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Jay, Chevy Mechanic
Category: Chevy
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Experience:  Several yrs experience, GM Trained,
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How do you open and close the the radiator drain valve on a

Resolved Question:

How do you open and close the the radiator drain valve on a 2004 Blazer 4.3L?
Submitted: 8 years ago.
Category: Chevy
Expert:  Jay replied 8 years ago.
HelloCustomer all you need to do to open the drain cock is turn it counterclockwise until coolant starts coming out and to close it you just push it in and turn it clockwise until it is fully threaded back in. It is located on the bottom of the rad on the drivers side.
Customer: replied 8 years ago.
There is no drain cock on the radiator on the driver's side. The fitting which appears to be the drain cock is on the passenger side and it does not have any handle or other obvious way to turn it open or closed.
Expert:  Jay replied 8 years ago.
O.K. I could not remember off hand for sure with that vehicle. It is likely recessed with an almost square pattern, I know it doesn't make sense but just use a pair of needle nose pliers or stick a screwdriver in their and try to turn it. They are not torqued very high so they usually give and when it does it will get very easy to turn.
Customer: replied 8 years ago.
The fitting that appears to be the drain cock is on the passenger side just above the bottom of the radiator. It is a molded projection from the bottom of the tank that has 2 narrow passages at right angles to each other. The larger passage faces rearward and is about 3/8 inch in diameter and 1 inch deep. With an inspection mirror you can see what appears to be a small, metal, male fitting at its bottom. The problem is - what type of fitting is it and how to turn it (if it turns). There is extremely little clearance in the passage between the fitting and the wall and I suspect that a special tool is needed. I have already tried 3/16 and 1/4 inch thin walled deep sockets and they do not fit. Needle nose pliers will not fit and there does not seem to be a slot that would engage a screwdriver of any pattern. I hope there is a solution because removing the radiator hose would be quite a mess.
Expert:  Jay replied 8 years ago.

HelloCustomer I'm not sure what to say except that I have never had much difficulty finding the drain cock. One tidbit I can give you is it is usually on the engine side of the radiator and will turn easily. Here is what GM service information has to say about it.


The radiator is a heat exchanger. It consists of a core and 2 tanks. The aluminum core is a tube and fin crossflow design that extends from the inlet tank to the outlet tank. Fins are placed around the outside of the tubes to improve heat transfer to the atmosphere.

The inlet and outlet tanks are a molded, high temperature, nylon reinforced plastic material. A high temperature rubber gasket seals the tank flange edge to the aluminum core. 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 cock located in the bottom of the left hand tank. The drain cock unit includes the drain cock and drain cock seal.

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


Cooling System Draining and Filling

Tools Required

Coolant and Battery Tester

Draining Procedure

    Caution: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if radiator cap or surge tank cap is removed while the engine and radiator are still hot.

  1. Remove the coolant pressure cap.
  2. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Place a drain pan under the drain cock.
  4. Open the radiator drain cock.
  5. Drain the cooling system.
    Object Number: 188052  Size: SH

  6. If a complete engine block drain is required, remove the engine block drain plugs.
  7. Inspect the coolant.
  8. Follow the appropriate procedure based on the condition of the coolant.
    Normal in appearance -- Follow the filling procedure.
    Discolored -- Follow the flush procedure. Refer to Flushing .

Filling Procedure

  1. Close the radiator drain cock.

    Tighten the radiator drain cock to 2 N·m (18 lb in).

  2. If the engine block drain plugs were removed, perform the following procedures:
    2.1. Apply pipe sealer to the drain plugs.
    2.2. Install the drain plugs.

    Tighten the drain plugs to 18 N·m (13 lb ft).

  3. Lower the vehicle.
  4. Open the cooling system bleeder screws.

    Important: Use a 50/50 mixture of DEX-COOL antifreeze and clean, drinkable water.

  5. Slowly fill the cooling system with a 50/50 coolant mixture. Close the cooling system bleeder screws.
  6. Install the coolant pressure cap.
  7. Start the engine.
  8. Run the engine at 2,000-2,500 RPM until the engine reaches normal operating temperature.
  9. Allow the engine to idle for 3 minutes.
  10. Shut the engine OFF.
  11. Allow the engine to cool.
  12. Top off the coolant as necessary.
    Object Number: 9972  Size: SH

  13. Inspect the concentration of the engine.
  14. Rinse away any excess coolant from the engine and the engine compartment.
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