2007 Honda Fit; Air in Cooling System Heater Core

[ltslimjim]

Hi all,

Recently, this vehicle had a radiator crack and lost coolant. The radiator was replaced, but air remains in the heater core. I tried bleeding with a spill free funnel on an incline, but the air seems to be trapped or especially difficult to remove. How important is it to do this on completely level ground? How soon must remaining air be removed from a system before it could become a problem? So far, it’s been this way for a few weeks since the repair and the heat works as well as the vehicle cools properly. I’ve monitored the temps. Just wondering if I might be doing something wrong or if anyone has any tips or advice.

Thanks

 

[GSCJR]

In your case, not that important, due to the fact that the air has escaped by now if everything seems ok; just monitor you coolant level in your reservoir, for a few more days.

 

[michaelluscher]

Is vacuum filling an option?
Any gurgling noises from the heater core?
If not, try putting the fill size of the car higher (curb or one ramp) while using the funnel, and giving it a few revs with the heater on
https://charm.li/Honda/2007/Fit L4-1.5L/Repair and Diagnosis/Engine, Cooling and Exhaust/Cooling System/Technical Service Bulletins/All Technical Service Bulletins/A/C, Cooling System - Gurgling Noise From Dash Area/

 

[ltslimjim]

In your case, not that important, due to the fact that the air has escaped by now if everything seems ok; just monitor you coolant level in your reservoir, for a few more days.

The overflow reservoir hasn’t dropped, but I still hear air moving through the heater core at startup.

That’s why I’m wondering if I didn’t bleed it properly. It was my understanding that any air should self purge through the overflow as long as the overflow has fluid, so as air escapes it will draw in fluid and not more air.

 

[ltslimjim]

Is vacuum filling an option?
Any gurgling noises from the heater core?
If not, try putting the fill size of the car higher (curb or one ramp) while using the funnel, and giving it a few revs with the heater on
https://charm.li/Honda/2007/Fit L4-1.5L/Repair and Diagnosis/Engine, Cooling and Exhaust/Cooling System/Technical Service Bulletins/All Technical Service Bulletins/A/C, Cooling System - Gurgling Noise From Dash Area/

Yes, I’m hearing gurgling from the heater core. I could try the ramp on the radiator cap’s side then redo the spill free funnel bleed. I did rev to 2-3k RPM uphill but I think the cap side was lower than the opposite.

 

[GSCJR]

Was it gurgling before? Further, now would be a good time to replace the rad cap; OE only.

 

[ltslimjim]

Was it gurgling before? Further, now would be a good time to replace the rad cap; OE only.

I did get a new Honda cap. It only began gurgling when the old radiator started leaking and caused the system to bring in air. Before the radiator issue, never heard it. Apparently, it is fairly common on this car.

 

[Hall]

Apparently, it is fairly common on this car.

Are these also known to be difficult to fully bleed air out ? The no-spill coolant funnel you're using seemed to really help with vehicles that are hard to bleed, but even then, some shops do vacuum bleeding. I presume it's even more reliable and possibly faster.

 

[ltslimjim]

Are these also known to be difficult to fully bleed air out ? The no-spill coolant funnel you're using seemed to really help with vehicles that are hard to bleed, but even then, some shops do vacuum bleeding. I presume it's even more reliable and possibly faster.

I’ve read of it happening on much lower mileage Fits of this generation. I’ll probably just try the spill free funnel bleed again.

 

[Tman220]

I had similar issues with trying to get all of the air out of the heater core on a 04 Civic. I tried everything as well and the thing that seemed to help the most was to get it hot with thermostat open, fan on etc, then go give it the beans to get the coolant circulating as quickly as possible. In the end, I was unable to get rid of the gurgling sound completely, but I was able to get it to the point where it was barely noticeable. If I still had the vehicle, I would have vacuum filled it to give that a try.

 

[ltslimjim]

I had similar issues with trying to get all of the air out of the heater core on a 04 Civic. I tried everything as well and the thing that seemed to help the most was to get it hot with thermostat open, fan on etc, then go give it the beans to get the coolant circulating as quickly as possible. In the end, I was unable to get rid of the gurgling sound completely, but I was able to get it to the point where it was barely noticeable. If I still had the vehicle, I would have vacuum filled it to give that a try.

Thanks for sharing your experience.

I checked both upper & lower hoses to make sure the thermostat was open and I had the radiator fans come on, etc. I think I tried idling and raising the RPMs up to 3000 off and on for about 30 minutes. Very stubborn bleeding the air, indeed!

If it’s cooling properly and providing heat to the cabin, is there any actual concern for leaving air trapped in the heater core? What does air in the cooling system potentially due to it overtime?

 

[Tman220]

If it’s cooling properly and providing heat to the cabin, is there any actual concern for leaving air trapped in the heater core? What does air in the cooling system potentially due to it overtime?

I can't foresee any long-term issues with a little bit of trapped air in the heater core. Theoretically, due to some air displacing some coolant, the heater core will be slightly less efficient but mine still blew all the heat I ever wanted so I wasn't much worried about it. It was only a slight annoyance when firing the car up in the morning to hear a couple gurgles from the dash.

 

[ltslimjim]

I can't foresee any long-term issues with a little bit of trapped air in the heater core. Theoretically, due to some air displacing some coolant, the heater core will be slightly less efficient but mine still blew all the heat I ever wanted so I wasn't much worried about it. It was only a slight annoyance when firing the car up in the morning to hear a couple gurgles from the dash.

I think you’re right.

It is definitely annoying and somewhat troubling to hear what sounds like a waterfall of air moving inside the dash for those first couple of turns or coming to a stop when cold.

 

[zzyzzx]

Won't the air work its way out eventually? I normally do nothing special just check the overflow reservoir and top off daily until it stops needing topping off...

 

[The Critic]

Did the vehicle overheat when the radiator cracked?

 

[ltslimjim]

Did the vehicle overheat when the radiator cracked?

No.

I was able to smell the spilled coolant that leaked from where the original radiator cracked. (it had been hitting the crushed radiator support bracket from a wreck 8 years ago…slowly but surely applying too much force until it cracked)

I discovered the above while topping off to address the sound of air in the heater core and its low coolant condition having brought air into the system.

I’m sitting in the car now after starting up leaving my job.

Heat is all the way on. When first starting, the rushing of air sound; gurgling, is clear as day and the whole time it’s idling I hear air moving and creeping slowly through the heater core. It’s really noticeable.

When I begin raising the throttle while sitting in park, I hear the air move more. It responds to throttle.

I don’t think it’s a head gasket issue…Because I’m not losing coolant after the radiator was replaced and it’s never overheated.

I tried zip tying a nitrile glove to the radiator with the cap removed, raised the throttle to 3k, and it didn’t expand the glove at all.

 

[ltslimjim]

Won't the air work its way out eventually? I normally do nothing special just check the overflow reservoir and top off daily until it stops needing topping off...

That’s my understanding. I’m just bouncing the current state it’s in and my overall experience off others.

 

[ltslimjim]

So, I did some digging and found results on forums for the Fit of this gen. It’s a fairly common issue to have air trapped in the heater core.

Some owners had to jack up the front of the car while burping at the radiator to get the air pocket removed.

Others had a small pin size hole in random tiny coolant hoses along the intake or in the tube from radiator cap to reservoir or the tube inside the reservoir itself.

I’ll have to meticulously try to inspect those small hoses; as it’s a possible air entry point, which just makes bleeding the system pointless as the problem recurs.