The V8 Owners Forum -

With a Rover V8 3.5 with carbs which direction does the coolant flow? Out the inlet manifold through the thermostat into the top radiator hose, into the top of the radiator through the radiator, out the bottom hose and back to the water pump or is it vice versa?

I have a Rover v8 with the 4.0 serpentine timing cover where the water pump turns the opposite way to the V belt 3.5. In the system I have the water pump takes the coolant from the engine block, into the bottom of the radiator up through the radiator and out the top of the radiator, back to the thermostat and into the inlet manifold etc.

The problem I have is that because the thermostat is closed no hot water gets to it to open it - yes the thermostat is all OK - you can touch the thermostat housing and it is still cold when the radiator is boiling. If you touch the radiator end of the top radiator hose it is very hot as it should be but the thermostat end is cold because the thermostat is closed (because everything is cold) an not allowing hot coolant back to to the engine.

It is almost as if I need the thermostat in the bottom radiator hose.

Open to ideas.

Thanks

Garry

Simplest is to drill a 1/4 inch hole in the outside of the thermostat and position this at top to help air bleeding.

It will allow some coolant flow and allow the hot stiff to get to the thermostat and allow it to open

Ian

Ian Anderson wrote: ↑

Sat Sep 14, 2019 7:40 am

Simplest is to drill a 1/4 inch hole in the outside of the thermostat and position this at top to help air bleeding.

Hi Ian - thanks for that but I am not sure I follow - can you explain a bit further? For a dummy

Thanks

Garry

Like this
https://www.google.co.uk/search?q=pictu ... VdkZzhTNEM:

Ian

Ok got it now - thanks - my initial thought was you were referring to drilling a hole in the thermostat housing .

Cheers and thanks

Garry

garrycol wrote: ↑

Sat Sep 14, 2019 4:48 am

the water pump takes the coolant from the engine block, into the bottom of the radiator up through the radiator and out the top of the radiator, back to the thermostat and into the inlet manifold etc.

That doesn't sound right to me.
I understand it that hot water comes in the top and cools and then out the bottom, so the water outlet in the inlet manifold goes to the top of the rad and the rad outlet at the bottom goes to the pump inlet.

Are you running the thermostat in the inlet manifold or the separate P38/Disco one?

Maybe this might help.

https://www.landyzone.co.uk/attachments ... jpg.65691/

regards
scott

unstable load wrote: ↑

Thu Oct 17, 2019 11:59 pm

garrycol wrote: ↑

Sat Sep 14, 2019 4:48 am

the water pump takes the coolant from the engine block, into the bottom of the radiator up through the radiator and out the top of the radiator, back to the thermostat and into the inlet manifold etc.

That doesn't sound right to me.
I understand it that hot water comes in the top and cools and then out the bottom, so the water outlet in the inlet manifold goes to the top of the rad and the rad outlet at the bottom goes to the pump inlet.

Are you running the thermostat in the inlet manifold or the separate P38/Disco one?

Yes, I agree doesn't sound right - it doesn't matter which direction the pump turns - in both versions (V-belt and serp) the coolant flows in to the pump from the bottom radiator hose (where it's coldest) - through the engine - and out the top hose into the top of the rad (where its hottest).

I presume you must have a remote thermostat housing in the bottom hose? as I find it difficult to understand how if you had a thermostat in the inlet manifold (top hose) that it could be cold when the engine is hot!
So presuming you do have a remote thermostat in the bottom hose? then there should also be a bypass hose from the inlet manifold outlet (hot) into the thermostat housing so the housing can 'sense' engine temperature and bleed the cooler rad coolant into the engine and so coolant still flows when the thermostat is closed.

Tom.

Appreciate this was a while ago.....But while searching through a few threads I thought it may be useful for others to bottom it out.

From recent experience with the cooling system on a gems type manifold, with crank driven oil pump.

The flow does indeed go to the bottom of the rad, then out from the top direct to the non active side of the thermostat, and into the inlet manifold.
What I found was there is potential for an air pocket behind the thermostat (i.e.in the inlet manifold), if you have a pocket at this point then the thermostat wont open, and you will be left scratching your head wondering why the engine wont cool. There is on many cars a by pass that goes from the top of the rad to the inlet manifold bypassing the thermostat, but even with this, it is still possible to have the air pocket. Solution for me was to fill the coolant system via the head tank, then finish the filling via the thermostat housing where the bypass hole in the thermostat is enough to all you to fill the air pocket.

Hopefully, this may help someone in the future suffering from the same air related issues.

jenko wrote: ↑

Tue Jul 07, 2020 1:05 pm

Appreciate this was a while ago.....But while searching through a few threads I thought it may be useful for others to bottom it out.

From recent experience with the cooling system on a gems type manifold, with crank driven oil pump.

The flow does indeed go to the bottom of the rad, then out from the top direct to the non active side of the thermostat, and into the inlet manifold.
What I found was there is potential for an air pocket behind the thermostat (i.e.in the inlet manifold), if you have a pocket at this point then the thermostat wont open, and you will be left scratching your head wondering why the engine wont cool. There is on many cars a by pass that goes from the top of the rad to the inlet manifold bypassing the thermostat, but even with this, it is still possible to have the air pocket. Solution for me was to fill the coolant system via the head tank, then finish the filling via the thermostat housing where the bypass hole in the thermostat is enough to all you to fill the air pocket.

Hopefully, this may help someone in the future suffering from the same air related issues.

Not sure I follow,
GEMS V8's have a separate thermostat housing in the bottom hose - but still have the same basic coolant flow path - out of the top of the engine.

https://www.google.com/url?sa=i&url=htt ... AdAAAAABAD

Unless Im getting gems confused (quite possible), but I dont think this is the case...The thermostat housing sits directly on the front of the inlet manifold.

Just did a quick search for gems thermostat housing to see if it came up with differnt types....Indeed it does!!!!. The one I have is this:
So all of the info above is based on the system I have:

I think there's some confusion here.

On all the engines, the water comes out of the top hose, down through the radiator, and back in via the bottom hose.
Then it goes into the pump, backwards into the block, up into the heads at the rear of the block, and finally forwards through the inlet manifold.

On GEMS, (and Thor), the thermostat is in the bottom hose, so what looks like a thermostat housing should be empty.

On earlier engines, the thermostat is at the front of the inlet manifold where the outlet is for the top hose.

That picture of a thermostat housing is not for a GEMS engine, it is for an EFi engine with air-con.

The heater circuit and thermostat bypass 'miss out' the thermostat and radiator, but the circulation path and direction is otherwise the same.

Chris.

jenko wrote: ↑

Tue Jul 07, 2020 2:14 pm

Unless Im getting gems confused (quite possible), but I dont think this is the case...The thermostat housing sits directly on the front of the inlet manifold.

On GEMS and Thor that is just an empty elbow directing coolant into the top of the radiator.
The actual thermostat (number 2) is a plastic remote housing in the bottom hose with connections to the bottom of the radiator, bypass circuit, heater circuit and pump inlet.
cooling_GEMS by Tom Cranmer, on Flickr

Further clarification regarding my previous clraification....

Ignore...Im talking complete bo!!ocks......a number of ill informed websites led me to belive the flow direction...they are wrong!!!!.

I hang my head in shame