S-10 blazer, no heat, challenge yourself on this one!

[Theevinman]

Thank you in advance. Here goes. Own a 2004 Blazer, last model made in the s-10 model? Anyway,I had no heat. Opened the radiator, discovered 'mud'. I drained and flushed all lines....started it and 'great success', heat again....for a little while then cold air, no heat. Hmmm....blocked heater core I think...again flush heater core (with hoses detached), in one side with the hose, flush water thru till clean water comes out other side, and reversed it just to make sure. Wallah, heat.....for a lil' while then nada, cool air again. Invested time and more money in a flush 'system', did it till, no doubt, clean water everywhere-it is as flushed as it will get!!! There can not be any clogs! Sometimes the inlet hose would be noticeably hotter than the 'return' hose so I started blazer and disconnected both hoses from the heater core to see...... There was no coolant going into the heater core, nor any coming out!!! Now what?? I assume, that sometimes there must be coolant making its way into the core, but then eventually stops. What's up? Be advised the temp gauge remains at normal the whole time no matter what is happening, it is not stuck however, it seems to be operating normally. TY

[JoshBarber]

I would assume its the thermostat.

Originally Posted by Theevinman

Thank you in advance. Here goes. Own a 2004 Blazer, last model made in the s-10 model? Anyway,I had no heat. Opened the radiator, discovered 'mud'. I drained and flushed all lines....started it and 'great success', heat again....for a little while then cold air, no heat. Hmmm....blocked heater core I think...again flush heater core (with hoses detached), in one side with the hose, flush water thru till clean water comes out other side, and reversed it just to make sure. Wallah, heat.....for a lil' while then nada, cool air again. Invested time and more money in a flush 'system', did it till, no doubt, clean water everywhere-it is as flushed as it will get!!! There can not be any clogs! Sometimes the inlet hose would be noticeably hotter than the 'return' hose so I started blazer and disconnected both hoses from the heater core to see...... There was no coolant going into the heater core, nor any coming out!!! Now what?? I assume, that sometimes there must be coolant making its way into the core, but then eventually stops. What's up? Be advised the temp gauge remains at normal the whole time no matter what is happening, it is not stuck however, it seems to be operating normally. TY

[Theevinman]

OK-Educate me, what's the therms job and how does it work, if it's 'broke' it could shut down flow to the heater core? Shouldn't there always be flow to the heater core regardless of 'outside' factors just because of the way the coolant hoses are laid out, the 'plumbing' so to speak, no?

[MT-2500]

Originally Posted by Theevinman

Thank you in advance. Here goes. Own a 2004 Blazer, last model made in the s-10 model? Anyway,I had no heat. Opened the radiator, discovered 'mud'. I drained and flushed all lines....started it and 'great success', heat again....for a little while then cold air, no heat. Hmmm....blocked heater core I think...again flush heater core (with hoses detached), in one side with the hose, flush water thru till clean water comes out other side, and reversed it just to make sure. Wallah, heat.....for a lil' while then nada, cool air again. Invested time and more money in a flush 'system', did it till, no doubt, clean water everywhere-it is as flushed as it will get!!! There can not be any clogs! Sometimes the inlet hose would be noticeably hotter than the 'return' hose so I started blazer and disconnected both hoses from the heater core to see...... There was no coolant going into the heater core, nor any coming out!!! Now what?? I assume, that sometimes there must be coolant making its way into the core, but then eventually stops. What's up? Be advised the temp gauge remains at normal the whole time no matter what is happening, it is not stuck however, it seems to be operating normally. TY

Remove heater hoses and see if you can blow air threw the heater core.
Also make sure you have coolant pressure out of the hot feed heater hose.
I have had good luck reversing the heater hoses for 3-4 days or a week to help clean out a part clogged core.

[Theevinman]

"Remove heater hoses and see if you can blow air threw the heater core."
Also make sure you have coolant pressure out of the hot feed heater hose.
I have had good luck reversing the heater hoses for 3-4 days or a week to help clean out a part clogged core.

1.....I have taken the garden hose and forced water from one side thru to the other, both ways- with water flowing generously in and out-no clogs!
2.....I do not have any pressure out of the hot feed, so what is it? Am I getting closer to an answer? Like I said earlier, I disconnected both hoses from the heater core while the car was warm and running and no coolant was coming out.
3....Please don't stop-HELLLLLPPPPPPPP!!!!!!

[MT-2500]

Originally Posted by Theevinman

"Remove heater hoses and see if you can blow air threw the heater core."
Also make sure you have coolant pressure out of the hot feed heater hose.
I have had good luck reversing the heater hoses for 3-4 days or a week to help clean out a part clogged core.

1.....I have taken the garden hose and forced water from one side thru to the other, both ways- with water flowing generously in and out-no clogs!
2.....I do not have any pressure out of the hot feed, so what is it? Am I getting closer to an answer? Like I said earlier, I disconnected both hoses from the heater core while the car was warm and running and no coolant was coming out.
3....Please don't stop-HELLLLLPPPPPPPP!!!!!!

Is engine running at normal tempt?
Rad full of coolant?
Good circulation in rad?
Check heater pressure hose back to engine.

[MT-2500]

Originally Posted by Theevinman

"Remove heater hoses and see if you can blow air threw the heater core."
Also make sure you have coolant pressure out of the hot feed heater hose.
I have had good luck reversing the heater hoses for 3-4 days or a week to help clean out a part clogged core.

1.....I have taken the garden hose and forced water from one side thru to the other, both ways- with water flowing generously in and out-no clogs!
2.....I do not have any pressure out of the hot feed, so what is it? Am I getting closer to an answer? Like I said earlier, I disconnected both hoses from the heater core while the car was warm and running and no coolant was coming out.
3....Please don't stop-HELLLLLPPPPPPPP!!!!!!

Check the heater hoses for being stopped up and the heater hose connections/pipe plugs to engine and intake and or water pump.
If water pump is circulating coolant it should be pushing water threw heater hose.

[srbianats]

Replace that radiator cap! Could be the cause of mud. If your holding temp at normal on the gauge then I think there is pressure. Could also be that the water pump is not circulating as much as it should. Maybe the fins are getting worn in the water pump.

[BlazerLT]

Replace the thermostat with a 192f version.

Replace the radiator cap with a version that is NOT Acdelco.

[Theevinman]

If the water pump wasn't working properly, wouldn't the temp in the car (temp gauge) be affected also? It's true, there is no pressure coming from the water pump-I too suspected the water pump, but then why is car not overheating, etc.?

[srbianats]

Try what BlazerLT said. Replace the t-stat and the radiator cap. T-stat could be stuck open and the cap could me malfunctioning and letting air in. This would explain the muddy coolant because air contaminated the dex-cool. Also this would explain no pressure in the hoses having a open stat and defective cap. Both are really cheap. 10 dollars total could fix this. If that doesn't fix the problem, then I would look at water pump. Hope this makes sence. It did while I typed it.

[rknorr]

I'm not really familiar with the late model S-10s but I know some vehicles have heater control valves that regulate the heated water going to the heater core. Maybe you have one of these and it is malfunctioning.

[someguy000001]

Are you sure that you're putting enough coolant in? You can't just fill the radiator and recovery bottle after you flush, you have to run it with the cap off until the thermostat lets go and the coolant level in the radiator will immediately drop. Then you top it off. Otherwise you won't have anywhere near enough coolant in the system.

[Theevinman]

You guys are a home run, and I do appreciate it (i am married, but the following is gay, I know...Its nice to see that there are strangers in this world who will another stranger, no questions asked). Thank you, I will try these latest things and will see. One more note, I go out today, pretty decent distance-no heat. Coming home, have heat for a little while........ Thanks again- i will advise of the cure when it happens.....

[BlazerLT]

Replace the 195f stat and the rad cap and run the engine with cap off and top off the coolant as the stat warms up and open and sucks coolant into the engine. Keep topping it off till it start puking out and then put the cap back on quickly.