Help - Bubbles in my Coolant!

[InsightValley]

Hello everyone,

On my 2000 Insight 5-speed, I'm getting bubbles in my coolant. Using a "spill-free" funnel, here is a video of what my car is doing:

Bubbles in Coolant - YouTube

Bubbles in Coolant - YouTube

It's a New Jersey car with 140K miles on it, well maintained, when I purchased it a month ago. Now it's in Arizona.
When the engine is cold, I remove the radiator cap, install the funnel and fill it up halfway with 50/50 coolant, then start the engine with the heater on high. Within 20 seconds, it starts to bubble, as seen on the video, and doesn't stop.
When the coolant reaches normal operating temperature, the bubbles remain constant, and the coolant starts to boil, erupting like a volcano! I usually shut it off soon thereafter.

Troubleshooting procedures:
Replaced radiator cap with new one.
Tested old thermostat. Old thermostat works correctly. Still bubbles. So I Replaced thermostat with new one, still bubbles. Removed thermostat. Still bubbles, but at a faster bubbling rate without the thermostat installed.
Tested for headgasket leak/combustion leak using this kit: Lisle Combustion Leak Detector Kit

No leaks detected. Ran combustion leak test twice for redundancy.

Did a compression test. All cylinders within 3% of each other.

I own 3 Honda Insights and none of them bubble except this one.

Any ideas of what's happening? Jacuzzi bubbling action is an indicator of a problem, yes?

Thanks in advance!

Garrett

[aisbell]

If the coolant were at full operating temperature, the bubbles might just be the coolant boiling (its boiling point is lower at atmospheric pressure than when the radiator cap is on). But you stated that the bubbles occur when the coolant is cold, so there goes that theory.

Do you still see the bubbles when you attach the funnel to the coolant air bleed valve as described in the Service Manual? If so, my guess is a leaking head gasket. When I changed the coolant in my Insight, I saw only tiny bubbles coming from the coolant air bleed valve (probably dissolved air being released as the coolant temperature rose).

[Willie Williford]

I assume you have the climate control set at max. temp. (Fan OFF) Like Art said, only use the bleed valve for "bleeding air". It is at the highest point of the coolant sytem.
You didn't put the thermostat upside down did you, I don't mean backwards....I think there is an actual "up" on the thermostat if I remember right.
HTH
Willie

[Cobb]

My general thought is blown head gasket. To make sure we would put the gas analyzer from the emission machine over the opening to see if it registered anything. Does these bubbles smell like exhaust related smells?

When you rev the motor does the bubbles come faster and more frequent?

Typically trapped air in the coolant will do that, but for like 5 minutes after the car reaches full operating temp. If it over heats or stays cold, I agree with the stat being put in backwards. I believe the general rule of thumb is to have the springie part inserted into the motor and the flat part facing out.

I typically test them in a pot of boiling water with a candy meter to make sure. Some t stats can be a pain to install and I want to make sure it works right the first time.

[gilbertguy]

I'm going to go with a blown head gasket, at some point it will get bad enough to begin allowing the coolent into the cyclinder while it is parked, once that happens the engine will no long crank over because fluid does not compress.

[kennysmith]

To reiterate: Willie was suggesting the thermostat might be upside down, not backward. I had never seen that feature before so if you don't remember noticing that, I would double check. If you look at it and can't tell, then it is probably the wrong thermostat. It is obvious, but still easy to miss if you are not familiar with it.

(Probably you know all this if you have 3 of them).

[InsightValley]

Thank you for your responses

I also believe the problem is the head gasket as well, though the head gasket leak detector test results don't show a leak. I'm going to test the accuracy of the leak detector test by holding up the test tube next to a running vehicle's exhaust outlet.

Keep in mind, my Insight does not have a thermostat in it currently and it still bubbles like crazy when heating up from cold startup. Also, I might add that when the car gets to normal operating temperature, the coolant start to boil and overflow like crazy... like an erupting volcano!

I performed a coolant/radiator pressure test and it holds pressure just fine.

Any other ideas besides the head gasket? A friend of mine who is also a mechanic said it might possibly be the water pump not circulating the coolant properly?

I'm leaving the country in a few days and won't be able to post the ultimate culprit to this problem for a couple months. But I will definitely follow-up! Thank you again for your responses and if you have any last minute ideas, please let me know! Thanks!

[Eli]

Leaving the country for a few months? Hope someone is driving your Insights, or bubbles in your coolant will be the least of your worries.

[Willie Williford]

Running without a thermostat is not recommended. (In my opinion)
There has to be a restriction to make the water pump "non cavational". If you are going to run without a thermo, cut the big spring out that holds the thermo disc closed and reinstall it.
On raceing engines I always installed a restrictor disc where the thermostat was installed.
Without the thermo installed you are circulating the coolant so fast, it doesn't have a chance to pick up the heat in the engine.
Without the radiator cap installed, it will act like a volcano.

With the engine cold, Pressurize each cylinder with air while that cylinder is TDC on the compression stroke. Make sure the engine doesn't turn while doing the test. Slowly increase the air supply from about 30 psi and if the head gasket is leaking from the combustion chamber to the coolant area, you should see bubbles from the radiator (With the cap off)
That's the way I do it.
HTH
Willie

[ackattacker]

What Willie is suggesting is known as a leakdown test. You can buy a leakdown tester from Harbor Freight but you do need an air compressor as well.

I'm going to go with bad water pump, though.