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MG MGB GT V8 Factory Originals Technical - Heater Valve for Rover V8??


I've a 4 barrel type manifold on my Rover V8 conversion, the hot water feed for the heater also heats the manifold. At the moment I have no way of turning off the heater without shutting off the flow through the manifold.

2 questions...... anyone know of a cable operated heater valve which will still allow a flow through the manifold and if I use a valve which shuts off this manifold flow, what will happen? Will it cause problems with poor running or unduly stress the water pump?

Guess I want some kind of by-pass valve, any suggestions?

Thanks

Andy
Andy

MK1 Golf from German and Swedish ?
RMW

Thanks RMW.

Looks like a good one, was a bit worried about not having a by-pass for the water pump, but I think it'll be OK!

Andy
Andy

Should be lots of cars. Look for a valve with 4 outlets. That switches from manifold only to heater first then manifold. My old subaru had a cable operated one.
PETER

This is a similar set up to the one I will be using. I wasn't sure of the function of the water through the manifold was to heat it or cool it - which is it?

Going back to Andy's OP - what are the consequences of shutting the flow off?
Liam

A small amount of water must flow through the engine and manifold while the engine is warming up and the thermostat is closed. Circulation ensures that heat is distributed evenly during this warm up time and you don't get red hot bits here and there, which is never good. During this period the mechanical thermostat is closed and no water is circulating through the radiator. Once the engine warms up the mechanical thermostat will open and water will circulate through the radiator and at that point the bypass become redundant.
The range rovers and RV8 have a outlet/plug just under the thermostat housing/radiator hose outlet which conects to the back of the pump via a small piece of rubber hose. Rovers and GM have (I think) an small inlet on the pump inlet.
Peter

Thanks Peter,

So the moral is - keep your heater going when the engine is warming up?

Have I got that right ?
Liam

Having the heater on shouldn't affect the warm up of the engine to any measurable extent. If anything it might delay the heatup a bit as it acts as a small radiator and would cool the water a bit. The purpose of the thermostat is to prevent flow through the radiator until the engine is up to normal operating temperature. Most heaters will tap off some flow to allow the driver to begin to heat the interior and demist before the engine reaches full temperature if wanted. The water pump pulls water from the bottom of the radiator and pushes it into the engine. When the thermostat is closed there is essentially no flow and the pump would cavitate and create excessive drag, the bypass hose just allows a bit of flow to help relieve drag on the pump and reduce cavitation. In addition the small amount of flow does help prevent 'hot spots' developing in the heads where the coolant could boil without some circulation. On most engines flow to the water pump is tapped off near the thermostat and returns to the inlet side of the water pump. For the most effective shut off the valve should be positioned in the supply line. This will prevent as much heat transfer through the coolant in the lines as possible.
Bill Young

Now that I've got my brain in gear, I realize a by-pass isn't needed for the heater valve and the Golf one will work fine!

Andy
a borris

If you've got a by pass plumbed in (you need to) then it's not a problem. If you've set it up without one, then you must leave the heater on while warming up (ie plumb one in asap).
The later range rovers and presumably the rovers, blanked off the thermostat bypass outlet on the manifold and instead used a vacuum operated "4 outlet" heater valves. These valves make use of the heater inlet and outlets off the motor as a thermostat bypass warmup circuit. When these valves are "heater off" they still allow a little water to circulate through the motor, "bypassing" the engine to radiator thermostat. When they are "heater on" then they just inclued the heater in the bypass ciruit. I didn't like the look of the 4 way heater valve (untidy, hoses all over the top of the rocker cover), and opted for the visually simpler RV8 style set up. Also MGB's don't have the range rover vacuum operated switches.
Since I used an earlier mid 80's front (same as the RV8) on a later 3.9 motor, I had to "unblank" the manifold bypass outlet and use that. As per RR 80's and RV8 design. I use just a single half inch cable operated ball valve for the heater (like the RV8).
Peter

Yes, the importance of a bypass in the cooling system is what prompted my original post.
I have a Offy manifold and that has a second small outlet on the thermostat housing feeding to the water pump which acts as bypass (it's always open!). That's the bit I had brain fade about!

Just got back V8 Conversions in Kent UK <http://www.mgcars.org.uk/v8conv/v8convs.html> he has a reducer hose pipe for the heater to water pump feed which works very well, replacing the metal pipe under the manifold. The metal pipe won't work with the lower aftermarket manifolds.

Andy
a borris

This thread was discussed between 11/01/2006 and 21/01/2006

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