Help please - No heat coming from heater.

Speeds87 · Post by **Speeds87** » 26 Aug 2020, 11:48

So I was having some work done on my transmission a few weeks back. I needed a new torque converter. Long story is don't tow a lot of weight with your XC90. The engine can handle it but the drive train is made of lesser strength

My mechanic did a great job with that part of it but when I picked up my car he had forgotten to clip in a few hoses and never plugged the fan back in. My car then overheated. It wasn't too bad and I caught it early. I had him do a coolant flush and check the car out. Everything checked out oaky from what he told me. About 15 minutes after I picked it up after he was finished with the flush I got a check engine light. When I scanned the car the error code was P0455 which indicated a gross evap leak. I believe this to be the Purge Valve which I have on order and will replace myself.

Then it has been cold in the mornings and I turned on my heater to notice that no heat is coming out. The blower fan blows hard so I don't think it is the resitor or the fan itself. Perhaps it is the heater core or the thermostat. I think this model also has some sort of a heater control valve as I can find the part online but I have no idea where to replace it once I got it.

My main question is would/could the overheating issue account for the failure of the purge valve and the heating issue?

Also if you have ideas on how to diagnose the heating issue correctly I would appreciate all the help I can get. My thought is if I can figure out what is going wrong I will make my mechanic fix it on his dime and time if the overheating did indeed cause these components to fail.

Post by **oragex** » 26 Aug 2020, 13:44

Was it working properly last year or you bought the car recently ?
The thermostat may be old, but if the heat is really weak, I would look first at the hoses that go inside the engine bay to the firewall, maybe those are not plugged in correctly (switched) or maybe one is kinked. I don't think overheating will damage a purge valve, maybe the mechanic just forgot to plug it in or maybe he pulled on the wires

Speeds87 · Post by **Speeds87** » 26 Aug 2020, 15:24

Thanks for the reply. I should clarify there is no heat coming out of the heater at all. The fan blows air but just not hot. And it was working as of March/April of this year. I checked the hoses and they seem fine. There may be a clog internally that I can’t see.

Do you have any idea on the location of the control valve?

Post by **oragex** » 27 Aug 2020, 03:17

There is no control valve, continuous flow system. Maybe the thermistor has failed, if the car battery was replaced or jumped. If you try replacing the sensor, have the battery disconnected and put the ignition key in POSII when disconnecting/reconnecting it (headlights on) www.youtube.com/watch?v=Zis5WN_if60

Speeds87 · Post by **Speeds87** » 27 Aug 2020, 08:25

After a bit of research it seems that it likely is the thermostat, I am going to replace it in the next few days. I also think that my coolant temperature sensor may be bad because my temperature gauge stays in the middle whether the engine is cool or warmed up. I’ll also be replacing that component when I get the chance.

If it fixes the issue I’ll post it here. Thanks for the help.

Post by **oragex** » 30 Aug 2020, 13:30

That's interesting about the temp sensor. You mean, when you start the car it jumps right to 12 ? Or it stays there even with the engine off? May also look at the wires going to the sensor. Maybe there is a short near the connector.

Speeds87 · Post by **Speeds87** » 30 Aug 2020, 15:44

Yes, It was jumping up to that immediately, I don't think it was staying there when off. I replaced the thermostat and that issue with the gauge resolved. I am still going to change the temperature sensor when it comes in the mail. Now the gauge seems to be responding as normal and slowly moves up as the engine warms up. But I still have no heat. I am thinking the heater core was damaged when the engine overheated? Is that a possibility? Do you have any other ideas?

Speeds87 · Post by **Speeds87** » 05 Oct 2020, 21:15

Okay so I am still with this car and no heat. I have replaced the heater core and still no heat. I played around with the system and took the inlet and outlet hose from the heater core off. I was able to get positive hot coolant pressure coming out the outet side when I put it under a vaccum. That's where my luck ran out. Once I reconnected the hose the pressure failed. My local mechanic thinks there may be an obstruction somewhere in the line. I am not so sure.

I did see an auxillary water pump that is relatively close to the location where I think I am having the problem. I am not sure what function the aux pump has? Could it be part of the mystery why my engine is not circulating the hot coolant through the heater core?

Speeds87 · Post by **Speeds87** » 05 Oct 2020, 21:19

https://www.fcpeuro.com/products/volvo- ... gLPm_D_BwE

There is the link for the aux water pump. I am hoping this may be the issue and then I can put this problem to rest.