Rep Power: 0

Hi all..Happy New year! I'm a bit stumped- I read up on many heating issues that folks are having but didn't see what I was after so here goes.. I have an '04 civic with 154,000 kms. 1.7L. Its been really cold here lately and I noticed that at low rpms, the temp gauge actually goes down in temp when I come to a slow down or stop .. I didn't notice it last year but honestly I really don't drive the car much so likely was the same but when I took it out a few days ago, thought its likely time to change the thermostat for a starting point. I did just that- Honda Thermostat, Honda coolant. Still seems to do the same thing. Super heat when driving , just doesn't seem to want to maintain or warm up very well at idle.. . I asked a friend of mine who has pretty much the same car and he says his is similar.. Heats up fine when temp isn't too cold so definitely outside temp related.. question is, is this normal? Should I be concerned?
PS. Just had timing belt done about 8,000 KM ago and dealer said not necessary to change water pump.. No coolant loss or evidence of Antifreeze in crankcase

 
Rep Power: 517

You're located where?
It's how cold there?

Yes it's common for small engines to lose temperature just by running the heater.
The small fuel efficient engines simply don't burn enough gasoline at low rpm/low load to keep ahead of the amount of heat that can be removed by the cabin heater.




I drive a 2012 with 1.8L engine, in the winter cold if I run my heater fan full blast the engine will never get to operating temperature unless I'm out on the highway.



It was -6*F (-21*C) this morning on my way to work.

I have remote start. Left the fan on lowest speed. I let the car run for 15 minutes this AM before I left, engine temp was only 120F.
Drive to work...... I finally had the engine temp up to about 150F and turned the heater fan up to full blast for some warmth.....I was going about 45-50 MPH at the time.......in 2 miles when I pulled into work the engine temp was down to about 130F.

It can cool down even more by sitting still with the heater fan on.
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Is your cooling system properly filled and trapped air expelled (system burped)?
It is normal for the temp gauge to drop a bit or run lower than usual when it's very cold, I remember seeing that explained in some factory service info.

 
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Thanks for the reply.. I'm in Nova Scotia, Canada.. -13 c here as we speak with a windchill of -21, so pretty cold .. I drove the car for a few miles at about 60 km/h and comes up to normal operating temp with no apparent issues.. System was burped and no air that I can hear- I ran it for some time in the garage, fans came up and air was purged as far as I can tell.. Running now with rad cap off and no air bubbles, etc.. If it were a head gasket issue what would I see for symptoms? oh and never noticed anything out of the ordinary when temp was warmer..Thanks again !

 
Rep Power: 517

Sounds like your heater description is gonna be normal for that car in that kind of weather.

Depends on the severity of the problem. Could range from tiny occasional bubbles to no heater output at idle, but that would be a real quick temperature change because it's caused by low coolant level.


This morning it was +4*F out.... I had my engine temp to about 165F, then sat in the parking lot at work idling the engine with the heater fan on full blast.....and the engine temp came down to 127F in less than 5 minutes.

 
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Ok, seems like it must be normal then.. odd thing today though, car threw a p0135 code..which from what I see is an 02 sensor.. seems odd that this would happen a day or two after changing the thermostat but maybe just a coincidence.. think its Related?

and 2nd question.. would it be a denso part # 234-9017

 
Rep Power: 517

UNrelated. Heater circuit, primary sensor. Sensors just go bad sometimes...and in my corner of the planet we see a lot of rodent damage (chewed wires). You could ohm check the heater portion of the sensor to check it if you want.

Depends on what your car/engine version is (usually need to know if it has vtec or not). Did you use the Denso website to look up your part?
04-05 use AF sensor for the primary, O2 sensor for secondary.

 
Rep Power: 118

Nothing odd at all about fixing one thing only to have another fail soon after..

Rarely do I work on a car that actually only has one thing wrong.. Sometimes it still amazes me to see the lengths poeple will go to save on repair costs.

Inside door handle broken, no problem roll window down every time and use outside handle.

Outside window broken from being used everytime car stops, no problem recline seat back and go out rear door.

Seat no longer stays locked in upright position, bring to shop and balk at cost and insist it’s just a quick 5 min job with welder..

 
Rep Power: 0

Sorry but you lost me there and pardon my lack of knowledge but code says P0135 so how do I know which sensor to change? I did look on Denso but lists 3 A/F and only one downstream o2 sensor..
here's the code description.. so the o2 sensor and not the A/F sensor?
https://www.obd-codes.com/p0135

And Thank you!!!

 
Rep Power: 517

P0135 code definition is "O2 sensor B1S1, heater circuit failure"

B1S1 defines the sensor position/location (bank one, sensor one) which is the first sensor in the exhaust stream, also may be called the upstream or primary sensor.

Heater circuit failure is the specific failure detected.

I already know all of those 1.7 engines from 04-05 use an AF (Air Fuel Ratio) sensor in the primary location instead of a plain O2 sensor.
So at the Denso website you have to look in the AF sensor section.


In their website they list three different primary AF sensors--one for each of THREE DIFFERENT ENGINES. Now you have to know which engine your car has to pick the right sensor. (assuming 100% stock engine and exhaust)



What car do you have?
Where are you located? (Canadian: trim levels aren't equipped the same as USA)
So far all I know is it's an 04 Civic with a 1.7 engine, no other necessary details I saw at a glance. Need to know if it's VTEC (D17A2) or not (D17A1) because their exhaust systems are very different, thus the sensor wiring is unique to each version.

 
Rep Power: 0

Thanks again for the help.. I'm in Nova Scotia, Canada, 1.7 non vtec and EX model .. So I would have the D17A1 from you message .(again my apologies, don't know the engine codes )

 
Rep Power: 517

I'm looking in one of the Canadian dealer parts catalogs.....I don't see EX trim level as a choice at all....
It only shows choices of DX/LX/SI, Si would be the only one with D17A2/VTEC

Anyway, the D17A1 (non-vtec) exhaust manifold and sensors are like this pic, top sensor #7 is the primary:

 
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ok, gotcha.. thanks .. i'll order one and see how it goes

REALLY appreciate the help!