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Coolant overflow

Tiny
LDANNYY
  • MEMBER
  • 2001 HONDA CIVIC
  • 1.7L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 80,400 MILES
Hi, the thermostat is about a year old, as well as tb/wp. Recently my coolant reservoir has been overflowing and bubbling slightly. Any ideas? Thanks
Thursday, April 7th, 2022 AT 8:14 AM

30 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,217 POSTS
Hi,

When you notice the bubbling, does the temperature gauge indicate it is overheating?

Do me a favor and try this. When the engine is cold, remove the radiator cap and start the engine. Does coolant begin flowing out from the radiator?

My concern is the bubbling you mentioned. If the car isn't overheating, that usually indicates a bad head gasket. Take a look through this link.

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

Let me know.

Joe

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Thursday, April 7th, 2022 AT 5:18 PM
Tiny
LDANNYY
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No, there is no overheating happening at all, which concerns me. I even did a leak test with that liquid two times and it was fine. I noticed the bubbles when I turned off the car, but only in the reservoir, not the radiator. Then when I had the car idling, I pressed the gas and saw it bubble again.
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Friday, April 8th, 2022 AT 5:33 AM
Tiny
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  • MECHANIC
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What I would do is get your hands on an infrared thermometer and see what the temperature is in the overflow. Do the same at the radiator. I'm questioning if the vehicle may be overheating, and the gauge may be inaccurate.

It's a theory.

Let me know.

Joe
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Friday, April 8th, 2022 AT 5:55 PM
Tiny
LDANNYY
  • MEMBER
  • 18 POSTS
I will do that. But what I think it was is that, when I changed the coolant. I didn’t bleed it correctly. So, I topped off the radiator again, blasted the heat and pumped the hose. Those 2 coolant sensors are fairly new. Let the car run until the fans kicked on, so now I got to drive and see if it happens again.
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Saturday, April 9th, 2022 AT 6:45 AM
Tiny
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  • MECHANIC
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Hi,

Absolutely that could cause what you experienced. Let me know if that takes care of the problem.

If I can help in any way, let me know.

Take care,

Joe
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Saturday, April 9th, 2022 AT 8:29 PM
Tiny
LDANNYY
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  • 18 POSTS
Update: I see it starting to rise again. When I checked hoses, they read in the 160-170s (i bought the thermometer). Clog in the system? Thank you for everything.
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Sunday, April 10th, 2022 AT 9:45 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,217 POSTS
Hi,

Most vehicles come with a thermostat that fully opens at 195 F. Your readings, which should be cooler when coolant returns to the engine, should be cooler, so what you indicated seems normal. If you check the radiator tanks themselves, what is the temperature? Also, how high did the gauge go again?

I have a funny question. Is the heater still working?

Let me know. Also, let me know if you are seeing bubbling in the reservoir again.

Take care,

Joe
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Sunday, April 10th, 2022 AT 7:16 PM
Tiny
LDANNYY
  • MEMBER
  • 18 POSTS
Gauge is always reading normal temperatures, maybe one or two ticks under the half mark. I bought an actual coolant bleeder kit, so I’ll be able to bleed it correctly again. Regarding the heat, it works phenomenal, haha. There’s no obvious sign of something which is the hard part, that’s why I’m really banking that there’s a lot of air in the system.
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Monday, April 11th, 2022 AT 12:29 AM
Tiny
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As you can see temperatures are normal, I caught the overflow rising back up again and a slightly bubbly when I pulled the throttle.
Video (Click to make bigger)
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Monday, April 11th, 2022 AT 12:03 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

The temperature at the top hose is perfect. The thermostat fully opens at 195F. I can't see what the temperature is on the bottom hose. Can you let me know what it is?

Also, when the engine is cold, if you remove the radiator cap, are there any bubbles when the vehicle is started?

Let me know.

Joe
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Monday, April 11th, 2022 AT 7:54 PM
Tiny
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It was at 180-190. I did a cold start this morning; no bubbles came up the radiator, but the coolant came up which I know that’s normal. Also, I noticed the coolant went down in the overflow. So maybe it’s bled correctly now? Thank you.
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Tuesday, April 12th, 2022 AT 7:03 AM
Tiny
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Never mind, I went for a long drive and it went even higher and the temperatures for the hoses and gauge were okay.
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Tuesday, April 12th, 2022 AT 9:42 AM
Tiny
LDANNYY
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Edit
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Tuesday, April 12th, 2022 AT 9:45 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

You indicate the temperature went higher than ever, but the gauge and hoses were okay. How did you determine the temperature went higher?

Let me know.
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Tuesday, April 12th, 2022 AT 7:53 PM
Tiny
LDANNYY
  • MEMBER
  • 18 POSTS
No, the temperatures for everything was fine. I meant to say the coolant in the reservoir was higher again. I don’t know if you saw it in the video well.
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Wednesday, April 13th, 2022 AT 2:38 AM
Tiny
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Hi,

I'm sorry but I couldn't really tell what it was doing in the video. When you say the coolant in the reservoir was higher, how high was it?

Joe
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Wednesday, April 13th, 2022 AT 6:10 PM
Tiny
LDANNYY
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I would say about 3/4 full. It was pretty close to the top. Then as it cools down, it goes back down.
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Wednesday, April 13th, 2022 AT 6:20 PM
Tiny
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Is it possibly overfilled?

Joe
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Wednesday, April 13th, 2022 AT 6:45 PM
Tiny
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Thank you so much for all your help. Is it possible the radiator can burn coolant? It doesn't stay topped off and there's no leak. Small hole possible?
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Saturday, April 16th, 2022 AT 8:18 AM
Tiny
JACOBANDNICKOLAS
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Hi,

Coolant can evaporate, but it is an extremely slow process to happen. How fast are you noticing it getting low? And just to reconfirm, you aren't noticing any of the symptoms I listed in the head gasket tests, correct? I ask because when there is coolant loss and no evidence of a leak, which is the first suspect.

Let me know.

Joe
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Saturday, April 16th, 2022 AT 5:09 PM

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