Position of coolant expansion tank

South Gippy Rover

South Gippy Rover

Active Member
Hi All,
When I purchased my 3500s the coolant expansion tank was missing.

I recently picked up this replacement, which is the same as in my previous P6.

BC733DFE-67FA-4967-833E-60DDE0BC3E01.jpeg
The problem is that it does not fit to the inner wing as the power steering and brake servo pipes are in the way. I’m guessing that the missing expansion tank was of a different design.

Can I ask those of you with a similar expansion tank where about in the engine bay it is fitted.

Photos would be much appreciated.

Cheers. Paul.
 
The P6B was never fitted with an expansion tank. People do retrofit them, I'll see if I have a pic somewhere of where I fitted mine.
 
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Thanks guys.
Quattro, the photo is just what I’m after. Thank you.
A couple more questions.
Does your expansion tank sit flush against the inner wing?
If I was to put my one in the same position with one of the expansion tank eyelets screwed directly onto the inner wing, then I would need a bracket or spacer behind the other eyelet as it will not sit flush.

Also, are the radiator caps the same on both the rad and expansion tank?

Thanks again.
Paul.
 
Hi Paul, the tank sits against the wing but the eyelets are about an inch away, so I made up a short distance tube (It may have been fuel hose) and used long bolts.

The radiator cap is now just a flat one, with no pressure release spring, so allowing the tank to be part of the pressurised system. The existing cap with pressure relief bits goes onto the expansion tank. The allows the expanding water to into the tank, and when it cools, it goes back into the rad.

Richard
 
retrofitting an expansion tank, using a flat cap on the rad does not make really give a big improvement (besides a few milliliter of additional cooling liquid in the circuit)

you need to fit the usual cap with spring-loaded valve, but the one with 2 gaskets. 1 seals on bottom, 1 seals on top. (belwo pic is a random pic, just to show the 2 seals)
71YJkLN5g-L._SL1491_.jpg

rad will get filled up to the neck. once the water gets warm it will expand and (depending on water-temperature and release pressure of the cap) it will expand into the expansion tank. if the engine cools down the water gets sucked (by vacuum) back into rad. therefore you need the 2nd gasket on the cap.

the expansion tank could be theoretically an open bottle, located in a random position of the enginebay...even lower than the rad. under no circumstances you must fit a pressurized cap on the tank with above desribed config.
 
seven7 said:
retrofitting an expansion tank, using a flat cap on the rad does not make really give a big improvement (besides a few milliliter of additional cooling liquid in the circuit)

you need to fit the usual cap with spring-loaded valve, but the one with 2 gaskets. 1 seals on bottom, 1 seals on top. (belwo pic is a random pic, just to show the 2 seals)
71YJkLN5g-L._SL1491_.jpg

rad will get filled up to the neck. once the water gets warm it will expand and (depending on water-temperature and release pressure of the cap) it will expand into the expansion tank. if the engine cools down the water gets sucked (by vacuum) back into rad. therefore you need the 2nd gasket on the cap.

the expansion tank could be theoretically an open bottle, located in a random position of the engine-bay...even lower than the rad. under no circumstances you must fit a pressurized cap on the tank with above described config.
Click to expand...

An interesting reply , thank you, I ask one question:
if the cap on the radiator is of a double seal type that your describe, how can the water be sucked back via vacuum , past the lower spring loaded seal?
The seal doing its job is preventing the passage of water to return to the rad!
I have fitted mine up with the non pressurized cap on the rad and a pressurized cap on the expansion tank, and it seems to be working OK!
The tank on my car , a p6b, is from a mini and made of brass, looks like gold but sadly is not ;)
Peter
 
ButterFingers said:
An interesting reply , thank you, I ask one question:
if the cap on the radiator is of a double seal type that your describe, how can the water be sucked back via vacuum , past the lower spring loaded seal?
The seal doing its job is preventing the passage of water to return to the rad!
I have fitted mine up with the non pressurized cap on the rad and a pressurized cap on the expansion tank, and it seems to be working OK!
The tank on my car , a p6b, is from a mini and made of brass, looks like gold but sadly is not ;)
Peter
Click to expand...

With a double seal cap the water gets sucked back into the rad by going past the little brass button that you see on the bottom of the cap when the cap is in the fitted position.
The button is on a spring, if you get a finger nail under it you can pull it away from the rubber seal.

I wanted to keep my rad full so I fitted a header tank on the inner wing, put a plain flat cap on the rad, a double seal cap on the header tank, and had an over flow bottle from the header tank. My theory was I could also keep the header tank full and the coolant would be above the carb tower so keeping that full.
It was not 100% successful, I don't know why. I took off the header tank.
I now run Evans coolant, at first with zero pressure and an overflow bottle, this used to put about 3/4 of a litre into the overflow bottle and not all went back at cold.
So I took a double seal cap and cut about a coil off the main pressure spring to give a very light cap pressure, this is on the rad. I still run the overflow bottle, with 20mm or so of coolant in the bottom.
When cold I take off the rad cap and run the engine at 2000 rpm. fill to the brim with coolant and fit the cap. Now when hot I get about 1/2 litre of coolant going into the bottle, and when cold it all goes back into the rad, been like this for several weeks now and seems to be working well.
I see no reason why this would not work with a full pressure cap and ethylene glycol 50:50 mix.
I wanted to run Evans as I did not want to run full pressure in the system.
 
Hi all,

Apologies for resurrecting my original post but I’ve finally installed the coolant bottle today, five and a half years after I purchased it.
It took me less than an hour.

This has now generated another question, with regards to radiator cap pressures.

From what I’ve read on this forum and Tridon’s website Radiator Caps | Tridon
I need to install a double seal recovery cap on the radiator and a single seal non recovery cap on the newly installed coolant bottle.

My question is do I keep the same pressure rating (currently 15lbs) on both caps or does one need to be different?

Thanks again as always,

Paul.
 
I used a flat (no pressure relief ) cap on the radiator so the expansion tank became part of the pressurised system, then the original cap on the expansion bottle to give the relief if required.
 
mine is same as quattro's set up, and it works well - expansion tank level rises from ~ 1/4 full when hot, drops as coolant is sucked back to rad.
rpyUf5M.jpg


And I have a plain cap on the rad, pressure cap on the overflow tank, as Quattro did.
 
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Thanks gents.
The set up with the flat non-pressurised cap makes sense to me and I’m pretty sure my last P6 was the same.
I suspect I have been overthinking this and have read too much conflicting information.
Decision made.

Thanks again.
Paul.
 
Top left inner guard seems to be the popular choice. Above the radiator fill cap.
The radiator used to dump fluid when hot and I was always refilling it.
My P6b came "factory" without the overflow tank and I didn't want a plastic job, so opted for a copper/brass unit out of an early Landrover. It is a "Rover" part of sorts.
On refection I should have stripped and polished the metal tank to bling up the engine bay.
I have a blanking-off cap on the radiator and shifted the pressure relief cap onto the overflow tank. Never had a problem with losing fluid again.
 

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Just for interest, I used a spare expansion bottle from my Alvis and strapped it to the screen wash bottle. It keeps it out of sight.
Annotated below.
1704223439374.jpeg
 
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