Suddenly Running HOT

Connie

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Last few weeks the cooling fan has been running for a few minutes, I'd say 5ish min after shutting the car off. Up until today I've not been worrying about it because the guage has been rock solid in the 2/3 location like always.

Today it got unseasonably warm, and the guage moved. I've done a bit of reading, and when the fan runs after shutdown, it means the oil temp or coolant temp is above 225F. That's too hot for me, and I want it to stop doing that.

So my coolant is less than 2 years old, but has some miles on it. It's Honda blue stuff. The thermostat is almost 3 years old, and also has some pretty significant miles. The A/C system components in front of the radiator have been removed, so I should be getting excellent airflow. There are no coolant leaks or smells. The radiator, and heater core have both been replaced within the last 2 years. Rad hoses are fine. Coolant level hasn't moved yet.

I noticed that after shutoff, only the rad fan runs; the condenser fan does not. The radiator felt hot on the condenser fan side, and cool on the side where the rad fan was running.

My plan is to replace the t-stat and coolant. I hope that gets it to calm down and get me through one more winter. I need to do the timing belt and water pump service soon, but I don't think that's my issue. They have over 100k km on them, but are less than 2 years old.

I am hoping it's not a head gasket, but at 350k on the engine, it's a possibility I suppose. No other symptoms of that yet. Car still runs perfect.

I hope someone who has experienced this before can chime in as to what my problem most likely is. I really can't afford a catastrophic failure at the moment, so I'm hoping to at least avoid that. I put this thing through 3 hours of stop and go commuting every day, and it's starting to get warm on the guage when I'm stuck in traffic.
 
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Eclipse99fwb

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Didnt have a chance to read your whole post in depth, will try to when i get home from work. First hondas blue coolant is their equivalent to toyotas pink super long life coolant. It is suppose to be good for around 100k or 120k before needing to be changed, me personally thats too long for coolant i would be more incline to change every 80k as this is when i have tested coolant at the shop i work at seems to really start breaking down. If u have less than 80k on it save ur money the coolant is not the cause nor will fix the problem. First thing i would do is check your coolant level in the morning when the car is cold. Make sure it is at full mark, also check ur radiator it should be right at the top if not top it off with only honda blue do not mix! Now the thermostat could be the problem and is cheap to replace. More importantly do you know if your fan is kicking on while driving also? Not sure where you live but here in colorado we got alot of cotton type crap from trees and this loves to get stuck between the condenser and radiator essentially blocking air flow, so check between it and see if it is clogged. If it is gently use air to blow it out, becareful the fins on the radiator bend very easily. Also that brings up another thing to check is the fin rows on the radiator, make sure they are not smashed up, id it is this will cause improper cooling cause the fan to stay on to try to cool it to what is acceptable. As for blown headgasket check your coolant for oil type substance in it, same with your oil it will look sort of like a milkshake type substance, if neither is found you should be safe. Also just for heads up when you do your timing belt make sure the tsb for the guard over the balance shaft seal has been installed, personally i have seen 3 f23 have to be replace due to the seal moving out of place causing a massive oil leak then blown engine. If you need a part number let me know and i will get it, i know it was this part number #06923-POA-306, may have been changed. Sorry for the length hope this helps you out, i hate to see people waste money on things to solve a problem, trust me there alot of mechanics out there who cannot diagnose and that is how they fix things is waste ur money till they replace the right part.
 

FNCONE

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+1 On checking The level. Had this happen to me once and thats all it was. Hopefully that is all you need also.
 

Nam1911a1

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Kinda weird that yours runs normally at 2/3. That seems already running hot to me. Mine stays a hair below halfway even on 100*F and higher days.

I changed my thermostat out after 19 years. It was still working but I just wanted a new one for preventive maintenance. The hoses were replaced so I figured the stat would be too since it's so easy. I replaced mine with a 170*F stat
 

Connie

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Kinda weird that yours runs normally at 2/3. That seems already running hot to me. Mine stays a hair below halfway even on 100*F and higher days.

I changed my thermostat out after 19 years. It was still working but I just wanted a new one for preventive maintenance. The hoses were replaced so I figured the stat would be too since it's so easy. I replaced mine with a 170*F stat

Typo, meant to say 1/3.

Sorry for the delayed response, been super busy over the last few days.
Managed to drag myself out of bed on Saturday morning before work to check the level since that's the only time all day the car isn't too hot, and sure enough, it was down.

Overflow was still full, but the rad took almost 2 quarts! It's been issue free since I replaced the heater core this past February, but it did deal with a lot of mountains and generally harsh conditions while I had it in Mexico this summer; I suppose some could have boiled of without me noticing. Even so, there had never been any smells or movement on the guage up until last week. The hose from the rad to the overflow is not blocked, and the rad cap was replaced along with the heater core.

After filling it back up, temps are back to normal. No fans running after shutoff. Has me kinda worried about where the coolant went, but for now it seems alright.

Let's just hope it's not head gasket time...

Thanks to everyone who replied!
 

Eclipse99fwb

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Glad it was nothing serious. Also i checked honda blue coolant at work on the bottle it says good for 60k or 5 years so i stand corrected. As far as where it went that is a good question as coolant just doesn't evaporate, keep a eye on it. It may be smart to change your oil and look for coolant mixed also try having someone watch you go from a stop and look for white smoke especially if it smells sweet as far as a blown headgasket.
 
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Connie

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It's only been like 8 days since I changed the oil, and it looked fine. I'll keep an eye on it and hope for the best. Have a spare engine, but really don't want to use it unless I have to. There is no smoke at startup or anything, but since I filled it up, sometimes after I park I get a whiff of coolant from the front of the car near the overflow, but nothing is leaking and the overflow level is still fine. She is pushing half a million spirited km, though. I suppose time will tell.
 

Connie

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Well i figured out where the coolant was going; the lower rad hose was leaking a tiny bit because the hose clamp wasn't as tight as it could have been. That rad has been in there for 3 years and was never an issue till now, so go figure. Now I can stop worrying about head gaskets and cracked blocks.
 

Connie

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Whew. Glad it wasn't leaking out of the head gasket or block :O

I actually found the leak a day after topping up the coolant, but forgot to update here.

Yeah; I was relieved, too.

Appreciate all the help, as always:waytogo:
 
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