Heater hose connections, which way round?

Post by **AJL Electronics** » Tue Nov 07, 2017 5:42 pm

To improve the heater you need to remove it and strip it. The foam on the flaps will have turned to dust by now and needs replacing. You could take the opportunity to replace the matrix too. Makes no difference which way round the pipes go, it is just the convenience of hose routing.

simmit · Post by **simmit** » Tue Nov 07, 2017 8:36 pm

AJL Electronics wrote: ↑
Tue Nov 07, 2017 5:42 pm
To improve the heater you need to remove it and strip it. The foam on the flaps will have turned to dust by now and needs replacing. You could take the opportunity to replace the matrix too. Makes no difference which way round the pipes go, it is just the convenience of hose routing.

But is it typical for Middlebridge not to have a valve in the hose between engine and heater?

Post by **AJL Electronics** » Tue Nov 07, 2017 8:45 pm

It is exactly the same as 6 series cars, no valve in the water feed.

Post by **Roger Pennington** » Tue Nov 07, 2017 11:06 pm

It's theoretically better from the point of view of heater efficiency, to not have a valve, as the heater matrix is always hot and ready to go as soon as the flap is open, rather than having a lag while hot water starts to circulate and heat it up. (of course it's efficiency may also be reduced if the matrix is blocked with 30-odd years of sludge, or the engine is over-cooled)

Post by **Terry Rickard** » Wed Nov 08, 2017 12:09 am

I know this is different to what is shown and that the hot outlet from the engine (from thermostat housing or back of inlet manifold if modified) usually goes in the top, but I now always fit the hot hose from the engine to the bottom heater pipe and plumb the top heater pipe back to the water pump.
This is because it is better and more efficient to push water in the bottom and let it come out the top to return to the engine – and the bonus is that it also pushes any air out and makes it easier to bleed the cooling system.
It is up to you which way round you fit your hoses, but I have found that 'in the bottom out the top' gives a far better heater (more heat into the car) and that it is much easier to expel the air from the system.
This applies to the SE6/6a/6b, GTC and MB heaters.

simmit · Post by **simmit** » Wed Nov 08, 2017 6:02 pm

Thank you gentlemen for confirming there is no valve. The Middlebridge parts book actually shows a valve and that completely threw me.

Only question remaining:- Is 30 degree flap movement on MB50 typical?