Expansion tank query

[widdowson2008]

Expansion tank - sawn in half - (ignore red lines - they are mine showing interconnection channels between cells)


Enlarged view of inlet/outlet pipes (circled red in pic 1)


Further enlargement of mystery bit


Not quite what I expected the inside of an expansion tank to look like - split into cells.
However, on a closer look, fitted to the outlet pipe (on the inside of the tank) is what looks like some sort of valve.

Has anyone any idea as to what this could be? and what it is for?

[mikeonb4c]

The cells are - at a guess - internal baffling intended to stop the contents from surging and slopping about. No idea what the valvey thing is

[Northern Bongolow]

hi steve, could it be a filter type gadget to stop solids entering cooling system.cheers jamie b

[dave_aber]

I think you may have gone a bit far there - Haydn's instructions say that you just drill one small hole!

[g8dhe]

Does it move push / rotate at all Steve ? Any idea what the metals are ?

[Diplomat]

Could the mystery item be either a magnet to attract ferrous particles
...or perhaps an anode to prevent corrosion?

Maybe a sensor for a low coolant alarm that was never developed.

[g8dhe]

Snap! but it doesn't look like one of the normal materials zinc / magnesium / aluminium and it would need to be connected electrically to the chassis to allow a current to flow.

[haydn callow]

It's NOT a valve or restriction of any type.....In fact I don't think the 2 tanks I have, have that in there ???
I supposr it could be the above....but defo not got em' in my 2 tanks...I can push a coat hanger right inside mine with no obstruction.

[widdowson2008]

Afraid I have no idea what it is - can only hazard a guess ( and that's dangerous), the following is what I have gathered so far.
Mike - internal baffling intended to stop the contents from surging and slopping about - Fair comment.
jamie b - filter type gadget to stop solids entering cooling system - Fair comment.

dave aber - ............oops - don't tell Haydn
g8dhe - Does it move push / rotate and material - I don't actually have one to physically take to bits so dont know. Material - been told its a brassy thing
Diplomat - Magnet? - have asked the question myself but not got a reply yet

If you take a closer look at the 3rd pic, you are looking at the return to heater circuit pipe. Now look at the pipe size compared with the brass bit (which is smaller). Not much room for coolant to pass through.

To be sure, I would like to examine one. I have asked around for an old one which could be donated for dissection but have drawn a blank. Is there anyone willing to donate one to be butchered?

[rita]

Hi widdowson2008,

Do you know what Make/Model/and Year of vehicle that this ET belongs.?

[widdowson2008]

Hi widdowson2008,

Do you know what Make/Model/and Year of vehicle that this ET belongs.?

Sorry, I don't, but I will ask the question.

You may have a valid point here - I should have checked.

MEL?

[widdowson2008]

When I originally asked 'what is it', I deliberately didn't put forward my thoughts, to avoid putting ideas into folks head.
My first impression was that it is a non-return valve. ie coolant can only flow in one direction - FROM the radiator TO the heater circuit. But this was a first shot only. Still not sure

[mikexgough]

not going to comment until I can see a pic from the other view point..... across the bore, maybe outside looking in so to speak...I have seen similar........

[widdowson2008]

The only way to be sure is to take one to bits until that happens, everything will be theory.

[widdowson2008]

Eureka - think the mystery may be resolved.
Just spoke to Mike (Wheelquick) and he is going to have a look to see if he has a spare ET for me.
I told Mike what I had seen in the pics and asked him what he thought it was. He has never seen inside an expansion tank but tells me that on the 2 litre Bongo, a non return valve is fitted between the radiator and the expansion tank. So it looks like the expansion tank on a diesel may have one built in.

What he DID say was that having the non-return valve between the radiator and the expansion tank (2 litre models) means that he can no longer fill up the system via the expansion tank because coolant will not flow into the radiator.
He also started wondering if the expansion tank mounted non-return valve could cause some of the bleeding problems (if they are blocked up)

They next question is 'Why put a non-return valve' in this position? It stops a backflow from the heater circuit from going into the expansion tank. Again, WHY would they want to do this?