Oil Leak at Rear of Head: Ranger / BT50 2.5L & 3.0L TD

Applies to models:

• 2006 – 2011 Mazda BT50 2.5L TD WLAT / 3.0L TD WEAT
• 2006 – 2011 Ford Ranger 2.5L TD WL-C / 3.0L TD WE-C

Issue

It has been seen in cases where a replacement head as been fitted to a 3.0L WE-C Turbo Diesel engine and similar that an oil leak comes from the rear of the cylinder head, typically commencing as soon as the head has been fittd. 

When examined, around half way up the rear of the head, a Welch plug exists. Just above this welch plug there's an oil drain hole that is naturally open. This hole is there to drain any oil that may pool in the injector tunnel area and should not be threaded.

However, when viewed without this knowledge it can appear that this hole should be blocked and threaded. That's not actually the case. 

Actual Cause

The cylinder head for the Ford Ranger and Mazda BT-50 have a bolt on cam carrier attached to the head. The lower part of this cam carrier includes four injector seals which must be replaced every time the injectors and valve cover are removed. 

It's very important to replace these seals carefully as any slight misalignment or breaks in the gaskets can case oil to leak into the injector valley and out of the drain hole in the rear of the head. 

This applies not only to the injector seals but also to the valve cover gasket.

Resolution

In the case where oil is seen to be draining out of the oil drain hole in the rear of the head, the simple resolution is to remove the injector seals and valve cover gasket then replace both. If you don't want to replace them simply reseating them can be attempted but this won't guarantee a seal as often any incorrect fitment will permanently damage the seals. 

If you do see any such leaks come into your workshop it's recommended to first check the valve cover gasket and the injector seals for any damage. That could easily fix the oil leak before having to do anything else!

Specified Tensions

Injector Clamp: 21-26 Nm
Camshaft Carrier/Caps: 8-11 Nm