Radiator cap Q

[Postie Bob]

I have fitted a new 3 core alloy radiator in my `Bedabago` and need a bit of advise....
After the motor ( red 186 ) has cooled right down after a run there is quite a bit of pressure in the cooling system when I remove the rad cap .
The cap that came with the new rad has 1.1 stamped on it and I,ve been told that the cap is for a coolant recovery system .
I don`t have that system .  Should I fit one?  Should I use a different cap?
Cheers, Bob.

[Sammy]

generally you can tell a coolant recovery system cap as it has an inner seal on the end of the spring loaded part then around the outside base of the cap there is another seal.... non recovery only has the inner one on the spring loaded part.

they are different pressures to allow both to blow off pressure if needed, but then the recovery one will be a lower pressure, as it willl then bleed that pressure off from the inner seal and into the overflow tank, then as the engine cools it will actually suck the coolant back in.

you will typcially find on a recovery system if its working properly and the cap is removed with the system cold that the radiator will be full, where as a non recovery will be half empty in the top of the tank etc.

the recovery option is the best if you have the room for a overflow tank as there less chance you'll run it dry, and to top it up you just make sure the overflow has coolant in it full when hot and it will then suck that back in when cooled.

obviously running the wrong cap for the setup will effect how much pressure the system can hold before bleeding off.

[Postie Bob]

Ta for the reply Sammy.
How / where do I find out what cap is right for my system?
My engine is a standard Holden 186 and temp sits on around 190 when cruising ( bit higher around town ).
I don`t have any shroud around the fan and am guessing that`s why it creeps up at slower speeds ( will work on that )
The coolant level remains constant .

[rumax]

I use a coke 2 litre bottle hooked on the passenger side bonnet hinge with 2 cable ties, so doesn't have to be high tech. 

[Postie Bob]

I think I have the room for an overflow container. Not sure about the coke bottle.... maybe a preserve jar or something  .
Is it critical what height it`s at with regard to the radiator cap?

[rumax]

No. As long as the hose is in the bottle (and there is water in it), it will refill the radiator. mine is on the passenger side, with the base at basically floor level.
 

[John Abbott]

I just bought one of those universal plastic ones and fitted it down on the drivers side below the master cyl. Tight fit but works great...