I don't think my response to Michael made the list; maybe I went over a size
limit? In case anyone needs good directions for purging air, here's a shorter
version of my note to Michael including Hank van Cleef of the Mercedes list
talking about "burping" any cooling system. As it happens, this subject was
discussed on the Car Talk rerun this morning as well.
Hank says:
Indeed, I probably should change the subject to "In which another DIY
learns that cooling systems need to be burped when refilling them."
Yes, they all need burping, and some of them can be rather cranky
about it. I've seen several cars that wouldn't burp idling on the
shop floor---needed to be taken out and driven around the block.
General procedure for refilling the cooling system, after doing a
thermostat or water pump, is to pour in about a gallon of coolant,
start the engine, and fill the reservoir until the level is above the
water pump and thermostat. Let it warm up. When the engine heats up
and the thermostat opens, you'll see a little steam coming out the
filler, and the upper hose will get hot (it says here). Often
accompanied by a belch out of the filler, followed by the coolant
level vanishing---that's when you add more. Following that, put the
filler cap on loose, and take it for about a 1-mile loop. Turn on the
heater---you should get heat long before the thermostat opens. Maybe
not a lot, but definite heat. No heat=no coolant flow. Watch the
temp gauge. If it starts heading for the moon, you're "test drive"
route should have been chosen to get you back to the shop (or shade
tree) before you get into serious overheat. Fill it again, and repeat
the test drive. I recalls some Ford products from around 1960 that
simply refused to burp out completely and took 3-4 iterations of
"around the block---refill" before they were full enough for road use.
Of course, you check for leaks while doing this. Don't be surprised
if some coolant burps out of the loose cap----just like burping a
baby. The steam coming off a radiator and tank after this can be
alarming, if you're not prepared for it.
Generally when your work on a system, finish the job, and discover
that something else involving that system is behaving oddly, it means
that you haven't really finished the job yet. A temp gauge that was
working before you started is very unlikely to quit working, as long
as you haven't done something to knock the wiring loose. That's easy
to check. In this case the temp gauge was simply saying "burp me."
--
Steven Newell
Littleton, CO
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