b16a2 - thermostat ? Heater ?

[ek4-uso]

I wonder if anyone can help me, I live in UK and its getting close to winter......

My civic warms up and drives fine (with heater on cold), but if I have the heater on the temp gauge goes down really low, if heater on say half heat it takes a while to warm and runs a bit cooler.

On full heat, the temp gauge is very low - is this due to faulty thermostat ?

Is it causing damage to my engine? what temp do other peeps civic's run at?

 

[RagingAngel]

sounds like the car is equipped with a low temp thermostat...

I would replace it with one from OEM Honda.

Unless it gets as cold as -20C like where I am from, I really doubt you would see that much fluctuation. You can also test this by taping a piece of cardboard to block the airflow through the radiator partially to see if this stabilizes the gauge.

 

[ek4-uso]

i doubt it'll get lower than about -6C over here

But because i'm gonna be using the heater, my car will take a lot longer to warm up or at least to show some temp on the standard gauge - so wouldn't this suggest that maybe the thermostat is stuck open?

cause say the car is fully warmed up (temp gauge stable @ about half-way up) then put heaters on full, the temp gauge will drop to about the lowest point on gauge with about 10mins driving at 70mph then will rise a bit

 

[RagingAngel]

hence my suggestion to test with cardboard and then the initial idea of replacing the thermostat entirely.

 

[ek4-uso]

Thanks for the advice RagingAngel - I didn't really know what you meant by:

"test this by taping a piece of cardboard to block the airflow through the radiator partially to see if this stabilizes the gauge."

But you were infact absolutely correct as the old thermostat was a low temp 78C I think, now everything is perfect. Getting at that bit is

 

[b16 mini]

78oC is stock thermostat, chances are the old one was just a bit sticky., just about every car i've ever owned has had the same problem as you described.
easily fixed tho.