Overheating TD5

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martin2107

New Member
Posts
18
Location
Southampton
Hi Guys,

We have just finished replacing the front shocks and rear air bags on our landy only to find that it is now overheating!

The heaters still blow out hot air but the temp. guage on the dash slowly creeps up whilst driving. Through fear of the blowing the head gasket the car is now permanently on the drive until we sort this problem!

The car went for an annual service and I noticied that when I turned the engine off after driving the car home there was a whirring / clattering noise which sounded like a fan slowing down. There was no noise before the service. We have flushed the radiator through as the radiator was not getting hot. The water flowed through the radiator until it was clear but unfortunately the car still overheats after this.

We are wondering if this could possibly be the water pump / coolant pump (same thing?) that has gone wrong?

Any help out there would be greatly appreciated as we need to know what is wrong before ordering parts to fix the car.

Thank you!

Chrissy.
 
martin2107 said:
Hi Guys,

We have just finished replacing the front shocks and rear air bags on our landy only to find that it is now overheating!

The heaters still blow out hot air but the temp. guage on the dash slowly creeps up whilst driving. Through fear of the blowing the head gasket the car is now permanently on the drive until we sort this problem!

The car went for an annual service and I noticied that when I turned the engine off after driving the car home there was a whirring / clattering noise which sounded like a fan slowing down. There was no noise before the service. We have flushed the radiator through as the radiator was not getting hot. The water flowed through the radiator until it was clear but unfortunately the car still overheats after this.

We are wondering if this could possibly be the water pump / coolant pump (same thing?) that has gone wrong?

Any help out there would be greatly appreciated as we need to know what is wrong before ordering parts to fix the car.

Thank you!

Chrissy.
Click to expand...

have you been off-road with it? could be the rad core is blocked with mud , is the engine actually getting very hot? could be a dodgy temp sender . worth a look ;)
 
sounds like the thermostat is stuck . how we usually build our discos is a custom built 5 core all metal radiator ,new thermostat and new waterpump , and we have not had any issues with them . i would at least do the thermostat and waterpump if i were you and maybe a new pressure cap . also check the fan clutch is good and the aircon fan if fitted ,is working .
 
dyte said:
Thermostat would be a good start if your not getting heat in the rad
Click to expand...

I agree, if the thermastat stays closed when the coolant raises to normal working temp, it will continue to raise giving the reading of overheating, simple fix and not to costly.
 
It seems as if the thermostat will be the easiest part to remove and check first. Is there any way of checking / testing a disco thermostat is working properly? I know the unit is sealed in a housing and cannot be dismantled any further.

If the thermostat is ok I guess the water pump would be the next thing to remove and check.
 
Hi Guys,

Quick update - we have now removed the thermostat. It appears to be working correctly as we poured boiling water through and after a few seconds the valve opended to allow the water through.

I am guessing that as we have ruled out the thermostat and the radiator as the cause of the overheating / cold radiator the only possible thing left to check would be the water pump?

Does anyone know if there is anything else that cold cause an overheating and cold radiator apart from a faulty water pump?

Thanks!
 
Take out the bleed screw, pull upwards the reservoir and lift it above the bleed hole, when a airless coolant flow comes out put the tank back, screw just partially in the bleed screw and start the engine. If the coolant will come out with a certain pressure there it means that the pump works...wait untill no bubbles are showing there and tighten back the screw.... if the pump is gone there will be no coolant pressure at the bleed hole.
 
martin2107 said:
Hi Guys,

Quick update - we have now removed the thermostat. It appears to be working correctly as we poured boiling water through and after a few seconds the valve opended to allow the water through.

I am guessing that as we have ruled out the thermostat and the radiator as the cause of the overheating / cold radiator the only possible thing left to check would be the water pump?

Does anyone know if there is anything else that cold cause an overheating and cold radiator apart from a faulty water pump?

Thanks!
Click to expand...

The whirry spinning down thing is likely to be your centifuge filter.

you cannot just pour hot water into the stat to test it as the thermostat has 2 parts to it and also a wide temp operating range compared to traditional stats. The operating range of the temp bit is 82-96 degs C and the bypass valve is opened once the engine revs exceed 1500rpm.
 
From Rave:

"Thermostat - Main valve

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)."​
However there is also the 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."​
 
Thank you for all your help.

Upon further investigation we may have found the source of the problem.

We tried the wire trick on the temperature sender to see if we had any jump in the temperature guage on the dash. Although the needle never moved when the wires were touched onto the engine block we did notice that with the temperature sender connected up normally and the ignition switched on the temperature guage on the dash was up quarter of the way.

The car has been sat for a few days in the artic weather so the temperature gauge with the ignition on should be right down at the lowest level.

Has anyone else experienced this issue before? I am guessing that this is indicative of a faulty temperature sender?
 
...and how is the gauge with the sensor unplugged and ignition on?

though this has nothing to do with the fact that the rad is cold wen the engine is hot

and by the way, dont mess with direct earth on temp sensor's plug cos on D2 it's connected to the ECU and the minimum resistance which it provides is over 100 ohm > "The ECT works as an NTC sensor. As temperature rises, the resistance in the sensor decreases, as temperature
decreases, the resistance in the sensor increases."
 
Last edited:
sierrafery said:
...and how is the gauge with the sensor unplugged and ignition on?

though this has nothing to do with the fact that the rad is cold wen the engine is hot
Click to expand...

With the sensor unplugged and the ignition on the guage dropped right back down to the bottom/zero.

We think we may have a sensor problem as well as the thermostat was sticking i.e. keeping the radiator cool. We filled the thermostat with boiling water and this did not open. It was only when we ran boiling water in over a few minutes did it finally open.
 
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