[urq] K26 rebuild

[Phil Payne]

> Justin, do not worry, you are correct, and Bob is surprisingly off planet on his reply to
you, an aircooled turbo? reverse nostril event! damn, that hurt! snort! all turbos are oil
cooled, the K-24 gets auxiliary water cooling that the K-26 does not to prevent coke deposits
on shut down heat soak that a K-26 can only avoid by a idle cycle, mine at 141K miles would be
a good case in point of "idle time" Bill

All turbos are air-cooled.  The heat removed by liquids is insignificant.

On the 10V I5s, there are two carefully designed air passages that take forced air from the
front grill and direct it down the side of the engine.  Some plays over the turbo, some over
the exhaust manifold.

This airflow is IMPORTANT.  Most of the turbo overheat problems I see have occured because
this airflow has been impeded - the most common culprit is an after-market dump valve, though
sometimes I find misguided people have put shielding between the manifolds.

The later engines have a water jacket around the centre bearing.  This is properly fed only at
rest, after the engine has been switched off for around a minute and subject to the water
temperature at the head union (where the water in the bearing jacket convects to) exceeding a
certain temperature.  The electric pump actually pumps water BACKWARDS around the circuit.
There is no meaningful flow in this circuit when the engine is running.

The cool-down advice applies equally to the original and to the so-called "water-cooled"
turbos.  There's absolutely NO WAY a pipe less than 1/4" in diameter can carry enough water to
deal with the kind of heat generated at the hot end of a turbo.  At least two orders of
magnitude, possibly three.

Equally, cool-down has to be done with the vehicle in motion.  Idling while parked doesn't
help - the only underbonnet airflow in such cases is provided by the alternator fan, and it's
pathetic.

--
  Phil Payne
  http://www.isham-research.com/quattro
  +44 7785 302 803