Heater core likely culprit - strong coolant smell inside
 

2010 ES350. About a year ago had to replace the radiator due to a leak that was causing a coolant smell inside the car. That got rid of the odor. Recently it began returning and has been getting worse -- directly associated with running the heater (I'm in S Florida so it's not often the heater is run). High heat and fan with recirculation makes the smell very strong very quickly.

From what I've read it's almost definitely the heater core.

There is no moisture or wetness on the passenger carpet.

I've read it's "probably" a leaky heater core and it needs to be replaced, but could "possibly" be a clogged heater core. From what I recall, the mechanic who replaced the radiator did not flush the system at that time. Is it possible a flush now could fix a clog it that's what it is?

Put the HVAC into recirculate mode see if the smell clears up. Heater core failure is quite rare BTW. Do you have coolant loss?

As I wrote:

"High heat and fan with recirculation makes the smell very strong very quickly."

If I turn off heat (set temp low and turn off AC), open the vents and windows, it goes away quickly. And if I then close the windows it doesn't come back -- until I turn on heat, and then it gets much worse very fast when I change from outdoor vents to recirculate and set heat/fan to high.

From what I've heard and read, a bad heater core is not that uncommon. And upon further research since I posted the OP, the question about it possibly being a clog no longer seems relevant since heat would not be strong and smell wouldn't be there or be strong.

I might mention that about six months ago I had issues with the blend doors. AC wasn't blowing cold on some blend settings. To resolve it I kept changing the blend settings and that kept clearing it up, and after about a week of that the problem disappeared. It reappared briefly about a week ago and then resolved within minutes. That was shortly after this smell issue came up.

So, at this point my questions seem to boil down to:

1. How bad is it to let it go like this until I get another infusion of cash into the business if I avoid running the heat? (Bad in terms of it getting worse and doing damage; I know to keep checking the coolant level.)

2. Assuming it is the heater core, is the massive job of removing the dash?

3. What are the odds it could be a hose leak or something else that doesn't require the massive job of removing the dash?

4. If I do have the job done to remove the dash, how much is it advisable to let the dealer do it for their top-dollar fee so I know it's not going to cause issues later? (Yes, I know. People here are and know top mechanics. I'd be hoping I found someone good.)

5. If I do have the dash removed, is there any point in testing the blend doors while in there or is that useless if they're not acting up at the moment? And for that matter should I invest in replacing all of them and/or all the servos since I'm paying the huge labor cost for the dash?

Thanks!

Jay

How many miles are on it? What is the overall condition otherwise? What is its value? How much are you willing to invest in it?

Do not go to the dealer for heater core replacement. You may as well take the car to a junkyard or trade it in and buy another newer used one as they will vastly overcharge you to an amount that is more than the vehicle is worth. Those guys work on commission and will then find 17 other things they insist you have to repair.

Search around for some independent shops that work on a lot of Toyotas and Japanese cars that has good Google and Yelp ratings.

You can also use this database to start your search for an independent shop that is highly rated. Then cross check on Google as some reviews are old.
https://www.cartalk.com/mechanics-files

You can probably bypass the heater by disconnecting the 2 hoses that go to the heater core and connecting them to each other so coolant just circulates without going to the heater core. Since you are in a warm climate this should buy you quite a bit of time to further diagnose and explore options.

You could then try blowing out the heater core with compressed air and / or a water hose. A friend just did this on some old vehicle and showed me photos of the sludge that came out of the heater core.

Have you noticed any wet areas behind the dash or front carpets that would indicate a leak?

Thanks so much!

It's got 80,000 miles on it. I just paid $5,000 to have the top surfaces repainted (black, South Florida, was neglected for too long; now looks awesome with regular detailing/waxing -- and soon I plan to paint the sides for door scratches). Now just needs tie rods (etc), new front seats, and, well, this heater core issue to be resolved. I'd prefer to keep it. Too much advice that it's a great model year and more likely to last than newer models, and I don't want payments.

I was wondering about terminating the hose. Didn't realize one can connect the hoses to bypass and circulate. Very interesting idea! Don't need heat where I live. Or rather I can live without it for now.

A friend told me blowing out the coolant could be a double-edged sword since crud/sludge in there now could be partially clogging the hole that's leaking and blowing it out could make it worse. I'm wondering your thoughts about that. How could blowing it out now help with the leak?

There no wetness on the carpet "yet."

To connect the heater hoses you get (from Home Depot- Lowes or maybe an auto parts store) a piece of pipe that will fit inside the heater hoses and a couple of clamps. Once you pull off a heater hose you can measure the connection point in the engine bay or the hole in the hose. It is probably 3/8 or 5/8 or 1/2 or similar size in millimeters. It needs to be long enough to connect both hoses.

In my Ford but ....... I put stop leak in the coolant 'cause of the heater core leaking. Worked for two years. There are a few times here that we need heat. I have recently found out that old antifreeze becomes acidic. This eats the head gaskets.
LOL Ed

Turns out in my case mechanic determined the smell was not an issue with the heater core of the evaporator but rather an engine oil leak at the rear valve cover gasket.