Coolant Overflow Tank

[Patrick67BJ8]

I am considering adding a coolant overflow tank to my BJ8 and I am thinking about putting it next to the radiator. I am considering a round verticals tank either 2” or 3” diameter with a 10” to 15” length.

Has anyone done this yet?

 

[BigGreen]

The things you need

Welcome to A.H. Spares!

cape-international.com

and some discussion

Radiator Cap

I have just installed a coolant recovery tank in the bugeye. It is the unit that Cape International sells. Expensive but handsome! I am using it in the Big Healey as well. This unit collects overflow from the radiator at the bottom of the tank and it has a drain line at the top of the tank to...

www.britishcarforum.com

I have the parts, and it is on the "to do" list

 

[GregW]

Hi Patrick,
I did pretty much what you describe. One snag I had was the top of the tank was right where the hood latch wanted to be. Something you want to be aware of.

 

[nevets]

I added an overflow tank, though not the Cape unit you are considering.

 

[BoyRacer]

I had a coolant recovery tank on my BT7 for over four years. I have an aluminum Wizard radiator with a 7 lb cap.
I removed it this last summer because I never lost any fluid from my radiator....ever! The only explanation I can come up with is that because I have the aluminum radiator the heat dissipates so quickly that it never had any boil over.

 

[Patrick67BJ8]

Hi Patrick,
I did pretty much what you describe. One snag I had was the top of the tank was right where the hood latch wanted to be. Something you want to be aware of.
View attachment 95044

Thanks for the photo Greg!
I searched and found Tanks like you have which is the type I think I want. Some searching I was able to learn more especially how they operate. I still need to identify the radiator cap I need to make it work. I recently purchased a polished stainless cap before I thought about doing a Coolant Tank, which I still have to install after finishing other work on my car. Photos below are of the types of Tanks with tech info. I did not know how they were constructed internally until I found this info.

 

[Michael Oritt]

I mounted an overflow/recovery tank to the right-side shroud support.

 

[Patrick67BJ8]

I mounted an overflow/recovery tank to the right-side shroud support.

That would be easy, but my BJ8 horns are there. AC stuff takes up too.
Thanks

 

[John Turney]

That would be easy, but my BJ8 horns are there. AC stuff takes up too.
Thanks

Once I put the AC in (and two reservoir tanks for the brakes & clutch), I couldn't find room for an overflow tank.

 

[Hamish Racing]

You want a period brass tank from an mg like this.

MG Midget 1275 MGB Tr7 Coolant Expansion Overflow Tank for sale online | eBay

Find many great new & used options and get the best deals for MG Midget 1275 MGB Tr7 Coolant Expansion Overflow Tank at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

Put a blanking cap on the rad and the pressure cap on the tank and run a tube from the rad overflow pipe to the tank.

 

[Michael Oritt]

You want a period brass tank from an mg like this.

MG Midget 1275 MGB Tr7 Coolant Expansion Overflow Tank for sale online | eBay

Find many great new & used options and get the best deals for MG Midget 1275 MGB Tr7 Coolant Expansion Overflow Tank at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

Put a blanking cap on the rad and the pressure cap on the tank and run a tube from the rad overflow pipe to the tank.

I think a recovery tank is a better choice than an overflow tank as It minimizes having to top off the radiator and eliminates having to drain the catch tank to prevent coolant overflow onto the floor.

 

[Patrick67BJ8]

I think a recovery tank is a better choice than an overflow tank as It minimizes having to top off the radiator and eliminates having to drain the catch tank to prevent coolant overflow onto the floor.

Wouldn’t the excess overflow tank fluid return to the radiator after the engine has cooled down by vacuum? I read that you need to put some coolant in the overflow tank so the radiator can make a vacuum to return it to the radiator? The drawings I posted show overflow function in the tank doesn’t start until about 2/3’s the way up inside the tank.

 

[Hamish Racing]

Patrick yes on the whole you are correct the overflow tank feed pipe needs to extend to the bottom of the tank and submerged to draw the fluid back.
what iim not sure of is if all pressure rad caps allow this reverse flow once the pressure snd temps drop and the pressure rad cap is closed by it’s spring ?

 

[red57]

Hamish Racing nailed it - you need the hose to go to the bottom of the expansion tank (stay submerged) and a cap that has the upper rubber seal that seals against the upper surface of the filler neck so it will maintain a vacuum when it cools down so it will pull the fluid back into the rad. With a one quart expansion/recovery tank you never need to add coolant, I've had this for 25 years. and it works perfectly.

 

[Patrick67BJ8]

Hamish Racing nailed it - you need the hose to go to the bottom of the expansion tank (stay submerged) and a cap that has the upper rubber seal that seals against the upper surface of the filler neck so it will maintain a vacuum when it cools down so it will pull the fluid back into the rad. With a one quart expansion/recovery tank you never need to add coolant, I've had this for 25 years. and it works perfectly. View attachment 95078

This is the two caps I have. One is old and a new polished stainless one. Both caps have the rubber as the one in the photo.

 

[red57]

So, both should work as coolant recovery type caps but in your picture # 0233 it looks like the stainless steel one is for a deeper filler neck than the other one - just make sure you use a cap made for the depth of your radiator. Mine is a custom made radiator and they used a 3/4" deep neck but a stock Healey radiator I have in my shop has a 1" deep neck (which I think may be standard for all Healey radiators). This picture is the stock 1" deep cap on the left and my 3/4" deep cap on the right - both 7 lb caps.

So, it looks like you show a 3/4" on the left and a 1" on the right in your picture. Measure your radiator from the top flange to the inner lower flange the cap seals against - cap distance will be about 1/16" to 1/8" greater when relaxed than the depth so the spring is slightly compressed when the cap is tight.

 

[Patrick67BJ8]

So, both should work as coolant recovery type caps but in your picture # 0233 it looks like the stainless steel one is for a deeper filler neck than the other one - just make sure you use a cap made for the depth of your radiator. Mine is a custom made radiator and they used a 3/4" deep neck but a stock Healey radiator I have in my shop has a 1" deep neck (which I think may be standard for all Healey radiators). This picture is the stock 1" deep cap on the left and my 3/4" deep cap on the right - both 7 lb caps.

So, it looks like you show a 3/4" on the left and a 1" on the right in your picture. Measure your radiator from the top flange to the inner lower flange the cap seals against - cap distance will be about 1/16" to 1/8" greater when relaxed than the depth so the spring is slightly compressed when the cap is tight.

The shorter cap has been on my radiator for a long time, but the stainless was a recent purchase. I’ll do a depth check.

 

[Patrick67BJ8]

So, both should work as coolant recovery type caps but in your picture # 0233 it looks like the stainless steel one is for a deeper filler neck than the other one - just make sure you use a cap made for the depth of your radiator. Mine is a custom made radiator and they used a 3/4" deep neck but a stock Healey radiator I have in my shop has a 1" deep neck (which I think may be standard for all Healey radiators). This picture is the stock 1" deep cap on the left and my 3/4" deep cap on the right - both 7 lb caps.

So, it looks like you show a 3/4" on the left and a 1" on the right in your picture. Measure your radiator from the top flange to the inner lower flange the cap seals against - cap distance will be about 1/16" to 1/8" greater when relaxed than the depth so the spring is slightly compressed when the cap is tight.

Depth check.
Radiator fill spout: 15/16”
Radiator Cap: photos attached.
*Image #238 is from the top of the rubber inside the cap to the rubber attached to the seal. Measurements done with cap upside down.
*Image #239 is from cap inside metal to rubber seal metal. Measurements done with cap upside down.
*Image #240 measurements are from the shorter radiator cap.

 

[red57]

If the shorter cap has been on your car for a long time, that's the height I would stick with. A 1" deep cap in a 15/16" deep filler neck means about 1/16" compression when the cap is on & tight which seems about right to me.

Was this taller one sold to you as fitting a Healey? If so, perhaps it's worth confirming with the supplier that it truly is correct, or perhaps not all Healey radiators are the same? If there is a local radiator shop in your area, I suggest asking them for a correct 7 lb cap for your radiator.

 

[Michael Oritt]

Wouldn’t the excess overflow tank fluid return to the radiator after the engine has cooled down by vacuum? I read that you need to put some coolant in the overflow tank so the radiator can make a vacuum to return it to the radiator? The drawings I posted show overflow function in the tank doesn’t start until about 2/3’s the way up inside the tank.

The fluid would return to the radiator only if the hose went to the bottom of the tank--which makes it a recovery tank. I don't know how the MG tank is plumbed but a mere catch-can does not provide for recovery.