Revised Cylinder Head Gasket & Retorque Procedure 
            on 1981-88 Saab 900 & 9000 Series Engines


Saab-Scania of America has released a new cylinder head gasket and installation procedure for all 1981-88 Saab 900 & 1986-88 Saab 9000 series engines.  This new procedure applies to 8 and 16 valve cylinder head engines produced after 1981.

The revised cylinder head gasket no longer requires retorquing of the cylinder head bolts after the engine has been started and warmed up for the first time.  Furthermore, retorquing of the cylinder head bolts after the first 1000 miles of service has also been eliminated.

Use the following chart to determine if the cylinder head needs to be retorqued:
 
        Engine Series                           Part Number *               Procedure

 1981-88 900 Series 8-Valve            75-85-037                   do not retorque
 1981-88 900 Series 16-Valve          75-61-301                   do not retorque
 1986-88 9000 Series 16-Valve        75-61-301                   do not retorque

  before 1981 900 Series 8-Valve    75-05-217                        retorque
  before 1981 900 Series 16-Valve  75-16-529                        retorque

* Saab-Scania cylinder head gasket part number

Engines manufactured before 1981, using head gasket part #75-05-217 or #75-16-529, must be retorqued as before.


                                     The AERA Technical Committee

                                                   Oil Consumption On 
                                      Saab 2.0L 16 Valve DOHC Engines

The AERA Technical Committee has become aware of another possible cause for abnormally high oil consumption on Saab 900 DOHC application.  Usually, oil consumption can be traced to piston ring, valve guide and/or valve seal wear.  An additional cause may be a reversed one way check valve for the crankcase ventilation system on turbo charged engines.

It is also possible for oil to enter the PCV system because of a slight distortion of the camshaft bearing cap to bolt mating surfaces.  At operating temperature, it is possible for oil to spray from underneath the bolt into the PCV system inlet.  Oil is then drawn into the PCV system and engine air intake system.

Although engine oil passes only through one of the camshaft bearing cap bolts, a sealing washer, Part #91-14-885, should be installed under all bolts to maintain equal pressure on the bearing cap.  Each bolt should be torqued to 11 lbs.ft. during assembly.

                                                                         The AERA Technical Committee

                                              Abnormal Combustion On
                                       Saab 2.0L B201 & B202 Engines 

AERA members have reported engine damage from abnormal combustion in Saab automobiles equipped with the 2.0L B201 and B202 engines. The resulting damage has ranged from premature head gasket failure to piston damage shortly after remanufacture of the engine.

After machining the deck surface of the cylinder head, it is important to chamfer the combustion chamber edges.  If left unchamfered, the sharp edges may act as a heat sink during the normal combustion process and start to glow.  This glowing or hot spot may increase the possibility of abnormal combustion, in
particular premature ignition of the air/fuel mixture, leading to a component failure.

Removing burrs, nicks and sharp edges from the combustion chamber
will result in longer engine service.

                                                                        The AERA Technical Committee

                                           Tuliped Intake Valves 
                        Shortly After Rebuild On Gasoline Engines

The AERA Technical Committee offers the following information concerning tuliped intake valves shortly after rebuild. This condition has been noticed after 
rebuild of engine or reconditioning of the cylinder head. A tuliped valve has an increased total valve length and the top of the valve has the appearance of a cup.

Combustion chamber temperatures that have exceeded the engine's original design parameters usually may cause a tuliped intake valve. Each valve used in an engine has a specific requirement, which results in different materials for intake and exhaust valve locations. Design engineers will specify which materials will economically work best for the intake and for the exhaust locations.

A typical automotive intake valve may be composed of a steel alloy such as Silchrome 1 (Sil 1). It is used because of its strength at the intake valve operating temperatures, relative low cost and the ability to be hardened at the valve tip. Intake valves run at a much cooler temperature than exhaust valves. The air and gasoline mixture temperature is generally in the range of 150- 250° F. This cool air passes over the intake valve while it's open in route to the engine's combustion chamber area. That process also has a cooling effect on the valve.

Some exhaust valves are made from 21-2N or 21-4N stainless steel, which 
offers greater temperature strength to lead oxide corrosion. The 21-2N and 21-4N material is used at the exhaust locations because it withstands higher heat temperatures. Exhaust valves usually have to endure temperatures that are 
generally in the range of 1000-1500° F as shown in Figure 1 while they are open and exhausting the cylinder. That process does not have much of a cooling effect. Exhaust valves rely on the head casting to transfer the majority of the valve temperature.

The two intake valves shown in Figure 2 are both out of the same engine. The one tuliped valve is .220 longer than its original length. This was the result 
of an abnormally high combustion chamber operating temperature. This temperature is in the cylinder of the engine, NOT THE ENGINE COOLANT TEMPERATURE. The temperature surrounding the valve got much higher than the valve was ever designed to withstand. That excessive temperature resulted in the valve material softening, allowing the valve head to stretch to create what is called a tulip shape.

A normal combustion process operating temperature in the combustion chamber could be considered 2500° F with cylinder pressures between 900-1200 psi. Engine valves will only survive the normal temperatures because they are seated during the combustion process and transfer heat as designed to the head casting. 

An abnormal combustion process may increase the operating temperature in the combustion chamber as high as 5000° F with pressures between 3,500 - 5,000 psi. If this tulip condition re-occurs after rebuilding of the engine or reconditioning of the cylinder head, the original problem has not been fixed. This condition may affect one or more valves at a time.

Items to check; properly working EGR system, correct ignition timing, ECU operation, vacuum leaks (intake manifold, hoses, etc.), correct air to fuel mixture, correct angles between the valve and the valve seat, excessive valve spring pressure and any other source that affects the combustion process.

                                                                        The AERA Technical Committee

                                    Excessive Oil Consumption On
                                 1986-94 Saab 2.0L DOHC Engines

AERA members have reported excessive oil consumption on 1986-94 Saab
2.0L DOHC engines.  The source of this oil consumption has been traced to the engine's positive crankcase ventilation system (PCV).  Apparently the original camshaft cover allows excessive amounts of oil to enter into the induction system.   

A modification was made to the camshaft cover Part #8788135 during the 1994 production year to reduce the amount of oil mist reaching the PCV system.  The part number for the cover, however, did not change.  The identification of the revised cover, requires removing it from the head and inspecting it for the additional tube shown in the illustration below.

                                                                    The AERA Technical Committee

                 Import Engine Bearing Problems

The addition of many aftermarket main bearing sets for import automotive engine applications has caused a frequent complaint that the thrust bearings cannot be installed.

The reason is that in most import engine applications, the flanged bearing length is increased with the undersize of the bearing.  This means those grinding the crankshaft must grind the thrust face of the crank to accommodate the increased bearing length and secure proper clearance of the crankshaft end thrust.

A typical example may be found with the 1.5L and 1.7L Saab engine utilizing a common aftermarket main bearing set:

The .010 undersize is .004 oversize length.  
The .020 and .030 undersize has a .010 oversize length and 
the .040 undersize has a .020 oversize length.

                                                                            The AERA Technical Committee

                                            Revised Cylinder Head On
                                             Saab 2.0L DOHC Engines

The AERA Technical Committee advises members of a design change on
Saab 2.0L DOHC engines.  Previously this engine used an external oil system feed to the cylinder head.  This design changed to an internal function beginning with engine #J0825B6 in mid 1988.  The affects of this change have reduced the number of locations for possible external oil leaks as well as shortening repair times.

This new head design can be retrofit on all previous engines and is available under Part #7586142, without valves.  All cylinder head specifications and mounting parts are still shared, excluding the external oiling tubes and fittings.  There are three external pipe plugs (Part #8123143) that also need to be installed on the new head.

Saab recommends pressurizing the oiling system before the first engine start-up when this new head is used.
                                         
                                                                         The AERA Technical Committee

                                      New Cylinder Liner O-Ring Seals On
                                      Cummins NH/NT 6 Cylinder Engines

Cummins Engine Company has released new O-ring seals for the cylinder liners in NH/NT 6 cylinder engines.  The new seals are made of an EP material and have a smaller diameter cross-section.

The new seal replaces both the old center seal #3008998 and the old lower seal #183049.  The new seal carries Cummins part #3032874 and is black in color with one blue dot.

The new O-ring seals are not to be intermixed with the former seals on the same liner.  Cylinder liner deformation will result.  You can use the former seals and new seals in the same engine as long as they are used in the correct combinations on each liner.  The illustration below shows the correct combinations.

                                                                       The AERA Technical Committee

                                               Oil in Cooling System on
                                         VW 1.5L & 1.6L Diesel Engines

AERA members have reported instances of engine oil in the cooling system on VW 1.5L diesel engines.  According to AERA sources, the problem is related to a crack in the cylinder head bolt hole located near the oil gallery feeding the cylinder head.

The oil feed gallery in the block is located on one side of the center head bolt hole and a coolant jacket is on the opposite side of the bolt hole.  Pressurized engine oil is diverted through a slot in the head gasket and is feed up the side of the head bolt to the cylinder head.  The oil also follows the bolt back down to the bottom of the bolt hole.  Should the crack in the head bolt hole extend to the coolant jacket, oil can mix with engine coolant.

This problem is generally found on engines equipped with 11mm head bolt holes.  Later design engines utilize 12mm head bolts and do not exhibit this defect.  At the time of this writing no successful repair procedure is available.

                                                                       The AERA Technical Committee