A while ago I posted about my RX overcooling- even after running on the interstate the temp needle was still less than 1/4 of the way up the gauge. As a consequence it almost always runs at cold idle, and the heater hardly works.

 

Put a new thermostat in last week and it made no difference. Still runs cool. The electric fan isn't kicking on, and nothing seems to be out of the ordinary... so before I remove the mechanical fan or put a piece of cardboard in front of the radiator, any other suggestions?

 

This is on my nonturbo converted RX with the XT engine in it, by the way.

MY SPFI sedan also only reads about 1/4 scale, but I am now convinced that it is just a misreading gauge/sender combo. Is the heater not working caused by low temp or plugged heater circuit?

 

I would try to verify that the temp is actually too low before trying to get your gauge to read higher. (Cardboard under controlled conditions could be used to help find this out.)

The heater works as it should, the output is just pretty feeble due to the low temp- that's what has me convinced it's actually running cold instead of a faulty gauge. It blows out ice cold when the engine is cold, and gradually warms up as the engine warms up- but the output is barely more than lukewarm, consistent with the engine actually running cool.

How cold is it running? Your engine coolant must be well under 100ºF if the heater isn't working to the degree you've described--which I find rather improbable. I'd have to guess that it's a clogged line to or from the heater core, or a plugged core. The heater in my Justy has always worked like a charm, and I've never seen the gauge go over 1/3 of the way; same for my old XT6.

 

EDIT: Have you tried changing to a hotter spark plug?

 

http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp?nav=31300&country=US

How cold is it running?

 

Good point. Is there any reliable way of measuring coolant temperature in degrees without shelling out the bucks for an aftermarket gauge?

I imagine you could top off the coolant, run it capless until it warms up and try the coolant temp with a meat thermometer.

I Have 2 ideas, and forgive me if they seem obvious, but its what the problem was with mine,

 

1. make sure that the thermostat is the right side up.

 

2. The thermostat could already be stuck open, happened to me with an aftermarket one, happened the first time it heated up, never got hot the rest of the summer, finally changed that one and had heat for the winter.

after 2 weeks of a after market one, mine did the same thing , i took it out put it into a pan of boiling water to see if it would open up and it did not , got a oem from the dealer

From what I've heard, ALWAYS stick with OEM T-stats with Subarus. The aftermarket ones never open at the right time, either too early or too late...