direction of coolant/water flow???

**uninformed** · 28th July 2008, 02:43 PM

ok landrover techs,

on a 1998 300tdi landrover defender, you have a 5/8 hose coming out of the top of the head at the back and going into the heat exchange, then from the heat exchange you have a hose that runs along the head in metal pipe then joins back into the main hose (from the bottom of the radiator) that then heads into the water pump......

WHICH WAY IS THE WATER FLOWING?

#1 out of the main pipe into the heat exchange, then down into the top of the head....

OR

#2 up out of the head, into the heat exchange, out and into the main hose....

Serg

**Rosco** · 28th July 2008, 03:13 PM

I'm certainly not a techy .. far from it

. But the old rule of thumb was that water flowed from the top of the radiator into the engine. Hot water being less dense is forced up by the cooler more dense water. Hence if it was the other way round the water would be forced by the water pump to try to flow against the rules of physics. Remember the old thermal syphon idea with early Morries etc. Does that help ??

Edit .... so I would choose #2 ....

**uninformed** · 28th July 2008, 04:06 PM

doesnt the water flow from the thermostat housing into the top of the radiator? then out the bottom back up into the pump?

Serg

**Rosco** · 28th July 2008, 04:25 PM

Not as I understand it ... but I'm sure a techy will be along soon enough ..

**Blknight.aus** · 28th July 2008, 04:53 PM

the coolant flows roughly thusly

from the bottom fitting on the radiator it comes up into the engine via the pump.

the return hose from the heater that joins into that main hose is the return from the heater matrix

the coolant is circulated throught the block, head and with a diversion into the heater matrix back to the thermostat housing

if the thermostat is closed then the coolant diverts back around into the pump to recirulate and when its open then the bypass is closed and all flow is back to the top of the radiator.

not 100% but near enough for what you were asking.

if you want I can cut and paste the relevent rave sections.

**Rosco** · 28th July 2008, 05:11 PM

Originally Posted by Blknight.aus

...

not 100% but near enough for what you were asking....

Maybe not 100% ... but is does prove I was 100% wrong ...

........

**uninformed** · 28th July 2008, 05:59 PM

Originally Posted by Blknight.aus

the coolant flows roughly thusly

from the bottom fitting on the radiator it comes up into the engine via the pump.

the return hose from the heater that joins into that main hose is the return from the heater matrix

the coolant is circulated throught the block, head and with a diversion into the heater matrix back to the thermostat housing

if the thermostat is closed then the coolant diverts back around into the pump to recirulate and when its open then the bypass is closed and all flow is back to the top of the radiator.

not 100% but near enough for what you were asking.

if you want I can cut and paste the relevent rave sections.

so you choose answer #2?

Serg

d@rk51d3 · 28th July 2008, 06:38 PM

Yep, hot water from motor goes into top of radiator, cools in its way down to the bottom of the radiator and cooled water then re-enters the motor via the bottom hose.

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