is give you a little more water in the cooling system,lighten your wallet and only makes it take longer for the engine to heat up in the morning.
I would check between the condensor and radator for leaves and crap.
If you install a trans cooler the temp will drop about 5 deg more.
I would also check the radiator cap to make sure the rubber seal is good.
Hope this helps.

 

Can someone put up a clear summary of when and when the fans will cut on or off. when the Primary Fan kicks in. Secondary fan joins it. When 1 cuts off. When they both cut off. Can you be fully exaustive-in other words, every single possible driving conditon will be covered. All speeds. With A/C on or off. Whether its 40 degrees outside and I am cold starting my engine after sitting for a week or whether it is already warmed up after start. A chart or table would be nice. Also, can you do both temperature readings (analog and digital everytime you quote a temperature.)

Also, when you say the A/C, is the heater the same thing? I have that auto climate control. I still haven't figured out how to work it completely even after reading the owner's manual. Do you mean as long as ANY air is blowing out the vents, that means the "A/C" is on? It's cold outside right now and I have the temp turned way up.

Thanks for all the replys and help. I just want this chart or table so I can make sure everything is working properly.

 

Well, I'll answer this part. When we say the A/C, it means just that. The air conditioning system. Not just air blowing out.

The A/C compressor has to be running.

It can do this in the winter with the defrost on. With the A/C compressor engauged, the cooling fans should be on. This assumes your a/c system is operating as it should. Low freon will not allow the compressor to engauge, and so no cooling fans either (unless of course the coolant reaches the temp limit that causes the fans to come on).

 

Primary fan on/off 228/219. Secondary fan 237/228. These temps are from the digital temp gauge, where the PCM gets its signal for the cooling fans on/off.

 

STL94LT1 - How did you reset the fan on-temps? Programming? Aftermarket hardware?

I've got the 160* stat, and the intake area is clear of leaves, but I'd still like to run cooler.

'93 Coupe - 96,000 miles

Terry

 

Terry, I can feflash the PCM on my 94. On your 93 you'll need a different ECM chip.

 

I would also like to know how to change the temp for the fans to come on.
Please share the info and tks. Don

 

I bought a kit to turn on the fans at 185 for under $50. I live in Miami and it gets hot down here year round. My car's temp never goes over 200...

 

These guys taught me what to do. Many c4's have never had the radiator properly cleaned of external crap. Because of the set up- the air which flows through the radiator often picks up road dirt, leaves, walmart shopping bags, etc. Your best bet to get the temp down is to pull the radiator shroud and do a thorough cleaning (or replacement) of the radiator fins. I would also put a new stock thermostat in (about $20.) That will drop the temp to normal levels.