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I have a Nissan Qashqai 1.5 dci. My car is not overheating and blowers are blowing cool. The lower radiator hose and the bottom of the radiator are cold. I changed the thermostat and drained the cooling system twice. Still no heat. Any ideas?

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  • Sounds like some gunk in your heater radiator prevents coolant from flowing through it. Consequently, it doesn't give off any heat. It's not uncommon that grease builds up somewhere in your cooling system, locally blocking the coolantflow.
    – Bart
    Commented Dec 4, 2016 at 14:10
  • Possible duplicate of Blocked water flow in engine?
    – dlu
    Commented Dec 4, 2016 at 21:45
  • 1
    Year and mileage of your car?
    – tlhIngan
    Commented Dec 4, 2016 at 22:34
  • Can you tell me whats the outside and coolant temprature after at least half of an hour driving?
    – Iman Rosstin
    Commented Dec 4, 2016 at 23:54
  • Is it a diesel? Do you have a EGR thermostat?
    – Iman Rosstin
    Commented Dec 4, 2016 at 23:57

2 Answers 2

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For the heater to be blowing cold, the air must not be encountering a hot heater core. There are a few reasons for this:

  • The heater core is blocked, it could be corrosion or a mixture of incompatible coolants forming sludge.

  • The heater valve or its control has failed and the heater is effecting shut off.

  • Air is trapped in the cooling system and is preventing coolant from passing through the heater core.

  • Hot coolant is flowing, but very slowly, and the air flow is able to cool it down completely.

  • Water pump efficiency is down and is unable to push enough coolant through the heater core.

Since you've drained the coolant, the first think that I'd do is to confirm that you've actually got coolant in the heater core. Identify the hoses going to the core (often on the passenger (right) side of the firewall) and remove one of them, check that it seems to have coolant in it and try pouring coolant into the hose (using a funnel will make it easier).

Next check that you can feel warmth when you touch the cooling system hoses. The hoses going to the heater and radiator should be uncomfortably hot when the engine is at temperature. The ones returning should be cooler, but still noticeably warm. It concerns me that you describe the lower radiator and hose as cold. That doesn't sound right (but you also say that the engine isn't overheating, the overall picture is contradictory).

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Sometimes, the servo that controls the temperature mix stops working properly. Here's what I need to do on my '96 Intrepid to change the temperature to either cold or hot:

  1. turn the blower on full speed
  2. quickly change the temperature to the opposite end where it is currently set (change to hot if it's set to cold, change to cold if it's set to hot)
  3. Wait, and listen for a little sound indicating the servo has changed position (different cars will make a different sound, could be a little swoosh, a light click, or a prolonged thud)
  4. If the temperature is currently set to where you want it, enjoy. If you wanted the temperature where it was set when you started, repeat steps 2 and 3.
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