Hi everyone,
I've started working on the cooling system, I removed the metal overflow reservoir tank because it's got a little leak that needs welding up (gosh there was some rusty metal that I shook out of the bottom of the tank!) my question is to do with the caps, I think someone has put the wrong one on the reservoir, it has the spring loaded one on the tank and on the engine filler (the main one) it has a flat cap, no thermostat, spring loaded. Which one should be on which? My gut tells me they are on the wrong way!
cheers
Scotty.

 

Flat and no spring and a good fit with the rubber on cap and radiator.

Spring pressure cap on overflow tank
Walter

 

Thanks Walter, dear I say that this the first British car that I have owned and worked on, all of my experience has been on Japanese cars (I whispered that!) with plastic overflow tanks.

 

Blank cap on the header tank(front of the engine), pressure cap on the expansion tank.

I run 16psi on the expansion tank and all works well. The blank cap is readily available at Repco.

 

My 83 had a plastic o'flow tank ala most if not all later cars. Sold along with other left overs after the lumping...


Now, is pressure cap on the radiator dumping into the tank behind the left outboard lamp. Has worked just fine since circa 2005, when it returned to the road...


Carl

 

Thank you so much for the photos!
I understand in Japanese cars how the system works, overheating happens, the pressure cap opens and it draws more water through into the system from the overflow, how does it work on a Jag when the pressure cap is on the expansion tank?

 

On the Jaguar, the blanking cap is at the highest point on the coolant circuit and is used for filling the engine with coolant. Whne cold this should be completely full with about 1/2" gap from the top of the blanking cap so you can see the two pipe apertures. One of these pipes goes to the expansion tank that has the pressure cap on it. When the coolant warms up it expands and passes into the expansion tank. On cooling down, the liquid is drawn back into the engine. When filling afresh, a small amount of coolant is added to the expansion tank, the Jaguar instructions tell you how much. Later expansion tanks were plastic.

 

I have a 1987 xj6, and I've never seen anything except the pressure cap on the expansion tank, no blank camp that I can see. is that right for my year? am I really not seeing a blank cap somewhere else? (i'm not ruling out my own idiocy here.)

 

Yes, you are correct. I also have an '87 and we have only the plastic expansion tank equipped with a pressure relieving cap. No other cooling system pressure caps. The expansion tank relieves to the overflow tank, located under the driver's side wing, which then returns coolant back to the expansion tank upon cooling.

 

Just how much of a hassle is it to get the metal overflow reservoir out?
Seems like an entire injection bank is in the way...

 

Hello, Scotty,
Your post reminded me of the 1969 Datsun roadster I used to have (part of me wishes I still had it), and the BRASS expansion tank, which needed soldered up once, but Never (of course) corroded!

Pressure cap on the tank, No cap on the rad (no room under that hood!)
Filling it was a rather tedious operation.
(';')

 

So it turns out that the bottom of the expansion tank was only being held together by the paint! A local radiator guy is rebuilding it for me including lining the inside of it with some plastic coating stuff. I guess sitting for ten years with water in it did the trick.

 

My Series 3 was a 1980 so had the blanking cap, but later cars didn't have it and also had a plastic header tank mounted a lot higher, and thus is could be used to fill the system. I remember my old parts manual showing the two types.

All rather a long time ago, like the late 80s. Funny, but i seemed to have a lot more energy then and would work in an unheated, freezing cold garage on the Jaguar. I must have been nuts !!