How do I burp the system?
Hi,
I'm not Carl, but if you don't mind a long drawn out description, I'll
toss my 2 cents in here... (and when I say LONG, it's LONNNNGGGG!
Sorry!)
First, double check your OEM t-stat. Is there a small hole drilled
somewhere in the flat metal section of the housing, probably with a
little jiggly thingie in it? It's even called a jiggle valve, and it's
purpose is primarily to allow a tiny bit of flow thru the t-stat when
things are cold. Theoretically, it should let air bubbles move thru the
system. I'd be careful about standing on that theory, though!
Anyway, IF your t-stat doesn't have this jiggle valve, ask your Subie
parts guy if you've got the right one. Maybe they've changed things, but
the older ones all had it. I've got an OEM and a Stant sitting here as I
type this: they've both got the valve, but I'd suggest using the OEM
because the opening is considerably larger diameter than the Stant.
Regardless of the brand you choose, most people I've talked to, and most
of the books I've read, say to install the t-stat so the jiggle valve is
pointed toward the outlet hose on a horizontally mounted housing, or UP
in a vertical housing.
Now, on headgasket fragility and air bubbles and all that...
You're probably gonna get zillions of ideas and suggestions, all of
which involve some truth, none of which tells it all! Subarus may or may
not have more than their share of troubles. I've got two Toyotas in
addition to my Subie, and BOTH of them have engines that are notorious
for blown HGs--one's the supposedly "bulletproof" 22R 4 cylinder, the
other the 3.0 liter V-6. I'm not sure what valid correlations can be
drawn, but both are also genuine PITAs to bleed the air out of, and some
sources blame the V-6 HG failures directly on air pockets w/ resulting
hot spots (same indictment that's leveled at certain Subies.)
What I've learned from the Toys has helped w/ my Subie. It seems a
horribly time consuming process for those of us short on patience, but
maybe it will help you. Plan on taking the better part of a day, and
probably making a mess, but you should end up w/ decent results if
you're careful. (And remember, too, mine is only ONE of several methods
people have found to work well. So don't take it for gospel!)
First, when putting in new coolant, mix your own using 50-50 antifreeze
and DISTILLED water. There's a growing body of information that links
both headgasket and premature hose failures to corrosion and other
damage from electrochemical activity within the cooling system. The
distilled water arguably MAY help reduce this in addition to the known
benefit of NOT adding any of the minerals in one's tap water. You can
buy pre-mixed 50-50 coolant, but I would rather know mine's REALLY mixed
w/ distilled water.
Then put your heater on full "hot." Many Subies have a constant flow
heater, unlike systems w/ shutoff valves in the coolant lines, but it's
still best to do this, "just in case."
Now, fill your system SLOWLY until it's full to the top of the filler
neck. You can do this on level ground, or with the nose of the car
pointed slightly uphill. Point being you want the filler neck at the
highest point in the system. Let things sit a few minutes to see if the
level drops BEFORE starting the car.
Now take a turkey baster or other siphoning device, and remove some of
the coolant until the level is just over the top of any tubes, whether
vertical or horizontal. Once this is done, you can start the car,
leaving the radiator cap OFF. Some models have an air bleed somewhere in
the system--if yours does and you know where it is, go ahead and open
it. Just let it idle for now until the t-stat opens. Check the temp
gauge frequently and watch the level of coolant in the radiator. You'll
see the level of the coolant in the radiator start to rise, maybe even
enough to spill even though you removed some, just before the t-stat
opens, then it should drop dramatically. The gauge MAY go a little
higher than normal before the t-stat opens on this initial part of the
drill. You may see movement in the coolant. Don't panic if you don't,
though. Be sure to hose off any spillage so your neighborhood pets don't
have a chance to slurp some up. It can be fatal to cats and dogs.
Now, if the coolant level dropped below the top of the tubes, add a
little until they've just covered again. Keep the cap off, check that
the top hose is hot, indicating good flow thru the t-stat, and check the
heater hoses. Both sides should be hot and you should be getting good
heat by now. If NOT, run the engine speed up a little, to 1500-2000 rpm
and hold it there for a minute or so to get coolant flowing thru the
heater and bleed air from the heater core.
Check the level in the radiator again, topping off above the tubes if
necessary. At this point you should have good heater response, the temp
gauge should be in the normal zone, and you shouldn't have too much
activity in the radiator. Shut the engine off and go get something to
drink, eat or whatever while you wait for the engine to cool. Give it an
hour or more, depending on how hot it is outside.
The coolant should contract some as it cools, and you may have to add
some to cover the tubes before starting the engine again. Keep the
radiator cap off. Start the engine, let it idle until the t-stat opens
again, check temp gauge, heater output and coolant level in the
radiator. All good? Ok, now you want to sit in the car and run the
engine up to around 2000 rpm and hold it there for at least a full
minute, then let it drop back to normal idle. Repeat a time or two.
Don't be surprised if you get some coolant splashing out of the radiator
(or bleed valve, if applicable.) It's more likely to splash if there are
bubbles in the system that are moving thru and blowing off in the top of
the radiator. Watch the temp gauge. It may rise a bit, then drop,
possibly more than once. If so, that's an indication there is some air
that's moving thru. After a couple of cycles, check the level in the
radiator. If you're getting lots of air out, it should drop a bit.
Refill to cover the tubes, then shut off the engine.
Let it cool AGAIN. Once it's cool, check the coolant level and repeat
the drill above AGAIN. By now, you shouldn't be experiencing much in the
way of bubbling over or jumping temp gauges and all. Shut the engine off
and let it cool completely with the rad cap still off.
When it's completely cooled off (radiator's not hot to the touch) you
want to make sure the radiator's filled enough to just cover the tubes
again, but NOT filled to the top of the tank and filler neck. Siphon
some off if required. Install the radiator cap. Make sure the air bleed
valve's closed IF you have one and it's been opened. Then fill the
overflow tank an inch or so above the "full" line and cap it.
Now it's time for a drive. Take the car for a spin of a few miles, with
some stop/start kinds of stuff, then a bit longer run. Keep the heater
on full. Make sure everything's ok: temp gauge not going nuts, heater is
putting out lots of heat. Then go home and let the car cool completely.
When really cool, check the overflow tank. Some of the coolant should
have returned to the engine. Take off the radiator cap, and the radiator
should be full. Take your turkey baster and remove coolant, putting it
in the overflow tank. Leave the tubes just covered as you did before,
and install the cap. Let the car sit until you need it.
First day you drive the car after this, check the coolant tank and
you'll see coolant's returned to the radiator. When it's cool enough,
remove the cap and siphon coolant into the overflow again. Watch
everything carefully the first few days you drive the car and top up the
overflow tank as necessary.
After you've done this a time or two, things should be pretty well
"burped." It's a long process, and hardly exciting, but has served me
well. And, just for giggles, it's always a good idea to measure the
coolant that comes out of the engine when you drain it to compare with
what goes back in to let you know if you're in the ballpark as for being
"full." For example, when I first drained my V-6 Toy that had last been
filled by the dealer, I ended up putting an entire quart MORE in the
system than I'd taken out. Tell me there wasn't lots of air in that one
somewhere! On the 4 cyl, it usually first appears "full" when I'm still
a quart short of what I've taken out--tells me there's more work to do!
Sorry to bore you with all this, but maybe it will help you avoid a
blown HG or other trouble...
Good luck!
Rick
