EJ25 Engine Failure After Rebuild



This EJ25 SOHC, adjustable tappet model, engine was rebuilt within manufacturer’s specs after a crankshaft bearing failure.

The installing mechanic reported noises in the running of the engine and diagnosed the noise as “piston slap” caused by excessive clearance in the honing of the Std. bores.

The noises were diagnosed as detonation by our member and the mechanic was cautioned to address this installation problem as a matter of urgency or engine damage would result.

The mechanic subsequently removed the engine and gave it back to our member with a demand for rectification under our member’s warranty.


The examination of the stripped engine showed the following evidence:

Unusual carbon build-up on all piston heads.

Very heavy scuffing on the thrust side of all piston skirts;

No discoloration under piston crowns;

Piston rings were not “dusted”;

Mains had seizures and B/E shells were damaged.

A forensic engineer was contracted to report on this evidence.

His report confirmed that hydro carbons in the engine oil was evidence of petrol/over-fueling from the injectors. This petrol had contaminated the oil and led to a break down in lubrication and associated bearing seizures.

The unusual carbon on the piston heads was reported as “beach marks” (from the white sand appearance) caused by the over-fueling and associated detonation.

This detonation also caused the heavy loadings and scuffing on the piston skirts and damage to the con rod shells and rod bushes.


The cure to this relates to educating our customers who should be able to diagnose these problems at the test-drive stage. The Australian Standard for reconditioning engines with the guide to engine fitting is not being used.

The mechanic’s business franchise has been contacted and a good response has been received. The engineer’s report will be forwarded with the account.

The engineer’s report sets a new standard for this industry and is worth a read as we all head into the higher-cost engine designs that we are now working on.

Obtain a copy from James at Pro Built Engines as required.