# No heat engine runs cold



## Patrick1 (Oct 2, 2018)

Heater blows tepid air and the temp guage never goes up. I replaced the thermostat and I'm polishing up a radiator flush as im writing this... No effect. The radiator fans run non stop... I'm ready to pull the plug on them since wintwe is coming up.

I thought the thermostat would have fixed the problem. Any other angles I can try?


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## rogoman (Dec 16, 2004)

Your best bet may be to drain down the coolant and start all over again with the filling of the coolant.
Here's how I do it:
1 - drain coolant
2 - open the bleeder screw
3 - optionally jacking up front of car helps to purge air pockets
4 - fill system until coolant starts coming out the bleeder hole
5 - close bleeder screw (not too tight; screw is easy to break off)
6 - continue filling until coolant is at the bottom of the filler neck
7 - do not put cap on the radiator
8 - start motor; as coolant starts to warm up, you may see a few air bubbles
9 - squeeze the hoses by hand to free up possible air pockets
10 - put cap on radiator


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## Patrick1 (Oct 2, 2018)

Having trouble finding the bleeder screw. Is it flush to the surface. I'm looking at the diagram in the owners manual but other than the general location its not helping much.

I don't think there are any air pockets in the system. I simply dumped out what came from the radiator drain screw, filled with distilled water ran a flush through the system and then repeated that three times with out the flush. I burped the system as I worked it and filled with 50/50. I'm going to dump and do 50/50 again in a few days running it but I have had zero loss in the over flow tank. Could it be anything else


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## rogoman (Dec 16, 2004)

If you can post the model,year and engine of your vehicle, I'll look through my list of FSMs for a bleeder screw.


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## Patrick1 (Oct 2, 2018)

Oh and I had it up on wheel ramps so the radiator was the highest point of the system. 

Its starting to run lean now I believe. Smell gas from exhaust and some hesitation on throttle.


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## Patrick1 (Oct 2, 2018)

92 b13 sentra 1.6liter


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## Patrick1 (Oct 2, 2018)

I meant rich, but I can flip a coin on that. I just drove home from work and it was running like a top. Go figure


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## rogoman (Dec 16, 2004)

Well I did some digging around in my FSMs and came up with this:

COOLING SYSTEM BLEEDING

On the 1.6L use 2 air relief plugs. 
Before filling cooling system, ensure heater valve is open to allow coolant flow through heater core. See OPENING HEATER VALVE table. When filling cooling system, ensure air relief plug is loose to allow trapped air to exit system. See Fig. 1, 2. Tighten air relief plug after filling cooling system.


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## Patrick1 (Oct 2, 2018)

I'm leaning towards the temperature sensor. What do you guys think?


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## Patrick1 (Oct 2, 2018)

Very good pictures. I will work though it again this weekend. Thank you very much.

Hope that's all there is to it but the problem started before I did the coolant change so I'm sure this will not be the end of my cold mornings. Its got to be a bad sensor or the non factory thermostat I installed. The only reason I don't think its the thermostat is that nothing changed when I installed it....

Maybe oxygen sensor too but I doubt it. I might pull the sensor from old Smokey my other identical b13. The heat doesn't work in that one because the switch is floating free and does nothing.


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## Patrick1 (Oct 2, 2018)

Its supposed to get below freezing this weekend. I'm waiting to see if the car stars getting choppy again. Its been running pretty smooth with the warmer weather.

Added some seafoam on a low tank yesterday and pumped in some premium this morning. When I do the coolant change again I'm going to clean up the intake and such.


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## smj999smj (Jan 1, 2006)

The bad sensor would cause the fans to stay on. A stuck open thermostat would cause poor heat. I always stick with genuine Nissan thermostats as I've seen to many aftermarket thermostats run on the cold side in Nissans. These engines will trap air, so you need to purge them using the bleeder screws.


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## Patrick1 (Oct 2, 2018)

Switched the temperature sensor. It seemed to help but the guage just kind of fluctuated on the low end but it was on the rise. Took it out and cleaned it up and it flat lined when I put it back in.

I over tighten it a touch and when I was messing with it I did lay it on the metal frame. Is too tight bad?? Could you short one of thiese out as easily as laying it on the frame? Or is this just the symptoms of an air pocket? I'm a newbie to DIY car repair so don't smack me too hard if I did something stupid.

The car is running great with the switch over. No more raw gas smell. 

The old one was blackened, I put it in old Smokey but didn't bother starting it up I just wanted to plug the hole.


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## Patrick1 (Oct 2, 2018)

Yeah I'm going to need to loosen it. Too tight is too tight apparently.


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## Patrick1 (Oct 2, 2018)

Put in brand new temperature sensor and had the thermostat checked out for kicks and it is doing exactly what its supposed to do. The sensor I switched out was good too but wanted a new one so I could have a good one in old smokey. Changed the coolant (the right way this time).

I'm checking electrical next. I can't find any fuses going to the heating system other than fans (which work). Unless anybody know different on that.

So I've eliminated the following:
Temperature sensor
Thermostat
Air in the coolant

Like I said when I first switched the sensor it was working a bit and the heat was starting to blow nice and hot, but I couldn't leave well enough alone and tried to clean up the terminals and the guage flat lined again.

If it turns out not to be the wireing I don't know what else it could be.


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