Hello,
Fellas, hope I find you all well and riding. Well for me, I've been dealing with my car running hot after a drive. I've changed the thermostat, new coolant (green), new radiator, new cap, new reservoir, new fans, temperature sensor. I'm starting to worry it could be the heads. Car starts right up, puurrrsssss. But after some driving, dips 3/4 on the gage. No smoking no misfire. My brother thinks maybe the water pump, but I see and don't hear anything for me to suspect. Any help? Appreciate it. Tryna get this car running great for my son.

1994...

 

When you say its heating up what is the actual temp showing on the digital temp reading? Does fan come on at 230? The analog gauge reading is useless..

 

Check your analog guage to the digital guage. I use a thermal temp gun for overheating problems. Debris gets caught in between the radiator and condenser too. Check a you tube video on how to check and clean that area for your year car. A waterpump is cheap enough and not too drastically hard to change if it's a high mileage engine. Make sure the fans are turning on at the specified temperature. If you suspect heads or gaskets, buy a cheap exhaust gas tester for the coolant. Just some of the things I can think of off the top of my head. If the car is running great then it could just be bad air flow through the radiator, or water flow through the engine. Make sure you bleed the air out of the system with the bleeder on the thermostat housing after changing the thermostat. Hope you figure it it out.

 

The analog gauge is useful as an indication of nominal operation, you'll learn where the needle is supposed to be depending on conditions. Don't try to interpolate an actual value from the analog gauge. Use the digital readout for an actual value for temp.


Low speed fan turns ON at 226F
Low speed fan turns OFF when the temp drops 5F
Minimum ON time for Low speed fans is 50 seconds.

High speed fans turn ON with any of the following conditions:
Certain DTCs are set.
ECT above 235F.
A/C head pressure above 248psi.
Fans will revert to Low speed when temp drops 5F
Minimum ON time for High speed fans is 26 seconds.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~

Run this test for cooling fan operation:

Use GAUGES button to select COOL in the Odometer section. The little number will display coolant temperature.
With the A/C off let the engine idle and watch the digital coolant temperature.
Both fans should turn ON in Low speed at 226F. (See Note 1). In the underhood fuse box find the Maxi fuse for Fan 1. Remove it. Low speed fans should stop.
Watch the digital temperature, One fan should turn ON at 235F in High speed. Install the Maxi fuse for Fan 1. Both fans should run in High speed. (See Note 2 below.)
When temp drops to 230F, both fans should revert to Low speed.
When the temp drops to 221F both fans should go OFF.

Note 1: Only both fans can run in Low speed. It is not possible for only 1 fan to operate in Low speed. If no fans turn on at 226F, and only one fan turns on in High speed at 235F, the relay with a dk green wire is probably bad.

Note 2: Removing the Maxi fuse for Fan 1 is necessary to force the temperature to rise to the Fan 2 turn-on threshold. If one fan does not turn on by 240F, reinstall the Maxi fuse, let the system cool to low speed turn off temp and trouble shoot the fan 2 system. (Probably a bad relay.)

If your fans behave as described above, there is nothing wrong with your cooling system or fan system.

 

Need to do that. I'm suspecting the water pump now that I've had some feed back. Gonna look into this. But i'm going by the gauge reading.

 

I'm suspecting water flow. I did change radiator and I know about debris and trash getting in between radiator. I'm sure I've bleed the raditor. Had it with my mechanic that also did the same. Maybe gonna try and bleed the system again. To me I think or hope that it is the water pump.

 

Before you do anything else, what does the digital temp readout in the center of the cluster show? If it never gets higher than 230 F or 235 F, and your fans come on around that temp, then you have no overheating issues.

 

You won't know if you actually have a problem until start start it and set display to Coolant temp, allow it to run and if the fan(s) come on around 228-230 and the temps start lowering in a minute or so the system is working as it should. If the fan(s) don't come on or if they come on and the temps don't lower you so have an issue. do those steps then report back with the results.

 

Just did that. Seems analog is off. Digital dips to about 226 then fans turn on and bring it down to 215 with ac on, dips to 190 idling.

 

Vehicle is operating correctly as per the digital reading. Analog show me otherwise. I think I am good.
Appreciate the help. So how do we fix the analog?

 

Sounds like your system is working as it should. I ran into an issue last year that the radiator cap wasn't holding proper pressure which caused coolant to dump into overflow tank and overheat due to not enough coolant in system. But in your case it seems like working as Chevy designed. Leave the digital coolant temp setting on if you want to keep track for a time to ensure peace of mind. Don't worry about the analog, it will never be accurate.

 

You can't fix something that isn't broken. What you can do is to learn how to use the analog gauge the way it is now. By the needle position. Ignore any graduations for value. Needle position. Over time with the car you'll learn where to expect the needle position to be when you do your scan. If the needle isn't where you expected it to be, evaluate the conditions (are they different than they usually are?) and if a value is needed for coolant temp, use the digital to obtain it.

I've seen numerous Porsche 911 tachometers (which are the largest of the 5, in the center of the layout) turned in the dash so that the desired shift RPM is when the needle is straight up. No need to evaluate the value, if the needle is at 12:00, shift! Same idea with the analog temp gauge. Learn where you expect it to be when you look at it. If it is, nothing is wrong. If it is different, evaluate why.

 

Sounds like it's all working properly. The analog gauge is just a simple single-wire sensor and is meant more just as a vague reference.

Here is the link to one of the stickys in the C4 section here about coolant temps. It's worth a read: https://www.corvetteforum.com/forums...peratures.html