"loewent via CarKB.com" wrote:
>
> Hi there,
>
> Wondering if anyone can confirm my diagnosis of my sister's car, 99 civic EX
> 175000kms automatic.
>
> Driving with AC on, the heat gauge will suddenly start to go up. Usually
> sits around 1/2, it goes up to about 3/4. The AC stops working. They turn
> off the AC, heat comes down.
>
> Just not entirely sure why the AC has anything to do with engine temp since
> the condenser and rad are separate? Belts are good, but here is a weird one:
>
> She checked the radiator level once it cooled off, and the fins were showing,
> it looked as though the rad was low. There was still coolant, and it wasn't
> overheated according to the gauge, so she proceeded to the local autoparts
> store to get some premix antifreeze. Once she got there, bought the
> antifreeze and came outside to fill up the rad, it was full!
>
> My diagnosis is as follows:
>
> 1. Bad thermostat - probably needs to be replaced anyways, the car has
> 175000kms on it.
>
> 2. Bad fan switch on rad - if the fan doesn't kick in, and the AC is
> creating more heat when its on, it could contribute to overall engine temp
> increase.
>
> 3. Plugged rad fins - we live in Manitoba, lotsa bugs! so maybe the rad
> fins need to be carefully cleaned out to allow for better heat transfer
> efficiency.
>
> Any other ideas? The timing belt was done recently, but the water pump was
> left alone. I did suggest they replace it, but they didn't I guess it could
> be the water pump too.
>
> Any input would be great!
>
> t
>
> --
> Message posted via CarKB.com
> http://www.carkb.com/Uwe/Forums.aspx...-cars/200605/1


-------------------------------------------------

The problem is in the glove compartment. There's an unread owner's
manual in there. Once she fills the rad to the top, and the reservoir to
the MAX mark, she will have to do it again the next two times the engine
is cool.

There's so much air in the system that the fan switch is sitting high
and dry when the thermostat opens. Without any coolant in the reservoir,
the system can't displace the air it expels when the engine is HOT.
Hopefully she hasn't cracked the HEAD.

'Curly'