HELP!n Heater Issues After Cooling System Flush 04 Prius

My 2004 Prius just turned over the 100K mark (yay!) So like a good girl, since the weather is starting to get cold, I also had the cooling system flushed/replaced when I had my oil change/filters etc. done today at the usual place I have my routine maintenance done.

When I left, I noticed the heater was not working properly. It randomly blows hot air appropriate to the temperature I have it set for a minute or two, then starts blowing cold air. Then it starts the hot air (and sometimes tepid) and this whole cycle continues randomly.) There is no rhyme nor reason to it --- doesn't matter if I'm going fast, slow, gliding, idling etc. I took it right back in and of course it refused to misbehave. They popped the hood and said everything was fine. Yet it started doing it again once I got almost home. The other thing I noticed was whatever the noise is that sometimes comes on for a bit when the car is shut off sounded a little odd when I turned it off tonight --- a little louder and a little less "constant" for lack of a better word.

So have these people completely screwed up my car? What is going on? Do I need to take it to a Toyota dealer or is there something I can tell them they need to fix? I'm in a bit of a fix since in a few days my busiest time of year starts which means over a week of working 18 hour days and driving over 100 miles per day. Plus the car is now just out of its warranty and I am broke!

Oh great Prius gurus, help me with figuring out what the issue is and how I should go about fixing it. Thank you!

 

Thank you, Patrick. You were right on the money with your diagnosis. And they had not used the Super Long Life Coolant either. The Toyota dealership got me fixed up. Now it's time to do battle with the fools with tools who got me into this mess.

 

Well, I am back already. The service manager warned me I might not have heat in the car for a day or so as there could be a few air bubbles that will rise to the top and eventually evaporate. I've driven about 20 miles since they gave her back, and indeed there is no cabin heat whatsoever. I'm not sure if this was bs or what.

BUT tonight what I believe was the master warning light and an alarm came on three times in about a one mile stretch. The reason I say "believe" is because the light and alarm came on and off so quickly and briefly that I couldn't even get a firm look at it, and if there was any information on the MFD it was gone by the time I looked there. All I know for sure is the light that came on was red. And of course I wasn't in a place where I could pull over.

Everything aside from the cabin heat seems to be working fine, although the coolant heat recovery system pump seems to be kicking in MUCH longer after I turn off the car (although it sounds back to the way it usually does.)

Yes, I am bringing it back to the dealership first thing in the morning. I wouldn't be so alarmed about it but I was planning on driving with my kids to New Mexico for Christmas to see my elderly mom on Wednesday morning. Just me and two little ones since my husband deployed back to Iraq at the beginning of the month. That's hundreds of miles of desolate highway without a Toyota dealer in sight and even though I have an auto club membership, I fear we could be stuck alone and vulnerable for hours. I have NEVER been afraid of depending on my car. I love my Prius!

Patrick or anyone else, do you have any idea what may be going on that might set my mind at ease that this is something minor that they can fix before I leave?

 

Thanks, everyone. It happened again on the way to the dealership this morning --- happening three times again in the same type of timeframe. It was definitely the master warning light, as I was able to actually see it and the MFD the second and third times since I was prepared. All the MFD said was "Trouble!" then that disappeared from the screen.

Now get this --- according to them, there was no record of a diagnostic code. There was an air pocket in the cooling loop and they took care of that. After the fix, the service manager and a technician then took it out for a long drive to see if they could replicate it without results. They could be blowing sunshine up my backside but they did seem genuinely stumped. I did explain to them I had a long trip on desolate roads planned and they did not think I should be concerned (of course that's easy for them since it's not them doing the driving!)

I drove about 60 miles afterwards today without any further issues and everything else seems fine. I did rent a car for our trip though --- I just can't risk our safety. Our friend who is staying in our home while we're gone will be driving it around town, so if there are any further issues she will apprise me of the situation.

Once again, thanks for your help and just being here to listen! If you have any further thoughts on the supposed missing code, let me know.