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Discussion Starter #1
Hello friends:

My fiance's 2012 Honda Civic EX is experiencing a strange problem and I'd really appreciate some help. After a 20 minute ride, parked in a garage, it smells like coolant / hot engine and a faint boiling can be heard coming from the block / head area (not the heater core.) The cooling fans do not come on. It does not smoke / no steam from tailpipe. There's no water in the oil. No oil or bubbling in the radiator. Spark plugs looked good / just replaced them anyway. No overheat light. Just ran a compression test (pics below):

CY1: 210
CY2: 180-190 (after several tests)
CY3: 180-190 (several tests)
CY4: 210

Are these readings enough to confirm a head gasket problem CY2 and CY3?

Other data:
Mileage - 101K
Maintenance - exceptional since owned, performed by me

Things I've already done:

- Replaced coolant 2x w/OEM
- Replaced thermostat w/OEM
- Replaced upper and lower temp sensors w/OEM
- "Burped" radiator -- Jacked front of car up 3 feet and ran for 30 min w/cap off
- Jumped cooling fans at lower temp sensor and they work both (1) jumped and (2) when AC is on, but never come on during hot temperature operation (45 min idle / hard drive)

- Bought an IR temp gun (love that Honda omitted a temp gauge on this car!) and gunned various areas on block / head / hoses / thermo housing, etc. Most readings after 20 minute hard driving topped out at 210, one area 215, except for trying to get a reading from the block in the area circled in the pic below which was 325<!?>. Upper hose was 175, lower hose was 135. Suspect the high reading was from exhaust manifold throwing off the readings but could mean internal blockage of coolant passages?

- Compression tested all cylinders (below)

Conclusions:
1. Its just hot out, car is fine, the IR readings confirm normal operating temps and the smell is normal/boiling sound normal, nothing to worry about; or
2. Fiance is right and the car is F*C**D and it's a blown head gasket that needs fixing ASAP (lol)

Help me out my friends :wigglesmiley: Thank you

Kurt

1.jpg 2_a.jpg 2_c.jpg 3_a.jpg 3-b.jpg 4.jpg IMG_3077.jpg
 

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I wouldn't jump to a worst case scenario just yet. Has the car ever overheated previously?
Is the coolant pushing into the overflow?
Do both coolant hoses seem equally hot to the touch? If no, thermostat should be checked/replaced.
Also you can do a combustion gases check on the radiator.
You mention you smell coolant, is there any leaking or dripping on the ground?

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Discussion Starter #3
Thanks :)

Has the car ever overheated previously? NOT IN THE 50K MILES WE'VE OWNED IT.

Is the coolant pushing into the overflow? YES

Do both coolant hoses seem equally hot to the touch? If no, thermostat should be checked/replaced. THERMOSTAT IS NEW. TOP HOSE 175, LOWER HOSE 140


Also you can do a combustion gases check on the radiator. THIS I HAVEN'T DONE. WILL LOOK INTO

You mention you smell coolant, is there any leaking or dripping on the ground? NO COOLANT ON THE GROUND OR LEAKS. JUST A FAINT SMELL. KINDA A BURNING SMELL TOO

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Thanks again. I just test drove it after new spark plugs and it seems peppy and doesn't hesitate now. Parked, head is at around 212, block area measured 225, radiator was at 175, hoses 175/140. Still the faint boiling sound and smell.

Peace
 

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Discussion Starter #5
Thanks for the input. I'd prefer to save $500 on a mechanic and fix it myself if I can. I have decades of automotive experience. Any other suggestions?

Peace
 

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My 2013 SI has always had a boiling sound coming from the engine. Of course only when its hot outside and only noticeable after shutting the engine off. I always assumed it was normal and just the coolant boiling within the engine or radiator. Since temps check out fine and the engine is not overheating I am not all that concerned with it.
 

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Discussion Starter #7
Thank you BB13si! It would be nice to know if other owners of a similar model Honda have noticed this boiling sound also. Your input is very helpful. It has been averaging 100 degrees in our neck of the woods recently.

We are getting close to tossing the towel. I'm fresh out of ideas except the exhaust gases check and forgot to mention that I did replace the radiator cap. The original cap had no residue or exhaust gas damage on it. We might just take it into a dealership. This car runs great but the boiling sound and faint smell (could be I spilled some coolant filling her up) is worrisome to my better half. Probably drop it off on Friday night for a Saturday looking over.

If others have had this sound, might save me some big dough. Thanks again, sir.

Kurt
 

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I have a '12 EX with 110k miles. No sounds or smells when parked. I rarely drive it hard, but I would expect 100°F days we have had recently would be as hot as your car, and I haven't noticed anything like what you are describing. I had a '78 Olds Cutlass with a 350 that made those sounds when I parked it.
A scan tool to plug into your OBDII port would be a worthwhile investment. Temperature sensors that disagree might point you in the right direction. I'd get the coolant checked for combustion gasses.

I use the Ultra Gauge when I want to know things that aren't displayed on the dash.
 

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Some info to compare: I connected the Ultra Gauge and monitored the coolant temperature. When just driving easy, the temperature was pretty constant at about 90°C. When driving "hard" it fluctuated between 88° and 94°. Idling in the driveway with AC off after driving "hard" the temperature climbed to 100°C when the fans came on. Fans turned off at 98°. Very slight smell of coolant. Turning the engine off, the only sounds I could hear were of the refrigerant in the AC lines (I had turned the AC back on to move into my normal parking spot.)
 

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OP, does the noise not happen if you don't use A/C? Had a car a few years ago that sounded like "boiling water" after shutting it off, came from the A/C in my case. I never did anything due to that noise. I assumed high pressure refrigerant was traveling to the low pressure side on engine shut off...or something like that.
 

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Discussion Starter #11 (Edited)
I have a '12 EX with 110k miles. No sounds or smells when parked. I rarely drive it hard, but I would expect 100°F days we have had recently would be as hot as your car, and I haven't noticed anything like what you are describing. A scan tool to plug into your OBDII port would be a worthwhile investment. Temperature sensors that disagree might point you in the right direction. I'd get the coolant checked for combustion gasses.

* * *

Some info to compare: I connected the Ultra Gauge and monitored the coolant temperature. When just driving easy, the temperature was pretty constant at about 90°C. When driving "hard" it fluctuated between 88° and 94°. Idling in the driveway with AC off after driving "hard" the temperature climbed to 100°C when the fans came on. Fans turned off at 98°. Very slight smell of coolant. Turning the engine off, the only sounds I could hear were of the refrigerant in the AC lines (I had turned the AC back on to move into my normal parking spot.)
Thank you Paulcet, this is really helpful info and matches some of my research about the fans not kicking on until 208 deg F, and going off at 198 deg F. Yes, an OBD II reader that gives me more than error codes (mine only does that), would be hugely helpful. I'm thinking with the radiator never going above about 175 deg F in my testing that it makes sense the aux fans aren't kicking in. I've even replaced the relay switches that control the fans / temperature sensors top and bottom too.

Your data is really useful to me and my better half. You rock, sir. Thank you, again.
 

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OP, does the noise not happen if you don't use A/C? Had a car a few years ago that sounded like "boiling water" after shutting it off, came from the A/C in my case. I never did anything due to that noise. I assumed high pressure refrigerant was traveling to the low pressure side on engine shut off...or something like that.
Now that was a great question. Truly. I asked my fiance to drive it today in 95+ F weather without using the AC at all. She did and parked it in the garage and, sure enough, no boiling sound. You've given me another great way of testing this situation and perhaps you're right, it's an AC compressor cooling down type of situation.
Might have nailed it right there, sir.

Next step is to drive the car myself after work tomorrow with the AC off and get 'on it' a few times and see if I can re-produce the hot car, no boiling. After that, I will have the exhaust gas check done / perhaps take it into the dealership.

You guys have really been a huge help in chasing this gremlin ! Thanks again, all

Kurt
 
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