TR6 Heater Flow

[PJM]

I have noticed that the heater in my 6 does not appear to be as effective as the one in my Spitfire 1500. Whilst browsing the Rimmer catalogue I noticed that the drawing shows the heater supply and return hoses as crossing over in the drivers footwell. My hoses do not cross over so am I reversing the water flow through the heater and therby affecting the flow rate or efficiency? I believe the heater matrix is fairly new.

[vanflyer]

The actual direction of flow through a finned heat exchanger will not adversely affect the heat output, although it is normal to put the hot water which is less dense in to the top of a heat exchager and let the cooler denser water out of the bottom, this way there is less mixing due to the cooler water trying to sink to the bottom of the matrix. The cross over, is I believe to put the flow from the pump, into the top of the matrix to aid air removal, as the pump at this point is still developing head or pressure, the matrix will have quite a bit of head loss so when the water comes out of the heater the pump has very little pressure left, the effects of thermo-syphon take over. I would think that there is air trapped in the heater and that it needs to be purged. I would also change the hoses over. I know on my heater it still has the warning label about not being able the completely drain it so by inference i would think that all of the air cannot be easily removed either. These heaters are pretty good compared to some cars I 've driven.

[Richard Crawley]

Have you checked the heater valve in the cylinder head is actually working or not blocked?

[PJM]

Thanks for the advice, I have fitted a new heater valve and flushed both the radiator and heater matrix prior to adding anti freeze at the back end of last year. I shall try swapping the hoses over to see if it makes any difference.