97 blazer heat blows cold

my 97 blazer zr2's heat blows cold air, new tstat heater core is fine, i heard it could be the trap door?? i have tried blocking the radiator but it still blows cold, the temp gauge i can go from cold to warm / warm to cold and it doesnt make the hissing noise that most other cars have. help its freezing here

You sure the heater core is fine?

How do you know for sure?

Could be the blending door is stuck or defective and it is not vacuum controlled.

[QUOTE=BlazerLT]You sure the heater core is fine?

How do you know for sure?

Could be the blending door is stuck or defective and it is not vacuum controlled.[/QUO

coolant is full in the radiator and at the proper level in the overflow, i got the car running and used a digital thermometer and tested both hoses at the heater core from under the hood the highest they got to was about 150F if i remember correctly with the heat off, then i turned the heat on and the hose going in stayed at 150 and the out dropped to 100F i believe

What is the temperature on the gauge when the engine is completely warm?

1/2? 1/4?

What is the temperature on the gauge when the engine is completely warm?

1/2? 1/4?



1 small tick mark over 1/4

my girlfriend has a 95 s-10 and the temp is the same as mine and her heat is awesome. when i covered my radiator i only covered it about 1/3 also

1 small tick mark over 1/4

Your thermostat needs to be changed.

Temperature should be one tick to the left of 1/2.

Why would the temp gauge stay near 210 (one tick to left of 1/2)? Wouldn't the temp drop down once the t-stat opens? I have a 195 degree t-stat in my '96 and when the engine is warming up I can watch the gauge go up to about the 210 mark (which I figure is 195 degrees) and then drop down to about one tick above 1/4. The only time it stayed near 210 was after I plowed through a snowbank and no air was getting to the radiator to cool down the coolant.

97blazr2, get your heater core back flushed.

i had the dealer change the thermostat when i brought it in to replace the idler arm, so they changed it and it stayed the same so then i changed it myself and still it wont get hot, that was only 2 months ago, the heater core hoses are at the same temp when the heat is off why would i need to flush it?

I was having the same problem of no heat even though the engine was running at the proper temp. The heater hoses were also hot to the touch (I don't know what temp). I had the core back flushed and now the heat works great.

i had the dealer change the thermostat when i brought it in to replace the idler arm, so they changed it and it stayed the same so then i changed it myself and still it wont get hot, that was only 2 months ago, the heater core hoses are at the same temp when the heat is off why would i need to flush it?

Your engine is not getting up to temperature.

As I said earlier, it should be one or two ticks to the left of half when fully warmed up.

Make sure you use a 192f/195f thermostat when you do the change.

Also, check your blending door and I would have your cooling system flushed and your heater core reverse flushed.

BTW, your blending door is not controlled by vacuum.

97blazr2, your t-stat is fine. Do a search for "temp gauge" and check out a thread called "temp gauge" started on 11/19/2004 by davydawg. He included a pic of his gauge at normal operating temperature and everyone agreed that it was correct.

97blazr2, your t-stat is fine. Do a search for "temp gauge" and check out a thread called "temp gauge" started on 11/19/2004 by davydawg. He included a pic of his gauge at normal operating temperature and everyone agreed that it was correct.

Are you talking about this thread????

http://www.automotiveforums.com/vbulletin/showthread.php?t=319304

Appearently you didn't read it! Everyone one said that it was close to theirs, but theirs were higher. And one guy said that when he tested it, that position is about 180 degrees. which is too low.

looks pretty normal to me for a car that has run long enought for the thermostat to open. Especially if it is cold outside.

Especially if it is cold outside

that is where my blazer runs at

His is probably stuck. A very common problem.

That's exactly where my 98 runs. Actually just brought it to my mechanic's attention because I could swear my old 98 ran one click left of center and the heat was not real warm on the newer one...turns out it was a clogged heater core. He said the thermostat was fine.

The new one is stuck. The old one was good. His mechanic is an idiot.

My Blazer is a 2000 and it runs a little warmer than that just by a couple notches and has from the day I bought it, never goes over the middle line but comes close if I run it really hard.

His is fine.

That reading is normal.

Turn your heat dial all the way to dead cold and watch the gauge go up a couple of notches.

BlazerLT is implying that it should be higher.

I agree with BlazerLT, between 210-260 is like overheating territory. My Blazer never goes above the tick below 210. MRogers, you may some underlying problem that needs addressing or maybe the gauge is messed up. Just my 2cents :)

His is fine

This was where mine WAS at and I put a CarChip EX on it and measured the coolant sensor...it read 177 - 183.4 tops....which means that the car isn't getting up to temp. So I yanked the thermostat with a ac-delco direct replacement and ow it's just one tick under the 210 mark and coolant sensor reads 194 - 197.5 all the time.

While it was warm enough to go into a closed loop, it's still not up-to-minimum operating temperature...188 min - 206 max.

Self explainatory

First, yes, that is the thread I was referring to.

Second, Apparently you didn't read it. ONE person said that their Blazer ran a little bit warmer than the pic shows.

Why would the temp gauge stay near 210 (one tick to left of 1/2)? Wouldn't the temp drop down once the t-stat opens? I have a 195 degree t-stat in my '96 and when the engine is warming up I can watch the gauge go up to about the 210 mark (which I figure is 195 degrees) and then drop down to about one tick above 1/4. The only time it stayed near 210 was after I plowed through a snowbank and no air was getting to the radiator to cool down the coolant.

sounds like your thermostat is sticking (not stuck..sticking). It is reaching 195 and opening as it should, but when the engine starts to cool, the thermostat isn't closing back to let it warm back up.

Where is the temp sensor located? What temp would the coolant be after going through the radiator? Obviously it won't be the same as the temp at the t-stat, especially this time of year. The lower temp coolant coming from the radiator heats back up to 195 degrees by the time it reaches the t-stat before going into the radiator again so it is cooler as it runs through the engine.

Incidently, I just changed the t-stat because the previous one (another 195 degree) was staying open and the vehicle wasn't reaching the proper operating temp.

The sending unit is on the drivers side head just above the #3 and #5 spark plugs.

The temp after going through the radiator depends on lots of things. Airflow, air temp, antifreeze concentration......

I'm not sure if you were asking or not, but this is how the cooling system works:

The engine warms up, the thermostat opens, when it opens it allows the coolant to circulate through the radiator. The coolant exits the engine through the thermostat (not enters as some people believe) as the warm coolant exits the cooler antifreeze enters and circulates through the engine and exits through the thermostat warmer than it entered. (how much warmer depends on how cool it was when it entered, how hot the engine is and few other things) It then enters the radiator and the cycle continues, the more it circulates, the more the engine cools, until it gets to the point that the coolant exiting the engine is so cool that it no longer holds the thermostat open. The thermostat then begins to close, as it does it restricts the flow of cool antifreeze in to the engine. This causes the engine to warm back up, opening the thermostat back up a little and letting it cool back down. This process is repeated over and over as the engine runs to maintain a fairly constant temperature.

Thanks for the sensor location info.

I wasn't actually asking how the cooling system works, just stating that the coolant temp will be different throughout the engine.

As for the reference to the other thread, I was just pointing out the discrepancy between what was "normal temp" there and what was said here.

Thanks for the sensor location info.

I wasn't actually asking how the cooling system works, just stating that the coolant temp will be different throughout the engine.

As for the reference to the other thread, I was just pointing out the discrepancy between what was "normal temp" there and what was said here.

I'm guessing that you are asking for the sensor location because you believe there is a problem with it, I just wanted to point out that it is rare for them to go bad, so you should test it before replacing it.

To test it:

1. Remove the sending unit from the engine and clip ohmmeter leads to the sending unit body and the terminal. Place the sending unit in a pan of water on the stove, with a cooking thermometer in the water. On a cold (50-80 degrees F) sender, the resistence should be 5,700 to 2,200 ohms. When it has warmed up to operating temperature (170 to 200 degrees F) the resistence should drop to 200-300 ohms.

You may also want to test the wire and gauge, to do this, just ground the wire to the sending unit housing, when you turn the key on, the gauge should go all the way up.

97blazr2, your t-stat is fine. Do a search for "temp gauge" and check out a thread called "temp gauge" started on 11/19/2004 by davydawg. He included a pic of his gauge at normal operating temperature and everyone agreed that it was correct.

No, IT IS NOT FINE!

We have a lot more experience than YOU do so how about you stop telling him that we are wrong.

If the temperature reading is only going one step over 1/4, you cannot sit there and tell him that it is ok.

You also forgot to tell him that we just fixed a guys truck on this forum with THE EXACT SAME READING ON THE TEMP GAUGE.

AND GUESS WHAT, IT WAS THE THERMOSTAT!!!

No, IT IS NOT FINE!

We have a lot more experience than YOU do so how about you stop telling him that we are wrong.

If the temperature reading is only going one step over 1/4, you cannot sit there and tell him that it is ok.

You also forgot to tell him that we just fixed a guys truck on this forum with THE EXACT SAME READING ON THE TEMP GAUGE.

AND GUESS WHAT, IT WAS THE THERMOSTAT!!!

To hell with the other guy.....I know first hand, mine was one step past 1/4, I changed it out and now it stays one step below 210. Just like all the other blazers with properly functioning thermostats.

To hell with the other guy.....I know first hand, mine was one step past 1/4, I changed it out and now it stays one step below 210. Just like all the other blazers with properly functioning thermostats.

Yip, mine too.

BlazerLT, check that other thread I referenced. Why did you say that it was reading normal and now you say that it's running cold? Make up your mind.

BlazerLT, check that other thread I referenced. Why did you say that it was reading normal and now you say that it's running cold? Make up your mind.

Because that one you referenced was not as bad as some are.

Thermostats can stick partially open and if it it only barely getting up to one tick over a 1/4, you bet your ass his stat is partially stuck open.

So if mine looks like the one in the pic, is it normal or running cold? I apologize for stepping on toes (or in this case, kicking shins), but it seemed like you were contradicting yourself with the two different "normal" temps. Since I have already replaced the t-stat and the one that I originally had was giving me the same reading, should I replace it again? Are there faulty t-stats from certain manufacturers like that recurring problem with the AC Delco rad cap?

After a good warm up, it should be one or two ticks to the left of the half mark depending on air temperature.

i flushed out my heater core only just to see if it did anything, i just disconnected the hoses and blew it out, connected everything back up and i have real good heat now. lets see how it lasts

I heard that air in the system from a leak might cause this problem. Idle the engine with the radiator cap off for about 10 minutes should get the air out. Make sure the heat is on full when you do this, to include the heater core.

Again, this is only what a heard once. Worked for me at the time.

I heard that air in the system from a leak might cause this problem. Idle the engine with the radiator cap off for about 10 minutes should get the air out. Make sure the heat is on full when you do this, to include the heater core.

Again, this is only what a heard once. Worked for me at the time.

The system will purge itself if you keep the cap on.

i have a 1997 4dr LS
i had a problem with my heater. i hooked up a hose to one of the hoses that run the radiator fluid through it. turned the water hose on for about 5 seconds, reconnect everything put some more coolant in it....then it started working fine.