The Automotive Engine Rebuilders Association (AERA) offers the
following information regarding cam timing chain marks on 1976-’88
Isuzu 1.8L and 1.9L engines. Confusion may begin when reading
the service manual information referencing marked plates on the
cam timing chain. Apparently, some aftermarket timing chains don’t
have the marked plates which indicate the correct positioning
for installation. The original equipment has two marked plates
that must align with sprocket marks when properly installed.
To ensure correct installation
of an unmarked timing chain, make sure that the correct number
of links are between the cam and the crankshaft sprocket marks.
Correct positioning of the sprocket marks also depends on which
direction you are counting – clockwise or counter clockwise.
There will be 24 plates
between the sprocket marks, counting in a clockwise direction,
when properly timed. Counting counter clockwise, there should
be 21 plates when the chain is properly installed. Both timing
methods are viewed from the front of the engine. See Figure
1.
Engine Rebuilders:
In a July 1994 technical bulletin, Ferrari North America, Inc.
offered the following information regarding oil leaks in the area
of the camshaft seal housing. Ferrari said that the leaks in many
cases are caused by the marking of the sealing ring (p/n 117275).
When the gasket is replaced,
rework the gasket by removing 1 mm of the material from the area
which contacts the sealing ring (See Figure
2). Also, take
care in the area between the two camshafts as the gasket must
lay completely flat there.
As a further precaution
it is necessary to chamfer slightly the cam cover itself (See
Figure 3)
in the areas shown. This chamfering can be done with light sand
paper and will prevent the sharp edges of the cam cover from damaging
the sealing ring upon installation.
It is important to use
a high quality gasket sealer in the corners (not on the entire
gasket) of the gasket where the gasket mates with other surfaces.
Ferrari recommends Kar Products RTV (silicon adhesive/sealant
80257) or 3 Bond.
Ferrari says that from
engine number 35334, this re-working of the gasket has already
been performed at the OEM level. Prior to this engine number,
the re-working had been carried out only on the following vehicles
(See Chart 1).
Remember that in cases
where repairs are being performed to eliminate leaks on early
vehicles, it is important that besides following the procedure
just described, the instructions detailed on Ferrari technical
bulletin 10-31 (10/10/91) are also followed. It is not always
considered necessary to replace the seal housing, the original
housing may be modified as follows:
Machine a 1.5 mm chamfer
around the seal housing using a lathe;
File a 2 mm draining
groove in the bottom of the housing as shown in Figure
4.
Ferrari notes that the
above described procedures are suggestions for resolving the occurrences
of oil leakage and are not intended to be an update or service
campaign. Ferrari says it is also possible to remove the fuel
tank in order to replace one leaking seal, rather than to remove
the entire engine assembly.
Brake Rebuilders:
BMW notes that in some cars, especially those equipped with Jurid
506 brake pads, vibration in the body and steering while braking
may be exhibited. When the brake discs are checked for runout,
they frequently are found to be within specification.
This vibration is caused
by the hard composition of the Jurid 506 pads which amplify any
variations in the brake discs and the vibrations are transmitted
into the body and steering. New brake pad compositions have been
developed and tested for various models which greatly reduce the
tendency to cause vibration.
The new style pads have
been phased into production approximately as follows: E36 – 5/93;
E34 M50 – 5/94; E34 M60 – 3/93; and E32 M60 – 9/93. There will
be no production changes on the E31, E32-M70 or Motorsport models.
BMW says it is not necessary
to replace the rear pads or discs to cure a vibration complaint.
If the rear pads and discs currently on the car are not beyond
specifications they do not have to be replaced. Whenever pads
are replaced, all metal to metal part contact points of the pad
and caliper should be lubricated with Plastilube, BMW p/n 81 22
9 407 103.
To prevent cold brake
squeal when replacing pads on the E36 models only, all edges of
the front pads should be chamfered with a file, cutting in 2 mm
to a depth of 3 mm. See Figure
5. Apply Permatex
Disc Brake Quiet to the back of the front pads, as per the manufacturer’s
instructions.
Engine Rebuilders:
Nissan offers the following general information regarding valve
train noise. Valve train noise is generally caused by improper
operation of the Hydraulic Lash Adjusters (HLA) and is loudest
in the cylinder head and valve cover area. HLA noise that occurs
under all operating conditions is usually caused by a failed HLA.
A failed HLA will compress easily and often will not return to
its extended position.
Not all HLA noise is
caused by a failed HLA. Keep in mind that HLAs require an adequate,
air-free oil supply to operate properly. Air in an HLA’s high
pressure chamber will allow the lifter to compress under pressure,
permitting excessive clearance in the valve train. If the rocker
arm can be forcibly compressed by hand more than 1 mm (0.040″),
it is highly probable that air is in the lash adjuster valve.
Air can enter a HLA in
several ways. Excessive clearance between the rocker shafts and
rocker arms can allow the HLA’s oil supply to leak back to the
engine’s sump. When this occurs, the HLA will become oil starved
and air can be easily drawn into the HLA. If there is a blockage
in the oil supply, such as a clogged oil filter or clogged oil
supply passage, air can also be drawn into the HLA.
The oil supply can become
aerated if the engine is over filled with oil and the crankshaft
beats it into a froth. The aerated oil can then easily be picked
up by the oil pump and distributed throughout the engine. Aeration
also occurs if there is leakage in the inlet tube to the oil pump,
or at any of the associated seals.
Engine Rebuilders:
In the Production Engine Remanufacturers Association’s (PERA)
May Current
Concerns publication,
a question was asked regarding cutting the rolled radius out of
crankshafts. Remanufacturers were interested in knowing if you
grind more than .010″ under on the journal, which leaves
very little rolled radius (about 50%), is this a problem?
Doug Anderson of Grooms
Engines, Parts, Machining, Inc., Nashville, TN, says that he has
found that it is okay to grind the journal flush with the “grooved”
part of the rolled radius without creating problems. He notes
that OEMs first cut the groove then roll the radius to give it
a more dense grain structure which provides greater strength.
Anderson says that care
should be taken when welding journals with a grooved or rolled
radius to be sure that the groove is filled completely. Leaving
an air pocket below the weld can create stress points that will
lead to breakage.
Engine Rebuilders:
In a May technical service bulletin the Automotive Engine Rebuilders
Association (AERA) notes that its members have reported oversize
valves and guides on 1990-’96 Ford 4.0L engines. It appears that
some of these engines were released by Ford with oversize components.
Ford also authorizes cylinder head service repair using oversize
parts. The parts required, though, are limited at this time.
To make a successful
repair, three component parts must be oversized – the valve, valve
guide and valve stem oil seal. Ford currently has .008″ (.20
mm) and .016″ (.41 mm) oversize valves available, but only
.015″ (.381 mm) oversize stem seals. See Chart
2.
AERA says that it is
unaware of any aftermarket suppliers of these oversize parts.
Ford also authorizes conventional valve guide replacement if oversize
components are not available.
Engine Rebuilders:
Engine rebuilders should be aware that on 1990-’93 GM 1.6L, VIN
5 and 1.8L VIN 8 DOHC engines, the two internal oil control valves
located below the intake camshaft are not included in a new cylinder
head assembly.
In a May technical service
bulletin, the Automotive Engine Rebuilders Association (AERA)
notes that the valves must be either replaced or cleaned and transferred
from the old head to the new casting. The oil flow check valve
(p/n 94325538) and the oil control valve (p/n 94360288) are currently
available from GM. Both valves are in the oil galley directly
below the intake cam between the number 3 and 4 cylinders. See
Figure 6.
The function of the oil
flow check valve (603 in Figure
6) is to prevent
oil from draining out of oil galleys in the head when the engine
is stopped. The oil control valve (604 in Figure
6) meters the
amount of engine oil going to the cylinder head.
