Welsh plugs are part of the engine block and the head. When the engine block and head are manufactured, part of the casting process is that these parts have the welsh plugs fitted where the machines are able to enter and then when the casting is finished a welsh plug is fitted to seal off the cooling or oil system.
THINGS TO LOOK FOR
Welsh plugs can leak at normal operating temperature. When this happens, stop the engine and get the vehicle towed to the garage.
IS IT EXPENSIVE TO REPAIR?
Nearly all welsh plugs are expensive to repair as they are hard to get to. The welsh plugs themselves cost only a few dollars each but the labour is the expense. Welsh plugs are either made of brass or steel, cup or dish. It is best to consult your motor reconditioner to work out which is the best one to fit.
TEMPORARY REPAIR AND LONG TERM REPLACEMENT
If a single welsh plug is found to be leaking it may be a consideration to get all the welsh plugs replaced at the same time. It really depends on how long you intend to keep the vehicle. Once any welsh plug is replaced, always change the water and add corrosive inhibitor on a regular basis, eg every 12 months or 10,000-20,000Kms.