ENGINE
3TNV88F Service Manual
6-61
EGR system
■
Cleaning the EGR valves
WARNING
Fume/Burn Hazard!
• Always read and
follow safety related
precautions found on
containers of
hazardous substances
like parts cleaners,
primers, sealants and
sealant removers.
• Failure to comply could result in death or
serious injury.
CAUTION
Flying Object Hazard!
• Always wear eye protection when
servicing the engine and when
using compressed air or high-
pressure water. Dust, flying
debris, compressed air,
pressurized water or steam may
injure your eyes.
• Failure to comply may result in minor or
moderate injury.
The EGR valves must be periodically cleaned every
3000 hours because, as exhaust gas circulates
through them for a prolonged time, carbon is
deposited on their inner surfaces, possibly
deteriorating the EGR ratio.
To remove deposited carbon, use compressed air
(0.19 MPa (2 kg/cm
2
) or lower). If the valves are
heavily fouled, use carbon cleaner, kerosene, or
some other liquid capable of removing carbon as
well as a soft brush to clean the valves, taking care
not to damage their parts.
When cleaning the valves, take extreme care to
prevent water, solvent, cleaner, and other liquid
from entering into the motor and coupler terminals;
otherwise, failure may result.
■
Lead valves
Similarly to the EGR valves, the lead valves must
be periodically cleaned every 3000 hours because,
as exhaust gas circulates through them for a
prolonged time, carbon is deposited on their inner
surfaces, possibly deteriorating the EGR ratio.
To remove carbon deposited inside the lead valves,
disassemble and clean them.
1 – Case
2 – Stopper
3 – Valve
4 – Machine screw
Figure 6-106
To remove deposited carbon, use carbon cleaner,
kerosene, or some other liquid capable of removing
carbon as well as a soft brush or cloth to clean the
valves, taking care not to damage their parts.
Upon completion of carbon removal, wipe off water
and liquid, make sure that the case, valve, and
stopper are free of foreign matter, and then reinstall
the valve and related parts.
Figure 6-107
4
1
3
2
Valve plate
Stopper chamfer
20
17.5
Exhaust gas
passage hole
Assemble without
misalignment.
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