[Makrohn]

@jiha1968, We are having some cold days here now, - 11 celcius today, and I just made a new discovery. I could suddenly feel some cold air around my feets, and it turns out it is leaking in ice cold air on the side of the heater core. I have attached a photo for you to see. I tried to switch off AC and just do manual adjustments, but the cold air kept flowing in. Now, I recon this is cold air is coming from the outside and is meant to pass through the heater core. The heater core itself is still hot btw.
Another thing I experienced today, was that when I parked the car, and left the aux-heater on, I could smell what I believe is coolant inside the cabin. Not much, but enough to notice. The coolant level has not dropped since I filled it up 2-3 weeks ago, is this normal?

Heater core XC90 2007
IMG_8133.JPG (707.23 KiB) Visad 238 gånger

[jiha1968]

The foam is supposed to seal that gap, try to gently force the heater core forward to close the gap, (loosen small screw)
or push on the foam to make it seal a little better, or aquire som new foam or alu-tape to stop the draft.

But I don't think the gap is large enough to cause any real heating problem, but it doesn't improve it... (the air that still pass through the H.core, should be nice and hot anyway)

The heater Core will be hot to touch even if it should have some fault, like internal short circuit between in/out-put, air pocket, misaligned flaps, or broken Evap-temp.sensor. (the sensor is visible near top left corner of your picture)

The coolant smell isn't supposed to be there, but sometimes when heating a cold H.core / hose it can make a faint smell, due to minuscule sweating from joints and connections.
(can't se any leaks from tube conections on your heater core)
And when coolant level is stable, there aren't any larger leaks at least.

[jiha1968]

Regarding leaks and smells, probably not the qause, but the hairpin clip for the lower tube at H.core is not seated properly. (see blue arrow )

IMG_20210106_164553.jpg (707.04 KiB) Visad 222 gånger

[Makrohn]

Thanks, I just added some foam I had lying around and it did the trick.

I also decided to replace the heater core with a more "premium" kind, but BEHR was all sold out, I went for the MAHLE version. Should arrive early next week. Not that I think this will solve the problem, but I just like to have quality parts, hence not blaming the budget parts. Regarding the clip, I know, it broke when I replaced the heater core last time, but I have new ones lying ready to the next heater core swap. But yeah, nothing is pointing in direction of a leak other than that subtle hint of coolant.

Regarding the evap. temp sensor.. I was told that if this is failing/broken, the symptom should be either no cold air or variations between cold/hot. In my case I only experience poor heating. The cooling is working as it should. Something you know anything about?

[jiha1968]

Both the Mahle and Volvo Original H.core are made by Behr.
When it arrives, you will probably notice that the "VOLVO" logo on the beige plastic sidewall is grinded off...

It doesn't seem likely that the Evap temp sensor could cause direct heating issues, since its primary an "ice-sensor" to prevent over-freezing of Evaporator.
But there seems to be some cases where it made a clear difference to heating, like: viewtopic.php?p=567152#p567152 , which gives a good reason to check the sensor at least.
I haven't personally investigated it any further, but I still check "all" temp sensors (CCM, Evap, Coolant and wing mirrors) when there are heating (and/or cooling) issues,
and I still change/repair any of them if they are out of range.

[Makrohn]

I see, then I´ll be good in either case :)

Seems you are right some people do experience heating trouble with the evaporator sensor.
I cant wait to get to the dealer and do some diagnostics, cause this is driving me mad on these cold days.

[jiha1968]

And while you're still "foaming" over the heat loss... (pun intended)
Find some larger foam strips or similar to put in the gap between steering column and dashboard:
(it will prevent draft from the large and cold empty cavity behind the dashboard, reaching your knees)

P2_Draft_steering_column.jpg (28.17 KiB) Visad 205 gånger

[Makrohn]

I owe you man, big time, I cant thank you enough for taking your time helping a mate out

[jiha1968]

It's a pleasure And hopefully you'll find the culprit soon.
When you remove the H.Core again, check the flaps movement, try to move CCM temp. adjuster, from Cold to Hot, wait and see if the flaps moves OK.
A mirror on a stick, or endo-/bor-scope makes it a little easier. (even if its not very likely that both right and left temp-flaps /step motors are malfunctioning)

[Makrohn]

Thats a good tip, I´ll be sure to do that!

I keep coming back here with more observations, and here is the latest;

Today I turned OFF AC, turned OFF Auto, and I also turned off the auto/manual recirculation function. Result? The air actually got significantly hotter. Still not as hot as it should be, but anyway. It still gets slighty colder when I crank up the blower speed, but at step 3-4 it actually gets "hot". And I mean "hot".

Could this be yet a sign pointing in the direction of the evaporator sensor?