Heater hose connections, which way round?

[AJL Electronics]

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]

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?

[AJL Electronics]

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

[Roger Pennington]

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)

[Terry Rickard]

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]

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?

[Djangoz]

Apologies for resurrecting an old thread - but it may be of interest to note that my car MB60 does have the valve set up exactly as per the Middlebridge parts list online. Possibly the valve was introduced during production sometime between MB50 and MB60?
I was reading through the thread as I believe my valve does not fully shut off the flow of coolant - judging by our par-boiled lower limbs travelling to the Silverstone Classic recently in 34 degree temperatures!
The car did not overheat though - although the cooling fan ran almost continuously all the way from Cornwall!

[scimjim]

Is it possible that the valve is fitted to the return hose (meaning the heater matrix is always full of coolant at engine temperature)?

The small sports got a valve later in production which totally cuts flow.

Does your car have a two speed cooling fan? There’s something wrong if the fan is running while you’re moving at anything over 30/40 ish mph.

[Djangoz]

Hi Jim,
The valve is fitted in the hose which runs along the side of the right hand cylinder bank to the top connection on the heater matrix. I believed that to be the flow from the top of the engine but am always willing to stand corrected?

The fan is single speed 14” Revotec controlled by a capillary type adjustable switch fitted to the offside wing near the radiator (original Otter switch redundant). Generally set at “90 degrees” on the scale (accuracy questionable). Under normal circumstances it is absolutely fine - never coming on at normal road speeds. After a run it will come on if you are trickling through traffic or just doing say 15 to 20 mph. I think the exceptional ambient temperatures on the day together with slow progress through roadworks and diversions were to blame. Indicated temperature never rose above 100 degrees and no coolant loss so all is well I think.

[Djangoz]

OK - a follow up on this one. As previously mentioned, my Middlebridge MB60 has the heater valve set up as per the parts book.[image]

valve.jpg (67.58 KiB) Viewed 41 times

[/image].
It is leaking very slowly from the operating spindle and I will need to replace it but i don't want to disturb it for a few days as I want to use the car for the local noggin this week and also for a local show at the weekend. Looks like it was made by a German company called Mecano Bundy and I can't at the moment find one with the correct "handedness". All the ones on Ebay at present are wrong.

Does anyone with an MB with this set up happen to have one of these valves OFF their car and could tell me what size the inlets are? Maybe they are 13mm or 15mm? They appear to be stepped and I cant easily measure them as they are deep inside the hoses and I really don't want to disturb them until I have to - as I'll have to move the alternator to get the valve high enough to remove a hose without losing too much coolant and potentially getting an airlock.

Also - the Bowden cable from the heater control lever operates a rocker on the side of the heater casing which transmits the motion onward to the valve. Does the rocker on the casing operate a flap inside the casing controlling airflow in addition?

[scimjim]

It would be pointless cutting the supply of hot water AND having a flap inside the heater box to stop hot air - equally it may have been nugatory effort to take apart the heater box as supplied, to modify It?