| If you have had the car serviced recently, an air-lock may have been
introduced, when the water flow thermostat opens the hot water can heat
the trapped air ( which may be in the Heater) causing sudden
pressurization of the cooling system. The expansion bottle may also
contain the pressure valve. If it does, water forced by the heated air
will fill the expansion bottle before pouring out of the valve.
So how is it cured ? You don't say what car you have, but a possible
way of clearing air apart from Manufacturers bleed-points in hoses, is
to leave the pressure cap off the expansion tank, let the engine heat
up (blowing water & air out the expansion tank, then top-up with hot
water/antifreeze. All safety rules apply as normal if you want to try
this, but its cheaper than stripping everything down.
Of course, it may not be air at all 8^)
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| On one occasion when I observed the level rise dramatically, I opened
the cap, the coolant oozed out completely and what's left is a dry
tank! Realizing that, I turned off the engine and let it cool down a
bit before adding some water in it and later bought a can of coolant
and poured it into it. Recent observations had shown that the water
rise is not that high anymore and the temperature is kept within the
normal range, about 80 deg C.
Your explanation about air-lock could be quite correct. I think this
time I should open the cap and heat the engine and let the coolant rise
and expand to force out possible trapped air!
I'm afraid to bring the car back to the workshop again because the cost
is too high to repair.
Regards
TTH
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| Air locks are a common problem in "header-tank" type cooling systems.
Many are self-bleeding, but some are not. I would guess that yours is
one of the latter. These fall into two types, those with a bleeder, and
those without.
To find a bleed "nipple", look for something valve-like in something
metal that a coolant hose enters or leaves. It will be at the highest
point of the engine, higher than the normal level of the coolant in the
header tank.
If you can't find one, then you will have to bleed it yourself. Often
it is impossible to get all the air out of such a system, but this
won't be a problem as long as you get most of it out. You need to find
the highest hose joint, either hose to hose, or hose to metal, and undo
it. Pour water into the header tank, holding said hose as high as
possible, until air stops coming out of it. Reconnect, and run the
engine for a minute or so. Repeat until no air can be extracted. Note
that you will lose coolant doing this, so have some spare. Also note
that squeezing the appropriate hose(s) can help release "trapped" air.
Laurie.
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|
I replaced the water-pump on my BMW and now seem to be plagued by an
airlock - almost no heater, temperature guage jumping around a lot, and
a bit of coolant loss when I stop.
There's no bleed valve/screw or expansion tank on this model ('86 318i)
and when I phoned the BMW service centre they just told me to jack up the
front and with the engine running, to add the coolant in slowly......
Ok I'll try it, but I want to get the set up right and not do any
unplanned damage ....
Should the radiator be full/almost full/partfull when starting this ?
Won't the stuff come pi**ing out once the thermostat opens ? Won't this
drag air around the system making it worse ??
If anyone cares to break this procedure down into simple steps or can
give any advice I'd greatly appreciate it
Thanks
Steve
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