Stag header tank

[Essex Stag]

I have just had an engine rebuild by Robsport , and a mechanic friend of relative of mine looked at it and said I ought to take the Stagweber tank off because it can over pressurize the water pump seals and blow the seals . I thought it was fitted for a very good reason and looking at it cannot see how it can do that because it goes to the rad first therefore the whole system must be the same pressure .Also I think I am right in believing that an expansion bottle is not reliable enough to send the water back into the engines thus emptying the heads and the pump of water and causing problems . I have a 20psi cap on the tank with 140 also marked on the cap so that must be the max pressure anyway. Has anyone any comments I am sure Stag Webber will have something to say .
Derek

[Hughesy]

You don't use this "mechanic" do you??? Clearly he has no idea. Craig

[milothedog]

I think you need to ask him to explain a bit more what he means . The cap will/should release excess pressure. However the way the tank is plumbed in, in my opinion, is not a good idea as it allows some of the coolant (via the top bleed hose ) to be returned to the engine bypassing the radiator.

Only my person opinion, others may disagree


Ian.

[Lingen]

Derek. What a load of old rubbish! The carbon water seal in the pump is spring loaded, and won't "Blow". The pressurised overflow bottle is not the cleverest idea for keeping the radiator full, and can be troublesome, whereas a gravity fed system like you (and I) have fitted will always work. The 140 on the cap is the continental method of pressure measurement, and is 1.4bar, which is 21 psi in English, so perfectly ok to use. Although my tank belongs on a 3 series BMW, it fits neatly ahead of the suspension turret, and since I fitted it in October 2012, the engine temperature has been much more stable, and I have only had to add about half a pint of coolant. I prefer to keep things as original as possible on the car, but I can see this modification staying put!
Mike.

[mjheathcote]

Personally would drop the pressure cap to something like 15psi, as can't really see the need for a higher pressure. If you do need it...you have a problem in my view.
Regarding header tank plumbing, I have a connection into the top hose, and a smaller from the original expansion bottle.
Yes you do get a flow, thus bypassing the radiator.
If you want the water flowing through the header tank, and thus a high point air pocket for any trapped air to gather below the pressure cap, this can't be avoided. Water can only flow from a point of high pressure (post pump, pre radiator) to low pressure (pre water pump, post radiator).
In reality, the water flow through the quarter inch 'bypass' compared to the 32mm inlet and outlet radiator connections is minimal and doesn't cause any cooling issue in my case. If you wanted you could also restrict the quarter inch hose to just a trickle, enough to just allow water movement through the header tank.
If you pipe any other way, the water in the header tank will remain stationary. No problem with that it will still work as a head of water, and water will expand into it, and out of it when cooling, but you won't get the benefit of any air bubbles in the circulating water being able to break the surface in the header tank as a natural high point in the system when being circulated around.
That's my take anyway!

[jakesmig]

Can't chose your relatives but you can pick your friends, your fault.

[Essex Stag]

Thanks for all the replies No I do not use that mechanic .

[milothedog]

Personally would drop the pressure cap to something like 15psi, as can't really see the need for a higher pressure. If you do need it...you have a problem in my view.
Regarding header tank plumbing, I have a connection into the top hose, and a smaller from the original expansion bottle.
Yes you do get a flow, thus bypassing the radiator.
If you want the water flowing through the header tank, and thus a high point air pocket for any trapped air to gather below the pressure cap, this can't be avoided. Water can only flow from a point of high pressure (post pump, pre radiator) to low pressure (pre water pump, post radiator).
In reality, the water flow through the quarter inch 'bypass' compared to the 32mm inlet and outlet radiator connections is minimal and doesn't cause any cooling issue in my case. If you wanted you could also restrict the quarter inch hose to just a trickle, enough to just allow water movement through the header tank.
If you pipe any other way, the water in the header tank will remain stationary. No problem with that it will still work as a head of water, and water will expand into it, and out of it when cooling, but you won't get the benefit of any air bubbles in the circulating water being able to break the surface in the header tank as a natural high point in the system when being circulated around.
That's my take anyway!

I think you misunderstand what I stated Mike. The SW tank has a bleed connected to the rad filler plug and can return directly to in pump intake pipe this allows (all be it a small amount (because of pipe ID) of hot coolant from the top hose to be drawn (return to the water pump) and straight back in to the engine bypassing the radiator.

I would personally like 100% of the flow to pass through the Rad. As I said just my views. other seem happy to run it.


Ian

[mjheathcote]

I think you misunderstand what I stated Mike. The SW tank has a bleed connected to the rad filler plug and can return directly to in pump intake pipe this allows (all be it a small amount (because of pipe ID) of hot coolant from the top hose to be drawn (return to the water pump) and straight back in to the engine bypassing the radiator.

I would personally like 100% of the flow to pass through the Rad. As I said just my views. other seem happy to run it.


Ian

No, not misunderstood, mine does the same, and as stated does not cause a problem with the pipe size being small.
At the end if the day, much better than the original system....I fitted a header tank throwing away the original bottle 30 years ago this year!!

[Stagdad]

My cooling system is fitted with a pressure gauge and runs at 10 psi that's with an 88 stat fitted.

[LD334]

My tuppence worth,
I have a cylindrical Stagweber header tank on my near side wing. I tied it in per the information supplied with the main pipe tied into the stub on the pump inlet and a small diameter return from the top hose to the tank, see the profile photo to the left. I use red pipe for anything non standard.
Now my car is an early Mk1 (LD334) and the bypass hose routing is different to a Mk 2, essentially the pipe from the thermostat housing ties in to the pump intake while the heater pipe ties into the side of the pump. When running I had some coolant loss and after some investigation I decided that the geometry of the tie in was allowing hot water from the thermostat housing to flow to the tank. This wasn't helped by the intake manifold design which doesn't allow for the long type thermostat with the foot so the bypass flows full time.
Essentially then the header tank tied in to the hot side of the cooling system and this has been an issue. I've now copied the Mk2 design tieing in to the heater pipe which is part of the cool side of the system.
What I've found is that the tie in of a header tank has to be considered carefully for your car. For the majority of Stags the tie in design supplied with kits works well but if you have an early car with one of the 10 intake manifold designs that Triumph tried you need to have a think.

[Paul Kelley]

Ah, the old header tank chestnut returns once more - well, I suppose it's been a while! For what it's worth: I have the SW cylindrical tank plumbed into my Mk 2 as per Chris Spain's (Mr Stagweber) instructions. It's been fitted for over a year/4,000 miles and all is fine.
PK