low engine temp

[bcapbcap@hotmail.com]

Hello all !

I'm new here. I have 4 Legacys.3 1990 5spds awd and one 1995 5spd awd.

My main everyday 90 Legacy (mileage 131k +/-) has had a sudden drop in gas mileage from an average of 28-32mpg to 22-23.

I assumed the ambient temp drop and the added o2 in the gas for the winter here in CT was a partial cause since I have experienced this before but not such a radical drop.

I have an OCT handheld engine monitor from my days as a service manager at a Sub dealer. I hooked it up and found my engine temp to be after warm-up less than 80 c and at speed dropping to under 58 c.Very low indeed.

Put in a new OEM therm stat no change.Have excellent cabin heat but poor engine temp.CAr runs like a champ otherwise.

Temp guage BTW has always read only 1/4 up from the peg since I got the car.

Any thoughts ?

[sea#3]

Well it could be :

A) the new stat you put in is defective - Doubtful

The ECT sensor is lying to the ECM and it's running to rich -possible , but the the dash coolant temp sensor says it's running cold ,(which it is a seperate sensor) which could be lying too -possible but unlikely

If it has the original ECT sesor in it you may want too change it and see

c) bad engine grounds at the manifold -possible , easy to clean up and check

 

SEA#3

[bcapbcap@hotmail.com]

Thanks for the reply and suggestions.I'll post at a later date with the results.

[Legacy777]

Just curious,

 

Did you use an OEM Subaru t-stat or aftermarket one?

 

I'd suggest replacing the coolant temp sensor as well. They can be had for about 20 bucks at some of the online subaru parts stores.

[Setright]

Yeah, is it a genuine Subaru t-stat? The problem you describe is typical of aftermarket t-stats on any brand of car.

 

 

Yes, we read the "OEM t-stat", but OEM is kinda meaningless, unless you meant OE. "Genuine" is my word :-)

 

Oh, and is it the correct t-stat for your engine?

[bcapbcap@hotmail.com]

Hello all,

 

Yes it is a "Genuine" stat 78 c,nice hefty coil springs and bulb. Had the car out tonight here in CT where it is about 3 f with windchill of -10 f. OCT monitor reads from a high of 76 c at idle to a drop to 57 c at speed. Have not had time to get other parts installed that were suggested,will check grounds at manifold as well. I did isolate the heater core by pinching off hose to engine which made the engine temp rise to almost normal .Guage appears to be a red herring since I checked the connection with an ohm meter and get poor readings as as per the change in temp in relation to the OCT monitor.When I stopped fiddling with the guage wires the guage atarted to read normal then dropped back down.

Thanks for the help and pointers.I welcome all I can get !

[Setright]

Dang it, it really does sound like a bad t-stat. I know its a pain to open the cooling system again, but I would recommend you start by replacing the t-stat.

 

OR, block off part of the radiator with a piece of cardboard to avoid overcooling. Which brings to mind: Is you radiator fan running? Like all the time?

[Tiny Clark]

If you have excellent cabin heat, it's my assumption that the thermostat is OK.

[idosubaru]

if the car runs fine and you have heat this is a non-issue. 1/4 up the peg is standard operating area for XT6's, so i wouldn't think twice about that. if you have heat inside, then the engine is obviously operating properly. if your engine were running significantly cooler than it should you would not have good heat.