2004 XC90 Heat problem

dcwpg · Post by **dcwpg** » 12 Jan 2015, 08:06

Hello everyone, really hoping someone can help me out. I have had my xc90 to a few different repair facilities and no one seems to have a solution to my problem. Here's what's going on: My 2004 xc90 heats up quick enough (according to the temperature gauge), but takes a long time for any real heat to blow. The colder it gets outside, the longer it takes to blow warm air. This has been happening the last couple of winters, so here are some observations: when I am accelerating, I get good heat blowing from the vents. When I come to a stop, the temperature of the blowing air drops dramatically. The blowing air temperature is hotter coming from the center vents than the air blowing from the side vents (I measured it). When the problem first occurred I took it in for service, although I didn't believe it was a thermostatic issue as they suggested, I agreed to a thermostat replacement. As I suspected, changing the thermostat didn't help. I took it in to a Volvo specialty repair facility for my fall/winter maintenance and spoke to them about the problem. Their recommendation: flush the heater core, if that doesn't work, replace the heater core. Before I spend more money on service that will not resolve my problem I thought I would see if anyone else has had similar issues and what they did to resolve them. Thank you in advance.

Post by **cn90** » 12 Jan 2015, 11:36

Depends on the engine (2.5T vs T6) but chances are the tstat is bad.
Replacing the tsat is not that hard.

For the 2.5T it is sold as an assembly, about US$90 for Wahler.

dcwpg · Post by **dcwpg** » 13 Jan 2015, 14:49

Thank you for the response. The engine is a 2.5T. I have changed the thermostat and it made no difference at all.

Post by **FLXC90** » 16 Jan 2015, 14:10

I am led to believe it's the nature of the beast, they just don't produce that much heat when idling. Noticed it last night in my 04 T6, but my 06 Beetle does the same thing, revs = heat, off throttle = cold. And the Beetle has done it since new, so it's not a maintenance issue.

I am willing to bet that our t-stat is mostly closed a lot of the time, because the cooling system is set to cool engine under higher stress conditions, but at low power in cold, coolant just recirculates in the block. I don't know if normal water pump pressure doesn't want to disturb the eddy in the cabin heat circuit or what.

Post by **FLXC90** » 16 Jan 2015, 14:12

I wonder if an aux pump in the heater hose would cure it, just ensuring flow in the circuit at low engine speed/load?