Heater problem gremlin
 

Hi All, had a problem with my heater, it worked perfectly, for about 15 miles, then suddenly it went cold, tried it the next day,on a short trip, and it went back to the normal temperature,has anyone had a similar problem, if so, is it anything to get concerned over, or is it just a dreaded gremlin attack :shrug:

Not usual with the diesel engine as air locks seem to be rare.

Is the water level in the header tank correct ?

thanks for the reply,i will check the level tomorrow, and will let you know,if it needs a top up.

Did you have the air con running? If so, that's what happens when the set temperature is reached.

no mate, didn't have the air- con on, but thanks for the suggestion,

We had an airlock in Debs diesel, the heater never got hot from the day we got the car, ended up backflushing the heater matrix then refilling the whole system, it now has a heater that's on par with a petrol model.

First symptom of low coolant level on these diesels is the cabin getting a tad chilly. :}

Just to back up previous comment, I had an airlock on my CDTi after water pump replacement and I experienced the cold heater.

Followed advice on this forum and all fine. I didn't empty and flush and refill slowly but did use the bleed screw on the hose near the battery box.

JohnnyBG

I may be barking up the wrong tree, but could be relevant. When you mentioned the 15 miles it reminded me of my first 'discovery' of this 'safety feature'.

When you say it went cold, did all the vents go cold? When set to auto, and it has reached its target temp, the upper vents on the driver's side will cool down. I always thought this was meant to be a few degrees lower, but mine feels much cooler than this, to the point it feels cold. The feet level vents will remain warm as well as all the passenger side vents. Once in this status it will be as follows;

Driver's side window vent = cool
Driver's side door vent = cool
Driver's side face vents (if used) = cool
Driver's side foot vents = warm
Driver's side rear foot vent = warm

Passenger's side window vent = warm
Passenger's side door vent = warm
Passenger's side face vents (if used) = warm
Passenger's side foot vents = warm
Passenger's side rear foot vent = warm

There is a way to over ride it, but I cannot remember, I think it was either switching off the auto mode, or putting it on to recirc. Increasing the temp will override it, but only until that target temp has been reached.

In my car, the target temp would be reached after approximately 15 miles (I drive with the window down a little). So if your next 'short' run as you described, was short enough that the target temperature within the car was not yet reached, then you wouldnt notice it. I would actually reckon most people do not notice it under normal use.

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if all the vents are cold, then it is likely to be an airlock or blockage somewhere, and just ignore the above lol.

Loss of cab heating indicates there's air circulating in the cooling system. A simple top up won't eliminate this. What you should do is the official bleed procedure. Basically, follow MGR's refilling instructions, but you're simply topping up the header tank level rather than refilling an empty system. Everything else applies. Here's the official method taken from RAVE.

1. Remove the bleed screw from fuel burning heater coolant return hose.
2. Have available the prepared coolant.
3. Fill the cooling system, keeping coolant level to neck of expansion tank, until a steady stream of coolant is emitted from bleed screw hole. Fit and tighten bleed screw.
4. Continue filling until coolant reaches expansion tank neck and remains static.
5. Ensure A/C is switched off.
6. With the expansion tank cap off. start and run engine and run at 2000 - 3000 rev/min. Fill expansion tank as necessary to maintain coolant level just below expansion tank neck. When coolant starts to rise up expansion tank neck, due to heat expansion, fit expansion tank cap.
7. Continue running engine at 2000 - 3000 rev/ min until cooling fan comes on and then run at idle speed until cooling fan stops.
8. Switch off engine and allow it to cool for 30 minutes.
9. Check cooling system for leaks.
10. Remove expansion tank cap and if necessary top-up coolant to MAX level. If MAX mark is not visible, remove excess coolant until level is at MAX mark.
Warning - To avoid scalding injury, do not remove the filler cap from the expansion tank while the system Is hot
11. Refit expansion tank cap.

A top up and bleed isn't exactly the same as refilling an empty system since the latter forces all air in the circuit upwards so it exits at the screw hole. It will therefore be worth removing the bleed screw after this routine to ensure no circulating air has collected in the area of the bleed screw.

TC