Bubbles in the coolant overflow tank

NICA MALAIMARE

MEMBER
2006 SUBARU FORESTER
2.5L
4 CYL
4WD
AUTOMATIC
202,000 MILES

I noticed bubbles in overflow tank after I drove. I tried to do a chemical block test but when I start the car with the radiator cap off, coolant keeps coming out and I can’t complete the test. I tested on the overflow tank but I’m not sure if it gives results in doing so. The car doesn’t overheat, runs normally. No white smoke in tailpipe, oil looks normal. I’m not sure if I have a head gasket problem or not.

6 Replies

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

I have to be honest, if coolant shoots from the radiator when cold and first started, pressure is getting into the cooling system. Most likely the result of a head gasket. Take a look at this link. In the link, jump to step 3. Read through that and let me know if that is what is happening.

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

Note, if it needs a head gasket, I can walk you through the process, so let me know.

Let me know.

Joe

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Friday, January 17th, 2020 AT 10:35 PM

JIS001

MECHANIC
3,411 POSTS

Is your vehicle overheating? If it is not then you may want to replace the radiator cap. If you want to do a block test then you will need to drain some coolant to be able to do the test properly. Here is a link with a video on how to properly test for a head gasket issue as well:

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

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Friday, January 17th, 2020 AT 10:38 PM

NICA MALAIMARE

MEMBER
4 POSTS

The car is not overheating. I know I have to drain some coolant from the radiator, but the problem is that as soon as I start the car, the coolant comes out of the radiator. I kept draining for about a minute or so, and kept coming out more or less, so then I decided to put the cap on and do it on the overflow tank.

Some people suggested to start the car with the radiator cap on and let it run for a minute or until it warms a bit, and then remove the cap and it shouldn’t come out anymore!

Any thoughts on what should I do?

Thanks!

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Saturday, January 18th, 2020 AT 6:11 AM

NICA MALAIMARE

MEMBER
4 POSTS

I checked the video you posted and at Step 3 (Test 3) it said to look for bubbles in the radiator cap. Mine is not like that. It doesn’t have a single bubble, it’s just the coolant coming out and spilling over.

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Saturday, January 18th, 2020 AT 6:15 AM

NICA MALAIMARE

MEMBER
4 POSTS

Now even stranger things happening. I tried to do the test again. Now when I removed the radiator cap there was no coolant inside. I said okay, I started the car and now coolant didn’t come out at all, nothing inside. I don’t know if this is how it’s supposed to be or if I should see some coolant inside the filler neck. Anyway I put the tester on and was negative. I don’t know if I should add coolant to my radiator cap, because the coolant level in overflow tank is already to full.

Now I let the car run for a while and also didn’t see any bubbles in the overflow tank. I don’t know what to think anymore, I’m now sure what is normal for my car and what’s not. The car drives perfectly normal, no issues.