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This is for the "I think I have a BHG" worry that comes
up I think at least once a week on the Supras
List. I wrote this so we wouldn't have to keep repeating the
same thing over and over and to collect the sometimes missed advice.
If you find you do have a BHG don't let it sit that way for a long
time. The coolant can do bad things corroding the combustion chamber
or worse. Plan on getting it fixed and also realize this is a good
time to upgrade the components while you have everything apart.
Or if your engine is high mileage you might want to go with a new
one. It all depends on your budget, do your research.
- I have a gurgling noise behind the dash
This is the main cause for people to fear they have a BHG. Basically
all it means is that you have air in your coolant system. This
noise you hear is the heater core filling up and the air gurgling
out. There can be many reasons for this and the the odds are much
greater that it is something other than a BHG.
- Coolant Change
This is normal after a flush and
fill until you work
the air out of the system. The best way to work the air
out is just park on a hill and run the engine with the cap off
the radiator and let the engine idle for like 10 minutes.
- Leaking Hose
A leaking hose could also cause this. Some thing that as the
car cools it allows air to be drawn into the system instead
of through the check valve on the radiator cap. Look for water
dripping from hose connections or water-scale from previous
leaks. It is always good to change hoses every couple of years
just to keep your cooling system in good repair.
- Crack
A crack in the radiator, turbo coolant housing or head could
also be the source of the air entering the system. This is much
worse than a bad hose because none of these are cheap, but luckily
this is a rare occurrence.
- BHG
A blown head gasket will let air enter the system by allowing
the pressurized exhaust gases to escape the cylinder through
the break. The break can let the gasses out, let coolant in
or both depending on the severity. A compression
test can determine which cylinder has the break or an "Exhaust
Gas Sniffer" Snap-On test can check the air in the coolant
system for traces of exhaust gases.
- The "bird cage" light on my dash comes on
This light, which is on the side of the coolant temperature gauge,
indicates that the coolant level in the overflow tank is low or
nonexistent. First you might see it when taking sharp turns, or
when you start your car as the system heats up it should go away,
but you should still check the system to find out why it is low.
I would fill it back up to the full line with distilled water
and see if it happens again. If you are just driving along straight
and happy, and the light comes on, worry. This happened to me
and it was because I had a big leak but I couldn't see the coolant
steaming out. Stop right away and check why it is on, remember
not to open the radiator cap if the engine is hot.
- White smoke is coming out of the exhaust
When you see white smoke coming out of the exhaust, but not black
(rich fuel) or blue (oil), it means that water/coolant is being
burned by the system. When this happens it is a good chance that
it is a BHG but you still have a chance if you are on the good
side of the Karmic universe.
- BHG
A pressurized coolant system can force coolant back into the
cylinder either while the engine is running or after you shut
it off. So that you can get a cloud of white smoke when you
start it up or just continuously while running.
- Turbo Manifold Crack
There is a coolant line the feeds the center housing of the
turbo with coolant to help keep the temperature down. If the
turbo cracks then that coolant can seep through and leak out
either through the exhaust or intake side. If it is on the intake
side you might be able to smell it or see the residue on the
Intercooler Piping. If it is on the exhaust side then you should
be able to tell because it won't effect the idle of the car.
- Head/Block Crack
Did you cut off a Nun? You cracked your head/block and coolant
is seeping through that crack into the cylinder or intake/exhaust
ports.
- Throttle Body Crack
The throttle body is warmed by a coolant line that goes through
it. If it forms a crack, which would be hard to do, it could
let coolant seep into the intake charge air.
- ISC Crack
The Idle Speed Controller is warmed by a coolant line that goes
through it. If it forms a crack, which would be hard to do,
it could let coolant seep into the intake charge air.
- Intake Coolant Hose Leak
The coolant line that goes to the TB and ISC comes out of the
head at the bottom of the intake runners. If the seal isn't
good it could leak into the intake runners.
- Coolant is leaking on the ground from my car
This most likely isn't a BHG, if it is then you probably would
have blown all the coolant out of your car in a matter of minutes.
Most likely it is a hose or a connection that is leaking. Trace
down where the leak is coming from and replace that hose and others
of similar age. Hoses are cheap, it is easy to replace them all
at once then for one to blow on the road and ruin you engine just
to save $30.
- When I start my car the idle is rough
When I get a BHG I get this symptom, 'missing' at high load, and
reservoir over flow. But what can cause a rough idle could be
a myriad of things. In the BHG case it would be water in the combustion
chamber. But a list of some of the possibilities are.
- Idle Speed Controller
- Spark Plugs
- Ignition Wires
- Clogged Fuel Injector
- Vacuum Leak
- Ignition Timing
- Fuel pressure up system
- Oil is milky
Milky oil, under the oil cap or when changing it, means that water/coolant
is getting into the oil. This could be a BHG that allows coolant
to leak from the coolant channels to the oil channels. It could
also be a crack in the head/block. A leak down should indicate
which.
- My coolant overflows out of the reservoir
When air gets in the coolant system it will expand as the engine
heats up. It can then push coolant into the overflow container
forcing it to over flow. When the system cools down it will then
not be able to suck enough coolant back so you will run low quickly.
See the section on "gurgling"
for possible sources of air.
- The coolant tested positive for exhaust contamination
If you had your coolant tested, with the snap-on tester, and it
tested positive for exhaust gasses it is pretty much a sign from
God that you have a BHG.
- My temperature gauge is reading above normal
My car has "never" overheated. And I have driven in
the hottest of weather blasting my A/C with the car full of dorm
furniture. If your car is overheating it is because something
is wrong with your cooling system. Once you see it start to over
heat pull over and let the car idle to cool off running the heater
at full blast. The first thing you should to fix it is to replace
the radiator cap and thermostat. A bad cap could cause the system
to fail to pressurize and a bad thermostat could be stuck open
or closed. Also check the radiator for obstructions like leaves
or lots of bent cooling fins. If it still persists check that
the hoses aren't leaking or old and do a coolant
flush. Use distilled water, 30% coolant (depending on your
climate), and RedLine
Water Wetter. Oil also has an important job of removing heat
from the engine. Both from reducing friction heat and pulling
it from the engine with synthetic being the best choices in all
cases.
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