The radiator split a seam and I removed it and had it recored. After
putting the radiator back in I flushed the system. The problem
started right off. The cooling system pressurizes and when you shut
the engine off it blows bubbles in the overflow tank. The system will
stay pressurized for at least two days without starting the engine.
While driving the temp gage will go almost to the red line and then
return to the normal range. It only does this little trick once each
time you drive it. There is no sign of coolant in the oil and no oil
in the coolant.
First of all replace the cap if you have not already done so and I
would suggest a lower pressure cap because you do not need a 16PSI cap
to begin with with proper coolant. Stant makes a 13 PSI one and a 9
PSI one as well. I have been using the 9 PSI ones for many years and I
have had no cooling issues even in 100 degree plus heat nor on Pikes
Peak. Second, coolant does normally expand when it heats up and will
purge into oveflow tank and when you shut off a hot engine is can
actually increase coolant temps for 5 or 10 minutes and cause it to
purge further so this is normal. Third if the system is not properly
purged of air it can get a air slug that can impeded cooling and cause
pump to cavitate too. When it heats up it purges into overflow and as
it cools and contracts it sucks coolant back into system to replace
any air that may have been burbed out (this is reason overflow tank
needs to be keeps full) If you remove cap and relieve pressure you
break the automatic purging cycle. Forth, if you feel you have
excessive pressure building all the time, you could have a bad head
gasket that is letting combustion gasses into cooling system and
causing it to pressurize excessively and inducing air slugs that are
Thanks for the info. I failed to mention that this is a 6.5 turbo
diesel. I assume from the last comment you wrote that I could have a
bad head gasket and not find contamination in either oil or coolant.
Yes you sure can. A crack in cylinder or head in waterjacket area can
cause it too. There is a LOT of compression in that engine to contain.
Not all blown head gaskets leak/mix oil and coolant though they
generally tend too.
You can swing by your local auto parts store and get a kit to test the
coolant for hydrocarbons. If you get a positive then you have a leaking
head gasket if you do not get a hit then it is something else. When I read
you post I initially though head gaskets...
get the tester .. you screw it on to your rad, pump it up to like 10-14lbs
and if it starts to drop roght away.. you have problems.. if it stays steady
for at least 2-3 min then you have an air lock or rad cap problem . HELL
your water pump may be bad if it is over heating..
Old school tester is as follows.
Remove radiator cap when cool
Remove coil wire (so it won't start)
Place hand over the hole where cap goes
Have someone crank engine over
If you feel pressure as cylinder strokes compression
....you have a blown head gasket.
6.5TD crack between exhaust and intake valve, also head gaskets. mostly pre
99 or 98 they went with better cooling in or after 98. Have the cap tested
first, it should relieve any pressure above it's rating so you shouldn't
have split a rad to begin with. You say it blows bubbles into the tank after
you shut it off, head gasket or cracked head should be making bubbles while
running. Also you say it holds pressure for two days or more so that kind of
says no leak.
Sounds like it has an airlock.
What year is yours ?
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