I have a 2000 gmc with a 4.8L. I noticed coolant leaking out of the resivoir bottle today onto the ground. I also have a small surge at low speed. All happened on the same day. Coolant seems to have oil in it. Maybe a coinsedence but it was a very cold night.

Low coolant light came on--Holy ****! - 1999-2006 & 2007-2013 ...

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Apr 22, 2006 - 13 posts - ‎10 authors I was driving down the freeway today and got a "low coolant" message. As you can ...Bob 2000 Ext cab Silverado 4x4 w/ 5.3. Back to top ... 2002 Silverado Battery light and low voltage on gauge ...
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Low coolant light - Ask the GM Technician - GM ...
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You may be able to braze (2) 1/2 in. copper 90 degree water fittings back to back to install as a jumper. Install jumper well ahead of bad hoses. I have never seen a stopped up heater core. Replace any suspect hoses and temp control valves.

check the intake gasket if it is leaking make sure the water pump is not leaking, check the heater core coupler sometimes those get brittle and crack.

Take it to a shop and ask them to put it up on a lift, take a look and figure out where it is leaking. They can tell you and also how much to fix.

There is a TSB for this problem. Here it is.

Bulletin No.: 04-06-02-007

Date: August 11, 2004

TECHNICAL

Subject:
Low Engine Coolant Level Indicator Always On (Diagnose Low Coolant Level System Operation/Check Sensor for Oil Contamination)

Models:
2000-2002 Buick Century, Regal
2000-2001 Chevrolet Lumina
2000-2002 Chevrolet Impala, Monte Carlo
2000-2002 Pontiac Grand Prix
2000-2002 Oldsmobile Intrigue

Condition

Some customers may comment that the low engine coolant level indicator is always illuminated.

Cause

The cause of this condition may be due to engine oil contaminating the coolant. Possible sources of oil contamination are internal engine leaks, improper service procedures, or the addition of some types of anti-leak additives to the cooling system. Once in the coolant, the oil leaves deposits on the level sensor creating an insulating film. This film results in a false activation of the coolant level indicator.

Correction

Diagnose low coolant level system operation and check the sensor for oil contamination using the procedure listed below.

Important: No coolant supplements should be used in GM cooling systems, other than what is approved and recommended by GM. The use of "aftermarket" over-the-counter sealing and cooling supplements may affect the operation of the low coolant level sensor. Discoloration of the coolant recovery bottle is normal and does not necessarily indicate that coolant contamination is present. Flush cooling system only when instructed by this bulletin.

1. Verify that the coolant is at proper level in the radiator and the coolant recovery bottle. If the coolant is low, add proper amount of 50/50 water and DEX-COOL(R) mixture. If the low coolant light operates properly, diagnose the cooling system for loss of coolant as outlined in SI. DO NOT proceed further with this bulletin.

2. Remove the low coolant level sensor. Refer to Coolant Level Module Replacement in the Engine Cooling sub-section.

3. With the key on, the engine off and the coolant level sensor disconnected from the vehicle wiring harness, observe the low coolant light:

^ Light is on - Chassis wiring or instrument cluster concern. Follow the appropriate diagnostic information in SI.

^ Light is out - Proceed to Step 4.

4. With the key off, connect the coolant level sensor into the vehicle's wiring harness. Connect a ground wire (1) to the battery negative terminal. Using a sharp probe (3) attached to the ground wire, ground the coolant sensor probe (2) as shown in the illustration. Make sure a good contact is made. With the key on and the engine off, observe the low coolant light for at least 15 seconds.

^ Light is on - Replace the low coolant sensor and re-check system operation.

^ Light is out - Proceed to Step 5.


5. Using a small wire brush or emery cloth, polish the low coolant level sensor probe to remove any film or oxidation. The probe should be a bright brass color when finished. Use Brake Parts Cleaner to flush removed deposits from the low coolant sensor probe. Re-install the low coolant sensor into the vehicle and proceed to Step 6.

6. Flush the cooling system and install new DEX-COOL(R) mixture as outlined in the SI. Check the vehicle's warranty history to determine if any engine gasket had recently been changed. If there has not been a recent gasket replacement, locate and repair the source of the engine oil contamination.

the coolant resvoir bottle is located above that fender well it's possibly has a small crack in it i just fixed one the other day

Look at the oil on the dipstick. If its milky you have a head gasket issue. Also if you can make it to a smog machine they can sniff the coolant fumes to see if gas is in the coolant. Head Gasket again. Any repair shop has a chemical that can test for gas in the coolant also.

The theory here is if your losing water and none is leaking on the ground its got to be going into the cylinder and getting pushed out the exhaust pipe.

Now if its just overheating you may have a stuck thermostat or clogged radiator or a coolang fan that dlesnt turn on when commanded by the computer.Also if its just overheating and the water lost is going on the ground somewhere then you may not have a head gasket issue.

I just did a head gasket on a Honda because as the engine was warming up the overfill bottle would fill up and overflow. The combustion pressure was leaking into the coolant and pushing the coolant out.

the water pump is leaking it will need replaced its possible the thermostat is now damaged and cylinder head

this is an overflow tube.
have you checked the radiator itself to see if it is low? need to do this only when engine cool.
if radiator is low and you just add to bottle it will **** it all out until radiator is filled properly.