Coolant loss

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tom1979

tom1979

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Evening all,

10P TD5 Defender - for some reason I am losing coolant out of the cap. I have tried two caps now both genuine so seems odd. Took it for a run with the bonnet off and for most of the time it's ok but under hard acceleration you can see the level rise and then starts spewing out.

Does anyone have any ideas? It's otherwise normal, no hard hoses etc.

Thanks
 
Is the expansion bottle plastic if so that could be the culprit. There may be a hairline split or cracking due to age. Under pressure this will show up. With old type being metal the seams eventually go.
 
saxavordian said:
Clearly the rubber seal not aligning to well. are you able to double up with a spare seal to add pressure.
Click to expand...

Is it normal for the coolant level to rise like that under acceleration though? There’s no overflow on the defenders, is it possible it’s just overfilled? I do make sure it’s at the cold level when it’s cold.

The clarify, it does not overheat. Even when the coolant starts spewing out the Nanocom shows normal temperature. The hoses are not hard when the engine is cold and not excessively hard when it's hot.

This was the allisport one with a new cap....

FF0B4508-1DF5-4877-BCD9-38A49E048B28.jpeg
 
Last edited:
That's very strange, watching the coolant flow diagram a logical deduction would be that there is excessive flow through the overflow pipe which can be caused by the thermostat's bypass valve stuck or restriction in the radiator... you should check somehow the flow through that pipe, e.g undo it from the tank, clog the port on the tank, direct the overflow pipe into a bottle and see ... there should'nt be serious flow through that pipe so if it is better replace the thermostat and flush the radiator.

btw i've seen cases when the thermostat was fitted the wrong way cos it's possible then the overflow gets pressure through the main valve and might cause such symptom, i'm not sure how the setup on the defender is but here's an example for D2 https://www.aulro.com/afvb/discovery-2-a/212384-thermostat-fitted-reverse.html
 
Last edited:
sierrafery said:
That's very strange, watching the coolant flow diagram a logical deduction would be that there is excessive flow through the overflow pipe which can be caused by the thermostat's bypass valve stuck or restriction in the radiator... you should check somehow the flow through that pipe, e.g undo it from the tank, clog the port on the tank, direct the overflow pipe into a bottle and see ... there should'nt be serious flow through that pipe so if it is better replace the thermostat and flush the radiator.

btw i've seen caes when the thermostat was fitted the wrong way cos it's possible then the overflow gets pressure through the main valve and might cause such symptom, i'm not sure how the setup on the defender is but here's an example for D2 https://www.aulro.com/afvb/discovery-2-a/212384-thermostat-fitted-reverse.html
Click to expand...

Does the bypass valve not open at something like 1500 revs? This is more when the engine is under hard load.
 
I think that the rpm is irrelevant if it's stuck closed and then the pressure in the overflow gets higher cos nothing bypasses that circuit and it gets full pump pressure ... though i'm just guessing here, you should check the flow through the return pipe cos what's certain is that it should not be too much
 
So I am going to change the thermostat today. I have a choice of either PEM101020 which is the 82*C "hard bypass spring" or genuine LR thermostat (somewhere, I bought it years ago). Which is better and what effect/benefit would the hard-spring version have? According to RAVE :

"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."

This suggests that a harder spring could put more pressure on the heater circuit? I would prefer the engine to run cooler hence why I got PEM101020

Edit: found what I thought was the genuine LR one and it seems I ordered the same part PEM101020 then as well o_O, only that this one is marked 82*C. Hope it's going to be ok!
 
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That PEM101020 was developped for freelander Td4 which is a bit different and had heating problems, if you want one to make the Td5 run cooler you need PEL500110, or fit genuine PEM100990.... i'd not fit that PEM101020 on a Td5 cos if it has a stronger bypass valve it's no benefit for cooling
 
sierrafery said:
That PEM101020 was developped for freelander Td4 which is a bit different and had heating problems, if you want one to make the Td5 run cooler you need PEL500110, or fit genuine PEM100990.... i'd not fit that PEM101020 on a Td5 cos if it has a stronger bypass valve it's no benefit for cooling
Click to expand...

The first thermostat I bought was advertised as “Thermostat with housing for Land Rover Discovery 2 td5 PEM100990 PEM101020”. Nothing about springs or temps but it is stamped 82*C, appeared to be a standard thermostat.

The later one I bought was advertised as a 82*C stat with “hard bypass sprint”, but the same part number PEM101020 and no temp stamp on the thermostat, and no mention of PEM100990

So which one to fit? I'm guessing the first one I got
 
Looking at the updated listing it just says "PEM100990" now, but PEM101020 is listed in the "part numbers for comparison" section. I think I'll fit that one for now and see, and order a genuine one as a spare.,
 
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