Information on Northstar Engine Mechanical Repairs

Now that parts are available to correct customer concerns of oil consumption and cold start conditions on these engines, there has been some confusion on what parts are for which repairs. This bulletin has a section listing a guideline of parts required for typical engine repair. Also included is a discussion of thread repairs, when and how many Time Serts should be used during repairs. There is also a chart that shows the correct special tool numbers to use for which model years when installing Time type serts. And finally, the head bolt torque specifications when reassembling the engine are listed at the end of this bulletin.

Important: When performing Northstar® engine mechanical repairs that require removal of the oil pan, oil manifold or separation of the upper and lower crankcases, use the RTV sealant procedure in bulletin 03-06-01-027 when reassembling. The RTV sealant has a better resistance to heat and will not shrink like the current gaskets material.

Important: Light vertical scratches that are not deep enough to catch a fingernail are acceptable. If any of the cylinder bores are scored, that is not acceptable and the engine will have to be replaced.

Important: When replacing pistons or rings, the crankcase halves do not need to be separated to complete the repair. It is advised at the time of the piston/ring repairs that the original crankcase seals be removed and sealed with RTV per bulletin 03-06-01-027.

This bulletin addresses Northstar® oil economy only. The cleaning procedure in this bulletin should be done first and the oil economy evaluated. In most cases, cleaning the cylinders per bulletin 02-06-01-009C will restore the function of the rings to wipe the oil down the bore. If the oil economy after cleaning is still not satisfactory, then the revised piston rings should be installed. For an oil consumption concern, it is not necessary to replace pistons. The original pistons can be cleaned. The critical part of the cleaning process it to remove all the carbon deposits from the piston ring groves.

Important: The cylinder bore surface does not require any preparation when installing new rings. The repair would be ineffective if any honing is done to the bore surface.

Recognize that the oil consumption mileage figure of 2000 miles per quart (3200 km per 0.946 liters) in bulletin 01-06-01-011A applies to a vehicle during the warranty period. As mileage accumulates on the engine, oil economy mileage will decrease due to normal wear in the engine.

This bulletin address cold start engine knock noise. Use of top engine cleaner, or the cleaning process for oil consumption is only a temporary fix for this condition on 2000 through 2003 vehicles. Unless the driving cycle is changed, the cold knock will return in a short time. The piston listed in this bulletin is the only recommended repair to eliminate a cold start knock from reoccurring.

Important: If only a single piston(s) is installed for another type concern, this part number can be used without any balance or performance concerns. P/N 89017413 is the only service piston and it is completely interchangeable with the original pistons. If the condition is for cold knock, all 8 pistons should be replaced.

Important: A small percentage of vehicles have exhibited a subtle ticking sound when the engine is at operating temperature. The noise is usually heard through the fender wells with the hood closed. This noise is a wrist pin noise and should be considered characteristic of this engine with these pistons. There is not any mechanical damage or wear from this noise, no further repairs should be attempted.

When performing either oil consumption or cold engine noise repairs, the following is a list of commonly used parts. The recommendation in SI to replace the rod bearings was based on the assumption that the engine has over 100,000 miles (160,000 kilometers) when engine mechanical service is being performed. The rod bearing should be inspected for signs of wear and replaced, if necessary.

When disassembling the engine, all head bolt threads should be inspected as they are removed. If there is any section of the aluminum block thread on the bolt, that hole will need a Time Sert repair. Typically, all the cylinder head bolt holes do not need Time Serts. The recommendation is to do a thread repair on the damaged hole(s) and the adjacent holes. As the clamp load is relieved from one hole (threads pulling), the adjacent holes threads load will increase and may be damaged during reassembly.

There have been some comments about Time Serts pulling out of the block in a short time after a repair was done. The manufacture of the insert also makes a larger size insert. This larger size insert cannot be used for warranty repairs. Due to the increased O.D. of this sert, it’s possible that when installing this larger sert that it will break out in the water jacket causing a coolant leak.

The most likely reason that a Time Sert pulls out after installation is that the incorrect J tools were used for the model year application. If the incorrect tool is used, installation of the sert could be either too deep in the hole or not deep enough. The table below lists which tool should be used for which model years.

Model Year:

1994-1999

TimeSert kit:

J 42385-500

Model Year:

2000-2003

TimeSert kit:

J 42385-2000

Important: Late in MY2002, cylinder head bolt holes in block were revised. Thread start height was raised by 7 mm, block bolt hole depth was reduced by 7 mm.

Model Year:

2004-2005

TimeSert kit:

J 42385-2030 Head

J 42385-2000 Main

1993-1999 Head Bolt Torque

2000-2003 Head Bolt Torque: