Expansion tank.....or something else?

Hi Everyone

I have a split expansion tank on my 300tdi. Split along the seam - not noticeable unless the engine is up to temperature at which point the coolant starts bubbling out.

Searching on the forums and read it is a fairly common failure point so have ordered a new tank.

However, I got thinking and am now concerned there may be something more sinister going on!!

Defender was off the road for a few months while I did a lot of jobs on it. Cooling system wise I replaced the hoses and radiator and refilled with new coolant. After noticing the leak I wondered if it blew due to air in the system so have subsequently bled it all through again.

Any thoughts??

I'd replace the tank and then keep an eye on it. Probably just a failed tank, it's not unknown.

zeaphod said:

I'd replace the tank and then keep an eye on it. Probably just a failed tank, it's not unknown.

Click to expand...

Cheers! I'll change it tomorrow when it arrives. I'm hoping I don't have to drain all the coolant AGAIN to change the tank??

Very common fault especially if your tank is the one made of black plastic. I wouldn't worry. No you don't need to drain the coolant. Just siphon out the coolant in the expansion tank with some rubber hose and store it in a clean container, remove the hoses from the coolant tank and tie them out of the way keeping them raised above the engine, fit new tank, fit hoses and top up. You shouldn't lose more than a couple of hundred millilitres of coolant that way at most.

I drain the system using the same method. Works every time. After draining the expansion tank, I shove a length of 10mm hose down the radiator hose that I would have just disconnected from the expansion tank and siphon that out. I usually drain about 5 litres in that manner. Then I remove the said 10mm hose, position the container under the vehicle, direct the free end of the bottom hose into it and let gravity do its job. Mess-free and if you need to re-use the coolant, you may do so (provided that the container you drained it into is clean).

Thanks Reiny!