Heat exchanger filler caps

[MontyMariner]

My heat exchanger filler cap is the basic half twist to secure, with a spring pressure seal and overflow outlet above the seal that drains into the bilge.
Is it possible to convert it so that the overflow goes up to a header tank or down to a vacuum reservoir so that the heat exchanger tops itself up?

 

[rogerthebodger]

yes i did that a little while ago

I replaced the pressure cap with a non-presser cap and then fitted a mini overflow/ expansion tank.

I then piped from the existing overflow to the expansion tank the old pressure cap fitted on to the expansion tank and a plastic over flaw take to collect any water from the overflow tank to keep the bilge clean

https://flic.kr/p/VGBmK7

The plastic bottle i to the right of the engine and the mini expansion tank is behind and above the plastic bottle

 

[RogerJolly]

Why are we overflowing (can't be normal)?

 

[Graham_Wright]

The engine needs pressure to raise the boiling point of the coolant. I mistakenly connected an overflow receiver (from a Vauxhall something or other) but eventually scrapped it.

 

[38mess]

I just have a plastic bottle on the end of the overflow pipe, any fluid at the end of the day gets poured back in to the HE.

 

[MontyMariner]

I replaced the pressure cap with a non-presser cap and then fitted a mini overflow/ expansion tank.

Good, that's what I had in mind.
Was the expansion tank the same as the sort used in cars?

 

[MontyMariner]

Would this do the job, it's quite small capacity .
350ml Car Overflow Catch Tank Cooler Coolant Reservoir Kit Universal aluminum alloy Expansion Tank Car Modification accessories - AliExpress 34

 

[VicS]

My heat exchanger filler cap is the basic half twist to secure, with a spring pressure seal and overflow outlet above the seal that drains into the bilge.
Is it possible to convert it so that the overflow goes up to a header tank or down to a vacuum reservoir so that the heat exchanger tops itself up?

I did that many years ago to a car that was troublesome after refilling the cooling system.
I routed the overflow pipe from the radiator neck to a bottle, dipping right to the bottom.
I also made a thin gasket to seal the cap against the radiator neck so that when the system cooled it sucked any overflow back into the radiator. This may not have been necessary but it ensured all the overflow was recovered.

I kept the original pressure cap on the radiator. This is essential unless you seal the overflow bottle and fit it with a pressure cap and use a sufficienly robust bottle or tank to withstand the pressure..
IMO a bit simpler than Roger's suggestion as any bottle can be used to catch the overflow.

 

[rogerthebodger]

I went to a scrap year and got one from a mini of BMC 1100 1300 and other BMC cars as I was used to those cars

The cap on the heat exchanger is like this

The pressure cat I took off the heat exchanger when on to the expansion tank

Or

Plus a plastic bottle to catch any overflow

 

[rogerthebodger]

Would this do the job, it's quite small capacity .
350ml Car Overflow Catch Tank Cooler Coolant Reservoir Kit Universal aluminum alloy Expansion Tank Car Modification accessories - AliExpress 34

You do not need the bottom connector but there are others which are larger that look they would do the job, but you may be able to get on from a scrap yard as I did

 

[rogerthebodger]

I did that many years ago to a car that was troublesome after refilling the cooling system.
I routed the overflow pipe from the radiator neck to a bottle, dipping right to the bottom.
I also made a thin gasket to seal the cap against the radiator neck so that when the system cooled it sucked any overflow back into the radiator. This may not have been necessary but it ensured all the overflow was recovered.

I kept the original pressure cap on the radiator. This is essential unless you seal the overflow bottle and fit it with a pressure cap and use a sufficienly robust bottle or tank to withstand the pressure..
IMO a bit simpler than Roger's suggestion as any bottle can be used to catch the overflow.

Yes you need to seal the hear exchanger and a tank that can stand the pressure controlled by the cap on the expansion tank.

My plastic bottle is just to catch any overflow from th expansion tank and not the hear exchanger

 

[Plum]

My heat exchanger filler cap is the basic half twist to secure, with a spring pressure seal and overflow outlet above the seal that drains into the bilge.
Is it possible to convert it so that the overflow goes up to a header tank or down to a vacuum reservoir so that the heat exchanger tops itself up?

As Roger Jolly said, it should not be overflowing. Coolant should only come out if it is overheating, the pressure cap is not holding the correct pressure or the coolant level in the heat exchanger is too high so there it not enough expansion volume.