Intermittent engine overheating

2003 SUBARU BAJA
2,500,000 MILES • 4 CYL • 4WD • AUTOMATIC
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GERALDD
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My car started to overheat a few weeks back, and I noticed the heater blowing cold. I did have plenty of coolant. I figured it was the water pump, so I put a timing belt kit with water pump.
Had the car idling for about 40+ minutes trying to "burp" the cooling system. It's cold enough in my garage that the fans never kicked on (so I'm guessing the thermostat never opened) but got plenty of bubbles. I had the heater on in the car on high and felt plenty of heat blowing inside the car and it never overheated. As I said tried to burp for 40+ minutes and saw many air bubbles released so I decided to try a test drive. On the test drive I kept the heater on but at one point it started to blow cold, and the engine temperature increased so I pulled over for a few minutes. When I started it up again +-10 minutes the heater was back to blowing hot and just before I got home it went cold again with engine temperature increase. What's going on here?
Jan 26, 2022 at 1:07 PM
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JACOBANDNICKOLAS
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Hi,

It sounds like you still have air in the system. Take a look at pic 1 below. Try the procedure indicated.

If that doesn't help, then I need you to check something. Allow the engine to cool and remove the radiator cap. Start the engine. Does the coolant shoot from the radiator? If not, leave the rad cap off and watch to see if it starts circulating when the engine warms up and if there are air bubbles in the coolant itself.

Let me know what you find.

Joe
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Jan 26, 2022 at 5:48 PM
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GERALDD
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Will try tomorrow morning, one thing I noticed was the coolant reservoir itself filled completely while trying to burp.
Jan 26, 2022 at 6:28 PM
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JACOBANDNICKOLAS
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I have a feeling it may be a faulty head gasket. Let me know what happens. Also, take a look through this link:

https://www.2carpros.com/articles/head-gasket-blown-test

Let me know what you find.

Joe
Jan 26, 2022 at 6:47 PM
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GERALDD
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While burping the system I saw sporadic bubbles but not foamy (like in the photo of the link you sent me) they were intermittent bubbles, so it doesn't seem that the head is pushing a strong or steady stream of compression gases into the radiator. I understand that that doesn't mean it isn't happening, but it doesn't seem so. If it is a head gasket, I may have to try the Blue Devil. I will let you know though whatever happens. I do thank you for your help.
Jan 26, 2022 at 7:36 PM
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JACOBANDNICKOLAS
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Hi,

You are very welcome. Interestingly, my neighbor and a good friend went through this same issue with the same year and model. He did use the Blue Devil and it worked. But don't do it until, we are sure. LOL As soon as you said Blue Devil, it brought back the memory. LOL

Take care and let me know what I can do to help.

Joe
Jan 26, 2022 at 8:16 PM
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GERALDD
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Hi again, sorry for the late reply (i had to work on my car sporadically on my days off). I found that there was some oil in my old coolant (slight oil slick on top) so I believe I did have a head gasket problem. As I said earlier, I decided to try Blue Devil and it seems to have worked wonderfully. Been driving to work the past three days (50-minute drive) with no problems I am grateful for all your help.

Gerald
Feb 14, 2022 at 10:23 PM
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JACOBANDNICKOLAS
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Hi,

You are very welcome. I'm glad to hear it worked. I have heard a lot of positive things about their products. However, as soon as I recommend one, it will fail. LOL

Regardless, please feel free to come back anytime in the future. You are always welcome here.

Thanks for the update and take care.

Joe
Feb 15, 2022 at 3:26 PM