Hey all, no heat unless I rev the nuts off of it.

[AradOnRadar]

Good morning all, I am in need of some help. I continually keep turning up with nothing.

This is for a 2015 Fiesta ST with 75000 miles on it. maintenance is up to date with having a coolant flush not more than 10000 miles ago, I swapped the coolant tank and used the standard Dexcool orange that the car calls for, AC works fine.

I switched out my cracked coolant expansion tank and the return coolant hose that also had a leak, I went with an aluminum Mishimoto expansion tank and got an OEM coolant return line. Switched all of that out, burped the cooling system topped off the coolant, now my heater doesn't work unless I get it to higher rpm range on the freeway, then the heater (mainly defrost is what I'm needing this time of year) blows hot and works just fine (telling me that its not a blend door actuator or anything), but I can leave my car running to warm up in the morning with nothing but cold air blowing through the heater.

I have switched out my cabin air filter and vacuumed it/ blown it out, I have had a shop pressure check my cooling system and they saw nothing of any significance, said they got a couple little bubbles out of the system but said my coolant expansion tank replacement job was fine and didn't say I messed anything up. That shop was saying their next step would be to do my heater core which I really don't want to have to do, and my warranty won't cover anything unless there is a leak coming from the actual heater core. So I am hoping there is something, someone on here has dealt with and fixed that can give me some advice. It is getting very frustrating not being able to defog my windows and this has just kept following the trouble tree of deeper head scratching.

I appreciate your time and hopefully we can come up with something. Thank you.

 

[MO15Fiesta]

There is likely an air pocket in the system. Take the cap off and let it run at operating temperature to see if you can get any air out of the system. if need be, jack up the passenger side of the car to make the coolant tank the highest point of the system, even though it already should be. that may help the air escape.

 

[AradOnRadar]

I really hope it is that simple. Thank you! will do that this evening.

 

[Mycooking]

Yup sounds like air trapped at the core. Been there on my first car. Make sure the heater is on when you go to burp it again and like the guy above said Jack up the passenger side.

 

[kivnul]

An awl and some time can make the heater core leak...

I take it that there is no difference when the heat is set to 'high'? My 16 had a programming bug where that was the only time it would blow warm air.

 

[Ford ST]

That shop is stupid heater cores do not go bad. They can leak and they can get clogged, but they do not need to be replaced over a lack of heat beyond stupid. You have air in the system for sure.
Also as the other person said make sure you have it set to high these cars have a stupid climate control system.

Sent from my SM-A526U using Tapatalk

 

[Sprinkle_Star]

unscrew the bleeder atop the rear side of the radiator since an air pocket is most likely to form there

 

[Dialcaliper]

Just to share my experience replacing my radiator - even with a proper vacuum filling of the system, it seems like air gets trapped in the solenoid valve going to the heater core and prevents the valve from opening and coolant from circulating. Yes, apparently the car has a valve to prevent hot coolant constantly circulating into the cabin instead of just an air diverter flap in the vent box. I guess it reduces the load on the A/C or something, not having a hot heater core constantly inside the cabin.

The trapped air happened to me all three times (flush, rinse, fill), even bleeding the top of the radiator and using with a proper vacuum fill set (I got the Mishimoto set and it worked reasonably well, but I used a vacuum pump meant for A/C systems instead of the venturi it came with)

1) Vacuum the system down to ~20inHg and then fill the system, then release the vacuum
2) Bleed the little valve at the top of the radiator. I found a red solo cup works quite well since you can squeeze it to fit behind the radiator. Just pull the cap and let it whizz into the cup until no air comes out and pour back in the reservoir
3) Turn the car on until it warms up, coolant is circulating through the radiator *and* the radiator fan kicks on.
4) Turn on the heat/high defrost and enjoy the cold air (grrr...)
5) Turn the car off, let it cool
6) Vacuum the system down *again* and hold vacuum (but don't let it boil/foam into your vacuum set). A few small bubbles will rise into the expansion tank.
7) Do this one or two more times for good measure until no bubbles come up
8) Start the car, let it warm and enjoy the toasty warm heater

I think it's just a quirk of how the car's coolant lines are set up that air gets trapped. Based on the experience I had where it happened *every* time, I'd expect it to happen even to a professional shop job.

If you don't have a vacuum fill setup available, or even just a vacuum system without the fill tubing, some "get 'er done" options:
1) Wet dry shop vac to the overflow reservoir, might be able to coax the bubbles out
2) Italian tune up - drive the car hard on some twisties with the heater running and it might dislodge the bubbles from the heater core valve.

 

[dhminer]

Echoing others.. Radiator swap left me with the same problem. Burped the system again at the bleeder valve on top of the radiator and ran the car with heat full blast with the overflow cap off for 10-15 min and some bubbles escaped. Problem gone.

 

[AradOnRadar]

I think it's just a quirk of how the car's coolant lines are set up that air gets trapped. Based on the experience I had where it happened *every* time, I'd expect it to happen even to a professional shop job.

If you don't have a vacuum fill setup available, or even just a vacuum system without the fill tubing, some "get 'er done" options:
1) Wet dry shop vac to the overflow reservoir, might be able to coax the bubbles out
2) Italian tune up - drive the car hard on some twisties with the heater running and it might dislodge the bubbles from the heater core valve.

Alright gave it a shot this morning with the car jacked up on the front passenger side as high as I could get it. Heater on full blast about 15 minutes of running while I was getting ready and making coffee... doesn't help that its 34 degrees (F). I just need more daylight, but its good to hear that others have experiences this super fun "quirk". One of those that makes you think you're going crazy trying to bleed bubbles out of nowhere over and over again. Looks like I'm going to invest in a vacuum bleeder but the shop vac is something I have right now. Also I do like driving windy roads. Maybe a weekend jaunt up to Diamon Springs?

Will let y'all know the result and how when I get it figured out.

Thank again. Now to find more daylight...

 

[kivnul]

Interesting how this doesn't happen to everyone (me included) who replace radiators. I'll keep this thread in mind if I ever have to crack the system open again.