07 xc70 lukewarm heat am stumped

[MoVolvos]

Does anyone have thoughts on SKP, 4 seasons or nissen heater cores?

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Nissen is used as OE by many car manufacturers while SKP and 4 Seasons has been around for a long time. I know all 3 of them for their radiators.
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[matthew1]

This post got me wondering what a normal temp delta is, and according to AI yours is good. I don't think it's the heater core.

A 30 deg drop between connections does sound like a lot but I don’t know what would be considered normal. It kinda sounds like the coolant is moving through the core very slowly.
When you saw the 30 deg drop was the blower fan running and was it blowing strongly, albeit not real hot, out of the floor vents?
How much does the temp drop if the blower fan ISN’T blowing.
What were the actual temps you witnessed going in and out of the core?
Did you flush the core in both directions?

Hi chrism, the specialist said 30 degrees was greater than normal. The temps he registered were out:105 in:140. It was only blowing about 95 degrees out of the vents inside. I'm not sure about the drop/ difference if the fan isn't blowing.
Yes, I did flush in both directions and saw some crud come out. At the end had good, clean flow

[chrism]

As Matthew’s attachment points out, the inlet temp should be somewhere close to engine temp which would be in the neighborhood of 185-190? Benbug is seeing 140. I would be surprised if there is really a 45 deg drop in temp in the hose between the engine and firewall.
Benbug, is your engine temp gauge running at mid point as most Volvos do, or is it running somewhere lower? Also, did you happen to sample the temp at the thermostat housing or upper radiator hose?
CN90’s advice to look into the thermostat may be the ticket. I would try almost anything before squeezing under the dash to replace a non-leaking core. I’ve replaced three of them in our P2 cars over the years (one was a premature failure of the replacement) and if I never replace one again it will be quite alright with me.

[cn90]

Remember that temp measured at firewall (using infrared reader) is temp of the plastic pipe and not the temp of the coolant entering or exiting the firewall.

[chrism]

Remember that temp measured at firewall (using infrared reader) is temp of the plastic pipe and not the temp of the coolant entering or exiting the firewall.

Yes I’ve thought about the coolant inside the hoses being hotter than the plastic pieces on the outside. However, both hoses will be subject to that same inaccuracy so, relative to EACH OTHER, I can still see a roughly 30 deg drop in coolant temp. But rather than a difference of 140 vs 105 it might actually be something like a difference of 165 vs 130. Whatever, it still tells me there is a significant level of heat dissipation off of the core. Keep in mind Benbug has verified there’s circulation through the core. Hence my questions about the temp gauge reading and the thermostat housing/upper hose temp.
So, in order to test the thermostat, what do y’all think about pinching off, or nearly pinching off, the upper radiator hose in order let the engine temp climb a bit (not TOO much) and see if it helps the cabin heater performance?

[cn90]

As long as you don't blow a head gasket, then it is fine to pinch the hose lol.

[cn90]

I posted all my experience in XC90 Forum.
At this age/mileage, best is to replace both Tstat + HC.

* Tstat: Facet (Italy) is about $55, works great. Wahler is $110.
* HC: Behr is NLA. You can try the eBay Estonia thing for $55.
The P80 ppl use it a lot. Or Nissens (made in China)....

Anyway, I will link the XC90 Heater Core DIY here.
I also posted the Temp Delta pics here.
They thing is not really the Delta but Exactly what temp comes out of the vent, when cruising at engine tach ~2500 rpm. The vent reading should be 160F (or 71C). You need this kind of temp to melt the ice and to keep the cabin warm.

viewtopic.php?t=82726

[vtl]

Run CCM calibration (DiCE/VIDA required). You may have a faulty blend door actuator. Common problem.

[benbug]

Run CCM calibration (DiCE/VIDA required). You may have a faulty blend door actuator. Common problem.

I believe the specialist I took it to did that but going to text him to confirm. But that had we thinking about the climate control module and how to rule out if it's gone bad or not. Apart from ordering one online, swapping it and testing the heat, are there any other ways to rule it out?

[benbug]

To all those who may read this, I've ordered a heater core online and am going to try replacing that first to start. If I can get access to them without removing the dash right now, I also plan to check the blend door motors.

If anyone has any tips on access (looks tight but doable with the panels around the center console off) it would be appreciated as always.

Will update once the core is in.