Aston / V8 4.7 Vantage / 2011 / Losing coolant

[Castello_Vantage]

Hello,
I have a problem with my Aston Martin V8 4.7 L Vantage S / 2011.

When the car heats up, the coolant immediately disappears
(it leaks through the overflow hose behind the left front wheel).

The car heats normally, and the hoses are not hard.

I tried ordering a new thermostat, but it does the same thing
(the water immediately comes out through the overflow hose).

Does anyone have experience with what this might be?
Thanks

[Calinours]

Castello_Vantage said:

Hello,
I have a problem with my Aston Martin V8 4.7 L Vantage S / 2011.

When the car heats up, the coolant immediately disappears
(it leaks through the overflow hose behind the left front wheel).

The car heats normally, and the hoses are not hard.

I tried ordering a new thermostat, but it does the same thing
(the water immediately comes out through the overflow hose).

Does anyone have experience with what this might be?
Thanks

Try a new coolant expansion tank cap.

https://www.pistonheads.com/gassing/topic.asp?h=0&...

[CatalystV12V]

Exactly what I had on my V12.. radiator cap… but don’t spend £90 on yours as I did, there are cheaper alternatives.

[Go60 Jay]

That’s so strange, mine started doing the exact same thing tonight. I had taken the expansion cap off to check the level. Later in the evening I saw it rapidly dripping water from under the car.

The coolant appears red/pink. Can I top it up with any red coolant for now, until it gets serviced in a couple of weeks?

Thanks,
John

[Go60 Jay]

Out of pure interest, how/why does the expansion cap cause coolant to leak out of the overflow pipe?

Thanks,
John

[Jon39]

Go60 Jay said:

Out of pure interest, how/why does the expansion cap cause coolant to leak out of the overflow pipe?

Thanks,
John

I have not looked closely enough, but are the expansion chamber caps similar to traditional radiator caps?
In other words, they maintain a pre-determined pressure within the coolant system. As they get old, the cap becomes weaker and less pressure occurs. Lower pressure permits the coolant to become too hot, expands and overflows.

Whilst talking about fluids under the bonnet, I don't like the arrangement of the windscreen washer container. Cannot see the contents to judge the level. Does a warning appear on the dashboard to indicate low level? I have never topped up the fluid, but can imagine the first indication that it is full, is when that long tube overflows making a mess. Any comments?

[Calinours]

Go60 Jay said:

Out of pure interest, how/why does the expansion cap cause coolant to leak out of the overflow pipe?

Thanks,
John

It’s a closed/pressurised system and the spring in the cap determines the maximum possible pressure within the closed cooling system.

Pressurised systems often run at above atmospheric pressure due to localised nucleate boiling in the water jacket close to combustion chambers. It’s the temporary liquid-gas phase change that results in a pressure rise within the system, and the pressure itself helps to collapse the nucleate steam bubbles as the coolant moves to a cooler area. The expansion tanks permit slightly varying mixed-phase status according to conditions and how hard the engine is working. The pressure cap on radiator (old) or expansion tank (new) simply governs peak allowable pressure within the system.

It’s just a spring and diaphragm - and they do fail, so trying a new expansion tank cap is usually a good start point.

[LTP]

Calinours said:

a lot of good, sciency stuff

But didn't add that there are two valves in a pressure cap. One (as Calinours outlined) controls the pressure inside the system and allows excess coolant (from expansion) to flow over into the expansion tank, and excess gaseous pressure in the expansion tank (caused by the hot overflow coolant flowing in) to escape to atmosphere.

However, there is also a second valve in a pressure cap operating the opposite way that allows gas (expansion tank) or coolant (radiator cap) to flow back in as the system cools down to avoid creating a vacuum and collapsing hoses.

Not all expansion tanks have a pressure cap. If anyone is interested
https://www.youtube.com/watch?v=jkhYt-OaipE

[Go60 Jay]

Hi all,

Cracking replies, thank you.

Luckily all is well with mine. I had replaced the water pump but had to remove a radiator hose to allow enough room to. Take the pump out. Anyway, I think I must have caused an air lock and somehow the back pressure caused fluid to flow out the system. I may be completely wrong, but after topping the system up and running it with no cap and then the cap back on, all is fine again. Done about 200 miles and it’s spot on.

Cheers,
John

[stevenichols]

Re. Washer bottle. Yes, there is a level switch that causes a warning to appear on the dashboard. The switch is quite high up in the tank so if it comes on you still have some left. I had a split in the rubber hose that connects the filler to the tank, so ended up with fluid over my shoes when filling!