VS Clubby overheating

[The Whale]

My VS Clubby 5 speed occasionally overheats and dumps around 2 litres of coolant from the overflow tank.

Over the last 12 months I've fitted a water pump, a new alloy radiator, replaced the temp sender and sensor, all the hoses, including to / from the heater, all the clips, the thermostat, and caps of the correct rating on the radiator and the overflow tank.

After all that work, a 30 minute drive on a 30 deg day with the aircon operating, and the auxiliary thermo fan also operating, results in the indicated engine temp increasing from its usual 25% FS to 50% FS.

When the engine is then shut down the radiator can be heard gurgling, and coolant spills into the overflow tank, and from there overflows onto the ground.

Once cooled down the radiator takes around 2 litres of coolant to fill.

I don't know where to go from here, so all help and advice greatly appreciated

 

[EYY]

Replace your fan clutch and try another new radiator cap.

 

[afstruct]

^ ^ ^ x2

 

[The Whale]

Might have to try that as everything else has been tested and / or replaced already

 

[Immortality]

Boiling is a classic sign the radiator cap isn't maintaining pressure which will allow the system to boil at a lower temperature and blow out all the coolant.

 

[Deuce]

My most recent cooling system drama was the thermofan clutch going soft. Fan had literally zero resistance to spinning when the engine was shut off.

Also, yeah I think that it is every 2psi of pressure will raise the boiling point of water by 1°
So a 16psi cap will raise boiling point of straight water to 108°

Maybe check the sealing surface of the cap in the radiator. I don't trust alloy radiators any more.

 

[gtrboyy]

Flushed the block properly?

As in taken 2 bolts out flushed it clean & not just cooling system.

I had original 1982 clutch fan on an angry 355 in vh...fan worked great yet practically no tension left in it whish surprised me big time as it never got hot with factory shroud & 2 extra holes in thermostat.

 

[The Whale]

Boiling is a classic sign the radiator cap isn't maintaining pressure which will allow the system to boil at a lower temperature and blow out all the coolant.

Changed the cap prior to the last incident (?)

 

[The Whale]

Thank you.....I'll try that, but even though a quick pressure test was OK, I'm starting to think that there's a small leak in the head gasket. Might do another test, and leave it hooked up for a while.

 

[The Whale]

Flushed the block properly?

As in taken 2 bolts out flushed it clean & not just cooling system.

Was flushed properly, but as per my previous reply to another comment, I'm going to leave the pressure tester connected for longer this time, as even though I can't see any bubbles in the coolant at the radiator neck, I'm starting to think that there's a small breach in the head gasket $$$$$