Question about 2001 Chevrolet Blazer

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2001 blazer has new radiator, water pump heater core and thermostat and new intake gasket but still runs hot

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Stuck or backwards thermostat, the spring should face the engine. If its a serpentine belt system, the belt may not be routed correctly around the water pump causing it to spin the wrong direction. Blown head gasket, or cracked head. If none of the above is the problem, try adding a engine treatment at next oil change. Most advanced friction reducer availible.

Haynes Manual suggests if the water pump has been replaced with a serpentine belt and a reverse rotating water pump it might have been replaced with an earlier, normal rotating water pump instead of the reverse rotating type. It also suggests the radiator cap not maintaining normal pressure, fan not functioning properly, radiator core blocked or radiator grill dirty and restricted, drivebelt defective or not adjusted properly.

Also, here I post the comment and solution from other Blazer's user...
Problem: when I turn off the motor after driving for a while and wait a few minutes (i.e. go into a store.) when I come back and start it up it is always between 210-240deg. Is this normal?

I am running a Jet 180º thermostat , green antifreeze with a bottle of Redline water wetter , TransPro "extra capacity" radiator, LS1 electric fans, cowl induction hood and a CS144 High Output Alternator.

The first change was to add the larger radiator. Around here in record heat , once the system was hot no amount of airflow would cool it back down. That was greatly improved after the addition of the new radiator.

Next step was to get a head start on cooling and not run quite so close to the edge. That is where a lower temperature thermostat comes in. I did have to relocate the IAT sensor in order to make the combination work. The 2001 PCM is just too tight to get away with it. That information is all in another thread - Relocating IAT.

Now to match the cooling fan to the lowered operating temperatures. I was unable to find a clutch fan in other than the stock temperature. The stock fan really does a pretty good job, but locks in way to late. I opted to go with electric fans. In order to maximize the fans operation a bigger alternator is needed. The stock alternator is already working pretty hard. The addition of the electric fans is not what it needs. As heat builds the voltage drops and so does fan speed. Adding a bigger alternator helps in several ways. You maintain voltage to keep fan speed maximized, and it runs cooler since it is not having to work as hard.

There may have been some other mods that are contributing to the package. Such as a free flowing exhaust system. Modified front license plate mount area (cut out for flip down plate mount). Cowl induction hood lets the heat out at slow speeds and draws cool air at higher speeds. 2" body lift makes some room for the air to move out over the engine and transmission. Auxiliary transmission cooler helps to dissipate some of the heat to the airflow rather than the coolant. New radiator cap that doesn't allow air into the system. Restricted EGR system doesn't introduce as much hot gasses to the intake.

Some of these "small differences" may or may not affect the outcome. Lots of small changes can make a difference though.

My package seems to be working pretty well in a high desert environment.

About this, HERE can find other comments and recomendations.

Hope helps.

Posted on Jun 03, 2010


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Heater fan blows good but only blows cold air. Is it the heater core? The thermostat? How hard are they to replace if i do it myself?

Check the heater core by checking the hotness or coldness of the 2 tubes at the firewall that lead to the heater core.

If both tubes are hot, the heater core is fine. If both tubes are cold, then the heater core is plugged up and will have to be flushed out or replaced.

The thermostat, if stuck open, will delay the heating up of the heater core. It's not hard to replace the thermostat.

Thermostat Removal & Installation 4.2L Engine To Remove:
  1. Before servicing the vehicle refer to the precautions at the beginning of this section.
  2. Remove or disconnect the following:
    • Some of the coolant
    • The upper radiator hose f150_42_thermostat.gif

    • The bolts (A).
    • The water outlet connection (B)
    • The water thermostat and paper gasket assembly (C)
To Install:
NOTE: The water thermostat is indexed and must be installed correctly.
  1. Install or connect the following:
    • The water thermostat
    • The thermostat
    • The water outlet adapter
    • The bolts
      1. Torque to: 80 inch-lbs (9 Nm)
    • The upper radiator hose
    • The coolant
4.6L/5.4L Engines To Remove:
  1. Before servicing the vehicle refer to the precautions at the beginning of this section.
  2. Remove or disconnect the following:
    • Some of the coolant
    • The upper radiator hose f150_46-54_thermostat.gif

    • The bolts (A)
    • The water outlet connection (B)
    • The water thermostat
    • The O-ring (discard)
To Install:
  1. Install or connect the following:
    • A new O-ring to position the water thermostat in the upper intake manifold
    • The water outlet connection onto the upper intake manifold
    • The bolts
      1. Torque to: 18 ft-lbs (25 Nm)
    • The upper radiator hose
    • The coolant
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My blazer is over heating. I have changed the thermostat and flushed the radator and heater core. I have no leaks, but it still over heats.

Is the water pump working? When you run your car until it is at the operating range on the gauge, does the top radiator hose get warm (hot). Your motor block might have a calcium block. Make sure to use distilled water to fill up the rad.

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Check the coolant level. It is common for the intake gaskets to leak causing the coolant level to drop. The first thing to stop working when the coolant gets low is the heater. Top off the coolant and determine where you are leaking coolant whether it be the intake gaskets, hoses, radiator, water pump, etc.

If the coolant is full what does the temp gauge say? Once the vehicle is warmed up it should read around the 200 degree mark. If its below 190 than the t-stat is stuck open. Replace the thermostat.

If both of those are fine and the coolant looks like mud than your heater core is plugged. You can try back flushing it with a water hose. Remove both of the heater core hose and use a water hose to flush out the heater core. This may take several tries before you start to feel some heat.

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How to change a heater core

hi try this save to file then zoom in.6332883.jpg

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Did I read that right and it has no thermostat?

Running it without a thermostat will cause it to overheat.

The problem is there is nothing to slow down / restrict the coolant and let the radiator do it's job.

A very common misconception on how cooling systems work..

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