Thread: Rover V8 - Direction of Coolant Flow

Originally Posted by 101RRS

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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.


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or in the opposite direction.

Thermo has the temp sensing bulb bit .. inside the engine.
If that's 'cold', then the hot water coming from the rad won't get to it because it's on the wrong end of the temp sensing bit.

Not sure(can't remember) the design of the thermostat housing and if it will allow you to fit the thermostat the 'wrong way' .. so to speak.

Can't see it working TBH.
Problem is, you're getting the radiator hot to allow it to open the thermostat, which is the wrong way to run a cooling system.
Rad is there to cool the coolant and thermo then opens to allow that cooler coolant to cool the hot bits behind the valve.

So yeah .. an inline type thermo between water pump outlet and the inlet to the radiator.
This is how it's set up on D2's anyhow .. with those strange potato looking multi pronged thermostats .. that many folks have removed to use an inline type.

Have a look at the D2 thermostat(if you never seen one) .. connects to hoses down near the steering box. Could be adapted to suit your needs if you had too.
The bypass port should be easily blocked if needed to suit the application.

Thermodynamics is important - hot water into top, sinks as it cools, cool water into block, rises as it heats up.

Trying to force it the opposite way - destined to fail.

Originally Posted by Tombie

Thermodynamics is important - hot water into top, sinks as it cools, cool water into block, rises as it heats up.

Trying to force it the opposite way - destined to fail.

Ok, and not directed solely to Tombie, so in a D2 4.0 V8 do you know what the direction the coolant is supposed to go - the logical way from the top of the engine to the top of the radiator or the way mine seems to work from the bottom of the engine to the bottom of the radiator and back via the top radiator hose.

This is my layout
My Truck Serp layout.jpg

And this is a standard layout
SAM_9266_zpsmbglsqus_LI.jpg

So essentially the serp layout is the same.

So on the standard layout does the Yellow pipe go straight to the top of the radiator? Does the Red pipe go to the bottom of the radiator with the thermostat (purple) on the lower hose? If so this indicates the circulation in a V8 D2 has hot water from the engine into the bottom of the radiator and cooler water out the top into the inlet manifold and then through the block back to the water pump.

Comments? I need to be set straight so I can fix.

Thanks

Garry

Attachment 154180
The purple pipe should send hot water to the thermostat.

Phil - Thanks for that diagram. Shows the flow should be conventional - top to bottom and discounting the odd thermostat arrangements should be working for my 3.5 inlet manifold and older thermostat arrangement.

So I am not sure why the bottom radiator hose and the radiator gets warm while the top radiator hose, thermostat and its housing stays cold. Once the thermostat does open all is good - it is just that the engine gets real hot until it opens - not good for a RV8.

I need to investigate further.

Garry

Real hot? Using a laser what are you calling real hot?

Originally Posted by 101RRS

..... Once the thermostat does open all is good - it is just that the engine gets real hot until it opens - not good for a RV8.

I need to investigate further.

Garry

slow acting(or old) thermostat?

I changed the thermostat in my Tdi a little while back and did some testing.
The original Waxstat was much slower reacting and when it did react(at >90°C) the opening was a millimeter or so.
Would finally fully open, but took many minutes(4 or 5 mins).
The Tridon thermostat I replaced it with was much earlier reacting(about 80-ish), and fully open with nearly a 10mm opening at about the mid 80's and by the high 80's over 10mm gap.
Faster acting and better flowing.

I see this now in lower general temps of about 80-83°C(on the digital gauge), and if it does get up into the high 80s' or 90° .. it also returns back into the mid 80's a lot quicker than it used too with the waxtsat.

Radiator blockage? What condition is the rad?

Originally Posted by Tombie

Real hot? Using a laser what are you calling real hot?

Enough to boil the correct mix of green coolant and lift the pressure relief valve in the radiator cap and my Engine Saver alarm showing 120c on the heads when normal running temp is 75 on the heads.

cheers

Garry