A major problem with the Bmw E34/E32 especially the 3.5l and 2.5l
is a headgakset failure caused by using unproper coolant (I always
use BMW coolant) or overheating.
Engine suddenly overheats, radiator hose or heater hose explodes,
a bubbling sound from the radiator overflow tank (may be a bad radiator
cap), large bubbles in or foaming of coolant in radiator while engine
is running, loss of coolant with no apparent leak, or persistent
white smoke coming from exhaust are the first warning that the headgakset
is going bad.
Thick white smoke coming out of the tail pipe (water inside
Coolant in oil (white residue on the oil cap or dip stick)
or oil in coolant (stick your finder in the coolant reservoir and
you will see)
Mysterious loss of coolants without traces.
Huge build up a pressure in the coolant circuit.
Temperature gauge acting weird (the temperature gauge will
get into the middle, and stay there for few minutes. Next, it will
rapidly shoot for the “red” zone. It will do this in seconds. The
moment the red zone is touched, the gauge falls just as fast to
the middle, where it will stay for duration of the trip. Next day,
When you first start your car leaking head gasket will introduce
gas into the head cooling space. It will replace fluid from the
area. The thermostat is closed so the gas has no place to go. The
gas acts like an insulator so it will delay heat transfer to the
thermostat. But other parts of the engine covered with the fluid
blanket will heat the water up to the boiling point. Finally engine
is hot enough to cause thermostat to open and let the gas go into
the radiator. After the gas goes the overheated water and that's
what causes your needle to rise on the gauge. Further operation
is normal because thermostat is open and the gas goes to expansion
tank as soon as it gets into the system. You need to repair the
leak as soon as possible if that's the cause or you will end up
with warped head due to spot overheating.
What test to perform to make sure:
The first is a carbon dioxide test performed on the cooling
system will tell you if C02 is going inside your coolant.
A leakdown test will allow you to check each cylinder to
look for pressure loss inside the cylinder. Failing the test could
also be seepage past a bad valve guide, piston ring...
Head Gasket Testing Kit
The best method is to have a service shop, or a friend who owns
a block test kit test your system for a compression leak to your
cooling system. I heard that some test kits can be purchased from
auto stores. This is a test unit and test fluid that changes color
with the presence of exhaust gas in the engine coolant. Another
test that should be completed is a coolant system pressure test
Test your system for leaks with nine to twelve Psi pressure. It
should not show any appreciable pressure loss within 5 minutes.
Sometimes it's worth it just to have a pro shop diagnose the problem,
even if you are planning to do the repair yourself.