Expansion Tank Temperature

[gingerprince]

Recently noticed my car leaking water from somewhere near the radiator. Had a closer look last night and I'm fairly sure it's the radiator itself (leak is coming from the top-centre of the radiator and running down, there's no pipes there and I saw kinda bubble where I guess it's seaping).

Anyway, whilst running the car to temperature to watch the leak, I noticed that the expansion tank wasn't getting hot. It seems that when the coolant heats up, everything is too hot to touch (swirl pot etc) but not the expansion tank. (it just feels like it's been warmed by the engine bay).

Now I'm not fully sure of the flow of things here, but should the tank actually get hot? I know it's not actually part of the "circulation" as such but I would have thought it would still get its fair share of hot water mixed?

I don't think it's blocked because I unbolted it and raised it when trying to remove the fans to inspect the radiator, and its level lowered as I would expect.

One thing I wondered about this - given that I've lost some coolant via the radiator (the swirl pot was about half full so I've topped that up), could air-locks in the system prevent the expansion tank from being fully in-the-loop?

I'm fairly sure there is air in the system, squeezing the top hose doesn't feel like it's "full" of water. I'm going to bleed it through tonight.

Sorry for lots of mish-mash questions, but you've probably guessed I'm not sure what is a problem and what is "normal"

[Ballistic Banana]

The expansion Tank is just that, where it kicks the extra water but should if the system is ok sit at the same level,doesnt get too hot like you say but still obviously pressurised.
Have you checked the swirl pot is Full too. people sometimes overlook this and think that along as teh expansion has water in it the Swirl pot will be ok.. not allways the case.

BB

[gingerprince]

Ballistic Banana said:

The expansion Tank is just that, where it kicks the extra water but should if the system is ok sit at the same level,doesnt get too hot like you say but still obviously pressurised.

Ah that's cool then, one less "symptom" to worry about!

Ballistic Banana said:

Have you checked the swirl pot is Full too. people sometimes overlook this and think that along as teh expansion has water in it the Swirl pot will be ok.. not allways the case.

Checked the swirl pot and it was about half full so I've topped that up.

[zippee]

I had exactly this problem recently and it turned out my thermostat was shot.
Was replaced and its now all working fine and heating up correctly.
Alternatively it may just be an air block.