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Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 14:01
by Fun.
Hi All
My expansion tank / header tank is full yet my top up tank (behind the number plate) contents are gone even after a 10 mile round trip. I have topped up to the max with water and then set off on short journeys twice this weekend and it's happened both times. Should I be worried? The expansion tank level has remained the same.
Any help appreciated.
Fun.
Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 14:56
by itchyfeet
Fun. wrote:Hi All
Should I be worried?
Fun.
yes, any fault with the cooling system is a potential problem waiting to happen.
Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 15:20
by Fun.
Thanks for your brutal honesty

Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 15:28
by slowcoach
It's going somewhere then- either a leak from a pipe join, or it's being blown out the exhaust via a gasket leak. Can you have a good crawl underneath while it's running, and see if you can spot any leaks?
Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 16:32
by itchyfeet
try driving 1 mile stop and check while engine running thenn drive another and stop to check etc. and see if its consistant.
I didn't think it drew from the top up tank until it cooled down.
I wonder if the top up tank is cracked.
Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 18:43
by Mocki
Does it only empty when the engine is running ?
By nature of the beast it should o lay empty as the engine is cooling down , so either the tank is split, the hose is split , or the cap is faulty
The engine running causes pressure to build up in the header tank , which would fill rather than empty the top up tank until the pressure becomes a vacuum as the coolant cools
Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 20:59
by Fun.
Thanks for getting back to me, unable to check things out tonight now but will look into it after work tomorrow.
I’ve had a look and think I can see a small crack in the expansion tank which won’t be helping at all I’m guessing.
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Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 21:03
by Mocki
Just to check, so we don’t get crossed wires,
Header tank is only accessible by lifting the lid off the engine bay , and has the pressure cap ,
Top up tank is behind the numberplate flap and is not pressurised .
Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 21:30
by Fun.
Yep, that’s exactly the right page
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Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 21:32
by Mocki
So which tank did you think may have a crack in it ?
Re: Top up tank empty after 10 mile round trip
Posted: 02 Sep 2019, 21:32
by Fun.
The header tank.
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Re: Top up tank empty after 10 mile round trip
Posted: 03 Sep 2019, 08:00
by jas915
My header tank got a small crack,but only leaked once coolant was warm.i would suspect a leak from the top up tank,as previously said the top up tank should in theory fill up a little when driving then empty slightly when cooling.could maybe try not filling the top up tank and go for a drive and see if the header tank level changes much,check regular as you don't want the header tank running dry.
Re: Top up tank empty after 10 mile round trip
Posted: 03 Sep 2019, 08:58
by Fun.
Thanks for all the suggestions, should get a chance to take Daisy out for a bit later and see what happens.
Re: Top up tank empty after 10 mile round trip
Posted: 03 Sep 2019, 12:39
by jas915
Where shouts in fife are you? I'm in cupar maybe I could come have a look?
Re: Top up tank empty after 10 mile round trip
Posted: 03 Sep 2019, 13:18
by Fun.
I'm in Dalgety Bay. Not exactly a short drive... You're more than welcome to venture this way though, don't want to sound ungrateful.