Micra K12 heater not blowing hot

Tzardine

Hi all,

Looking for some help if you can with the wifes 2004 Micra (March)

We had a replacement engine fitted in the summer. It was fitted by mechanic friend of my brother. Since we got the car back the heater was not working, the fans were blowing etc but no heat would come out.

As it was the summer i put it on the long finger to bring back to the mechanic. Unfortunately he has since passed away so I dont have that option anymore.

Wife is obviously unimpressed now that the cold weather has arrived.

The heater worked fine until the engine was swapped so I think something has not been connected or something small (hopefully)

Doe anybody have any suggestions / possible causes.?

Much appreciated !

biko

Check coolant level
Burp car

biko

Burping a car as no heat inside can be airlock in the hoses.

Easiest way to burp is to park car facing uphill, drive around until you find a steep hill (air will burp faster this way).
Then remove cap on expansion tank (beware, hot steam will spray out. You can use a face towel and cover cap and tank so it doesn't spray in your face). Gloves are good too.

Then have ready mixed (50/50) anti-freeze and water (distilled if you can find it) in a two litre old milk jug or similar.
Remove the top bleed screw on the radiator.
While engine runs and heaters inside are on full blast and max heat, slowly pour the mix in until the coolant starts coming out through the bleed hole.
You may have to push the throttle a little to increase flow.
Once the mix coming out the bleed hole doesn't have bubbles you should be fine.
Replace bleed screw and the fill coolant to the designated limit.
Replace expansion tank cap.
Make sure both are firmly in place, there is pressure in the system and if they aren't firmly on coolant will evaporate. Don't break them though.


If you're not sure what to do, give car to a professional.

Tzardine

biko wrote: »

Check coolant level
Burp car

Coolant level is good.

Very helpful info regarding burping , I will give that a go and report back.

Stephenc66

If you find it's not an air lock (air lock very possible after an engine change) it could be a faulty thermostat stuck in the open position or no thermostat it having been removed and not replaced. This is often done when a thermostat fails to open and causes the engine to overheat (a quick fix is to remove the stat to get home)

In this case when idling or moving in slow traffic there may be a small amount of heat then the air will get colder as you drive quicker.

The engine temperature gauge will be reading very low

Tzardine

Thanks for the replies. It will be monday before I can look at it properly.

I checked the two hoses running to the heater core. Both are nice and hot. Would that still be the case if there was an airlock in the core ?

I also dont seem to see a any heater control valve on the hoses. Is this normal for a Micra ?

The car also has air conditioning if that is relevant.

Many thanks again, much appreciated.

Tzardine

Just to update on this.

I did the burping and checked out the pipework but it turned out that the heater matrix was fine. I stripped away the lower dashboard and discovered that the arm controlling the mixer flap ( or whatever the proper name of it is )in the heater box had sheared off.

Bit of epoxy and a big screw and we are nice and cosy again.

Many thanks for the advice