Have a 2015 1.5EB Focus, seem to have a coolant/heater core issue:

No visible coolant loss, but definitely a sickly (sticky toffee?) smell coming from vents though. If I leave the vents off and turn them on at the end of my journey, boom, windows are caked in moisture and more of that smell. Leaving vents on for the whole journey is fine as I guess it doesn't allow so much coolant to build up before blasting it at me

No damp footwell material or pipes I can feel out, I'm guessing the small leak is at the heater core itself.

So, is it worth popping Radweld into the tank first before trying to get the dashboard out and replacing? What experiences have you guys had with it?

It feels a bit counter-intuitive popping a congealing fluid into the car

Cheers

It can work as with other brands as long as it used as per directions, surely a better option is to find the leak and repair, pour a strond dye colour in the cooling system then see where it appears, hopefully NOT the matrix as most are a pig to do.

I wouldn't use radweld or anything like that, personally. I'd rather just fix the issue as @Jimpster says.

I'm a great fan of Radweld, and yes it most definitely works for the right kind of problem like a slight weep on a head gasket. However !! to use Radweld on an Ecoboost engine which have a reputation for cooling issues and to try and fix an unknown problem is not something I'd recommend it for.

Just as a side note, when was the pollen filter last changed ? These get wet and smell if the air intake for the heater gets a bit clogged up.

Yes, I've used Radweld very successfully in the past on older type engines (BMC A-series, Ford Kent sort of era) when I might have had an inkling what the issue was but was too skint to fix it properly.

I don't think I'd use it on more modern stuff though, especially something with known cooling issues as @unofix mentions.

Well.. no leaks from coolant tank or local pipes, no change in coolant levels, (I did see two air bubbles pop out of the large hose into coolant reservoir after tapping it), no obvious damp around the footwells, though *I think* the drivers footwell had a sickly sweet scent to it similar to what comes through the vents sometimes, but hard to tell for certain at the moment as the whole car is saturated with it sometimes. So who knows! Time to strip the car apart all day to find a mm wide crack!

Edit: I did note that the smell was somewhat stronger when the car was going up hill.. not sure how much of a good clue that is

 

I had a fiesta 1.6tdci. Coolant leaked (checking level) but I couldn’t find leak.  So I put radweld in it.  It worked a few weeks but then leaked again.  I checked for leaks and found it was the thermostat cover.  I found it because the red radweld left a red stain where the leak was. So radweld was useful as the red stain from it showed me where it leaked. Not quite the use they advertise it for.

Just a thought - do you have aircon? If so, when did you last fumigate it?

When you say the windows mist up - does this happen when you turn the aircon off in damp weather, and go away when you turn it back on?

ADDENDUM -  the symptoms described are similar to those associated with the aircon system - condensation forms in there not all of which drains out quickly. You get mould growing then you get smells. If you are driving on a damp or rainy day with the aircon on, blowing on the screen, then turn the aircon off the screen will mist up, almost instantly. Turn the aircon on and it will clear.

Edited November 16, 20223 yr by RMurphy195
Further explanation

Turns out there was a small crack in the top-rear of the expansion tank, explains how intermittent this was, and validates the uphill smell increase clue, shame I didn't clock onto that myself.

But now after a few days of none toxic fumes, the sweet smell is back with a lot more moisture floating around the car, just with more mystery now as I had it fully checked out at the dealership for another opinion and it was fine 🙄

And the air conditioning doesn't make a difference to the state of the windows really, no excess steaming or change in smell. But there is now commonly moisture hanging around the car, where the handbreak, gauge display or arm rest are wet to the touch (I have been using a dehumidifying pillow throughout all of this, with regular, almost daily, drying in the house, so it must be a lot) 

On 11/15/2022 at 5:52 PM, RMurphy195 said:

Just a thought - do you have aircon? If so, when did you last fumigate it?

When you say the windows mist up - does this happen when you turn the aircon off in damp weather, and go away when you turn it back on?

ADDENDUM -  the symptoms described are similar to those associated with the aircon system - condensation forms in there not all of which drains out quickly. You get mould growing then you get smells. If you are driving on a damp or rainy day with the aircon on, blowing on the screen, then turn the aircon off the screen will mist up, almost instantly. Turn the aircon on and it will clear.