Air in Me Pipes?

[Oldone]

Hello Persons
A minor niggle. After the traumatic misery of a blown cylinder head I have been keeping a close watch on the coolant level of my truck. It’s a 1992 2.4 ssr-x. Now I find that even after leaving the beast for two or three days unused. A small residual pressure remains in the cooling system and is released when the filler cap is removed squirting coolant around. My first thoughts were that the new head had failed. After removing the thermostat temporarily I pushed my thumb into the filler cap hole to see if I could detect any pressure when the engine was running. My thumb got a little warm but I could not detect any pressure. No coolant was pushed out of the filler hole and a good flow could be detected. Could the water pump be sucking air and inflating the rubber hoses. Someone may have experience the same symptoms. If you have I would like to hear about it.
Don

[Smurf]

Hi Oldone

I have just done my head, infact i was at the pit parked next to "Lickit" with my bonnet up checking the coolant as i only finished the job the night before.
The water pump should not be able to suck air, if it had a problem there it would weep water when the system warms and pressurises.
I cant see that the pressure could be due to a faulty head or even gasket as the air pressure would be very high and if run without a rad cap it would force most of the water out of the system.
Do both your heaters work nice and hot????? if so you shouldnt have any airlocks.
The only feasible explanation i can think of is that the water return channel in the rad cap is blocked and what you actually have is a vacuum once it has cooled. The sudden change in pressure of the system when you remove rad cap causes water to rush out as it "expands"??????
Check to see if the expansion bottle level rises when engine is warm then drops again when it cools, this should tell you if the cap is at fault.
Is it using any water????
Hope that may help in some way, if on the other hand it is a load of old rubbish then i apologise in advance but cant think of any other reason.

[NiftyNev]

Hello Persons
A minor niggle. After the traumatic misery of a blown cylinder head I have been keeping a close watch on the coolant level of my truck. It’s a 1992 2.4 ssr-x. Now I find that even after leaving the beast for two or three days unused. A small residual pressure remains in the cooling system and is released when the filler cap is removed squirting coolant around. My first thoughts were that the new head had failed. After removing the thermostat temporarily I pushed my thumb into the filler cap hole to see if I could detect any pressure when the engine was running. My thumb got a little warm but I could not detect any pressure. No coolant was pushed out of the filler hole and a good flow could be detected. Could the water pump be sucking air and inflating the rubber hoses. Someone may have experience the same symptoms. If you have I would like to hear about it.
Don

If there are none of the other symptoms associated with a cracked head then don't worry.My 2.4 will do the same after being left over night.It cools quite a bit and will warm up slightly in the morning just because of ambient temperature.If the cap is removed then a small amount of coolant will escape due to the small amount of pressure buildup.

Neville

[Oldone]

I have just done my head, infact i was at the pit parked next to "Lickit" with my bonnet up checking the coolant as i only finished the job the night before.
The water pump should not be able to suck air, if it had a problem there it would weep water when the system warms and pressurises.
I cant see that the pressure could be due to a faulty head or even gasket as the air pressure would be very high and if run without a rad cap it would force most of the water out of the system.
Do both your heaters work nice and hot????? if so you shouldnt have any airlocks.
The only feasible explanation i can think of is that the water return channel in the rad cap is blocked and what you actually have is a vacuum once it has cooled. The sudden change in pressure of the system when you remove rad cap causes water to rush out as it "expands"??????
Check to see if the expansion bottle level rises when engine is warm then drops again when it cools, this should tell you if the cap is at fault.
Is it using any water????
Hope that may help in some way, if on the other hand it is a load of old rubbish then i apologise in advance but cant think of any other reason.

Hi Smurf
Thanks for your interest. I think I have worked out what is happening.
When I fitted the new head I also fitted a new rad. Very shiny with no pinholes. Now with no escape route a little pressure remains trapped in the system. Most of the older Surfs I have looked at have had pin holes in the top tank of the rad and will not have the trapped pressure when cold.
Don

[Oldone]

If there are none of the other symptoms associated with a cracked head then don't worry.My 2.4 will do the same after being left over night.It cools quite a bit and will warm up slightly in the morning just because of ambient temperature.If the cap is removed then a small amount of coolant will escape due to the small amount of pressure buildup.

Neville

Hi NiftyNev
I think you have the answer. Ambient temperature changes must affect pressures in a completly sealed system and only change when the engine warms up and lifts the rad cap to release the higher presure into the expansion tank.
Don