Overheating C4 LT1
Thread Starter
Heel & Toe
Joined: May 2011
Posts: 18
Likes: 0
From: TEMECULA CA
Overheating C4 LT1
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.
Also, changed the oil and inspected it for foam, the old coolant was brown, rusty, but no oil residue or oil remnants.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
"Hot", BTW is over 235*F.
Safety Car
Joined: Jan 2004
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Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
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?
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?
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
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.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
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.
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Team Owner
Joined: Mar 2001
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From: Boston, Dallas, Detroit, SoCal, back to Boston MA
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.
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.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
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.
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.
Team Owner
Joined: Aug 2004
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From: Park City Utah
Hmmm....seeing a trend here....
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
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.
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.
Thread Starter
Heel & Toe
Joined: May 2011
Posts: 18
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From: TEMECULA CA
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.