Hi...nice to see you back on here!
Below is a quote from Badger.....
Thanks for that Brian, however, I believe the jiggle valve in the manifold has been removed, when I disconnect the pipe from the stub coolant flows freely from it, also I can blow through it easily.
I am at present having a bite to eat whilst I wait for the engine to cool a little before I perform yet another 3 point bleed, ive performed yet another sniff test and am confident that no gas is present, I've taken a short video of the coolant flow returning to the tank and the aeration of the coolant is quite alarming, (I'll try and post it later for your perusal), something I read somewhere was that it might be adviseable to fit a 2mm restrictor to reduce said frothing......could this possibly be feasible , in your opinion?
The ball valve is fitted to reduce the flow from the orifice when the engine is running and helps stop the chance of a blockage.
When the engine is running the ball will be pushed forward against the hole reducing the flow but when the engine is stopped it will roll back, this movement of the ball reduces the chance of a blockage. If it was just left as a very small hole it would block up very easily.
Obviously during the design of the cooling system the pressure differential before and after the valves will have been calculated to have the minimum flow to the expansion tank to allow the de-saturation to take place.
The other bleed/jiggle valve is at the left side of the engine which is in the heater circuit; this allows any air in this part of the system to go back over the top of the engine to the expansion tank through the long thin hose. This should connect to a ‘T’ piece just before the expansion tank with the other bleed valve outlet from the cylinder head/manifold, remove this pipe at the ‘T’ piece and blow down it to check it’s not blocked.
By the removal of the ball in the cylinder head/manifold valve and because of the pressure differential (higher pressure closer to the pump) you may be sending coolant via the ‘T’ piece into the heater circuit without going to the expansion tank first so not allowing any de-saturation, this may also stop any flow from the heater circuit back to the expansion tank.
If you are going to try to fit your 2mm flow restrictor to simulate the ball being re-fitted make sure that it is fitted between the outlet from the manifold and the ‘T’ piece, if it’s fitted after the ‘T’ piece and the expansion tank it may exacerbate the issue.
Brian.