What is the normal operating temp? Seems to be running hot during stop/go city traffic...how high is too high?

Background info: My fan wasn't coming on, so I took it to my local chevy dealer. They installed a new ecm and heater core, after installation said it needed a new water pump. I gave it the go and $1,900 later ($800 parts/$1,100 labor) I got my white 92' vette back with 108,000 miles.

I took it out and it seems to be ok on the highway, but getting stuck in city traffic the temp goes way up. At what temp should the fan kick in? Is this ok or should I take it back to the shop? Also, are they responsible or will I have to fork out more dough?

thanks,
Scott
Alexandria,VA

 

The fan should come on at 225 F. I have a '92 with the same mileage and I would suggest two things to bring the temp down. Flush the radiator, (if it has not been done in a while), and clean the area in fron of the radiator where road debris builds up. If you hav not done this, you would not believe the amound of crap that builds up there.

 

You are a new member, always check your mechanical problems in here before you go to a dealer and say,"Fix anything it needs".

 

Yikes - $1900 later.......

 

I live in AZ so you know it gets pretty hot here. When the car is cruising, the coolant temp never goes higher than 180. When stopped I have rarely ever seen it go past 210. It usually hovers around 200.

 

Scott,
I hope you didn't take it the dealer on Rt1 in Alexandria? If you took it over on Rt7 I may have a contact for you.
Chris

 

Yeah, good point. Next time I will post it up... I will let you know what happens with the cooling problem. My last purchase will be some Perelli P-Zero Nero's M&S and I should be good to go!

 

Noraml temps for the LT1 are about 190-205 on the highway depending on what gear you are in and how much traffic.

For sitting in traffic, 230 is not out of line. Over 240 is when you should be concerned.

I've switched on my A/C in traffic and watched the temp drop from 230 to 210 in about a minute.

 

I had the same problem and solved it pretty quickly. The 92 LT1 coolant temp sensor is located back by the oil dipstick at the back of the block. To get a more true reading of the coolant temp I chose to buy this from my local GM dealer:

Part No Description

GM 10096181 PCM/Gauge sending unit $14.81

GM 12102748 Connector pigtail (incl. termls) $17.29

it is now located at the front where it should be. The new sending unit is a dual fuction sensor. All it took was about 30 minutes of my time. With checking the other items to make sure they are working properly and this MOD, my temp has never gone over 215 "in traffic w/ac running" in Southern CA. It brings a big piece of mind. All temps were verified with other instruments. Goodluck.

 

The temps that M.r Mojo mentioned are right in the normal ranges for an LT1. My 92 runs in that area and it still has the original water pump, radiator, and temp sensors.

The biggest thing you can do to keep C4's cool is to make sure there is no junk in front of the radiator and A/C condensor. Use your garden hose to flush out all of the junk by directing a stream of water behind the radiator. You can also stick a vacuum hose and extension into the radiator shroud from the passenger side to suck out dirt and debris.

As mentioned, turning on the A/C forces the secondary fan to come on and that will drop temps quickly. The secondary fan should come on right around 225 to 228 and runs until coolant temp drops to about 210.

As for temp sensors, there are two in the LT1. The sensor on the water pump is used for input to the ECM and fan control and the digital temp display. The one on the cylinder head is for the analog water temp gauge. The analog guage is not a linear gauge and the size of the gauge face doesn't really provide for a good temp reading. I usually run with the digital temp displayed under the speedo.

Hopefully the dealer installed all new coolant when you had the car serviced. What did the dealer say about the condition of the heater core? Was it plugged or leaking? Why did they say you needed a new ECM? The first thing they should have checked for proper fan operation was the fan motors themselves followed by the relays.

At first read, it sounds like the dealership took you for a ride. I certaily would have questioned the heater core and water pump unless there was a problem that you knew existed with either one.

 

ahh..I took it in because I was getting coolant gook all over the inside of the windshield (couldn't see a lick). Tech said there was a leak in the heater core. So he replaced the heater core, he called and said after he replaced the core the water pump went bad. So he replaced that as well.

They did diagnostics on it to find the ECM was not kicking on the fan.

My concern is that the fan is still not kicking on. Is there anyway to test this? Also, the gauge temp seems to be a little different from the temp displayed digitally when I push guage info.

I couldn't believe how much they charged me for labor, I guess the heater core and water pump are more difficult to replace, but the ECM is a cinch. (They had labor at $80/hr and it was only there a day or two, so $1100 seemed a bit high)

Thanks for all the great points!

 

It sounds like your heater core was bad, it is very difficult to replace, and the water pump takes a few hours as well, so the dealers labor price is high, but not that outrageous.

As far as your fan not coming on, it may be the ECM, or maybe a $12 fan relay. I'm not sure.

 

Test it start the car let it idle and watch the temps. The fan comes on at around 212. The fan should start somewhere around there. Turn on the air and see if the fan comes on.

If the fan is not on by 220 it isnt working. I wired my fan direct with a toggle and turn it on when the temps hit 200.

Theres quite a few ways to make a LT-1 run cooler. The ideal temps are 212.

Clean the front of the radiator.
180 thermo.
Reprogram the fans to come on earlier.
Use a remote switch.
Corvette America sells a kit.

If heat is a problem you can add a oil cooler, and a trans cooler.
Check the front air dam and make sure its in tack.

 

If its not real warm out, the secondary fan will kick on and off frequently with low air flow and a low fan speed. Turning the AC on should cause the secondary fan to startup, it may not stay on long though, however it will stay on if the coolant temp gets up there 225 and beyond. Below it cycles.

 

Which fan do you think is not coming on? Primary or secondary? You can do a quick test by using a paperclip and ground pins A and B on the ALDL. This will cause both fans to start. Looking at the ALDL, the top row of holes are labeled in this fashion: E D C B A Insert the ends of a small paperclip in the upper right two holes and turn the ignition switch to the "RUN" position but don't start the engine. Both fans should start. If one doesn't it's usually the relay. The fan relays are located on the radiator shroud near the hood support rod mount.

If this doesn't happen, I would take the car back to the dealer that did the work and tell them one fan is not working. This is from the 92 Service Manual: the primary fan comes on at 226 degrees and off at 221. The secondary comes on at 235 and off at 226. Also, any ECM diagnostic code that is set will force on both fans.

Operation of the primary fan depends on the following: input from the A/C system (pressures), Coolant Temp Sensor, Engine Oil Temp Sensor, Vehicle Speed Sensor and engine RPM. The ECM controls the relays thru grounding of the relay.

As I mentioned, the analog water tem gauge is not very accurate. The digital display is much more accurate and is the one to pay attention to.

I really don't believe in extra items to keep the motor cool. As long as the ECM, fan relays, sensors and the fan motors are working properly and the cooling system is in good condition, you should not need override switches, coolant additives like Water Wetter, or lower temp 'stats.

A thermostat is designed to open at a given temp and allow coolant to flow thru the system. Once that temp is reached and the 'stat is fully open, it does not control temps to the extent of helping overheating conditions. A good ethlelyne glycol coolant in a 50-50 mix and a clean radiator should provide all the cooling necessary. Modern motors are designed to run "hot" in order to curb emissions.

The front air dam is an integral part of the cooling system as it forces air up into the radiator passage. If that piece is gone or broken, there may not be enough air flowing into the radiator.

 

Will check fans.... I will post what I find. Thanks!