DIY: 2005 XC90 Heater Core Replacement

CN90 continues his documented DIY tear with this fine 2005 XC90 Heater Core Replacement piece. The cabin heater in his XC90 was blowing lukewarm air. Now it's hot again.


CN90 continues his documented DIY tear with this fine 2005 XC90 Heater Core Replacement piece. The cabin heater in his XC90 was blowing lukewarm air. Now it’s hot again.

UPDATE, outside temp today was in 32F.
Normally, it is lukewarm with the OLD heater core.
With this brand-new Heater Core, it is so HOT that I have to turn the fan down to minimum speed and the temp control down to near the BLUE color.

Anyway, if you have heat issue, do 2 things as mentioned:
1. Thermostat replacement.
2. New Behr Heater Core.

You will be happy. It will make windshield cold weather and snow defrost a lot better too.

This DIY (follow the link down below to get to the rest) is good because it also includes CN90s foray into fixing the Temp Control linkage.

I think I found the reason why I broke the Temp Control linkage! My Temp Control knob was in COLD!

When set in COLD, one of the arms in the linkage blocks the HC, so when you pull the HC, you will break one of the linkage arm!

So, turn key to position I, fan at some low speed, turn the driver Temp Control knob to HOT, then remove the key.

You will see the linkage arm moving out of the way.

Heater Core Replacement Specs and Characteristics

  • 2005 XC90 2.5T with 109K miles.
  • Heater Core did not leak but only put out 145F at center vent (heat max, tach at 2500 rpm cruising speed).
  • After replacement, the center vent reads 160F (heat max, tach at 2500 rpm cruising speed), so I am ready for winter.
  • Time for new Heater Core. A little research showed that Nissens ($90) may leak at the crimp. A little more research showed that Behr is OEM, bought it for $95. Make sure you get the 2 new Volvo O-rings, the factory O-rings broke apart during removal.

Heater Core Replacement Parts

  • Behr Heater Core (Made in France)
  • Two (2) new Volvo O-rings
  • Plastic Bag
  • Torx #25 key
  • Coolant + Distilled water
  • Pair of channel-lock pliers


1. Remove Trim (pull it out toward you) and Under-dash trim (2 T25 screws, on the LEFT side, there is a little tab…pry it out).

2. Place plastic bag to collect coolant, then gently pry the metal clips. The LOWER metal clip will hit the plastic housing, so turn it downward to remove it.


3. For the UPPER clip, I used this setup: something to act as a cushion so I could pry the clip out:


4. Disconnect the pipe: pay attention so you don’t damage anything. I damaged the arm that controls the driver’s side temp control (what a bummer, I will fix this later!). You need to bend the pipes a bit to the FRONT to allow the old heater core to come out.


5. Remove the single T25 screw holding the HC. Remove the old Heater Core. In the XC90, there is more room, so no need to remove steering column or pull hard like the S80 (which can cause some dent in the heater core, see rpsi video on youtube).

– Pay attention to the factory foam, do the same for the new heater core.


6. During installation:
– Clean the pipe ends with fine sand paper to remove old O-ring material.
– I used a bit of grease on the new O-rings, install them on the pipe side, not the HC side.
– Install new HC.
– Re-bend the pipes back and insert them in. Gently tap with your hand to be sure it is fully seated.
– The metal clips: if bent, straighten them out before insertion. Re orietation: I switched the LOWER clip around b/c it is easier this way.
– Re-install the single T25 screw holding the HC.


7. Refill with coolant + distilled water, you will need approx 1/3 gallons or so.
Fill it to about 1″ above MAX. Reinstall the cap. Test drive around the neighborhood for leak etc. Carry some distilled water with you in case you need to stop and add coolant (add only to cold engine).

8. Re-install trim pieces.

That is all!

*** I broke the arm controlling the driver’s side temp control. I will have to fix this later, what a bummer!!!


DIY: 2005 XC90 Heater Core Replacement

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