Another header tank question

ihatesissycars · Post by **ihatesissycars** » Mon Jan 15, 2007 3:19 pm

I've relocated my header tank to under my n/s wing just behind the headlight but the problem i have now is that its pretty much level with the rest of my engine meaning the airgap in the tank wouldn't stay in the tank it would spread itself amongst the rest of the engine if the car were even slightly uneven.

At the moment The next higest point is the top hose which incorporates a swirl pot with airtrap and a airbleed pipe. I'm going to get that shortened which when accompanied with an sd1 stat outlet which should also help me to lower the whole tophose assembly by about 1 1/2" so the tank becomes the highest point but it won't be by much.

The question is do you reckon i'm going to have a 3.9 ltr v8 kettle?

ChrisJC · Post by **ChrisJC** » Mon Jan 15, 2007 3:47 pm

My header tank is lower than the rad top hose. Works just fine. To be pedantic it's really an expansion tank.

The cooling system is completely full of water. When the pressure gets over 15psi, it passes the rad cap and fills the expansion tank. As the engine cools, it sucks it back in from the expansion tank.

See http://www.cowdery.org.uk/v8rebuild.php
Bottom pic but one shows the expansion tank. The brass piece in the top hose has an outlet at theback feeding the bottom of the expansion tank.

Chris.

ihatesissycars · Post by **ihatesissycars** » Mon Jan 15, 2007 3:52 pm

I did think of brimming the whole system and using a seperate resevoir as an overflow but my header tank won't allow this as it doesn't have an over flow on its filler neck should the pressure get too much. I'd have to brim it and hope for the best!

I can't change it for another though as very little else will fit in the available space.

chodjinn · Post by **chodjinn** » Mon Jan 15, 2007 4:22 pm

mate I might be getting a new header tank in the next couple of months - you could have my old one off me? Its got a single entry at the top, singel outlet at the bottom and a rad cap with overflow/puke connection. Its only a few inches in diameter, probably less than 10" in length - any good?

ihatesissycars · Post by **ihatesissycars** » Mon Jan 15, 2007 4:53 pm

Ooooooooooo got any piccies?

Paul B · Post by **Paul B** » Mon Jan 15, 2007 10:22 pm

ihatesissycars wrote:I did think of brimming the whole system and using a seperate resevoir as an overflow but my header tank won't allow this as it doesn't have an over flow on its filler neck should the pressure get too much. I'd have to brim it and hope for the best!

I can't change it for another though as very little else will fit in the available space.

On my Morris I made a temporary 'header tank' by tie wrapping a plastic glue bottle to the bottom of the radiator core, a foot below the top. I filled the radiator as per normal, put the rad cap on, ran the overflow hose down into the plakky bottle and topped that off with a few inches of water.

Engine gets hot, water expands, overflows in bottle via the pipe. Engine cools, sucks water back up the hose into the system. no leakage, no air bubbles.
The header tank can be anywhere, even in the boot if you wanted. Unless the water in the header tank gets below the end of your hose you can't get air into the system.

chodjinn · Post by **chodjinn** » Mon Jan 22, 2007 10:02 am

Gav I'll get some pics sorted this week, just seen a header tank on ebay with my name on it (need more connections than the one I have now!).

Cheers

. . got that alu flywheel by the way

ihatesissycars · Post by **ihatesissycars** » Mon Jan 22, 2007 10:10 am

Sweet, thanks bud!

Congrats on the flywheel, make sure you put it in the lounge display cabinet for a while before you hide it away!

I had some luck also, i got the tvr heads the same chap had for sale.

chodjinn · Post by **chodjinn** » Mon Jan 22, 2007 9:58 pm

ha ha yeah the flywheel does look pretty nice

the clutch is pretty trick too

those heads are a beast tho, gonna work well with the bigger bottom end you're planning.

header tank is about 20cm high including cap, with an overflow connection. Has a small connection on the top (8mm i think) and a larger one on the bottom (15mm?). Used it in the MG with the old engine and worked well, i just need more connections.

housemate has taken the camera but will get some pics soon

olly

tetlow · Post by **tetlow** » Tue Jan 23, 2007 10:50 pm

Gents
I must be dim here but I thought the Header Tand is a expansion Tank and is solely there to allow for the expansion of the water when hot. As the water cools it shrinks and the level lowers.
My tank is connected directly to the radiator and the 15psi cap is to allow the system to go above 100C and not boil,and when exceeded to allow excess pressure to vent onto the TVR behind, trying to keep up!

Should this not mean that you can put the tank where ever you want?
Of course you would initially have a few problems getting rid of the air but bleed valves etc should do that job.
Dave

Post by **katanaman** » Tue Jan 23, 2007 11:34 pm

Two types of tank are in common use

Header tank which is what you have and is pressurised. This needs to be at the highest point in the circuit and usually has the pressure cap as part of it.

Expansion tank which isn't pressurised. It just acts as a catch tank and when the coolant contracts after cooling it sucks it back into the system. The pressure cap is generally on the radiator but needs to be at the highest point as its the filling access as well. The actual tank can be anywhere including hight. Expansion tanks tend to be popular on Asian make cars so they are a good source to find them. Its also a different pressure cap from the header tank as it has to allow the coolant to return to the coolant system.

ihatesissycars · Post by **ihatesissycars** » Sun Feb 11, 2007 7:17 pm

I've beent hinking about this lots and i'm not convinced i'm gonna be k with the tank where it is.

Another option i thought of was to have a pressure cap put onto my swirl pot in the top hose and then just running a line from that to a catch tank under the inner wing?

Sound good?

Post by **katanaman** » Sun Feb 11, 2007 9:11 pm

so long as you use the right cap it will work

ihatesissycars · Post by **ihatesissycars** » Mon Feb 12, 2007 6:42 pm

Sweet, thanks Marki.

What cap would be best do you reckon?

mikeinatruck · Post by **mikeinatruck** » Tue Feb 13, 2007 12:50 am

When I changed my Landy from diesel to V8 the cooling pipes had to be changed as well and that left me with a problem. The bubble escape went into the top of the header tank, but the V8 had the escape on the carb tower as well and the bottom hose did not have a T piece back up to the header tank. Still with me. Well it turns out that the V8 landy header tank has a small pipe on the outside that the bubble escape pipe goes onto, but it extends into and down inside the header, so when the water is full it creates an air space under the cap. As the coolant contracts it syphons it back into the engine, so if it is lower than the engine it makes no difference.
Due to the angles the vehicle is designed to operate at I believe is why it was done like that on the V8.

Doubt I explained that well, due to my day off beer intake but you get the point ...I hope...