Thermostat was getting stuck closed

CMCDOWALL

MEMBER
1999 SUBARU OUTBACK
4 CYL
AWD
AUTOMATIC
200,000 MILES

This car was running fine until about 1 week ago. The only symptom is that the temp gauge begins to read hot after about 20 min drive time. This happened once, then self-corrected after sitting on the side of the road for about 2 min. Then it didn't happen again for 3 days. Since the water pump had been replaced 1.5 yrs ago, we figured that the thermostat was getting stuck closed. We had it replaced but then the same symptom occurred again after the vehicle was driven about 25 - 30 min (25 mls). This time, I actually got steam and overflow from the radiator. Do you think that we just got a bad replacement thermostat?

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,269 POSTS

Hi,

Replacing the coolant thermostat isn't too hard of a job. When they fail, they can cause an engine to overheat or even never warm up.

Here is a link that explains how one works:

https://www.2carpros.com/articles/how-an-engine-thermostat-works

To get you started, here is a link that explains in general how one is replaced. You can use this as a guide.

https://www.2carpros.com/articles/replace-thermostat

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Here are the directions specific to your vehicle. The pics below correlate with the directions.

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1999 Subaru Legacy Outback AWD F4-2.5L DOHC
Procedures
Vehicle Engine, Cooling and Exhaust Cooling System Thermostat Service and Repair Procedures
PROCEDURES
A: REMOVAL AND INSTALLATION
1) Drain engine coolant.
Set container under the vehicle, and remove drain cock from radiator.

pic 1

2) Disconnect radiator outlet hose from thermostat cover.
3) Remove thermostat cover and gasket, and pull out the thermostat.

pic 2

4) Install the thermostat in the intake manifold, and install the thermostat cover together with a gasket.

CAUTION:
- When reinstalling the thermostat, use a new gasket.
- The thermostat must be installed with the jiggle pin upward.
- In this time, set the jiggle pin of thermostat for front side.

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I hope this helps. Let me know if you have other questions.

Take care and God Bless,

Joe

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