Pegmakr1

Have an overhaeting problem. Replaced the thermostat, and water pump,removed and cleaned the radiator, oil coolant radiator. No excessive dust or particles in vents. but it still overheats, digital read is cool never gets to 150, but the analog ramps right up to 230 quickly. Fans do not turn on. Did not replace the ECT coolant sensor on the front of the pump. New serpentine. How do I test the three relays on the left side of the radiator housing?

Also, changed the oil and inspected it for foam, the old coolant was brown, rusty, but no oil residue or oil remnants.

Tom400CFI

Sounds to me like you need to confirm your ACTUAL coolant temps. The analog gauge is basically junk and is only intended to give a rough "estimate" of the temp. Digital gauge is where the accuracy is. Use some type of temp measuring device of known accuracy to find out what's really going on. My guess? It's not getting hot.

"Hot", BTW is over 235*F.

vetteoz

Why would you decide that one gauge is correct when you have so much variation between the two?
One says hot and the other says cold

96GS#007

Codes / Check Engine Light?

Did you remember to install the coupler for the water pump drive shaft (goes between the pump and the shaft that sticks out of the timing cover)?

What were the temps before your took it all apart?

Pegmakr1

Yes the coupler and the ECT were the first things I did. The fans aren't turning on I think thats an issue .... I will check codes

Pegmakr1

yeah I don't trust analog too far ... the fans are the issue or some relay .... acode check is probably the thing to do

lt4obsesses

Coolant temp sensor on the waterpump? This is the one that feeds the digital temp gauge and the one that feeds the fan relays. I would think that it is likely that this sensor is not working properly if the digital temp reading is not going over 150, that is very low for an LT1 at idle with no fans running.

Did you try running the AC? If you turn on the AC it overrides the coolant sensor and turns the fans on. If the fans come on with the AC then your relays are probably okay.

Tom400CFI

Well we don't know if it's an issue or not. If the thing is only reaching 150*F, then the fans not turning on...is not an issue. Don't worry about codes yet.

Find out what the real engine temps are...go from there. W/o knowing that, all anyone can give you is a bunch of WAG's.

BrianCunningham

you can test the relays by applying power to the appropriate terminals and seeing if the circuit opens (the diagram is right on the relay)

You can test the fans by running power to them.

What year is the car?
LT1/4 cars need to be burped to get all the air out.

desertmike1

First things first!! What is your real temperature?

After the car has had a chance to sit for about 24 hours compare the ECT with the OAT on the HVAC. The ECM/PCM process's data from the ECT, not the Analog Probe.

Secondly, as a rule of thumb.. you can touch a 150/160° surface for more then a few seconds, you cannot with a 180° surface.

Tom400CFI

Hmmm....seeing a trend here....

lt4obsesses

I most certainly can gaurantee that if you let an LT1 sit and idle for a length of time, the coolant temp will definitely be over 150*. So yes, the question would be then, what is the actual temp of the coolant?

I would also find out if that sensor is malfunctioning, as it most likely is. Because that is the sensor that the ecm reads to kick on the fans. If that sensor never reads the correct temp, the fans will not come on.

Pegmakr1

To set the record I brought it to a GM mechanic and he did all his test. He had removed the wiring from the block temp sensor. Which is the ANALOG sensor and plugged i back in and it worked fine from that point on! Huh! Go figure, so it has been running in the ideal 185-230 range correcly ever since. Thanks Corvette Forum. Now I know to always trust digital and triple check analog.