Thermostat

[killick]

I am replacing the thermostat on an Westerbeke two cylinder 12 hp diesel engine with a pirate part as the original part is to expensive to import.The present thermostat has a very small hole drilled through it which the replacement does not have. What is the purpose of this hole and is adviseble to drill one in the new thermostat? Advice will be appreciated.

 

[Trundlebug]

As I understand it the small pilot hole was there for allowing some small movement of water in very cold conditions to prevent cracking of the block as the water expands as it freezes, by allowing some water through.

Therefore not necessary in almost all circumstances, just make sure you have enough antifreeze in the system (if your motor isn't raw water cooled).

 

[LittleShip]

It also allows air to leak out from behind the stat when refilling the engine.

I drilled a small hole in my new stat to help bleeding and to provide a little water flow just in case the stat was to fail shut.

Personally I would drill a small hole, it was there in the original for a reason.

Tom.

 

[VicS]

I cannot see that it will help if the water freezes .

I always assumed the purpose was to allow trapped air to escape.

Id feel inclined to drill a small hole to match the original. Provide you dont drill a larger hole I'd not think it could do any harm and it might just prevent problems that trapped air could cause.

 

[david_bagshaw]

I always thought it was there to ensure the thermostat didnt remain in colder pocket and below opening temp while the cylinder head overheated, along with ensuring water is on the bulb & not in an air pocket