Page created by T April 6th 2013:
- 1 Thermostat Housings:
- 1.1 Thermostat Housing Securement:
- 1.2 High And Low Pressure Points:
- 1.3 Alloy And Cast Iron Thermostat Housings:
- 1.4 Grey 6 Cylinder Motors:
- 1.5 149 and 179 Engines:
- 1.6 161 And 186 Engines:
- 1.7 HQ/HJ 173 And 202 Engines:
- 1.8 HX And Later 173 And 202 Engines:
- 1.9 Thermostat Cover:
- 1.10 The Thermostat Cover Securement:
- 1.11 Six Cylinder VK Commodore Thermostat Housing:
- 1.12 Vacuum Controlled Heater Tap (3 Way Heater Tap.):
- 1.13 HJ Thermostat Operation:
- 1.14 HQ Has No Heater Tap:
- 1.15 Links:
- 1.16 Terms:
Thermostat housings on Holden grey, red, blue and black 6 cylinder engines changed with varying models. The changes were dependent on the location of the heater and whether or not the inlet manifold was heated by the exhaust or coolant.
Thermostat Housing Securement:
The Thermostat Housing is secured to the cylinder head by 3 bolts.
High And Low Pressure Points:
Locations in the cylinder head are points of high pressure, pressurised by the water pump. The intake to the water pump is a point of low pressure.
Alloy And Cast Iron Thermostat Housings:
Early thermostat housings were made from cast iron. Later thermostat housings were made from alloy. Retrofit alloy thermostat housings are available to replace the early cast iron type.
Grey 6 Cylinder Motors:
These used exhaust heated inlet manifolds and had no coolant supply lines in the thermostat housing. The heater supply line came from the rear of the cylinder head on the manifold side. The heater return was tapped into the water pump.
149 and 179 Engines:
These used exhaust heated inlet manifolds and had no Coolant supply lines in the Thermostat Housing. The Heater supply line came from the rear of the cylinder head on the manifold side. The heater return was tapped into the water pump.
161 And 186 Engines:
These engines used coolant heated inlet manifolds and were the first to use thermostat housings with cooant supply points. This type only allows for coolant flow when the thermostat opens.
HQ/HJ 173 And 202 Engines:
These engines were the last to use coolant heated inlet manifolds. This type allows for coolant flow only when the thermostat opens.
HX And Later 173 And 202 Engines:
These engines used exhaust heated manifolds and used thermostat housings with coolant supply points modified to supply the heater only. This type allows for continuous coolant flow, whether the thermostat is open or closed. They were used with an horseshoe hose fitted between the thermostat housing and the low pressure return pipe on the water pump.
This is made from alloy and sits on top of the thermostat housing. From HX onwards these held a Thermal Vacuum Switch for controlling the Distributor Vacuum.
The Thermostat Cover Securement:
The thermostat cover is secured to the Thermostat Housing by 2 bolts.
Six Cylinder VK Commodore Thermostat Housing:
The six cylinder VK commodore thermostat housing integrated the thermostat cover with the thermostat housing. The EST VK mounted the Coolant Temperature Sensor in the top. The EFI VK mounted the Vacuum Advance TVS in the top.
Vacuum Controlled Heater Tap (3 Way Heater Tap.):
This is correct except for HQ 350 V8s.
It goes like this.
Without Factory A/Cond
HQ/LH/LX/UC - No Valve
HJ - No valve for base models, 3-way cable valve with 'forced-air' ventilation.
HX/HZ/WB - No valve for base models, 2-way cable valve with 'forced-air'. With Factory A/Cond
HQ(Exc. 350)/HJ/LH/LX (without ADR27a) - 3-Way Vacuum Valve
HQ 350 plus all cars with ADR27A - 2-Way Vacuum Valve. Dr Terry End of Submission by Dr Terry.
HJ Thermostat Operation:
By Another_HQSS 02/07/13@12:12
The standard HJ heater demister doesn't use a water tap. The internal heater box flaps direct the air flow through the core or bypass it depending on hot or cold selection on the controls.
If you change the internal heater box to use the middle vents you do need a three way tap and a T piece on a HJ, as it provides a bypass for water flow.
If you have a HJ engine you need continuous water flow through the inlet manifold, as the heater inlet is also the inlet manifold pre-heater. HX-Z use the two way tap as they use exhaust heat for the inlet manifold pre-heating and it doesn't matter if the water flow stops. Three way can be also be used with a gas converter on later models to maintain flow through the converter while cutting off the heater flow.
Anthony - Lettuce Alone SS
End of submission by Another_HQSS
HQ Has No Heater Tap:
No heater tap for HQ's. Heating is controlled by a flap that opens/closes. The heater core is always the same temperature as the radiator water. I thought maybe the aircond HQ's may have had a tap, but my diagrams show they don't. The flap is prone to rusting if the heater core leaks, which I believe is common (I had to replace my Monaro (Kingswood for the trolls) flap, hence the amount of these cars today you see that do not have the heater hoses connected up.
End of submission by Keijames.