Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSVOLVO1993850 L5-2.4L VIN 55 B5254SREPAIR AND DIAGNOSISENGINE, COOLING AND EXHAUSTTECHNICAL SERVICE BULLETINSALL TECHNICAL SERVICE BULLETINSENGINE - THREAD RECONDITIONINGSPARK PLUG THREADS
1993 Volvo 850 L5-2.4L VIN 55 B5254S
Spark Plug Threads
1993 Volvo 850 L5-2.4L VIN 55 B5254SSECTION Spark Plug Threads
RECONDITIONING SPARKPLUG THREADS
Note
Reconditioning of sparkplug threads must be done with the cylinder head removed!
Remarks:
Denatured alcohol facilitates operations when working with aluminum.
Tapping thread in sparkplug hole
Use combined tap 998 5823-5 and thread insert
P/N 948756-2.
Note
Do not drill out sparkplug threads,
Combined tap
A: Thread section
B: Reamer section
C: Guide (old thread)
INSTALLATION OF THREAD INSERT
Because of restricted space, the retaining nut cannot be used on the installation tool. Instead the nozzle must be taped into position.
Note
For thread inserts that are finer than usual, it is extra important not to apply pressure to the tang when threading (both in the nozzle and the material).
Screw down the thread insert approx. 10 revolutions and check that the uppermost thread is at least 1/2 revolution in the bore and that no part of the insert is protruding from the bottom end of the bore.
If the insert has been screwed in too far, it must be turned until it is all the way through.
Break off the tang with a pair of flatnose pliers.
Test the reconditioned thread with a sparkplug. It should be possible to screw the sparkplug in easily by hand.
Note
Reconditioning of sparkplug threads must be done with the cylinder head removed!
Remarks:
Denatured alcohol facilitates operations when working with aluminum.
Tapping thread in sparkplug hole
Use combined tap 998 5823-5 and thread insert
P/N 948756-2.
Note
Do not drill out sparkplug threads,
Combined tap
A: Thread section
B: Reamer section
C: Guide (old thread)
INSTALLATION OF THREAD INSERT
Because of restricted space, the retaining nut cannot be used on the installation tool. Instead the nozzle must be taped into position.
Note
For thread inserts that are finer than usual, it is extra important not to apply pressure to the tang when threading (both in the nozzle and the material).
Screw down the thread insert approx. 10 revolutions and check that the uppermost thread is at least 1/2 revolution in the bore and that no part of the insert is protruding from the bottom end of the bore.
If the insert has been screwed in too far, it must be turned until it is all the way through.
Break off the tang with a pair of flatnose pliers.
Test the reconditioned thread with a sparkplug. It should be possible to screw the sparkplug in easily by hand.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.