What the Cylinder Head — Cummins QSL9 CM850 does
The cylinder head carries the valves, injectors and coolant passages above each cylinder. On the Cummins QSL9, a cracked or warped head — usually after overheating — causes coolant loss, compression loss and oil contamination.
Some heads can be repaired by pressure testing and skimming; a cracked head usually has to be replaced.
Signs it needs replacing
- Coolant loss with no visible leak; white smoke.
- Coolant in the oil, or oil in the coolant.
- Overheating after a previous overheat event.
- A cracked head confirmed by pressure test.
Get the right part first time
Send us these on WhatsApp and our engineers will confirm the exact part before you pay:
- Engine serial and CPL number from the Cummins dataplate.
- Hour-meter reading.
Fitting notes
Head replacement is an engineer's job: new gaskets and bolts as specified, valve and injector setup, correct torque sequence, and a full cooling system check. The original cause — usually overheating — must be fixed.
Frequently asked questions
Can a cracked head be repaired?+
Some cracks can, but most cracked heads are replaced for reliability. A pressure test shows the extent.
How do I confirm this head fits my engine?+
Send the engine serial and CPL number from the Cummins dataplate.
How long does supply take?+
This is an order-in part; availability is confirmed when you enquire.