I have a 97 blazer 4door and no matter how long I drive it or let it sit running I cannot get the temp up past the first notch on the gauge I think its about 140-150° mark. I have replaced the radiator cap and thermostat but neither helped. I have noticed that both the heater hoses get hot to the touch and the upper rad hose gets warm but the lower hose is cold even after driving 45 min down the highway at 70 mph. I'm wondering if it might be a water pump issue or a clogged radiator. Also after driving it 30 min the rad cap is not hot and I can open it without it spraying all over the place plus the coolant in the radiator is only Luke warm and not hot as it should be so I'm guessing its not a bad temp sensor either. Any help would be greatly appreciated. I'm gonna do a flush and fill this weekend and see how that turns out

 

Im having the same problem on my 96 blazer LT .. i had a buddy look at mine and suggested that the old coolant might have blocked up a hose and i should think about trying to clean the lines of any blockage. well i havent done this yet but what steps have you taken to get your heat back?? any help or ideas would be great....

 

If the water pump doesn't circulate the coolant, or the radiator is restricted, or a radiator hose is restricted, the engine will overheat. If the thermostat is stuck open, even a little bit, the engine will not achieve operating temp. Just because it's new, doesn't mean it's good.

Both heater hoses, and the upper radiator hose at the thermostat housing, should be very hot, ~195F. You can only hold on about 3 or 4 seconds with bare hands, (if you're tough ). The lower hose should be ~130F.

 

Well today I flushed the system and removed all the hoses and cleaned them out as well as the overflow. I did get a lot of crap out of it and seams to heat up quicker and I have some pressure now if I take the cap off after its been running for awhile which it did not have before. The pump should be OK I started it with the heater hoses off and I shot fluid out of the tubes on the intake and water pump where the heater hoses connect too. I also noticed after all this work that I now have a small puddle of what seams to be new dexcool on my passenger side floor mat. I figure I need to to a heater core but would a small hole in the heater core possibly suck air in and keep the system from achieving optimal temp. I drove it for 35 min down the high way today and when I got home the lower hose still felt cold and the cap wasn't hot either but had pressure when I opened it.

 

When you had the heater hoses off of the heater core, did you flush into both of the hoses to flush the block?

When the engine was running at operating temp, were both heater hoses hot?

Did you remove the thermostat and make sure it was completely closed?

Did you remove both radiator hoses and flush the radiator?

Any coolant leak will allow air into the system after the reservoir is empty, if the radiator cap is working properly. OEM radiator caps are not the greatest quality to begin with, and if they get a little crud in them, they usually won't work at all. When the system is low on coolant, it will try to draw in coolant from the reservoir. If the reservoir is empty, it will suck in air.

 

Yes I flushed the block as best as I could. I had every hose off except the lower rad hose because I could not get to the spring clip I flushed the rad out waited for the water running threw the block to turn clear. I can't seem to get the vehicle up to normal operating temp but yea the heater hoses felt pretty hot and it was blowing hot air from the vents inside the car as well.and the reservoir is cleaned out and full as well

 

I didn't remove the t- stat as I just put it in the day before

 

If it's not achieving operating temp, check the thermostat. Just because it's new, doesn't mean it's good. Needs to be a 195F stat. Among other things, using a colder stat will cause poor fuel mileage and not give enough heat.

 

After all I did yesterday not the water pump started to leak so I replaced that so we will see how the next few days go.

 

Did this vehicle have ethylene glycol in it, (green coolant)?