Drilling holes in thermostat?

[SimonA]

My BMC 1.5 has been running cool ever since it was rebuilt, and the water in my calorifier takes around 2 hours of engine running to heat up. On taking out the engine thermostat I found it has 3 holes drilled into it. Reading on the interweb it seems this is done to help bleed the cooling system when it's first filled.

I think the holes must be causing the engine to run cooler, but is there any valid reason for drilling holes in the new thermostat?

 

[VicS]

You may be right about holes to allow air to escape while filling with coolant.

I would only drill one small hole and only if necessary

 

[DownWest]

How big are the holes. As Vic says, one 1mm would do. ( and often used to there from new)
DW

 

[sailorman]

My BMC 1.5 has been running cool ever since it was rebuilt, and the water in my calorifier takes around 2 hours of engine running to heat up. On taking out the engine thermostat I found it has 3 holes drilled into it. Reading on the interweb it seems this is done to help bleed the cooling system when it's first filled.

I think the holes must be causing the engine to run cooler, but is there any valid reason for drilling holes in the new thermostat?

the flow & return to the calorifier may be air locked

 

[SimonA]

How big are the holes. As Vic says, one 1mm would do. ( and often used to there from new)
DW

About 4 or 5mm.

 

[DownWest]

Those are pretty big, just to let some air past. Def slow up the heating process. These engines where designed to run at faster RPM in road vehicles, so chuntering along in a boat at low RPM the water needs to be kept in the block/head intill it reaches around 80c and maintained there. Otherwise it is running inefficiently and will lead to other probs.
DW

 

[VicS]

About 4 or 5mm.

I should think 3 holes that size will prevent it reaching anything like the correct operating temperature.

.

 

[Bilgediver]

I should think 3 holes that size will prevent it reaching anything like the correct operating temperature.

.

I usually only do 1 hole at 1 mm if needed.

 

[Lakesailor]

It was a common mod on "A" series engines that had been tuned, perhaps someone assumed it was a "good thing" for any engine.

 

[Bilgediver]

It was a common mod on "A" series engines that had been tuned, perhaps someone assumed it was a "good thing" for any engine.

Some had the hole in rom new with a wee captured brass ball that locked in place under pressure and fell away when no pressure from pump.

 

[jackro]

There is no need to drill holes in a thermostat as there is already means to bleed air via the jiggle pin (a valve in the form of a brass ball that seals the hole under pressure). Should you drill holes the engine will not run at the correct temperature. To test a thermostat place it in a saucepan with a thermometer and check that it opens at the temperature stamped on the thermostat, usually at the bottom of the wax capsule.

 

[2Tizwoz]

Some had the hole in rom new with a wee captured brass ball that locked in place under pressure and fell away when no pressure from pump.

Whilst others have a piece of brass or plastic which allow air to escape but moves to restrict the water flow.

No doubt a pice of plastic of some nature can be fitted to yours.