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cmoore74

2000 Blazer No Heat And Engine Temp Running Cool

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Hello,

 

My wife's 2000 Blazer (4.3L) at about 83k miles started getting luke warm heat and a decrease in engine temperature. I had the dealership perform a reverse chemical flush of the heater core. I also replaced the thermostat, the water pump, and the fan clutch (usually only good to about 100k anyhow).

 

The problem is still there.

 

Could the heater core be totaly clogged? I'm confused as to why this would cause the engine temperature to be running around 160 deg. I would think the dealership would have confirmed the heater core was flowing as part of the flush procedure.

 

What would cause both of these symptoms?

 

Please help.

 

Thanks,

Chris

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Sounds like everything I would have done. Are you sure you put in the correct temp. thermostat? Could also be that you got a bad thermostat out of the store...would be bad luck but it could happen.

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Even if it was an incorrect colder T-stat, I would think the heat would be somewhat warm.

 

I changed the T-stat right in the beginning and no change from stock on the temperature guage.

 

Next I had the dealer flush the heater core.

 

When that didn't fix it I tried a new water-pump and fan clutch.

 

Any other ideas (asside from trading this thing in before next winter)?

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Man this sounds crazy. I would have to agree with Chris. I feel you have a defective T stat. If it is stuck open, it could easily be running too cool but I would also think that the heater would still be pretty hot. I would certainly try ithe stat before doing anything else.

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Agree, sounds like the thermostat. It's also possible that you put the thermostat in backwards, fairly common oversight.

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I could try a 3rd T-stat or at least test the one I just put in (on the stove in water with a thermometer) to make sure it opens at the proper temperature, but I have my doubts that is the problem. Even with the engine temperature at 160-170 deg the heat out of the vents should be quite warm. Something is causing both the engine temperature to be low and no heat.

 

By installed backwards I assume you mean upside down. That's not possible with this set-up as you wouldn't be able to bolt down the flange with it upside down.

 

Anyone know of a good description of how the cooling and heating system works on the 4.3L V6 including schematics showing how the coolant flows through the system?

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Sounds to me that you have a busted HVAC system. you switch over to hot air but the plate doesnt move causing you to only take in cold air and not pass it over the heater core before entering the car. I would check the relay or cable (not sure how a 2000 blazers system operates) and see if its functioning properly. I'd bet $$$ to doughnuts thats your prob man.

 

I mean you have changed everything else that there is to change...you have to move inside now.

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Sounds to me that you have a busted HVAC system. you switch over to hot air but the plate doesnt move causing you to only take in cold air and not pass it over the heater core before entering the car. I would check the relay or cable (not sure how a 2000 blazers system operates) and see if its functioning properly. I'd bet $$$ to doughnuts thats your prob man.

 

I mean you have changed everything else that there is to change...you have to move inside now.

 

It does switch over as I go from outside air to luke warm air, maybe not completely so I agree there may be something there to check out, but that doesn't explain the engine operating temperature being low.

 

This is driving me nuts...

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do you have a cold thermostat....the cold ones open at 173* a hot one opens at 198*

Both are acceptable. and with a fluid flush recently done on your engine it would run a little cooler that it always has.

 

you may want to pull your heater core hoses off the engine hook a hose connection to one side and see what kind of flow is coming out the other side. they may have flushed the system but not noticed a blockage in the core.

 

also....you may have a busted rad cap. they are designed to keep the cooling system pressurized...around 15psi...if its busted your system will stay in an open loop and pass all the fluid through and never get to op-temp in colder conditions.

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I just looked at you water pump on the NAPA web page, it looks like it might be easy to instal the hoses incorrectly. Just something to check, also, you could disconnect the heater hoses from the firewall and check flow through the core to verify for yourself. good luck.

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Thanks for all the help guys, but I don't think I've found the problem yet.

 

I did install a new radiator cap with no improvement.

 

It's not possible to swap the bypass hose with the heater hose from the water pump as the bypass hose is not long enough to reach where the heater hose plugs in. They actually made this somewhat fool proof.

 

As for the T-stat it is a Stant and Stant only makes a 195 deg F T-stat for the 4.3L V6 blazer. I still think I will pull the T-stat and check it on the stove to see at what temperature it opens.

 

I may also try to swap the heater core hoses to see if the makes a difference (swap inlet and outlet).

 

Would a clogged heater core somehow cause the engine to run cooler? That's about all I've got left for an idea at this point.

 

If it is a clogged heater core that doesn't exactly make me happy as it is a lot of work to replace it myself or big $$$ at the dealership (I think they estimated close to $1000).

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I replaced the heater core in my 1991 Sierra, it wasn't that hard of a job and I bought a new core from NAPA for just under $50. You could do the job in less than a couple of hours.

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Could I pull the two heater core hoses off and connect them together and bypass the heater core entirely?

 

If the engine temperature comes back to normal then I found my problem (clogged heater core).

 

I'm still struggling as to why a clogged heater core would cause engine temperature to be low unless it somehow forces more coolant through the engine.

 

Thoughts?

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The Heater hoses that attach to the core at the firewall are different diameters, it might be easier to just perform a flow check there than try to bypass it. If the flow test proves to be okay, you have eliminated one probable cause to your problem. If it does not flow it needs to be replaced anyway. Attacking one issue at a time is easier than trying to solve multiple issues, that can get pretty frustrating. (been there,done that).All I ended up doing was :). Other than poor circulation(Caused by plugged heater core) I can't think of what might be the cause of the low temp. when you tested the thermostat did you note the temperature of the water?

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i had the EXACT problem in my 96 blazer... after about 12 t-stats, aggrivation, and freezing thru the winter, the weather got warm, and we found the problem.. or actually, my son found the problem. when we recharged the AC (because it was broke from last year), the compressor was running, and the condensor was dripping water, but there was no cold air coming out of the vents..... hmmmmm... it was the AIR BLEND door causing the problem. it was stuck all the way open. letting all air, from the heater core, and outside air in... so we got the door back on the track, and presto! it works again. engine back up to temp, blows cold, and hot!

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