Dwomby wrote:
In reply to a message from Frank Andersen sent Mon 6 Apr 2009:
Frank
I agree, 8 litres is way too much to be lost just to constricted or
blocked coolant passages but I am wondering if there is some point
that there is enough blockage to cause a big air pocket. To all
intents and purposes, the cooling system looks full when I have
only put 10 litres into it!!!
An eight liter air pocket defies credibility, David - and even deducting
coolant remaining after draining a large air pocket cannot be sustained.
As air is lighter than water it will be forced upwards and there are
simply to many ways of the air escaping to be trapped over time…
I definitely only put in less than 3 jugs of water/coolant
mixture. Each jug is labelled 1 US Gallon / 3.78 L. So that is
why I say around 10 litres went in. Also confirmed by measuring
the water that I drained out of the lower radiator pipe drain plug
which came to just over 2 of the above jugs.
Water will be retained in the engine unless caps are removed to allow
air to enter. Any further loss due to parts removal…?
I also know that the water rail was full because I pulled and
replaced the temperature sensor (for gauge, not the CTS) and it was
full to the brim.
Which, if the engine is left standing indicates that the system is
indeed full - however strange…
The vent lines do run as you say from header tank to top of
radiator and expansion tank respectively. For what it is worth, I
noticed when engine was running and header tank cap was off that
coolant flowed from the top of the radiator line into the header
tank. I will check the line to expansion tank next weekend when I
get home.
However the system is filled; it fills up from the bottom and up,
forcing air out through the various passages. Filling at the header or
expansion tank coolant flows ‘backwards’ through the pump and up the
radiator - air there being vented through the vent hose to the expansion
tank. While block air escapes via the water passages in the head into
the rails either though the header tank opening or vent hose there.
Other air back through the heater core via the open heater valve to the
rail. And water rail is vented through the vent hose at the header tank
to the top of the radiator and to the expansion tank. There is no place
for air to be trapped for any length of time…gravity wins…
I did not run engine long with header cap off, but although coolant
level came up maybe a 1/2 inch - it did not overflow.
Nominally the coolant volume varies by around 1 1/2 pint between cold
and hot. Completely filled up this amount is forced out of the system on
the first heat cycle. So when the coolant again ‘shrink’ as it cools an
air pocket is left on top of the remaining coolant. To be compressed to
the normal system pressure as the coolant again expands - in this phase,
and during further cycling of the engine, the ventlines transfer coolant
and air internally, nothing is vented outside…
Thoughout the filling the thermostat remains closed, but as you can see
there is ample venting either side. The ‘jiggle pin’ hole allows
crossflow and ballances coolant distribution during normal cycling, but
another intent is to ensure that hot water rail coolant can ‘wash over’
the thermostat ensuring that it get the right idea about rail temps…
I am away all week but should get a few hours to try things again
this weekend. I will run the engine longer with the header cap
off, re-exercise the heating system, try to raise the front end to
encourage ‘burping’. If that fails, I will get a flushing solution
and a flushing ‘T’ for the heater hose and maybe remove the block
drain plug too and hope for the best.
Until this ‘is it full of coolant or not’ issue is resolved, I will
leave alone the ‘why does the gauge read so high / is it really
overheating or not’ issue. One thing at a time - right?
Right you are, David - the main point is not to be stuck with a fixed
idea of what is the fault…
Frank
xj6 85 Sov Europe (UK/NZ)>The original message included these comments:
full 18 liters is still unlikely to be drained off. Are you sure that
you have counted the refills properly. Ie, have you filled it in
forgotten instalments?
On another tack; are you soure that the vent lines are properly
connected and not obstructed? As yours is a 78 the cooling system may be
parts of the engine - I simply cannot conceive 8 liters of rust taking
the part of coolant…
You can backflush through the heater hose at the end of the water rail,
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