I have just acquired a mint Mk2 3.4 Jag that has had a lot of worthwhile upgrades done to it. One thing that is missing though is the change to a sealed cooling system by adding a pressurised expansion tank. I have seen several with this done but can anyone help with advice on teh bits needed, the cost and the correct siting of the tank please?

 

Cass (Rob) can give you advice. He has fitted a windscreen washer bag in the left wheelarch. Your choice of container could vary.

 

That, or just don't overfill the rad, the top of the rad is the expansion tank.
It's filled just to the bottom of the tank.

 

I really wanted a sealed system though so the container has to be a pressure vessel that can take hot water and up to 15 psi. You then have a plain cap on the rad and the pressure cap is in the container. It all means no fluid loss.

 

It's not necessary as the draw back system via the cap valve as the engine cools works equally well with no fluid loss. If you want a fully captive system you are going to have to find a pressure tank that is easily mounted. Take a look on Amazon. There are numerous options from other cars or specialist manufacturers. Don't exceed an absolute Max of a 9lb cap on your Jag. I run a 7lb cap. Water pump seals don't like high pressure.

e.g. Original Austin Minis had brass expansion tanks like this. Still available to my knowledge.

 

What Jeff wrote is correct. However, I found that I regularly had to check the level in the radiator, which can be inconvenient on a long road trip. Attachng an expansion tank (in my case for a BL Princess) to the overflow pipe was an easy and convenient solution for my Mk2. I kept the standard pressure cap on the radiator and a lower pressure one (I think) on the expansion tank. I was told that I should put a seal between the top lip on the rad and the pressure cap, but it worked fine without.

Over the years, Jaguar recommended a wide range of pressure values (2 to 9 psi?) for rad caps, so you have plenty of choice.

 

The main problem with the Jag filler neck is actually seeing what the level really is in the rad top tank. In SA we are inclined to want as much coolant in the system as possible but it's pointless if over filling just sees it expelled onto the road hence surge tanks are popular. I run an uprated radiator so I've become accustomed to letting it find it's own level & she runs at about 75 deg C. (cool by modern standards for greater engine efficiency)

 

As Glyn states I added an expansion tank which is a screen washer bag mounted under the left front wing. £12.95 for the kit. https://www.ebay.co.uk/itm/Universal...EAAOSwQotfMWTC
The bag and its mount fit over the metal tangs that hold the wiring loom in place under the front wing. No need to drill holes and can be removed at anytime. It is connected via the plastic tube from the radiator overflow tube to the bottom of the washer bag. Any excess water or steam flows down the tube to the bag instead of being dumped on the floor or watching steam come out from under the bonnet. When the engine cools it draws fluid back from the bag to the top of the radiator. Before I fitted this I had to top up my radiator once a week and I am talking a litre or more each time. Now when I check the levels I only have to top up every month or so.

 

Much of my Mk2 came in boxes. Included in one of the boxes was an overflow tank much like the one pictured above. I assume that it was fitted somewhere in the engine bay and not just accidentally included.
I have a series I E-Type 4.2 which did not originally include a catch tank but someone had retrofitted one from a Series 2 E-Type at some point. It looked a lot like the tank above and mounted with a metal strap to the firewall. I have seen the original Jaguar catch tanks on Ebay from time to time so they are out there. Since they are brass they tend to survive.

 

my 3.8 S type came with a simple overflow / expansion bottle out of a 1968 Volvo 1800.

it consists of a hose from the overflow port of the radiator filler neck, going down and then up to the bottom of the expansion bottle.

About two inches of coolant is added to the bottle to keep a "vacuum" or closed
/ sealed system, so that when the coolant expands, it flows into the bottle and as the coolant cools, the vacuum returns the coolant to the radiator where it came from by action of the vacuum.

the Volvo 1800 bottle is long and thin and fits between the brake fluid container with a home-made aluminium bracket and the spring clamp from a fire extinguisher.

There is an excellent study on retrofitting these expansion tanks to any 1960's car in one of the better known MG sites.

Keep it simple..