# `13 Sentra HVAC and cooling system qustions



## TT_Vert (Jan 6, 2018)

2013 Sentra HVAC and cooling system qustions
Sorry guys saw the 2002+ and thought it applied to this car but it appears it doesn't. I cannot delete this but I did put it where it belongs as well. If you could help I would still appreciate it.

Hello guys. I have a friend w/ a 2013 Optima who has no heat. He apparently has had this issue for a few years. Recently the thermostats were replaced (New to me but apparently this car has two?). Anyway, can anyone perhaps tell me why there are two just for my own knowledge really. So combined w/ this info and the fact that I noticed the system has no pressure and the lower radiator hose is cold I instantly assumed the water pump was cavitating and not circulating coolant. Mind you it is a balmy -10 here in Chicago right now so the car isn't overheating. I assume it would have if it wasn't so damned cold. I tried to burp it for him in a parking lot the best I could while heading home one day but It was too cold and I just couldn't get it out. I'll get into my further diags. later but I told him in the meantime that the shop he had the work done needs to get that air bubble out first and foremost. He took it back and they did say there was an air pocket and did bleed the air out. My friend reported a bit of heat but intermittent which I find very odd. What I'd really like to know is, is there some odd design of this system which prevents the system from pressurizing? That'd be new to me as far as cooling systems go but some cars do use water less coolant these days which do not rely on pressure, is this one of them? While I was in the parking lot trying to burp the system I did check the blend door and it seems to be functioning as I do hear a different pitch of the air passing so the direction of air is changing but does anyone have a diagram or schematic for this system or know where I could get one to just get a visual for how the HVAC system works on this car? I also considered a blocked heater core but I've never seen one on a 4 year old car, perhaps you cuys could share some wisdom on if these are a known problem (Didn't see much searching so I assume no). Is there a coolant bypass valve for the heater core on thse? Searching did tell me that some nissans do in fact have these so perhaps the sentra does too. 

I'm trying to get as much info on this thing so I can help him as quickly as possible. I really don't want to pull one of my cars out of the garage and heat it for a long period of time given it's never seen snow and I'd like to keep it that way . I think my next step is to back flush his heater core to ensure it ins't blocked but I find it very unlikely to be the blocked after only 4 years. I also hope someone has some service manuals or diagrams available for me to look at to understand this system a bit further before getting too deep into this. Especially if it has some form of coolant diverter valve for the heater core somewhere (Didn't see one while looking in a dark parking lot but that doesn't mean it isn't hidden in the upper thermostat housing or behind the firewall in the heater box somewhere.


Steps I've performed
1. Checked blend door best I could (Hear a different pitch sound of airflow and also feel a slight change in temp which indicates to me it's moving at least somewhat)
2. Checked temp/pressure of upper/lower hose. Lower rad hose cold, no pressure in system and heater core hoses are same temp as upper radiator hose.
3. Had friend go back and have them bleed the cooling system after I determined there was an air pocket (Friend still reports that there is no pressure in upper radiator hose)


Also anyone know the book time on a heater core R*R for this vehicle?

Thanks much guys

Dave


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