Another Header Tank Question

[Dave M]

Ive recently fitted a header tank to my Stag, very similar to what V Mad sells and installed as per his kit (bought the tank before Chris started selling them) bottom entry on the tank is plumbed into the heater return with the top entry teed into the top hose. At the moment I have not removed the original expansion bottle, my question is where does the expansion go if the expansion bottle is removed as my header tank is virtually full, wont removing the expansion bottle put stress on the hoses etc?

Dave

[Ian Durrant]

I think the answer to that is not to completely fill the header tank. Modern header tank installations don't also have an expansion tank.

[Staggard]

Ive recently fitted a header tank to my Stag, very similar to what V Mad sells and installed as per his kit (bought the tank before Chris started selling them) bottom entry on the tank is plumbed into the heater return with the top entry teed into the top hose. At the moment I have not removed the original expansion bottle, my question is where does the expansion go if the expansion bottle is removed as my header tank is virtually full, wont removing the expansion bottle put stress on the hoses etc?

Dave

I presume you have a Mk2 so the heder has a pressure cap so you block off the orignal expansion pipe from the rad that went to the expansion bottle

[Dave M]

Yep its a mk 2 and I understand how easy it is to remove the original bottle and block off the pipe but Im worried about stressing the hoses etc if the expansion bottle is removed from the system. Im currently running the car with the header tank and expansion bottle fitted which gives me a header tanks worth of extra coolant located above the pump with the added advantage of a low level switch. I guess as Ian says not filling the header tank to the top would be the answer.

[V Mad]

You dont need to worry about stressing the hoses, they will be designed to run at 20PSI. If you have the correct 20lb cap, this will release any excess pressure, even if you have overfilled your tank (fill to about 2/3 full).

If you do overfill your header tank, then the excess coolant will be expelled from the tank via the overflow outlet (tube in the filler neck). This should then leave an air gap for any expansion so that next time it heats up no more coolant will be lost.

[Staggard]

Yep its a mk 2 and I understand how easy it is to remove the original bottle and block off the pipe but Im worried about stressing the hoses etc if the expansion bottle is removed from the system. Im currently running the car with the header tank and expansion bottle fitted which gives me a header tanks worth of extra coolant located above the pump with the added advantage of a low level switch. I guess as Ian says not filling the header tank to the top would be the answer.

OK so orignally you have a expansion bottle with a pressure cap 20lb? so the hoses are protected from being( stressed ) by the pressure relief cap. so all you are doing in effect is replaceing the bottle for a header/expansion tank its just mounted higher above the water pump this also has a pressure releif cap when the coolant heats up and expands it will push out the excess out of the overflow when it cools the leavel drops anyway finds its own level if you keep the orignal bottle you are left with the orignal problem coolant expanding into it and not returning when it cools also you have two pressure caps why? if you worries about stressing the hoses fit a 13lb cap Graham

[Dave M]

Thanks for the replies guys, I will remove the expansion bottle a see where the header tank level settles. Must say having the header tank makes it far easier to check levels.

[Jeff]

Dave, just fitted my header/expansion tank today and I think you are missing the point that the header tank is also the expansion tank in one.

Jeff.

[Dave M]

Dave, just fitted my header/expansion tank today and I think you are missing the point that the header tank is also the expansion tank in one.

Jeff.

Jeff, I was worried because I had filled my header tank to the top, hence no room for expansion. I will lower the level in the header tank and remove the expansion bottle.
Dave

[Jeff]

That should work.

Jeff.

[TIMBO]

I have a header tank and the origional expansion bottle fitted and the combination works perfectly.

The principle is as follows: The header tank, fitted above the water pump level, remains full to the brim while the expansion tank is about half full when cold. When the system gets pressurised and the cooling fluid expands, it fills up the expansion bottle in the intended way. When it cools again the level in the expansion tank returns to half full. The new header tank always remains full, hot and cold.


The presure cap on the expansion tank is 20 lbs, while the pressure cap on the header tank is a metric equivalant which equates to about 21 lbs, hence the 20 lbs cap on the expansion tank would be the one that should activate first.


As mentioned the set up works perfectly for me. I have had it set up for approx 4 years now without any issues.

[jleyton]

Hi Timbo,

I'm interested in your arrangement. How have you got your header tank plumbed in and can you post any pictures?

I quite like the idea of having a header tank as insurance but I would like to have the simplest arrangement possible. That sounds like what you've done ! I seem to remember one of our overseas members - a former mechanic? - also has a similar arrangement but I don't recollect who it was.

Cheers

Julian.

[Dave M]

Julian, mines currently installed similar to Timbos, header tank is always full and expansion bottle works as normal. The installation was simple, tee peice into the U shaped heater hose which is then plumbed into the bottom port on the header tank, top port of header tank into tee peice into top hose. Ive obviously now got two pressure caps which is probably overkill. I connected the low level switch in parallel with the brake warning light switch on the brake shuttle switch, not fail safe but very simple. I am now considering removing the expansion bottle and lowering the level in header tank.

[Jeff]

Hi Timbo,

I'm interested in your arrangement. How have you got your header tank plumbed in and can you post any pictures?

I quite like the idea of having a header tank as insurance but I would like to have the simplest arrangement possible. That sounds like what you've done ! I seem to remember one of our overseas members - a former mechanic? - also has a similar arrangement but I don't recollect who it was.

Cheers

Julian.

Hi Julian,

I'll take pictures of mine and send them to you, very simple but effective, well pleased with it as I have been 'playing' with this set up for years now and finally cracked it, looks foolproof and should have been included in the original production.

Jeff.

[jleyton]

Thanks Dave & Jeff,

I'll look forward to your pics

Cheers

Julian