# Funny Thermostat Problem...



## Alin99 (Aug 3, 2005)

Hi,

Firstly, I'm trying to investigate a problem with my mom's 2003 sentra xe that did not want to produce heat unless the engine was reved. After several attempts at removing this air from the system and getting heat with no success, I've gone to the next step and replaced the thermostat.

Now, the car produces "mild" air when the engine is cold but immediately switches over to freezing cold air once the engine gets warm. What's going on? I put the new thermostat the same way the old one was in. The engine temperature does reach the operating temperature (half way up).

Any ideas? I have to try and fix this problem before winter returns to Alberta...


Thanks!


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## djkid (Apr 2, 2008)

check your coolant level. make sure its not low. make sure there is no discoloration. also check your oil make sure its clean and not foamy. if it is foamy then u have a head gasket problem. i had the same problem. if not . then look into getting a coolant flush. which will clear out and debris in the system. also when the car is warm. there are two hoses going into the firwal towards the center of the car from the engine compartment. try to feel them and see if they are warm. if they are not. then u dont have any coolant going into your heater core that supply;s heat to the car inside. also get check for coolant leaks around radiator. if there is a small leak that will cause no heat. hope it helps..


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## smj999smj (Jan 1, 2006)

These cars had some problems with heater control levers breaking and mode doors sticking. It's addressed in TSB# NTB03-005a. Your problem likely has nothing to do with the coolant system, but with the heater system. Start by checking the temp mode cable operation.


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## Alin99 (Aug 3, 2005)

The coolant level is high. Before I replaced the thermostat, I got to this point where I suspected the coolant wasn't flowing past the thermostat. Basically.. I open the rad and after the pressure release, the level in the rad would be low and the reservoir above full.

I suspected air was in the system so I filled the rad up and let the engine run. It bubbled away, the more I revved it, the harder it bubbled (thought that's good..letting the air out), except that the last time I tried it, I decided to turn off the engine and noticed that there was very little coolant in the rad and I could not get it to pop-up by squeezing the hoses... To me, this is suggesting I was evaporating coolant when reving the engine. Meanwhile in the cabin... bone cold air.

As for the two hoses heading into the cabin, one barely gets "mild" at best. What I thought was initially the case was the air bubbles being trapped into these two hoses.. but after removing the thermostat, I started getting coolant coming from up front(albeit,a slightly different shade of orange)

I can't check the oil at the moment unfortunately.

As for the "temp mode cable", I'm not sure what/where that is.


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## smj999smj (Jan 1, 2006)

The temperature mode cable runs from the temperature control lever of the heater control to the temperature mode door of the heater case. You'll need to get under the dash and move the temp control lever back and forth to observe the cable movement. If no movement, then you'll need to pull out the heater control assy. and inspect the lever and cable connection.Also, IIRC, the heater cock (or control valve) lever is attached on the opposite side of the temp mode door. When the cable operates the door, it also operates the contol valve which controls the flow of coolant through the heater core. For this reason, based on the differance of the temperature of the heater hoses, I would stick suspect a cable or heater control lever issue.


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## SPEEDO (Jun 9, 2003)

to get the air bubbles out, lift the front end (jack stands etc) take the rad cap off and start engine, air bubbles will work out. the color of your coolant is a concern... any white smoke? ruff running at start up?


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## Alin99 (Aug 3, 2005)

The oil looks okay, no bubbles or anything. I'm not sure if it smokes or not as it's -10c outside and most cars I've seen create steam with a cold engine at this temp. Only odd thing, once in a while, right after starting it doesn't idle right. Like a piston isn't in sync. Turning the key off, waiting, and then starting it again fixes that.

As for seeing if the cable is okay, I guess that'll have to be a weekend check as it looks like I have to remove part of the lower panel/dash to see.

Speedo, I've put in prestone long life premixed coolant. It's orange. Also, that's how I went about trying to remove the air bubbles. Trouble is, it never got to a point where all that would be expelled would be coolant. I put a container on the ground below the rad and it looks like it got practically all of the coolant I put in (half a bottle of coolant....) 

I think that cooling system flush is in order..
Does anyone think it could be a waterpump issue? Do those ever fail in these cars? In at least one occasion, the car was ran with little coolant (it also would not heat..but adding coolant fixed it before).


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## jdg (Aug 27, 2009)

You got the wrong coolant for one thing!!!
http://www.courtesyparts.com/pdf/2003-Nissan-Sentra.pdf
Mixing the two isn't SUPPOSED to have a negative impact and maybe the evidence is anecdotal at best, but I've heard of a number of cases where using 'orange' in place of 'green' would eat up the metal on the head gaskets. Whether that's actually true or not, I don't know.
What I do know is the book calls for green and you've got orange and it's wrong.


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## SPEEDO (Jun 9, 2003)

^ correct! Get the orange stuff out of there! Flush it out to make sure its all out, then put some good stuff in there!


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## Alin99 (Aug 3, 2005)

Well.. the cooling system clean took things from bad to worse...
The heater core was supposedly blocked, and now fixed... but there is no warm air coming into the car.

Not only that, but now the engine is overheating.  Any other ideas? Could it be the water pump? The only upside.. if there is such a thing right now is that one of those heater core hoses gets warm rather quickly.. but like I already mentioned, there is no heat coming into the car.


Not that this is really a concern right now but they did put the green stuff in...


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## jdg (Aug 27, 2009)

Define "overheating"


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## Alin99 (Aug 3, 2005)

Engine temperature has risen from the usual midpoint place to hot (it has never done this!). Coolant container filled up to the very top and apparently smoke coming from the rad....


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## jdg (Aug 27, 2009)

Do a compression check.


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## SPEEDO (Jun 9, 2003)

the heater was blocked and is now fixed? dosent sound like its fixed, both heater hoses should be warm or your not getting water flowing in/out of the core...


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## jdg (Aug 27, 2009)

Ya, the one heater hose is getting warmed from STEAM!


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## 3GEclipse (Dec 2, 2010)

FYI OP, there is a bleeder on the T-Stat housing. It's a bolt so you wouldn't think about it being a bleeder. There is a copper gasket on it so be careful not to loose it or burn yourself.


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## Alin99 (Aug 3, 2005)

Yea I found it... car's still at the shop now, and not sure about if they found it.

They used a vacuum in the cooling system and it sorta temporarily worked...
Apparently the car was creating some "mild" air (at -14c, +7 deg f) today with a normal engine temp, then it went back to cold, started overheating and actually died on the highway (smoke under the hood and all..).
After it got cold, it started with the check engine light, very little coolant left in the reservoir.... and ofcourse no heat. Apparently.. the temperature stayed at normal while being driven back to the garage....

So this is just getting disturbing... and all because something was wrong that it would only create heat when pressing the gas...


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## jdg (Aug 27, 2009)

Sounds like you'd better change shops...
"They used a vacuum in the cooling system...."
That sounds like a load of crap to me.
Any shop worth anything should've been able to easily figure out if you're water pump is shot, if you've got a blown head gasket, blocked heater core, collapsed hose, whatever, without much trouble.......unless you told them to do only one thing.
Otherwise, let the shop do what it needs to do to get your car fixed. If you overheated it bad enough that it "died on the highway", I'd be willing to bet you did a fair amount of damage to the engine (seized it up by overheating it, warped the head, blew the rest of the head gaskets, etc).


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## camoy (Apr 28, 2004)

to the OP did you ever try a new radiator cap? A bad radiator cap can cause all the symptoms that you first had, and now have aggrivated to the point of overheating. To me if I saw that the overflow was completely full and the radiator low that tells me you possibly have a bad cap.

The bad thing is overheats tend to warp heads and warped head require removal, redecking, and a new head gasket.


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## jdg (Aug 27, 2009)

camoy said:


> The bad thing is overheats tend to warp heads and warped head require removal, redecking, and a new head gasket.


And a new radiator cap


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## 3GEclipse (Dec 2, 2010)

jdgrotte said:


> Sounds like you'd better change shops...
> "They used a vacuum in the cooling system...."
> That sounds like a load of crap to me.
> Any shop worth anything should've been able to easily figure out if you're water pump is shot, if you've got a blown head gasket, blocked heater core, collapsed hose, whatever, without much trouble.......unless you told them to do only one thing.
> Otherwise, let the shop do what it needs to do to get your car fixed. If you overheated it bad enough that it "died on the highway", I'd be willing to bet you did a fair amount of damage to the engine (seized it up by overheating it, warped the head, blew the rest of the head gaskets, etc).


Actually it's not uncommon to use a vacuum style kit to fill cooling systems. What you do is hook the tool up to the radiator, then plug in your air line to it. Then proceed to suck out all the air in the system. Once it's ready the hoses will colapse. then flip the lever and it fills it up.


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## jdg (Aug 27, 2009)

3GEclipse said:


> Actually it's not uncommon to use a vacuum style kit to fill cooling systems. What you do is hook the tool up to the radiator, then plug in your air line to it. Then proceed to suck out all the air in the system. Once it's ready the hoses will colapse. then flip the lever and it fills it up.


Ok...I can admit it. I've been officially "schooled"! 
I Google'd the term, read about the process, etc.
Looks to me like engine manufacturers found a new way to keep themselves, and repair shops in business once again, by designing engines/heads/etc that readily trap air.


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