I replaced stat today. Everything seemed to go well but lost more than a pint. Refilled overflow tank.

I have noticed that my low speed fans don't come on until the DIC reads about 230. Then High speed kicks in at 239. As far as I can tell both fans are turning. I can't see the driver's side fan well but I can get some stiff paper into it and hear/feel it hit the fan.

If in low speed mode the fans are in series, then with seeing one fan and feeling the other, things should be good there. Then the same for high speed fan mode. Hear the difference in fan speed, see one, feel the other. Even in this high speed mode, the temps do not fall fast, they stay even. I'm letting it cool down right now, but will got for a short drive.

Before changing stat, once I've been above 40 MPH the motor runs cool and only starts to heat up while stuck in traffic. It stays about 190 or less on DIC.

Could it be that the temp trigger numbers have been corrupted? Also, right now I don't feel any water in either radiator hose, Pump/stat hose or back from radiator hose. Also the coolant really bubbles back up through the overflow tank.


Any help would be great. Thanks

 

Make sure that you have all the air out of the system. Sounds like to me that you have some left.

 

Thanks, just got back from a short ride and over tempt again. Before my ride and after changing out stat. I let the motor run and come up to temp. Added more coolant and left the cap off while the system started to bubble up out of overflow tank. I let the system cool off a bit before putting cap back on. I guess I can do it again, but right now it's too hot to pull cap. It went back to 260 on short drive, over 50 MPH in a few spots and started to cool off, but not so long of a drive. By the time I pulled back into driveway, back to 260.

I looked for burpping procedure, but most say there is none, really. Just leave the cap off while you come back up to temp. There is no release valve/screw anywhere that I can see for that.

 

Here's my trick. With engine up to temp get towel on hose that goes from the driver side radiator to the water pump. Squeeze it a bunch and hold it almost closed a couple of times. Make sure your heater is on in the car. Doesn't have to be full blast but so long as the heater is on.

LSx engines hate air in the system and a pain sometimes.

 

If the hoses are cold then the system has a bunch of air or the pump is out. Whatever you do, do not drive it anymore and shut it down and let it cool down naturally if it gets around 235 don't keep it running if it goes higher.

 

I really am starting to wonder if it is the water pump. This over temp just happened one day. Hot but not the worse day the car has been in. I drove to work and then to quicky mart at lunch time. That's when it all happened. The pump don't seem to make any noise. I don't remember hearing anything when this all started.

When I checked the hoses hot they feel empty and hot, tight with steam I think. Today when I went to change stat, I could feel water in the stat hose and sure enough, there was water in there, when I removed hose for stat swap. Fans seem to hold temp at 235 in driveway, but in traffic not so good. I guess it's time for a pump change.

Oil looks good, so no head gasket breakage (I hope). Thanks

 

According to the service manual:

1. Fill the system through the surge tank opening.
2. Fill half the capacity of the system with 100 percent DEX-COOL® coolant.
3. Slowly add clean drinkable water to the system until the level reaches to the base of the neck.
4. Start the engine.
5. Idle engine for 1 minute.
6. Install surge tank cap.
7. Cycle the RPM, idle to 3000 in 30 second intervals until engine coolant reaches 99°C (210°F).
9.Shut off the engine.
10. Refer to step 3 above to remove the surge tank cap.
11. Start the engine.
12. Idle engine for 1 minute and fill surge tank to 1/2 inch above COLD FULL mark on the radiator surge tank.
13. Install the surge tank cap.
14. Cycle the RPM, idle to 3000 in 30 second intervals until engine coolant reaches 99°C (210°F).
15. Shut off the engine.
16. Top off coolant as necessary, 1/2 inch above FULL COLD mark on the radiator surge tank.
17. Rinse away any excess coolant from the engine and the compartment.
18. Inspect the concentration of the coolant.

 

Engine Overheating
Step
Action
Yes
No

1
Inspect for a missing or damaged radiator upper or lower baffle and/or radiator air deflector.

Is the baffle and/or deflector missing or damaged?
Go to Step 8
Go to Step 2

2
Inspect for a loss of coolant.

Is there a loss of coolant?
Go to Step 3
Go to Step 4

3
Fill the system to the specified level. Refer to Loss of Coolant .

Does the engine overheat?
Go to Step 4
System OK

4
Inspect for low coolant protection.

Is the coolant to the correct concentration?
Go to Step 5
Go to Step 8

5
Inspect for a loss of cooling system pressure.

Is there a loss of system pressure?
Go to Step 8
Go to Step 6

6
Inspect for a faulty engine coolant temperature (ECT) sensor. Refer to DTC P0117 , DTC P0118 , or DTC P0125 in Engine Controls - 5.7L.

Is the sensor operating properly?
Go to Step 7
Go to Step 8

7
Inspect for a cracked coolant surge tank or a leaking hose.

Is the coolant surge tank cracked or is the hose leaking?
Go to Step 8
Go to Step 13

8
Repair or install new parts as necessary, then retest.

Does the engine overheat?
Go to Step 9
System OK

9
Inspect for incorrect drive belt tension.

Is the belt tension correct?
Go to Step 10
Go to Step 8

10
Remove the water pump. Refer to Water Pump Replacement .
Inspect for a damaged water pump driveshaft.
Is the water pump driveshaft damaged or is the seal leaking?
Go to Step 8
Go to Step 11

11
Inspect for obstructed radiator air flow or bent radiator fins.

Is the radiator air flow obstructed?
Go to Step 8
Go to Step 12

12
Inspect for blocked cooling system passages.

Are the cooling system passages blocked?
Go to Step 8
Go to Step 13

13
Inspect for inoperative cooling fans. Refer to Cooling Fan Inoperative .

Are the cooling fans and the motors operating correctly?
Go to Step 14
Go to Step 8

14
Inspect the thermostat. Refer to Thermostat Diagnosis .

Is the thermostat stuck in the closed position?
Go to Step 15
Go to Step 16

15
Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Does the engine overheat?
Go to Step 16
System OK

16
Inspect the radiator cooling capacity.

Is the proper sized radiator being used on the vehicle?
Go to Step 3
Go to Step 17

17
Consult the current parts catalog and replace the radiator. Refer to Radiator Replacement .

Is the repair complete?
System OK
--

 

2002 Model Year Corvette
Cooling System Description and Operation
Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.

The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

Engine Coolant Indicator(s)
COOLANT OVER TEMP
The IPC illuminates the COOLANT OVER TEMP indicator in the message center when the following occurs:

• The PCM detects that the engine coolant temperature exceeds 124°C (256°F). The IPC receives a class 2 message from the PCM indicating the high coolant temperature.

• The IPC will also illuminate the CHECK GAGES indicator and a chime sounds when this condition exists.

Cooling System
The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system is designed to remove approximately one-third of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the system cools slowly or not at all. This allows the engine to warm quickly.

Cooling Cycle
Coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. Some coolant will then be pumped from the water pump, to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost.

Coolant is also pumped through the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders where it absorbs heat.

The coolant is then forced through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the water jackets surrounding the combustion chambers and valve seats, where it absorbs additional heat.

Coolant is also directed to the throttle body. There it circulates through passages in the casting. During initial start up, the coolant assists in warming the throttle body. During normal operating temperatures, the coolant assists in keeping the throttle body cool.

From the cylinder heads, the coolant is then forced to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine is warmed, or it will flow through the thermostat and into the radiator where it is cooled and the coolant cycle is completed.

Operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components:

Coolant
The engine coolant is a solution made up of a 50-50 mixture of DEX-COOL and clean drinkable water. The coolant solution carries excess heat away from the engine to the radiator, where the heat is dissipated to the atmosphere.

Radiator
The radiator is a heat exchanger. It consists of a core and two tanks. The aluminum core is a crossflow tube and fin design. This is a series of tubes that extend side to side from the inlet tank to the outlet tank. Fins are placed around the outside of the tubes to improve heat transfer from the coolant to the atmosphere. The inlet and outlet tanks are molded with a high temperature, nylon reinforced plastic. A high temperature rubber gasket seals the tank flange edge. The tanks are clamped to the core with clinch tabs. The tabs are part of the aluminum header at each end of the core. The radiator also has a drain **** which is located in the bottom of the left hand tank. The drain **** includes the drain **** and drain **** seal.

The radiator removes heat from the coolant passing through it. The fins on the core absorb heat from the coolant passing through the tubes. As air passes between the fins, it absorbs heat and cools the coolant.

During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling system. Coolant without bubbles absorbs heat much better than coolant with bubbles.

Pressure Cap
The pressure cap is a cap that seals and pressurizes the cooling system. It contains a blow off or pressure valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring of predetermined strength, which protects the radiator by relieving pressure if it exceeds 15 psi. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, might cause the radiator to collapse.

The pressure cap allows pressure in the cooling system to build up. As the pressure builds, the boiling point of the coolant goes up as well. Therefore, the coolant can be safely run at a temperature much higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant is, the faster the heat moves from the radiator to the cooler, passing air. The pressure in the cooling system can get too high, however. When the pressure exceeds the strength of the spring, it raises the pressure valve so that the excess pressure can escape. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the cooling system. This equalizes the pressure in the cooling system with atmospheric pressure, preventing the radiator from collapsing.

Surge Tank
The surge tank is a plastic tank with a pressure cap mounted to it. The tank is mounted at a point higher than all other coolant passages. The surge tank provides an air space in the cooling system. The air space allows the coolant to expand and contract. The surge tank also provides a coolant fill point and a central air bleed location.

During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling system. Coolant without bubbles absorbs heat much better than coolant with bubbles.

Air Baffles and Seals
The cooling system uses deflectors, air baffles and air seals to increase system cooling. Deflectors are installed under the vehicle to redirect airflow beneath the vehicle to flow through the radiator and increase cooling. Air baffles are also used to direct airflow into the radiator and increase cooling. Air seals prevent air from bypassing the radiator and A/C condenser. Air seals also prevent recirculation of the air for better hot weather cooling and A/C condenser performance.

Water Pump
The water pump is a centrifugal vane impeller type pump. The pump consists of a housing with coolant inlet and outlet passages and an impeller. The impeller is a flat plate mounted on the pump shaft with a series of flat or curved blades or vanes. When the impeller rotates, the coolant between the vanes is thrown outward by centrifugal force. The impeller shaft is supported by one or more sealed bearings. These sealed bearings never need to be lubricated. With a sealed bearing, grease cannot leak out, and dirt and water cannot get in.

The purpose of the water pump is to circulate coolant throughout the cooling system. The water pump is driven by the crankshaft via the drive belt.

Thermostat
The thermostat is a coolant flow control component. It's purpose is to regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a piston. When the element is heated, it expands and exerts pressure against a rubber diaphragm. This pressure forces the valve to open. As the element is cooled, it contracts. This contraction allows a spring to push the valve closed.

When the coolant temperature is below 91°C (195°F), the thermostat valve remains closed. This prevents circulation of the coolant to the radiator and allows the engine to warm up quickly. After the coolant temperature reaches 91°C (195°F), the thermostat valve will open. The coolant is then allowed to circulate through the thermostat to the radiator where the engine heat is dissipated to the atmosphere. The thermostat also provides a restriction in the cooling system, even after it has opened. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block.

Transmission Oil Cooler
The transmission oil cooler is a heat exchanger. It is located inside the right side end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant that surrounds the oil cooler as the transmission fluid passes down through the cooler.

The transmission oil pump, pumps the fluid through the transmission oil cooler feed line to the oil cooler. The fluid then flows down through the cooler while the engine coolant absorbs heat from the fluid. The fluid is then pumped through the transmission oil cooler return line, to the transmission.

Coolant Heater
The optional engine coolant heater (RPO K05) is rated at 400 watts and supplies 1365 btu/hr. The engine coolant heater operates using 110-volt AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather -29°C (-20°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The unit is equipped with a detachable AC power cord. A weather shield on the cord is provided to protect the plug when not in use.

 

Thanks for all the responses. I've had to let it sit as the rain started today. Funny how the procedure above has you removing/checking the water pump before checking fans, stat, and even obstructions for radiator. So maybe the water pump is the most probable failure. That's more work then I want to do, I think. Anyone know a good Vette repair shop/tech in the Chantilly, VA area? I'm starting to get worried.

Anyway I think the cap is good, being able to hold under pressure, as when I loosen it when hot, the water in tank will bubble up and you can hear the pressure release. This thing is just all of the sudden not being able to cool. The motor seems to have good power.

Replacing stat does not seem to be the fix and fans seem to work OK. Again I wonder if temp trigger points have been corrupted. Is that possible and programmable? There is plenty of coolant and I see no leakage anywhere. The only thing I can't see is the water pump pumping. I guess I could pull a hose and check. I'll get coolant everywhere if it works. I can also try to burp the system again. I have run the car with the overflow tank uncapped and had all the boiling settle down, so I hope this means no more air. Levels seem to be good. IDK

 

 

I just put the engine back in my car. The entire system was bone dry. I connected all coolant hoses except the one from the rad to the tb. When I filled the system, this allowed air to escape from both the rad and the engine block. When coolant began to leak out, I connected/tightened the hose and topped it off. The system holds 3.1 gallons. I got three in there without ever starting the engine. This method is simple and allows the air to escape. In general, vehicles with expansion tanks usually are self burping.
My concern with your running hot is the air bubbles. Do you have the factory air bleed tube under your intake? You can pm me if you want. Include a cell. I'd be happy to help

 

Did the burp thing. I undid the hose on cross over tube. I was surprised how much coolant/water I put into the system (more than gallon mix), but I finally got it to run out of the tube. Put everything back together, Started car and the temps climbed slowly, but got to the low and high fan trip points. I let the overflow cap off and got some over boil. I may have added a bit extra before seeing the flow out of cross over tube.

Went for short drive and temps went to 250. Got some air across the motor and the temps went back down in 225 area. A little more driving and they went back up, so it's back to driveway and cooling. Let it cool enough to remove overflow cap, so I hope any air bubbling around will work out. I got the car level as I could (maybe nose up a little) when doing the burp/air purge thing above. Any suggestions now

 

After it gets hot, you let it cool down and restart it does it start easily and runs good? Do you see any smoke from the exhaust? Sounds like the air bubbles you mention could be for a combustion leak. Either that or your having air or coolant circulation problems and the coolant is boiling. You did check the air deflector and ducting.
With the engine idling on a 90 degree day, ac off, the engine should be able to run until the fans come on low. They should be able to bring the temp back low enough to turn off again.
A couple thing to consider
1. Remove the tstat. Reinstall the cover. Remove the upper hose from the rad. Cap off the rad where the hose came off. Tie the hose up out of the way as high as u can. Top off the coolant. Have someone start it and rev it to about 2000rpm for 2-3 seconds ( be prepared for a mess). A LOT of coolant should flow. If not pull the pump. If so get a new rad.
2. Remove all 8 plugs after it has been hot and cooled. Keep them in order. Look for 1-2 that r washed down clean. Unplug your coils and injectors and have some one crank it over. If you get coolant, the heads need to come off.

 

The motor starts fine after cooling down naturally. And even hot. When I have taken it out for a drive, the motor seems to run strong until the temps above 240 and heading higher, and I get messages on DIC. I have cooled the motor by driving higher speeds (50 MPH plus, air cooled) and temps have come down to 225 area, and last week back to 190 or less. But I don't want to drive too far from home, so back in the burbs, it gets hotter. If I put the car in nutral, and coast, it seems to cool. Back in the gas to get speed and temp goes back up until the air cooling takes over.

The motor does feel strong, no misses, good response. No steam out the pipes that I have seen in driveway reving motor or nothing obvious during start up. Oil seems/looks clean too. I'm wondering water pump, but I guess the only real way to find out is pull a hose and make a big mess. All this happened all at once, like something just broke/went wrong fast one day. I have run the car to work (in the past when this happened), where I get alot of unitterrupted hwy time/speed and things are fine. Car runs great, got power. Getting into traffic and lower speeds is where I get into trouble, of course. I have had to let her sit and may try to take to mech.

The four bolts for water pump doen't seem that bad, but the mess of coolant is one of the biggest problem for me. I catch everything I can but..... I spent more time washing down the drive and hoping that the local animals don't lick up the coolant, then replacing stat and burp'in the motor. Being 60 (and out of shape) doesn't help either, bending over this low car to work on the motor gets to me back. I can do simple stuff, it just takes me longer.

 

Oh No! Someone just told me that mixing the original coolant with prestone can cause the coolant to jell. I had just done this mixing yesterday, as I had the prestone (green) in the garage. I drove only a few miles, but as above, got to the heat. So I should get this thing flushed out asap. Any opions out there on this?

They said the red coolant can jell by itself. The car has 84k miles on it. I didn't see any problems of jelling as it flowed pretty easily out of the stat hole (water pump, cold) when I changed stats. I could have original coolant, so that would be the dextron stuff. Is this supposed to be red or at least reddish brown in color?

 

When was the last time you cleaned your radiator? These cars love to suck up road debris.

 

I see. It's starting to sound like a water pump simply through the process of elimination. For the year, his car is low-ish mileage, and I've read that the LS1/6 pumps tend to digest themselves if the engine isn't run for long periods. I don't know how much truth there is to that, but my '02 is on its second one with 97k (was leaking and replaced at 85ish).

 

Thanks folks for continuing to give me input. While low milage, it is pretty much a DD. Cause I love to drive it. It's just strange how this all of the sudden happened. Stat I could go with as being a sudden failure, but this does not seem to be the case.

I talked to a shop that is willing to track down the problem at not much of a cost to T/S the system. They can also do a flush with a BG coolant flush machine and he said he could figure out if the radiator is blocked. After talking he said that with the water pump failing, I would probably over heat on the Hwy as well as traffic. We had long discussion. So maybe my coolant is burnt out, maybe blockage somewhere. It has made me wonder why I get boil up back into the overflow tank. Maybe I waited too long to have it swapped out, IDK. I'll post what the next set of experts find. Hopefully sometime tomorrow. Thanks again everyone for following and posting.

 

dexcool is nasty. I have seen many a gunked up gm cooling system.