Range Rover V8 Carb Heater water flow help required

[fenair]

Good Morning Ladies & Gentleman,
I am in the final stages of launching a new air conditioning kit for the 2 door range rover running 3.5 carb engines.
I have one concern that i get a conflict of views on, and those views are from lads half my age as to yeah its fine,
but i'm not so sure and the opposing conflict in my head continues,, so the issue i have is:

the original RRC heater had no water flow valve to control the flow, just a flap in the heater box to divert air so you modulated the air flow to get the desired temperature in the car, our system is a complete replacement for the heater box, with combi heat exhangers ( heat & a/c as one unit joined together), water is controlled by a electronic flow valve, so we connect to the two pipes ( one from the water pump and the return into the inlet manifold) to our system with one pipe ( return ) having the control flow valve in, now for my concern;

when the heater is in the cold position no water can flow back into the inlet manifold, will this cause problems with cooling of the block / head / manifold?
i understand water is present in the cylinder head and flows out through the open thermostat, but until the stat opens, does a small quantity of water flow through the inlet manifold and out into the water pump when the thermostat is closed? if so my heater valve is closed will not affect the cooling of the heads / manifold ? does the return flow from the heater simply join the flow from the block / head or is the heater route part of the circulation flow of the engine and have i stopped water flowing around the engine?

I have googled for days and can not find a definitive diagram to show the exact flow route, just generalised flow based around silhouetted engine diagrams and pipe work external on the engine, and that seems to relate to GEMS engines, which this is not.

So if someone with the knowledge of the Rover Carb 1978 engine cooling flow can either give me the news to sleep well tonight or frighten the life out of me that would be greatly appreciated.

Thanks in advance
Pat Foster
(Fen Air International ltd)

[SuperV8]

Some variants use the heater circuit as a thermostat bypass circuit, some have a separate bypass circuit.
I can't help on which exact version the old RRC uses - but I can say if it uses the heater circuit as a bypass this should NOT be closed off.

[fenair]

Some variants use the heater circuit as a thermostat bypass circuit, some have a separate bypass circuit.
I can't help on which exact version the old RRC uses - but I can say if it uses the heater circuit as a bypass this should NOT be closed off.

Thanks that was my fear, the client has one system installed and i questioned it at the time on the prototype, his fitter said yeah be alright.. but looking at my donor heap, i couldn't be sure how the water kept flowing when the stat was closed, my heater pipe goes in the rear of the inlet manifold, weather it T's into the block water flow returning back to the water pump or the flow actually comes out of the inlet into the heater, out of the heater and back to the water pump i dont know, this is what i am trying to find out which direction the water flows out of the water pump...

[SuperV8]

Any pipe connected to the pump is an inlet.

The pump sucks in the coolant - then the pump outlet is straight into the engine block. It then flows around the block and up into the heads, then into the inlet manifold.

Any coolant port on the inlet manifold is an output. An outlet port on the back of the manifold would be the heater input.

If there is a little pipe from the front of the inlet manifold to the back of the pump this is a thermostat bypass pipe.

[fenair]

Thanks, I do have a
Short pipe from manifold adjacent to the stat housing to the water pump assume this is the thermostat bypass?

Pipe connection to heater from the inlet manifold but also the other pipe runs under the inlet back to the water pump, so this must be a inlet into the pump from the heater.

If the heater flow is blocked water will exit the manifold to the closed valve, leaving the heater in a vacuum as the water has been sucked into the pump.

The short pipe from the front of the manifold next to the stat housing into the rear of the water pump must be the thermostat bypass then?

I have tried to put pictures up but with no success...

Thanks for your guidance here much appreciated.
Pat

[fenair]

Hope this shows the set up?

Pat

[SuperV8]

Thanks, I do have a
Short pipe from manifold adjacent to the stat housing to the water pump assume this is the thermostat bypass?

Pipe connection to heater from the inlet manifold but also the other pipe runs under the inlet back to the water pump, so this must be a inlet into the pump from the heater.

If the heater flow is blocked water will exit the manifold to the closed valve, leaving the heater in a vacuum as the water has been sucked into the pump.

The short pipe from the front of the manifold next to the stat housing into the rear of the water pump must be the thermostat bypass then?

I have tried to put pictures up but with no success...

Thanks for your guidance here much appreciated.
Pat

Yes, that short pipe next to the thermostat housing is the thermostat bypass.

Your heater circuit exit's the manifold at the back, into the heater matrix, then the heater return runs under the manifold into the back of the pump.
So you are fine to shut off this heater circuit.

The centrifugal coolant pump won't be able to pull any meaningful vacuum so don't worry about that.

[fenair]

Thanks, I do have a
Short pipe from manifold adjacent to the stat housing to the water pump assume this is the thermostat bypass?

Pipe connection to heater from the inlet manifold but also the other pipe runs under the inlet back to the water pump, so this must be a inlet into the pump from the heater.

If the heater flow is blocked water will exit the manifold to the closed valve, leaving the heater in a vacuum as the water has been sucked into the pump.

The short pipe from the front of the manifold next to the stat housing into the rear of the water pump must be the thermostat bypass then?

I have tried to put pictures up but with no success...

Thanks for your guidance here much appreciated.
Pat

Yes, that short pipe next to the thermostat housing is the thermostat bypass.

Your heater circuit exit's the manifold at the back, into the heater matrix, then the heater return runs under the manifold into the back of the pump.
So you are fine to shut off this heater circuit.

The centrifugal coolant pump won't be able to pull any meaningful vacuum so don't worry about that.

Many thanks for the help and advice on the matter, to get a second opinion now puts my mind at rest, I have seen P6 cars with heater taps but as the RR had not my concern was if there was a change on the earlier ones as to why smith's didn't fit a tap valve, as said the fitter lad said no worries, but he was not born when the P38 came out so i was looking for reassurance.. shows there are some bright kids out there who actually take a interest in what they are working with rather than just turning up and take the money.. many thanks once again. Pat

[ChrisJC]

Sorry to throw in a spanner...

So, the water enters the inlet manifold at the front. From there, there are a number of ways on:

Out the front via the thermostat to the top of the radiator.
Out the front via the thermostat bypass pipe into the water pump.

And there is another way that I believe is a problem, but really I need a carb manifold to look at.
There is a flow from the front of the manifold to the rear heater outlet via the carburettor 'tower'. The heater return is then just a pipe screwed to the bottom of the inlet manifold which returns to the pump.

So if you block the heater circuit, then there will be no water running through the carb tower, and you might get icing in cold weather.

Chris.

[garrycol]

On my 3.5 (now 4.6) carb engine.

The heater outlet is at the back of the inlet manifold and goes through the heater and rejoins the system at the bottom radiator hose via a T junction.

The combined coolant then goes into the water pump and back into the block and up into the heads etc and out the thermostat and into the radiator and a small amount back to the heater circuit.

Block the heater line and all is good - no impact on the system - the coolant that would have gone out to the heater just stays in the main system. Remember the heater system is about 10mm where the main top and bottom radiator pipes and systems are about 50mm diam.

So on the early carb 3.5 system blocking the rear oulet or the heater line will have no impact on the cooling of the engine.