Had the reduced engine performance message so replaced the auxiliary coolant pump and voila the message is gone. BUT now I'm loosing coolant somewhere, can smell it but can't see where it leaks. We checked the pipes we took off and put back onto the new pump and it's not leaking there.

Im going on a 3500km trip within the next 2.5 weeks with caravan and now this - so frustrating - any idea what it could be or should I rather send it to workshop to have a look

I would use some absorbent paper like kitchen roll & wrap it around whatever you can - that should help narrow down where it's coming from

UV dye kits aren't expensive.

How much are you losing? If it's not much the smell might only be from spillage when you changed the pump.

it seems to be quite a bit - about 500ml on 750kms and then another 100ml or so within the last 60kms.

Before I never had to fill it up. I have triple checked the pipes that we've loosened to see if it leaks there but nothing - nada?

simple question but can it be that the previous auxiliary coolant pump did not let water through?

if its leaking at the bleeding nipple on the coolant reservoir will it dry so quickly that one cannot see it after driving; however it does not leak when the car is idling.

As i said aargh?! as I've just had a dual battery system installed in the car with plugs for the fridge/freezer and a 4-way USB plug and now this

I had a loss of coolant that was rather random. Was a small prick in corner of rad, could only see it when I did gearbox service, worth a look, aux pump shouldn't stop water flowing through it if duff, just won't pump it.
Expansion tank not splitting when hot? Seems reasonably common among the seam, then closes up and your can't see it.. 2003 4.4 Adriatic Blue FF

Just pop down your local garage and ask them to pressure test it, they just pump air into the system to raise the pressure, simulates driving at speed whilst stationary, should show up where there is a leak... Pete
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