Header Tank Height

[Guest mcramsay]

Does the bottom outlet of the header tank have to be above the top rad hose? As mine is around 6" lower, and without drastic redesign I can't move the header tank any higher!

[Big Jim]

post deleted as not relevant

Edited April 2, 2016 by Big Jim

[Guest mcramsay]

Sorry I should have been more clear, the header tank is part of the pressurised cooling system, the rad has s blanking cap fitted and bleeds off back to the header tank which has a twin seal cap fitted, currently with the header tank half full the rad is not fully topped up and the top hose is empty.... Not sounding good....

[Big Jim]

Well then the answer to your first question is, yes, it should be higher than the top of the tank or you'll have problems

[Guest mcramsay]

Now I need to find a tank that will fit in the most awkward of places, the radiator top pipe is the highest thing in the engine bay, finding a tank that will be at least level and still allow me to close the bonnet will be hard.

[alanrichey]

Shouldn't really get involved in this with all my problems but with the Superspec design, that uses the same principle, you have to fill the expansion bottle to within 1" of the top to ensure the top hose and radiator are full.

[Guest mcramsay]

Doesn't that not leave any room for expansion? I will post up some pics in a bit, I'm hoping I can squeeze a different type of header tank somewhere a bit higher

[Guest mcramsay]

Ok so here are some pics, I would really appreciate any advice as I want the car on the road this year and I need to get to iva ASAP. It seems a major oversight in my part, but all I can do now is try to re-engineer again!!

 

Ok so with the marlin space is limited for the radiator, this meant I had to go for a tall and thinner rad. I used the Honda Civic alloy one from eBay. As you can see below I have had to do a really horrible bend to get the outlet of the thermostat up to the top of the rad

 

 

 

This gives the problem of the rad inlet being pretty much the highest thing in the engine bay.

The header tank is shown below

 

 

So looking at it now the outlet of the header tank is sitting around 6-8 inches lower than the rad top hose. This is giving the problem that when the header tank is half full there is no water in the top hose/ top of the radiator.

 

I have to pretty much brim the header tank to get atleast some water in the top of the rad. Which defeats the point of the header tank.

 

So thinking of my options, I either have to change the radiator and try find a more rectangular one with an inlet that sits at least level with the thermostat outlet. Without going custom I think this will be difficult as I spent weeks looking for something that would fit when originally fitting the rad.

 

The other option is to use a different header tank possibly a funky shaped plastic one that I can sit higher in the engine bay, the problem is that I have very little room with the bonnet, it would have to be rectangular and thin, width isn't really an issue though. I cannot lower the current rad at all so That is not an option

 

So open forum, any advice welcomed. And a beer to the first person to call me a twat for overlooking such a simple thing!!

[alanrichey]

Doesn't that not leave any room for expansion?

 

You would think so, but with a 20psi cap it seems to work OK. Probably just pretends to be a sealed system instead

[Guest 2b cruising]

Looks like you could cut the 90' pipe where it goes to the t/stat housing.

This would bring you top hose down a little.

You could also do with a bleed point at the highest point of your top hose as BMW use now.

Can you fit an electric pump (once again BMW type), even if it is in the heater feed pipe, low in the system.

You could then use this to pressurise your system when bleeding.

E45 1.8 of my daughters had one in the heater system to actually feed the heater.

It was mid way on the o/s chassis rail.

I used it to successfully bleed her system with the nose of the car at maximum hight on a high lift trolley jack.

Pleanty of problems last year until I carried this crazy action out.

Edited April 2, 2016 by 2b cruising

[Guest mcramsay]

Just to clarify I am running a sealed system, the header tank is part of the pressurised circuit and has a twin cap fitted, the rad cap is a banking cap and has no pressure release

[Guest 2b cruising]

Yes I understand that part.

A bleed point on the top hose would help in this matter.

Is your system temperature pressurised or electric pump pressurised.

Either need the highest point bleeding.

[Guest mcramsay]

Temperature pressurised, running the standard water pump.

[Guest mcramsay]

I have not run the engine yet with this set up, just to add

[Guest 2b cruising]

It is ok to run a pressurised system as your is laid out.

Would be a little better with a higher bottle but not an absolute requirement.

The only problem is in the air free fluid flowing freely through the system.

Check if the M series from 2000/2006 has the same size top hose as you are currently using.

You might be able to cut the bleed section out of it and fit to yours over a suitably sized steel tubing.

That's if the M series used the same type system as the e46 models.

The top hose was above the rad and header tank on those, but a much smaller pipe than yours.

And of coarse they had the electric water pumps.

Edited April 2, 2016 by 2b cruising