I’ve got an issue with the heater in my 07 1.9 Multijet. My previous 1.9 JTD used to get warm air coming through the vents after just half a mile or so and I could have it set at say 23 and it would blow hot air until it got to that then the fan would reduce and the air cool down until it needed to heat up again.
Now this Multijet does nothing like this. I can set the temp at say 25 deg and bugger all happens for perhaps three or four miles then warm air will start to come through. It’s better if I put the fan on 4 but not allot. After about ten miles it will be warmer but it’s nowhere as good as the old JTD.
Now on top of this yesterday a funny thing happened. It was cold on setting off and I put the temp up to around thirty but still no real heat. I did notice after four miles that the temp gauge had gone up to four bars, and then went on to five. Now usually it never moves off three, so I though that was odd and kept watching it. Suddenly the temp gauge dropped straight down to two bars and heat started to come out the vents, but still not really hot. So I thought to myself, is this a sticking thermostat? Any ideas.
Also are there any sensors in the cabin or heater ducts that may be faulty to cause such a meagre performance form the heater?
Thanks.
Chris.

The thermostat is a weak point and if the car is slow to heat up and in cold weather doesn't heat fully, then it would be suspect. It's not easy to change in the newer models like yours. While your recent experience might suggest a sticking stat, the fact that you got no heat when you had 5 bars is unusual- you don't need an open stat to get flow to the heater. Look for air in the system first. There are bleed points on the pipe lines in including the pipes going to the heater. Check for coolant loss also.

Dermot said:

The thermostat is a weak point and if the car is slow to heat up and in cold weather doesn't heat fully, then it would be suspect. It's not easy to change in the newer models like yours. While your recent experience might suggest a sticking stat, the fact that you got no heat when you had 5 bars is unusual- you don't need an open stat to get flow to the heater. Look for air in the system first. There are bleed points on the pipe lines in including the pipes going to the heater. Check for coolant loss also.

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Thanks very much for that. Bleed points on the pipes! I'll have to look for those then. Any Ideas where? I did think it might be air in the system. I did bleed the one on the radiator. There does not seem to be any coolant loss that I can see and certainly plenty in the bottle!

While I haven't the car with me now, I am pretty sure you will find two pipes going into the bulkhead from the engine bay in the center of the car behind the engine. These are feeding the heater matrix and if I remember correctly, one of those has a bleed screw (operated by thumbwheel) on the pipe. I hope I am not confusing this with another car.


While I said the thermostat is a weak spot, be sure it is the problem first. In our 06 Eleganza, it took 4 miles of winter driving to see even one bar on the temp gauge and if you were lucky it might eventually get to 2 bars; a clear case thermostat issue especially when normal temp turned out to be a healthy 4 bars when the stat was replaced and the heater actually produced heat!

Hello again.
More questions about the heating system! To my mind the car does not run hot enough although the temp gauge usually runs at the third bar, which I seem to think, is about right. Even so the heater is poor.
With the aid of ’Multiecuscan’. I drove to Liverpool and back whilst recording the water temp. When the gauge is on three bars then the engine water temp is 85 deg C. Going up the long hill from Manchester to Saddleworth moor, it went up to four bars and 88 deg. C.
When I got back I took the cap off the filler bottle and there is no pressure in it. I would have thought there should have been some. I’ve done this a couple of times and there never seems to be any pressure in the bottle. Is that because the water never gets hot enough? Does anyone know what the normal running temp should be?
Thanks again.
Chris.