Another Header Tank Question

[Ian Durrant]

well i am completely confused. I am pretty sure the whole point of a header tank is that there is some flow through it. The small diameter of one of the pipes means that the amount of flow is miniscule compared to the thousands of gallons per hour the pump is capable of. If you have both pipes on the same side of the rad then as far as I can see all you get is the same effect as just raising the level of the existing expansion tank. Maybe I am missing something?

[Staggard]

well i am completely confused. I am pretty sure the whole point of a header tank is that there is some flow through it. The small diameter of one of the pipes means that the amount of flow is miniscule compared to the thousands of gallons per hour the pump is capable of. If you have both pipes on the same side of the rad then as far as I can see all you get is the same effect as just raising the level of the existing expansion tank. Maybe I am missing something?

Why does water need to flow through a header tank ? It flows in on expansion and out on contraction, in days gone by before cars had water pumps they were cooled by convection hot water rises from the top of the engine into the rad down through the finning cooling as it goes out the bottom and back into the engine, the same way gravity feed indirect hot water cylinder work's hot water from the boiler (mounted below the cylinder) rises up through the coil (heat exchanger) cools and returnes to the boiler All I am saying is there has got to be cirulation via convection because the water rising from the top of the engine has got to be hotter than at the bottom of the rad even though its on the higher pressure side

[GTJones]

Graham is right, water does not need to flow through the header tank, it is just there to compensate for any expansion or contraction of the water due to temperature rise.
The problem with the original system was that the return of the coolant relied on vacume to suck the coolant back from the overlow (expansion) bottle which in most cases was not sufficient enough to replenish coolent into the system so air pockets were caused normally at the highest point in the system and with the stag this is the pump!

This is why all you have to do is ensure your tank is higher than the pump, so air is expelled into the header and not trapped in the pump and also have enough coolent in the tank to replenish the system when it cools.

Well as they say, there is more than one way to skin a cat

Gary

[Staggard]

Graham is right, water does not need to flow through the header tank, it is just there to compensate for any expansion or contraction of the water due to temperature rise.
The problem with the original system was that the return of the coolant relied on vacume to suck the coolant back from the overlow (expansion) bottle which in most cases was not sufficient enough to replenish coolent into the system so air pockets were caused normally at the highest point in the system and with the stag this is the pump!

This is why all you have to do is ensure your tank is higher than the pump, so air is expelled into the header and not trapped in the pump and also have enough coolent in the tank to replenish the system when it cools.

Well as they say, there is more than one way to skin a cat

Gary

I just knew pussy would come into this sooner or later nite nite all

[jleyton]

I just knew pussy would come into this sooner or later nite nite all

Hi Graham - if you haven't yet gone to beddy buys - have you seen my earlier post in the joke section ?

Cheers and good night !

Julian

[GTJones]

My pussy went to bed a long time ago

I just knew pussy would come into this sooner or later nite nite all

[peterrc]

Hi Graham,

You are correct in what you say but if the 'expansion' tank is fitted high enough, it also becomes a header tank.

My picture shows the height of the tank compared to the top hose and is the highest point it can be fitted.

This is all getting too complicated yet again and is quite a simple modification.

Jeff.

So as understand it all I have to do is raise the existing expansion tank, cut a hole in the bonnet to accommodate it and fit a scoop over the hole/expansion tank which will provide cooling to expansion tank and engine. Watch this space.
Peter, Cupar

[CLASSICCHAV]

so as understand it all i have to do is raise the existing expansion tank, cut a hole in the bonnet to accommodate it and fit a scoop over the hole/expansion tank which will provide cooling to expansion tank and engine. Watch this space.
Peter, cupar

just drop the rv8 in now peter and save the aggro!

[Jeff]

So as understand it all I have to do is raise the existing expansion tank, cut a hole in the bonnet to accommodate it and fit a scoop over the hole/expansion tank which will provide cooling to expansion tank and engine. Watch this space.
Peter, Cupar

Yep, you got it.

[V Mad]

Whilst not essential, a flow and return system is desirable because:

1.Cooling system can be filled through the header tank. Without a return pipe there will be airlocks making filling difficult.

2.Allows additives (antifreeze, leak additive etc) to be put into the tank and mix properly.

3. Provides a path for trapped air to be expelled into the tank.

The top return pipe should not be too large though, or too much coolant will bypass the radiator.

[Giles]

So to go back to the original post! . With the original system there was a large pocket of air. You can compress air but not fluid. I assume the old system probably hardly ever reached 20psi? as it would just compress the air. With a header tank that is almost full it will compress the air and expell any excess water when it reaches 20psi and so find its own level, which is what Ihave done with mine. I would assume that this now means that overall it does run at a bit higher pressure? Just thinking out load really

[V Mad]

Yes, I think the pressure in the system is greater if there is a smaller volume of air, on the basis that the coolant will expand by a fixed amount. Same if you overfill the expansion bottle; pressure will then be greater when hot due to smaller volume of air.

[Staggard]

Whilst not essential, a flow and return system is desirable because:

1.Cooling system can be filled through the header tank. Without a return pipe there will be airlocks making filling difficult.

2.Allows additives (antifreeze, leak additive etc) to be put into the tank and mix properly.

3. Provides a path for trapped air to be expelled into the tank.

The top return pipe should not be too large though, or too much coolant will bypass the radiator.

I,ll quit after this posting because my head hurt's Ok No1 not true I fill my rad through the filler plug in the top of the rad (slowly) until a couple of ins from the top then finish off by filling from the header tank until it overflows out of the rad filler thus expelling any air. No2 mix antifreeze/additive's before pouring it into the system and fill as in No1 and No 3 I don't get trapped air (only after dinner) My only point in all this is No 1 it's cheap No2 it's simple to fit No3 and most important it's been tested in temptures up to 40 deg c it's been driven up Tedi (the higest mountain in Spain) these conitions you wont experience in England. The car does not overheat or loose any coolant So it work's I find people make things far more complicated than they actually are just rember KISS happy staging Graham

[Staggard]

Hi Graham - if you haven't yet gone to beddy buys - have you seen my earlier post in the joke section ?

Cheers and good night !

Julian

Very good Julian although I've never seen a cat riding a horse before!! Don't know though I have been to Bancock Cheers Graham