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overheating at idle/low speed

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Old 03-17-2017, 02:48 PM   #1
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Default overheating at idle/low speed

I drained my dexcool out during a power steering cooler delete and replacement of the upper and lower lines. I then replaced it with the prestone GM approved dexcool, filled it up then ran it till the t stat opened and refilled the coolant, meanwhile massaging the upper and lower tubes for air while it was on rhino ramps. Driving around town she does ok for awhile, however as she heats up from driving if im at low speeds like 30 and below or at idle she will creep up and move past 210 after awhile (car is a 98 with true temp gauge) which it used to never go past 180. At idle in my garage it will go well past 210. If i go to WOT the temp will drop very fast back to the 180 range but as soon as i return to low speeds it will creep up again. Any ideas? or do i still have air trapped in the system and thats my issue?
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Old 03-17-2017, 02:51 PM   #2
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Have to ask the obvious, Fan kicking on? If that's not the issue I would guess you still have air in the system.
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Old 03-17-2017, 03:06 PM   #3
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You could have a t-stat that is not fully opening....but at higher rpms the water pump will move enough coolant to cool it down......

Or maybe a fan stopped working. Or maybe they are not going into the HIGH setting together.

Start it up cold.......let it get hot. Stand there and see if both fans come on together.....then if both fans work in the high setting also.

Check you coolant again......is it low? If its topped off after driving it around for awhile, then all your air is out.

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Old 03-17-2017, 03:39 PM   #4
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Originally Posted by LLLosingit View Post
Have to ask the obvious, Fan kicking on? If that's not the issue I would guess you still have air in the system.
I checked after the second time i went to bleed the system, fan was spinning but i never checked for both to be spinning

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You could have a t-stat that is not fully opening....but at higher rpms the water pump will move enough coolant to cool it down......

Or maybe a fan stopped working. Or maybe they are not going into the HIGH setting together.

Start it up cold.......let it get hot. Stand there and see if both fans come on together.....then if both fans work in the high setting also.

Check you coolant again......is it low? If its topped off after driving it around for awhile, then all your air is out.

.
Could be the t stat, however all i did coolant wise was drain the old stuff and replace the upper and lower lines so idk how all of a sudden it no longer holds stable temps, always used to go to 180 and never rise above even in heavy traffic or long idle periods. I did visually watch the coolant in the radiator as i was burping the lines, and after about just north of 180ish the level dropped about an inch then you could see it flowing through the system.

Now that you bring up the fans, if im not mistaken the high setting is fairly loud and noticeable, and i dont recall hearing them ever switch to this mode, perhaps they are stuck in low? I did have her on jacks for a long time and did motor mounts and full exhaust swap, replaced the starter and wired up the racetronix hotwire kit so maybe in the process of all this removal and install i clipped something or messed with something.

As far as the level goes, how i "bled" the system the first time was drained it all, replaced the lines and then filled it back up, massaged the lines cold, then started it up massaged it a bit more, drove the car around the block came back and let it get cold, it was low so i filled it back to the top and then from cold to hot while on ramps i burped the upper and lower lines for about 10 min while she held at about 190 temp and coolant was flowing. From cold, she will idle all day in my garage and never overheat it seems. As soon as i drive it for awhile i can come back to the garage and as she sits you can watch the needle slowly climb over 210 and go on.
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Old 03-17-2017, 03:55 PM   #5
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Son of a bitch, just went to the garage and started her from cold to watch when the fans kick on to HIGH and from cold idle, fans are not spinning at all anymore, either one. Correct me if im wrong but they should be spinning in low from startup. They never came on at all and i waited till the gauge came to 210 before shutting her off. Either i nicked a wire somewhere or my fans just decided to crap out, odd considering they worked just fine until i flushed the coolant.

going to be searching the forum but any suggestions on wire bundles or something i may have disconnected/nicked/damaged during the above mentioned removal/installs i did alongside this?


***update***

So the fans will only work when i turn the heat on, but they spin at the low setting and never kick on to high. However once the heat is turned off they shut off again, nto sure where to go with this.

Last edited by usnfenix; 03-17-2017 at 04:15 PM.
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Old 03-17-2017, 04:29 PM   #6
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Son of a bitch, just went to the garage and started her from cold to watch when the fans kick on to HIGH and from cold idle, fans are not spinning at all anymore, either one. Correct me if im wrong but they should be spinning in low from startup. They never came on at all and i waited till the gauge came to 210 before shutting her off. Either i nicked a wire somewhere or my fans just decided to crap out, odd considering they worked just fine until i flushed the coolant.

going to be searching the forum but any suggestions on wire bundles or something i may have disconnected/nicked/damaged during the above mentioned removal/installs i did alongside this?


***update***

So the fans will only work when i turn the heat on, but they spin at the low setting and never kick on to high. However once the heat is turned off they shut off again, nto sure where to go with this.
The fans should not come on if the engine is cold....they will only come on after it reaches the setting in the PCM, whatever you may have the PCM set for.

The fans should always run at the same time together.....and they will always go into HIGH at the same time together.

If I turn the A/C "ON" in my car the fans will not automatically come on.....don't know why, its always been that way. My fans only come on when a certain temp is reached.

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Old 03-17-2017, 04:57 PM   #7
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maybe i didnt run it hot enough to trigger them, im going to try again right now and let it go past 210 for a bit, but again something is off, ive never any of these issues before. I ordered the SLP manual fan switch as that might help the issue, however im starting to think i still have air trapped in the block. Any good methods for getting this out? Im about to do my FAST intake swap so nows the time.
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Old 03-17-2017, 05:04 PM   #8
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maybe i didnt run it hot enough to trigger them, im going to try again right now and let it go past 210 for a bit, but again something is off, ive never any of these issues before. I ordered the SLP manual fan switch as that might help the issue, however im starting to think i still have air trapped in the block. Any good methods for getting this out? Im about to do my FAST intake swap so nows the time.
You shouldnt have to buy manual switches.....that does not fix the root of the over-heating issue.

Also do this right now....after you see the temp pass 210.....put your hand on top of the intake. If you can keep it there no problem....its only really warm and not HOT.....then you are not really getting to 210+.....

If you cannot keep your hand on the intake when the temp guage reads above 210....then you are really getting hot.

Also:
A lot of times......when you drain the coolant.....two things sometimes get fouled up. The coolant level sensor........and the Coolant temp sensor. If thats the case, you fouled the coolant temp sensor in the head.

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Old 03-17-2017, 05:27 PM   #9
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Also:
A lot of times......when you drain the coolant.....two things sometimes get fouled up. The coolant level sensor........and the Coolant temp sensor. If thats the case, you fouled the coolant temp sensor in the head.

.
Coolant sensor is most likely brass so there would be nothing to foul up and if the temp gauge is working then the ECU should be getting the same signal unless there are two or more temperature sensors.
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Old 03-17-2017, 05:37 PM   #10
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Problem solved, Burped the system one more time and swapped fuses, now the fans come on when she passes 210 and temp drops like they are supposed to.I then went for a drive in stop/go traffic and then sat in a parking lot at idle to simulate sitting at a light and the fans worked correctly, dropped the temps as they should. Thanks everyone, im still going to do the manual fan switch since its not a bad idea anyway.

Im starting to think that my sensor was covered in crap or something, since temps never fluctuated before the flush. I did drain out milky sludge that is evidence of the power steering cooler leak, so perhaps my gauge always sitting at 180 was from the sensor getting a bad reading or something.
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Old 03-18-2017, 06:18 AM   #11
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Coolant sensor is most likely brass so there would be nothing to foul up and if the temp gauge is working then the ECU should be getting the same signal unless there are two or more temperature sensors.
When I say fouled....Im meant dirty.

This has happened to me a couple times. Drain the system and coolant level light comes on......I had to take it out and clean it. It was covered in a film of crap. Put it in...it works again. BUT....not too long, it failed a couple months later so I just bought a new one.

Same thing with the Coolent Temp sensor.......it completely failed once time after a flush.

I have no clue how a sensor (both of those) can work fine with dirty slime on them RIGHT BEFORE the flush.....then they do not work after you put fresh clean coolant back in. BUT.....it has happened.

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Old 03-18-2017, 06:21 AM   #12
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Problem solved, Burped the system one more time and swapped fuses, now the fans come on when she passes 210 and temp drops like they are supposed to.I then went for a drive in stop/go traffic and then sat in a parking lot at idle to simulate sitting at a light and the fans worked correctly, dropped the temps as they should. Thanks everyone, im still going to do the manual fan switch since its not a bad idea anyway.

Im starting to think that my sensor was covered in crap or something, since temps never fluctuated before the flush. I did drain out milky sludge that is evidence of the power steering cooler leak, so perhaps my gauge always sitting at 180 was from the sensor getting a bad reading or something.
Glad you fixed it.....

Absolutely it could have just been dirty, and draining all the fluid out...I THINK, just my opinion, because it has happened to me......the dirt, slime or sludge on the sensor now had a chance to dry a little bit and it changes the composition of that dirt on the sensor. I think it gets thickened as is dries and then when you put the new clean coolant in....that layer of crap throws off the way it senses the new clean coolant......and gives wrong readings. The wrong readings can also affect the way the PCM operates the fans. Garbage in=garbage out.

Just my guess.....but it has happened to me with both the LEVEL and TEMP sensors.......changing them or cleaning them by hand fixed the issue each time.

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Old 03-18-2017, 06:23 AM   #13
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Also, I would check the coolant level 2-3 more times all week......top off if needed.

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Old 03-18-2017, 01:28 PM   #14
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If I turn the A/C "ON" in my car the fans will not automatically come on.....don't know why, its always been that way.
The fans will always come on with the A/C or defroster to pull air over the A/C condenser.


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Im starting to think that my sensor was covered in crap or something, since temps never fluctuated before the flush. I did drain out milky sludge that is evidence of the power steering cooler leak, so perhaps my gauge always sitting at 180 was from the sensor getting a bad reading or something.
Could be, or maybe you had a bad/wrong thermostat?
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Old 03-18-2017, 02:04 PM   #15
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You can also run the car without the thermostat in for a while to bleed out air.
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Old 03-18-2017, 08:18 PM   #16
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The fans will always come on with the A/C or defroster to pull air over the A/C condenser.
Tried it many times.......they will not come on if my engine is cold. I never tried to select defrost to see if that makes them come on. Not sure at what temp they will come on though...I never stood around to wait and see.

Another thing that never happens with my engine.....I have never heard my fans running after I shut my engine off. (((Only once when I overheated into the red when I lost my serpentine belt on a highway run))).


I'll get a video of it next time I'm home.

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Old 03-18-2017, 08:19 PM   #17
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You can also run the car without the thermostat in for a while to bleed out air.
Then you will let a ton of air back in when re-installing the t-stat.....

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Old 03-20-2017, 03:55 PM   #18
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The fans will always come on with the A/C or defroster to pull air over the A/C condenser.




Could be, or maybe you had a bad/wrong thermostat?
didn't change the t-stat.
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