Solution Number: 70025
Solution Summary: 8.1L CNG HFNO1->HFN04 - Repeat Exhaust Manifold Bolt/Capscrew Breakage & Loosening

Publication Date: Sep 2 2010

**Paner copies of solutions may not be the most current solutions**

Complaint or Symptom ;

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Repeat exhaust manifold bolt/stud breakage & loosening.
Problem or Situation :

Earlier one piece exhaust manifold designs side loads the studs/bolts during thermal expansion, followed by stud
breakage. Exhaust manifold part Number R529840 with slots for the mounting location has addressed this issue.

Solution ;
Follow the steps below to resolve issue:

e Inspect flatness of the exhaust manifold and the mating surface of cylinder head to ensure that there are no
irregularities or warping. If no irregularities or flatness concerns, please proceed to next steps. If cylinder head or
exhaust manifold mating surfaces are not flat or are damaged, please contact DTAC for further assistance.

e Remove broken bolt/capscrew material from cylinder head in such as way as to not damage the cylinder head c+
threaded cylinder head holes. Drilling the studs for removal may not work well because the studs are very hard:
Welding the small diameter of a 5/16” (8 mm) washer to the remaining portion of the stud, then welding a nut to
thevasher, followed by immediate removal has worked very well. The washer may need to be “peened™ to reach a
stud broken off below the surface of the head; this will help prevent any damage to the threads in the head when
welding the washer to the remaining portion of the stud. To protect the cylinder head during the welding process.
wadded up tin foil, a water soaked rag, etc. can be placed in the exhaust port to protect the port, valve etc. aud can
protrude to the outside of the port to protect any flat surfaces of the head that would affect a good seal with the
manifold. As usual. disconnect the ECU or any other components that could potentially be damaged prior to any
welding operation.

« Use HFN04 studs to mount the manifold if possible. Also use slotted exhaust manifold R529840. Check
positioning of studs in regard to the mounting slots in the manifold; the front of the exhaust manifold will have to
be held up by one stud to maintain the correct mounting position. There should be at least 5/32” (4 mm) clearance
between the stud/threaded hole in the head and the manifold (in the direction from the stud towards the turbo).

e Apply Loctite® Primer 7471 to the threaded end of the stud that screws into the head; let it dry for 30 minutes
e Start with a clean threaded hole in the cylinder head.

Debris - If any debris exists in the threaded hole it must be removed: a 3/8-16 NC tap may be run down the hole
followed by flushing or using compressed air to dislodge any loose particles. we

Oil'£ Any oil must be removed from the hole prior to installing the stud with hand-applied Loctite®. Flood the’
threaded hole with Isopropyl alcohol (rubbing alcohol) to float the oil out and then blow the hole out with
compressed air.

The hole should be dry in about 2 minutes. DO NOT USE LOCTITE® PRIMER TO CLEAN THE HOLE! ,

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e Make sure all manifold to stud clearance is adequate, holes are clean, studs are Primer coated, nuts and washers are
available, ete because the next steps should be done as quickly as possible. The 266 Loctite® to be used has a
fixture time of 10 minutes and full cure time of 3 hours, so every effort should be made to accomplish the next
steps as quickly and accurately as possible.

¢ Apply 3 drops of Loctite® 266 (High Temperature) near the end of the 3/8-16 UNC (coarse) thread on the stud that
screws into the head. Also apply 3 drops of Loctite® in the cleaned hole, about 1/2-3/4 inch (13-19 mm) deep into
the hole.

-e Install the stud to the proper depth. The exhaust manifold attaching stud should be installed with 1.5+0.02 inch.

~ .(38.1+0.5 mm) from the surface of the cylinder head to the end of the 3/8-24 UNF (fine) end of the stud.

¢ The exhaust gaskets and manifold should be installed, spacer washers installed and the 12 point attaching nuts
torqued to 35 ft-lbs (47 Nm) as soon as possible after the studs are installed into the cylinder head. Start the torque
sequence of the nut on the stud within 10 minutes of installing the stud if possible. Ideally, the torque sequence

~ should start at 10 ft-lbs (13.5 Nm) on the center studs, working toward the ends alternating front to back, then
torque to 25 ft-lbs, (34 Nm) and finally to 35 ft-lbs (47 Nm). The Loctite® will take a set relatively quickly (see

» table below for Fixture/set Cure time) and will be fully cured in three hours.

Torque

Loctite® Product Fixture (Set) Cure Timel/Full Cure Time
Breakaway / Prevail -

266 __|[270 In-Ibs (30.5 Nm) / 35 In-Ibs (4 Nm)][10 Minutes [3 Hrs

« Retorque the exhaust manifold nuts to 35 ft-lbs (47 Nm) after the engine goes through several heat cycles or several
days of operation. Retorque of the exhaust manifold bolts at regular maintenance intervals has shown to
dramatically reduce problems with exhaust manifold area leakage and subsequent repair. While in the manifold
area, retorque the intake manifold as well.

Additional Information :

6081

BROSEN, NG, EXHAUST. CTM87, POWERTECH, FAIL, ADJUST, PTS, R502681, R503382, R503821, ENG. F0410

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