disco 2 coolant problems - help !

andtee said:

Guys
message from Holland
I have an 1999 td5
I recently put in a new radiator; because the old one leaked
Since then the system is throwing up the coolant and the radiator doesn't get warm. We put in a new thermostat still the same problem.


The pump works, when cold you can see it running in the reservoir ! It's pour's out of the air screw ! So works fine

It still looked like that the thermostat doesn't open !
The coolant boiles but the temp. sign at the dash stays right in the middle !
anyone any idea what it could be ?
Thanks a lot

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Thermostat - Main valve
The thermostat is used to maintain the coolant at the optimum temperature for efficient combustion and to aid engine
warm-up. The thermostat is closed at temperatures below approximately 82C (179F). When the coolant
temperature reaches approximately 82C the thermostat starts to open and is fully open at approximately 96C
(204F). In this condition the full flow of coolant is directed through the radiator.
The thermostat is exposed to 90% hot coolant from the engine on one side and 10% cold coolant returning from the
radiator bottom hose on the other side.
Hot coolant from the engine passes from the by-pass pipe through four sensing holes in the flow valve into a tube
surrounding 90% of the thermostat sensitive area. Cold coolant returning from the radiator, cooled by the ambient air,
conducts through 10% of the thermostat sensitive area.
In cold ambient temperatures, the engine temperature is raised approximately 10C (50F) to compensate for the heat
loss of 10% exposure to the cold coolant returning from the radiator bottom hose.
By-pass flow valve
The by-pass flow valve is held closed by a light spring. It operates to further aid heater warm-up. When the main valve
is closed and the engine speed is below 1500 rev/min, the coolant pump does not produce sufficient flow and pressure
to open the valve. In this condition the valve prevents coolant circulating through the by-pass circuit and forces the
coolant through the heater matrix only. This provides a higher flow of warm coolant through the heater matrix to
improve passenger comfort in cold conditions.
When the engine speed increases above 1500 rev/min the coolant pump produces a greater flow and pressure than
the heater circuit can take. The pressure acts on the flow valve and overcomes the valve spring pressure, opening
the valve and limiting the pressure in the heater circuit. The valve modulates to provide maximum coolant flow through
the heater matrix and yet allowing excess coolant to flow into the by-pass circuit to provide the engines cooling needs
at higher engine rev/min.

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andtee said:

stat is new and tested
rad is also new

at what temp is the stat opening ?
what to do about the airlock
we filled here up with the reservoir lifted up 10 cm !

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sierrafery said:

are you sure you didnt mix the pipes when you fitted the stat as it could happen to fit it as the main flow to go to the bypass valve and vice-versa, you have the flow diagram attached ckeck it out, about the stat

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listerdiesel said:

Both the Discovery 2 engines habe a bleed needle in the header tank that take air out of the top of the radiator and back to the header tank.

You can see the needle through the header tank filler cap, it is not removable.

If the needle gets blocked, air can remain in the main coolant flow and will cavitate the water pump if enough is there.

It is a very small orifice so that water doesn't flow through at significant volumes, and you'll need compressed air or a rad flush liquid forced through to clear it out.

When clear, you can see bubbles being released from the needle for a short while.

Mine was clogged with water scale, the result of not using the proper coolant by the previous owner.

The pipe runs from top right of the radiator, across under the fan guard and along the battery box and up to the header tank.

Peter

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RAVE said:

Excess coolant created by heat expansion is returned to the expansion tank from the radiator bleed pipe at the top of
the radiator. An outlet pipe is connected into the coolant pump feed hose and replaces the coolant displaced by heat
expansion into the system when the engine is cool.

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sierrafery said:

i agree with everything you said except the bolded part... IMO that's not for air but for excess of coolant due to heat expansion and coolant recirculation:

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sierrafery said:

undo the bleed screw and push the throttle...if it squirts coolant out hard the pump is good... if not then it's fubar'd

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sierrafery said:

i agree with everything you said except the bolded part... IMO that's not for air but for excess of coolant due to heat expansion and coolant recirculation:

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