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Greg A
Greg A, Master Troubleshooter
Category: Chevy
Satisfied Customers: 6106
Experience:  Working with Electronics & Cars for 25+ Years
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2000 Chevy Blazer: I thought the heater core might be bad..warming

Customer Question

I have a 2000 Chevy Blazer. The heater does not get warm so I thought the heater core might be bad. Today I noticed the temp doesn''t show the engine as warming up. I live in Houston so it''s not due to extreme temps. Would the temp gauge cause the heater not to heat?
Submitted: 6 years ago.
Category: Chevy
Expert:  Greg A replied 6 years ago.

HiCustomer Thank you for asking your question on Just Answer.

Do the temperature gauge move at all, after the engine has been running for about 5 minutes?

Do the engine cooling fans come on when the engine is started?

Thanks

Customer: replied 6 years ago.
Reply to Greg A's Post: It moves a little but not over 150. I don't think I've heard the fans come on.
Expert:  Greg A replied 6 years ago.

Hi again.

It sounds like your thermostat may be stuck open. I have the same issue with my 2001 Chevy Van, and it seems to take forever to get warm, and my heater is real slow to get going, but it does work eventually.

If I let it sit and idle for a while (like in the driveway or when sitting in a drive-through), then the gauge will go up to around 200 degrees, because no air is flowing through the radiator. Then the air temperature coming out of the heater vents gets up to about 120 degrees (I have measured it).

If you want the instructions on how to change the thermostat, please let me know. But what I would do first is check the heater hoses (going to and coming from the heater core) and make sure they are both HOT to the touch once the engine is warmed up. If both sides are not hot, you could have a flow problem through the core.

I would also make sure that the cooling system is absolutely FULL. Sometimes when it is a little low, there is limited flow of coolant through the heater core, and you will not get much (if any) heat transfer from the core. You can check the level in the radiator when the engine is cold. It should be right up to the top of the radiator neck. If not, start the engine and watch the level as the vehicle warms up. You should see it drop when the thermostat opens, or it will drop and you will see it flow if the thermostat is stuck open. Just top it up to FULL, once you see it flow, and put the cap back on. Then test the heater again, and see if it is any better.

Please let me know what you find and if you want those instructions.

Take Care, Greg A.

Greg A, Master Troubleshooter
Category: Chevy
Satisfied Customers: 6106
Experience: Working with Electronics & Cars for 25+ Years
Greg A and other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
Reply to Greg A's Post: The engine is running and the coolant seems to be okay on level. I'm not sure where to look for the hoses going to and from the heater core.
Expert:  Greg A replied 6 years ago.

Hi again. Sorry about the delay - my wife was having a "computer emergency."

The heater hoses should be at the rear of the engine compartment, on the firewall.

Here is the procedure to replace them, with diagrams. This should at least let you know where they are and where they run. You do not have to replace them at this time, only if it becomes necessary.

Heater Hoses Replacement 4.3 L

Removal Procedure

  1. Drain the engine coolant.

    graphic
  2. Release the heater inlet and outlet hose clamps at the heater core.
  3. Remove the heater inlet and outlet hoses from the heater core.

    graphic
  4. Release the heater inlet hose clamp at the intake manifold fitting.
  5. Remove the heater inlet hose from the intake manifold fitting.
  6. Release the heater outlet hose clamp at the water pump.
  7. Remove the heater outlet hose from the water pump.

    graphic
  8. Remove the heater outlet hose from the retaining clip at the engine water outlet.

    graphic
  9. Open the heater inlet and outlet hose retaining clip above the right side valve cover. Use a flat bladed tool to open the clip from the bottom.
  10. Remove the heater inlet and outlet hoses from the vehicle.

Installation Procedure

  1. Apply lubricant (GM P/N(NNN) NNN-NNNN to each end of the heater inlet and outlet hoses.

    Important

    When installing new heater inlet and outlet hoses, place the clamps on the hoses before installing the hoses to the vehicle.

     

  2. Install the heater inlet and outlet hoses to the vehicle.

    graphic
  3. Install the heater outlet hose to the water pump.
  4. Install the heater outlet hose clamp at the water pump.
  5. Install the heater inlet hose to the intake manifold fitting.
  6. Install the heater inlet hose clamp at the intake manifold fitting.

    graphic
  7. Install the heater inlet and outlet hoses to the heater core.
  8. Install the heater inlet and outlet hose clamps at the heater core.

    graphic
  9. Install the heater outlet hose to the retaining clip at the engine water outlet.

    graphic
  10. Place the heater inlet and outlet hoses in the retaining clip above the right side valve cover.
  11. Close the retaining clip. Ensure that the clip locks.
  12. Fill the engine cooling system.

Please let me know what you find.

Take Care, Greg A.

Customer: replied 6 years ago.
Reply to Greg A's Post: Thanks. I replaced the thermostat so now the temp is reading correctly. The hoses are not very hot near the firewall. They are warmer near the engine but certainly not hot to the touch.
Expert:  Greg A replied 6 years ago.

It sounds like you have a flow problem through the heater core. I don't believe there is a control valve in the heater hoses, at least there is no mention of that in the manual. Sometimes "crud" builds up in the core or hoses and can block the flow of coolant.

What I would do is disconnect the heater hoses, as close to where they connect to the engine as possible, and flush water through the heater core in BOTH directions. You should be able to do this with a garden hose. Just make sure the engine has cooled off before disconnecting the hoses. You can also disconnect the hoses close to the core, where they pass through the firewall and flush the core from there. If there is a blockage in one of the hoses, I would just replace them (they are cheap).

I hope the core is not blocked, because they can be a real pain to change.

Please let me know what you find.

Take Care, Greg A.

 

Customer: replied 6 years ago.
Reply to Greg A's Post: Okay. I flushed the hoses both directions. There was some "gunk" in there. I tried the heat again and there was a hint of heat but certainly nothing that would warm you up.
Expert:  Greg A replied 6 years ago.

Did you flush both the hoses AND the core in both directions?

Are the hoses now HOT to the touch after the engine is warm? That is what will tell you if you have good flow through the core.

I have to go out for a few hours. Be back after noon (pacific time).

Take Care, Greg A.

Customer: replied 6 years ago.
I had to replace the hoses to flush the core but well worth the $40. I now have heat!
Expert:  Greg A replied 6 years ago.

Excellent Work! And its nice to be warm.

Thanks for the accept & Feedback.

Take Care, Greg A.

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