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1998 OBW 2.5L 5speed 150 k miles
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13 Posts
Discussion Starter #1
Been fighting an overheating problem. At first cooling fans would not come on at all. I changed the coolant temp sensor as well as the cam and crank sensors. The cooling fans come on together now but only when gauge
gets all the way to hot. OBD scanner shows running 195 degrees. The radiator, cap, and thermostat (Subaru original) have been changed. When they do come on only run briefly not enough to cool down 3/4 of way on gauge before go back off. Getting bubbles in overflow bottle now so probably looking at HG repair now. But don't want to lay out 1k until gets fans problem fixed. I checked the relays, they may be weak but are working.
 

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Looking at your previous posts, it appears the car is a 1998 2.5. That engine has two separate coolant temperature sensors -- one sensor for the Engine Control Module, which manages all of the engine functions including the fans, and a second sensor for the combination meter (instrument panel) temperature gauge.

Both sensors are mounted on the water (crossover ) pipe, fairly close to each other. The ECM sensor has, I believe, a two-wire connector, while the gauge sensor has only a single wire.

If the OBD scanner is indicating 195 degrees, which is essentially reading what the ECM sensor is reading, then the fans are probably not going to be turned on, or might just be at the switching point, so that might explain the fan operation. If, at the same time the temperature gauge is at HOT, the gauge sensor could be defective.

That said, still, the bubbling and high temperature gauge indication combination could well be due the head gasket, and not a bad gauge sensor. But you could try replacing the sensor first just in case.

Suggestion: Why not add the model, engine, transmission etc information to your ID data in the column at the left (use the User CP button at top), or make sure the info is in each post, so we don't have to look it up . . .
 

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1998 OBW 2.5L 5speed 150 k miles
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13 Posts
Discussion Starter #3
Will try the gauge sensor since already replaced the ECT sensor. Not sure that would cause the fans to long enough to bring temp down.
 

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Not sure that would cause the fans to long enough to bring temp down.
If the OBD scanner is saying the temperature of the coolant is around 195 degrees Fahrenheit, then that's fairly normal. There isn't a need at that point for the fans to come on for any length of time; rather, the fans will come on for short periods, just enough to keep the temperature in the right range.

The other sensor, the one for the temperature gauge, doesn't affect the fans; it only affects the temperature gauge. The sensor might be faulty and is causing the temperature gauge to read far higher than the actual temperature of the coolant.

If the gauge sensor is faulty, and it's replaced, then the temperature indication will more likely be in the normal range when the OBD scanner is reading around 195 F.
 

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1998 OBW 2.5L 5speed 150 k miles
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13 Posts
Discussion Starter #6
Put in new sensor today. Seems to have solved problem. Ran until fans came on and turned on AC; fans ran like supposed to gauge read constant at 9 o'clock. Thanks for the trouble shooting assistance.
 
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