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Discussion Starter #1
02' 4.6 87,000 miles

No idea where the coolant is going!

You can fill it full in the morning, drive it all day, and the level will be the same when you come home. Doesn't matter if it is 50 miles or 500. Coolant temperature NEVER goes above 197f above 15mph, or 203f at a idle.

BUT..

You leave it overnight, and a litre of coolant will be missing...poof, just gone.

No coolant in the oil, none burning off in the exhaust. No white smoke in the morning. Cooling system pressure is fine.

No leak spots from the TBH, overflow tank, or on the ground.. At least not in the morning.


Before I start filling the cooling system with petrol and magnesium (to react to whatever water is left..), what should I do?

Will a pressure test help in this situation? I reckon I would find a leak with the cooling system hot and pressurized. But not an expert there.
 

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1995-2002 Range Rover P38A
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417 Posts
If you stick your fingers up by the passenger side ac outlet(little triangular thing)behind it feel for any anti freeze from your orings to the heater core. After you turn off the car the pressure is greater so that is the time to find the leak.
 

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Pressure test should show you the culprit. From your explanation, I suspect the expansion tank cap. Maybe the cap is slightly faulty and releasing fluid. It's trickling out the coolant, so the hot engine compartment may be evaporating whatever fluid that's been pushed out out of the cap.
 

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Optimistically I have the same problem. I noticed low coolant about one inch above the neck on the expansion tank. I filled it. About 100 miles later, it was down by the neck again. But no real coolant smell (anymore). I used K-seal to hopefully cure the leak that I suspect is head gasket. But, maybe it will stay at current level and run fine. Anyway, that's my story. I will watch this with interest.

xrav, would you post indicate a leaky heater core?
 

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If you are losing a litre of coolant overnight it has to be going somewhere. Heater core or O rings would mean it is soaking into the RH footwell so will probably be getting dangerously close to drowning the BeCM by now. Water pump seal can leak when not running but be fine while running but unless it is particularly hot where you are so it evaporates rather than leaving a puddle, I'd expect at least some of your litre to be visible on the ground. A pressure test may show you where it is leaking from but if leaking when parked after a run, the system will be pressurised anyway. One car I had was losing coolant, although nothing like the quantity you are losing, but not leaving a puddle. That was also not pressurising the system when hot. A pressure test showed that to be leaking through rusted core plugs.
 

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My guess would be that the coolant is not leaking out to atmosphere after engine shut off, but simply draining into the cooling loop from the expansion tank once the temperature of the coolant cools down sufficiently. So, there would be no puddle leading to a mystery coolant loss.

If the cooling system is not retaining a required pressure either due to a leak or a faulty pressure cap, the effective evaporation temperature of the coolant is reduced leading to expansion under normal operating condition. With faulty pressure cap, the expanded coolant is slowly leaked out through the purge pipe into the hot engine chamber, making detection of any remnant of coolant loss difficult to detect, as coolant evaporates into thin air.
 

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1995-2002 Range Rover P38A
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When you write fill it up I hope you mean fill coolant to the low level if engine is cold or to max when hot.

If you would top it up fully while cold the expansion tank will discharge the surplus coolant when hot. Therefore when cold the level is lower again. Where did it go? Strange...


But that’s not what’s happening here right?
 
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