Coolant expansion tank .
I had already fitted an overflow bottle in an attempt to keep the radiator relatively full of water , but unfortunately it only seemed to work one way . Water discharged into the bottle as it warmed up , but never returned to the radiator on cooling . I had ensured that the overflow pipe , which had the open end cut at an angle , went right to the bottom of the bottle and that the added joint between the rad cap and the rad was air/water-tight . This set-up appeared to be extremely sensitive to the slightest air leak so I decided to try something else .
A spherical expansion tank from a VW Golf was obtained from the local breaker's yard and fitted just in front of the battery and as high as possible . The bottom pipe was connected to a T-piece on the heater return pipe and the small top bleed pipe was connected to the overflow pipe on the radiator . A thin strip of aluminium was placed under the rad cap pressure valve to keep it from seating , thus providing a permanent bleed . This system appears to be much more efficient so far , but has shown up a very slight leak where the filler neck joins the radiator body ( no wonder the overflow bottle never worked ) .
I intend testing this for some time , and if successful , the next step will be a recore , without the starting handle hole , and the filler neck will be cut off and blanked off , leaving just a small pipe for bleeding to the expansion tank .
April 2004: The radiator came back from the local repair shop with a new core and all the joints resoldered .I had finally decided to keep the original filler and neck but not the starting handle hole , so it was a semi-stock rad that was refitted to the car .At the same time the pressure rating was checked on the VW header tank cap and this turned out to be much too high at about 2 kg/cm2 or 30 psi . After much trial and error , the pressure was reset to about 400gr/cm2 or 6 psi . After a couple of months use , the cold water level is always exactly at the half-way mark on the transparent header tank , which means that it is very easy to check without having to undo the original radiator cap , thus avoiding stressing the soldered joints where the filler neck joins the radiator .
