Bizarre cooling issue ???

Happy new year to you all. I am looking for some help again lol. My cooling system still is not right no over heating at all just done a 2000 k trip with no problems however I am paranoid so I keep lifting the bonnet to check coolant level. On the main 1000 k run nothing wrong coolant level good the next day when cold. Did a short trip over to Germany and back the next day my expansion tank was about 2.5 inches a pice the max mark ???? So bled the system all ok for a few days then it did the same thing again ???? So bled again all ok did the 1k trip home runs like a dream next day coolant level high I did start the engine on all occasions to see if the level would drop but It did not. On the last occasion the level returned to normal. All through the trip every time I stopped the cooling fans came on with in a minute at full pace this is annoying.the bottom pipe is always stone cold. I saw that there was a mod I could do on the thermostat by drilling a 3mm hole to allow some coolant to pass what are your thought on this !!!!!. Could I have a blockage Anywhere the engine is new expansion tank new cap new thermostat 1.5 years old now I appear to have no leaks. Any advice would be greatly appreciated i await your wisdom thanks in advance.

Darrenbunn6969,

I have this with my L Series - ie check the coolant and its OK, check it again and the bottle is empty. I know the heater matrix leaks and the expansion bottle has some cracking on it.

I put it down to how hot the engine has got, how much pressure has built up in the cooling system etc - maybe even whether the heater has been on.

When the temperature gauge sits in the middle, this covers a range of temperatures, so even if the gauge says the same from 1 journey to the next, its possible the coolant may have got up to different temps/pressures.

I should add that as time has gone on, its more likely to have dropped.

Is the pressure cap holding? And are there any cracks in the expansion tank, which can open up under pressure.

Nodge68 said:

Is the pressure cap holding? And are there any cracks in the expansion tank, which can open up under pressure.

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Hi Nodge the expansion tank is brand new no cracks and a new cap fitted just before I set of on my trip

Darrenbunn6969 said:

Hi Nodge the expansion tank is brand new no cracks and a new cap fitted just before I set of on my trip

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Ok. It can take quite a few drive cycles to expel all the air in the V6 engine. It has quite a few spots where air can get trapped. This causes quite large swings in coolant levels in the reservoir.

Darrenbunn6969 said:

Hi Nodge the expansion tank is brand new no cracks and a new cap fitted just before I set of on my trip

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I had overheating problems with a Disco V8, a mechanic pressure tested the expansion tank cap and it was caput. So he ordered a new replacement. When that arrived he pressure tested that before fitting it, and it was even more caput than the old one! The next new one was OK. Just a precautionary tale.

GrumpyGel said:

I had overheating problems with a Disco V8, a mechanic pressure tested the expansion tank cap and it was caput. So he ordered a new replacement. When that arrived he pressure tested that before fitting it, and it was even more caput than the old one! The next new one was OK. Just a precautionary tale.

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I have 5 new caps call me paranoid lol none of them seem to make any difference????

Nodge68 said:

Ok. It can take quite a few drive cycles to expel all the air in the V6 engine. It has quite a few spots where air can get trapped. This causes quite large swings in coolant levels in the reservoir.

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Is this anything to be worried about ????

Darrenbunn6969 said:

Is this anything to be worried about ????

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The only time I'd worry is if the coolant blows out the tank, or the coolant disappears rapidly.

Nodge68 said:

The only time I'd worry is if the coolant blows out the tank, or the coolant disappears rapidly.

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Thank you Nodge