LT1 cooling question/problem

**CStewTAMU** · 12-30-2007, 09:24 AM

I just got a 94 Corvette as a weekend driver. I notice at low speeds or idling my engine 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 220 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. Sometimes the digital gauge seems to run a little lower than the analog. And sometimes its the other way around.

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.

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

**5.0THIS** · 12-30-2007, 01:01 PM

Well, you want to make sure your cooling fans are coming on when they are supposed to. LT1s will run hot, especially in traffic. Your temps on the highway are about right. If you want the car to run cooler, get a 160 degree thermostat, and a manual fan switch, which allows you to control when the fans are on, as well as retaining factory operation. Also, it might be a good time for cooling system service if it hasnt been done in awhile (flush the cooling system, new coolant, etc).

**morton** · 12-30-2007, 07:40 PM

i just had the same problem with my 97 z28. when all was said and done i had a air pocket in the cooling system and it was low on coolant. what i would recommend doing is let the car idle till its get to about 195 then shut it off carefully loosen the radiator cap but keep it on to make sure the fluid is not going to shoot out and then once you have made sure that it is not going to over flow take it off if the coolant level is low then fill it up to the top of the raiator start it back up let the thermostat open back up and get to about 195 again and do the same thing over and over again until the radiator is full at opperationg temp. it sounds like the car does not have enough coolant to circulate to keep the engine cool while you are at low speeds of idle. but i would not let the car get over 210 while you are doing this. repeat this procedure until the the radiator is completely full at about 200. it may take 3+ times to get it to where it needs to be.

**hoz55** · 01-01-2008, 05:08 AM

My 95 has the same issue, when i'm in traffic i turn on the A/C, that kicks on the cooling fans, and lowers the temp. I'm not sure if vettes have the bleeders on the hose and thermostat housing, if it does then thats where you bleed the air out of the system. just make sure the distributor (otpi) doesn't get wet....

**johnd** · 01-01-2008, 05:41 PM

The temp. sensor is in the head and with stock programing, the fans come on around 220 Deg. F. What you are describing is normal. I got tired of looking at it and got a dual sensor for the waterpump. Now my gage never reads higher than 212 or thereabouts.

**Firebirdjones** · 01-03-2008, 12:28 PM

Originally Posted by morton

i just had the same problem with my 97 z28. when all was said and done i had a air pocket in the cooling system and it was low on coolant. what i would recommend doing is let the car idle till its get to about 195 then shut it off carefully loosen the radiator cap but keep it on to make sure the fluid is not going to shoot out and then once you have made sure that it is not going to over flow take it off if the coolant level is low then fill it up to the top of the raiator start it back up let the thermostat open back up and get to about 195 again and do the same thing over and over again until the radiator is full at opperationg temp. it sounds like the car does not have enough coolant to circulate to keep the engine cool while you are at low speeds of idle. but i would not let the car get over 210 while you are doing this. repeat this procedure until the the radiator is completely full at about 200. it may take 3+ times to get it to where it needs to be.

There are air bleeds in the cooling systems on LT1's so you don't have to go through all the hassle you just explained.

**Firebirdjones** · 01-03-2008, 12:34 PM

Originally Posted by CStewTAMU

I just got a 94 Corvette as a weekend driver. I notice at low speeds or idling my engine 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 220 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. Sometimes the digital gauge seems to run a little lower than the analog. And sometimes its the other way around.

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.

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

That sounds about normal,,,,I don't believe the fans will come on until around 225 degrees or so in the factory programming.

Let it idle and check the fan operation to make sure. You can also turn on the A/C as I believe the pressure switch will turn the fans on sooner.
When moving down the road you'll get more airflow and the temps will come down, fans should shut off at programmed temperature.

If you want the fans to come on sooner, I would suggest changing the programming,,,it's really the best way, it's fool proof and you don't have to worry about switches to play with.

If this is a new vehicle to you a new thermostat and coolant flush is probably a good idea.