12 replies to this topic

[Hulk]

Modified Van 1380cc/386cam/Dellorto45 carb PLUS more:
1976:
Top of radiator empties after running at high speed. I'm confident everything else is working well i.e. fan/thermostat etc. On normal running I don't lose any water however when I boot it I tend to lose water from my radiator. : After searching for expansion tanks in NZ I can only find imports from Japan which seem to have alot of inlets/outlets.

http://www.trademe.c...n-303286195.htm

Any advice would be greatly appreciated.

[bmcecosse]

It should NOT blow water out past the rad cap - try a higher pressure cap......... On my similar A series engined car - I simply have a plastic bottle on the end of the overflow pipe. Any water that comes out - is sucked back in when the engine cools.......

[Hulk]

Thanks for the reply. The water isn't coming out of radiator cap itself it's coming out of the overflow pipe. By water from the top of rad I meant the amount - it's just enough to expose the radiator matrix.

The plan:: if I place a expansion tank under the wheel arch and run the overflow hose into the bottom of the expansion tank any water I do lose will be sucked back into the radiator once the water has cooled. Does in matter that the expansion tank will be lower/higher that top of the radiator? Does the system need to be air tight? Do I need a pressure cap on the top of the expansion tank?

[Yoda]

On my similar A series engined car - I simply have a plastic bottle on the end of the overflow pipe. Any water that comes out - is sucked back in when the engine cools.......

I have just done the same to my sons Mini, i used and old washer bottle and bracket, fixed to the bulkhead and it works perfectly well.

The plan:: if I place a expansion tank under the wheel arch and run the overflow hose into the bottom of the expansion tank any water I do lose will be sucked back into the radiator once the water has cooled. Does in matter that the expansion tank will be lower/higher that top of the radiator? Does the system need to be air tight? Do I need a pressure cap on the top of the expansion tank?

You will not need a pressure cap for this type of setup, and as quoted, we placed it on the bulkhead, by the wiper motor. As long as the pipe is below the level of water in the expansion tank, it will work. If you want to have a cap on the bottle, make sure the hose goes to the bottom of the bottle and that the cap is vented, either by a short hose that sits just below the cap but above the water level or just a small hole drilled in the cap.

we put it on the bulkhead rather than under the wheel arch so its easy to see and easy to maintain. the system must NOT be air tight as explained above,

Edited by customcart, 20 July 2010 - 09:27 AM.

[Ethel]

I can't see how such a system will suck back the water - it takes excess pressure to blow steam past the cap. Suction should just seal the cap even tighter. The water will also be blown off as steam, once it has condensed is will have much less volume, so would be likely to suck out more coolant rather than push the water back into the rad - if it's a sealed system. If it's not sealed, lower pressure in the cooling system is as likely to collapse the hoses to equalise with atmospheric pressure..

A higher pressure cap is one option; if you're trying to increase the expansion volume you need something on the radiator side of the cap. http://www.minispare...=...5013&title= would allow you to attach a pressurised expansion bottle (which should have a proper pressure cap.


I think the real issue is likely to be inadequate cooling, which is allowing the water to get hot enough to boil, even at the pressure of the rad cap.

[cooperrodeo]

The correct cap to use is one which has two 'valves' in it. There is the heavy spring holding back the pressure inside the radiator and a lighter spring and valve in the centre. Positive pressure in the radiator holds this smaller valve closed, but negative pressure allows it to open and suck water back in from the expansion bottle.

[Yoda]

I can't see how such a system will suck back the water

Sorry, My mistake, i forgot to mention the reverse valved cap i fitted to the rad. Just happened to have a good one in my collection of old classic car parts . The other option as Ethel states is to use a non valve cap on the rad and a pressurised header from a later car with pressure cap.

I think the real issue is likely to be inadequate cooling, which is allowing the water to get hot enough to boil, even at the pressure of the rad cap.

This is true, the only reason for doing this on my sons car, is for a temporary fix until his new engine is finished.

[Hulk]

Thanks fellas for all your advice and input. I guess really I should be looking at upgrading my cooling system. I'm going to start with the simplest thing if giving the whole system a good flush!.

I will report back . . .

[Dusky]

 

I can't see how such a system will suck back the water

Sorry, My mistake, i forgot to mention the reverse valved cap i fitted to the rad. Just happened to have a good one in my collection of old classic car parts . The other option as Ethel states is to use a non valve cap on the rad and a pressurised header from a later car with pressure cap.

I think the real issue is likely to be inadequate cooling, which is allowing the water to get hot enough to boil, even at the pressure of the rad cap.

This is true, the only reason for doing this on my sons car, is for a temporary fix until his new engine is finished.

 

Where do you buy one of those caps/how are they called? :)

[Spider]

Most Auto Parts spares stores have them.

 

And while not the current conversation here, i always fit a Header or Overflow tank. IMO, these (and all cars for that matter) really should have one to prevent any air getting in to the cooling system. Most other cars BMC / Leyland / Rover produced using the A Series (and all other) engines had one, even our Mokes had them from the factory!

 

Coming back to Caps, here's a small variety of them;-

 

 

and a Recovery cap in some detail

 

 

 

 

 

 

BUT, be very careful that not only the 'poundage' is correct but also the reach of the cap, otherwise, when fitted it will have the wrong poundage. You need to measure the reach for your radiator or header tank. The wrong combination, which is dead easy to do, will take the poundage up from 13lb, to around 50 lb.

 

Checking the Radiator;-

 

 

and the Cap;

 

 

 

The combinations that give the correct Poundage will compress the Spring in the cap by only 2 - 3 mm, ie, a 20 mm neck in the radiator will generally have a 23 mm reach cap on it. If this is more like 4 - 5 mm it's not the right combination.

Edited by Moke Spider, 14 October 2016 - 07:39 PM.

[Dusky]

And then Just a case of searching 'recovery cap' on eBay and search for one with the right dinensions?
Or Are there easier ways to find one?
Got one of those wimpy Small motorcycle ones atm(untill I get the copper radiator delivered and Im Back on the good side :) )
40-41mm on the top side (visible side)
21mm reach and 28mm on the radiator side

Edited by Dusky, 14 October 2016 - 09:46 PM.

[Spider]

I don't know if this helps, but in a CPC Brand and for a long neck radiator, ie 25 mm on the Radiator Neck, The CPC P/N is 543-13. That is a recovery type. You maybe able to cross reference that brand and P/N with what ever you have locally or what you find on flee-bay.

Edited by Moke Spider, 15 October 2016 - 12:02 AM.

[Leonrjohnson]

I use a Mini Moke setup on all of my Minis: works great 

http://www.moke.com....5-radiator-caps