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TECH ARTICLES
**Tech Articles are published monthly in The Bahn Stormer and P4 Magazines.
Goin' Topless: Convertible Tops
Valve Train of Thought Part 1
Valve Train of Thought Part 2
Valve Train of Thought Part 3
Valve Train of Thought Part 4
Out of Hibernation
Inflate
with Nitrogen
Clusters and Cables
The
Real ATE Story Tires:
The Break-In Process Timing
Belt Maintenance
Cats 'N' Heat
Head
Studs Fuel
Tanks: Internal Corrosion Hydraulic
Clutch: Disappearing Fluid
Sway
Bars: Binding and Breaking Flex
Couplers Forgotten
Fluids: Gear Oil
Clean Your Cores
Sealed
Wheel Bearings Convertible
Tops: Water Leakage Heat
Goin’ Topless: Convertible Tops
In
this section of each issue, I would like to share bits of experience and
information to the Porsche community. This
month I want to talk about “goin’ topless”, the convertible top, for
example, on 911 power tops and also many other models.
There are no less than 16 points of pivot, 2 synchronized lifting motors,
servos, 4 micro switches and the list goes on and on. The BEST single piece of
advice I have is: observe, listen and look.
Don’t assume that because it’s moving, it’s moving properly.
When the top is 90 degrees from the ground
“wiggle the top”, you can then assess the condition of the top. The right and left must mirror each other, no excessive
play on either side. This is the
best position to check the top because it’s in a neutral position with little
strain on the components. Smooth
closing operation and pin alignment can all be observed from this upright start
position. Thorough maintenance,
tightening pivots, servo arms and mounts, is essential to save costs incurred
from careless observation and operation. It
should be looked at during a routine maintenance.
Valve
Train of Thought Part 1
For
the next few issues I would like to go over the process and precautions of
executing an air-cooled 6-cylinder valve adjustment.
This service needs to be performed at least every 15,000 miles to prevent
unnecessary wear and performance loss. Although you can always hear a loose
valve, a tight valve, which is a larger concern, is much harder to detect. Good
habits to have and a procedure to follow will be mentioned in the following
articles.
The things that will be covered are valve cover:
warping and corrosion, updated gaskets, fasteners and torque.
Rocker shafts: leaking and walking. Head
studs: broken or missing studs. Valve springs: broken or
weakened. Valve retainers: check for cracks. Things to do on
the way: warm leakage test and check spark plug burn and condition. These things and more we shall cover during the disassembly
and assembly process.
You need to see more then a rocker shaft and an adjustment screw.
As the cars continue to age, they need a little more attention and visual
inspection.
Valve Train of Thought Part 2
Last issue we started into components and serviceability of valve train
prior to adjustment. After the
plugs are out labeled and checked for burn and condition, although you adjust
valves cold, while the engine is still warm is the time to do a compression test
or leakage test to get a baseline of engine condition.
All numbers for leakage or compression tests should have very little
deviation between them. Then valve covers are removed.
The covers need to be checked for warpage, corrosion and serviceability.
The C2 – C4 models have a tendency of corroding lower valve train
covers in the area of the sealing surface from moisture.
If corrosion is excessive and replacement is necessary, the dealer list
cost for lowers is over five hundred dollars and uppers are over seven hundred
dollars, which is a 500% increase over the past year or so.
The next things to be checked are cylinder head studs.
All studs can be checked with a mirror and a flashlight on either side of
the rocker shaft. There must be 4 studs per cylinder. Often found are
loose or broken studs and previously removed hardware laying in the galley.
This is information you need to know.
Another thing to be inspected are rocker shafts for oil leaks.
Rocker shafts can be inspected at either end, look for a clean oil wash.
Leaks often occur after first removal of shaft due to scratches while
removing or reinstallation from deviation of surfaces.
Valve Train of Thought Part 3
The next thing to look at would be valve springs.
With a mirror and a good flashlight you can see the condition of the
valve springs and retainers. Look
for cracks in retainers and valve springs that are broken or are not uniformly
coiled. If you can push a rocker arm in so that the valve opens, you have a
valve spring problem.
A special tool is needed to get between the rocker swivel and valve stem.
It can be purchased at your local dealer with replaceable blades. The new blades
are stamped out of shim stock. The
edges need to be taken off for a smooth approach. This can easily be done by
sanding the edge with extra fine sandpaper until edge has a small taper.
The adjustment has a certain feel that you need to get used to. The
center of the valve stem needs to be in the center of the lash blade.
If the blade handle sags from its own weight, the valve is too loose.
Be sure to make small corrections to adjustment screw because small
amounts will move clearances more than you might think.
The feel that you are looking for is when the lash tool stays in
position, but is still loose enough for you to rotate the blade and remove and
reinsert smoothly and easily. Be
careful not to over-tighten rocker adjustment nuts.
Valve Train of Thought Part 4
After rotating the engine to adjust valves on each cylinder at TDC, inspect
valve covers for warpage, corrosion and a generally flat surface. Install new
valve cover gaskets or rubber seals (for C2/C4). I like to use the silicon
beaded lower gaskets which has a thin bead of silicon tracing the sealing
surfaces on a standard gasket; this is something the dealership does not sell,
it is aftermarket only. The silicon bead helps the sealing process in minor
surface deviations. New nuts and sealing rings should also be installed. Torque
the 8mm nuts to 16 ftlb. and the 6mm nuts to 7 ftlb. Before installing plug
wires, inspect resistor for corrosion. Small of amounts of electrical contact
grease never hurt anything. Top up the oil, making sure not to overfill the
system. Keep the oil level between the two dipstick marks with the engine
running at normal operating temperature. And that will conclude the Valve Train
of Though Series. If you have any individual questions feel free to call or
e-mail.
Out of Hibernation
This issue I would like to talk about hibernation!
Here are some of the top seven things that I feel are the most important
things to do to your car before you put it away for the winter.
A fresh oil change is always a great idea before storage to rid most of
the combustion contaminants from the crankcase. Make sure the fuel is full to
help displace moisture. Increase the tire pressure to about 58 lbs. (4 bar) and make
sure you leave a note on your dash to remind you of this pressure increase.
This will help prevent flat spots from occurring on the tires.
Roll car occasionally during the winter, the tires need to have a
different contact patch to also help prevent flat spots.
Cycle the air-conditioning system one last time to lube the front
compressor seal. Remove the battery and store it in a non-frozen environment.
This keeps the battery from freezing and displacing battery acid into the
battery compartment. The coolant
density should be down to at least –32 degrees Fahrenheit. One last
recommendation would be to keep birdseed and any kind of pet food as far away
from your car as possible! I have seen mice carry its newfound food into air
filters, exhaust pipes and heater ducts!
Inflate With Nitrogen
Nitrogen
is an inert, dry, non-flammable gas that is used in tires for all commercial
aircraft, LeMans, Formula One, the U.S. Military and more.
The benefits of Nitrogen include: Better tire pressure retention,
elimination of rim rust, removal of oxidation, cooler running tires, improved
fuel economy and on-the-road reliability.
Nitrogen improves tire pressure retention because
its molecules are larger in size, which allows it to migrate through a tire 3 to
4 times slower than regular air, which keeps your tire pressure where it should
be that much longer. By maintaining
proper inflation pressures the recommended “contact patch” of the tire is on
the road. Keeping the correct inflation pressure on your tires maximizes vehicle
handling. Having your tires at the right inflation pressure can improve your
miles per gallon by lessening the rolling resistance that under inflated tires
have. Tire life can also be improved by filling your tires with Nitrogen.
If your tires are under inflated, they may quickly wear on the shoulders
and if they are over inflated they may quickly wear in the center of the tread. Tires inflated with Nitrogen run cooler than tires inflated
with regular air. Removing the
oxygen also eliminates the oxidation and condensation that can damage inner
liners, steel belts and rims.
Clusters and Cables
Lately, we have seen quite a few pedal bushings seized
and clutch shafts worn to the point of no return. This problem is usually caused
by a stiff clutch, lack of lubricant and a generally dirty environment. A real
good replacement for the plastic bushings is an aftermarket kit that comes with
oil-lite bronze bushing replacements for the clutch shaft, brake pedal shaft and
the bell crank for the accelerator. It also comes with a brass bushing for the
clutch shaft and a double roll pin to put it all together.
If your clutch pedal starts to get stiffer as the years
go by, you should take a look at the pedal bushings and the clutch shaft before
any major clutch replacement. You also may notice a squeaking noise every time
you press on the pedals.
It is a little bit of a procedure
to get the assembly out of the car, but once out it is fairly straight forward
to replace bushings and shafts. Make
sure all the bushings are impregnated with oil. The other thing to check on the
way is the helper spring at transmission pivot.
If the spring is broken or the spring arm is seized to the clutch shaft,
it will cause an excessively stiff pedal, which will wear out the pedal bushings
and pivots prematurely.
The
Real ATE Story
I would like to share with you the difference between ATE Super Blue
Racing (ATE Blue) and ATE TYP 200 (ATE Clear) and why I prefer ATE Clear. They both have the same Wet Boiling Point (200°C) and Dry Boiling
Point (280°C), which is
the important part. The ATE Blue is not DOT approved because it is blue. It also
seems to have a long-term affect on the plastic reservoirs, staining them blue
from the inside. This makes it
become difficult to see the fluid level when it should be easy.
It appears to me that the reason why they make the
fluid blue was to separate the clear from the blue during brake fluid changes.
If you run enough fluid through the system and do it often, the ATE Clear is
what I would recommend.
Tires:
The Break-In Process
Make sure you are
careful when you are exploring the capabilities of your newly installed tires.
All tires, including winter tires, require a break-in period of a few hundred
miles for optimum performance. It is also important for you to understand that
new tires will be a little slower to respond and that new, full tread depth
brings with it a little more tread squirm until the tread wears down.
Winter tires have
their own personality and handling traits and will feel different than the
summer or all-season tires being replaced. New winter tires begin with deeper
tread depths and more open tread designs that may contribute to more tread
squirm and you may notice a reduction in handling responsiveness.
Another thing to
check when installing new tires is setting and maintaining inflation pressure.
Make sure it is at its recommended inflation pressure and it will benefit you to
check it frequently.
Timing
Belt Maintenance
This week I would like to go over the schedule for timing
belt maintenance. Water-cooled
timing belts should be maintained on a regular basis to prevent catastrophic
engine failure such as bent valves and crushed lifters or camshaft damage. A
timing belt and balance shaft belt replacement is due every 45,000 miles. They
should be tensioned every 15,000 miles and tensioned 1,000-2,000 miles after
initial installation.
When the timing belt and balance
shaft belt are replaced, all associated tensioners and rollers should also be
replaced. Also check oil leaks from
camshaft and balance shaft while replacing the belts. Oil can cause a new belt
to fail very quickly. The condition of the water pump should also be checked at
this time. A special stagger tool is required to set proper belt tension. A belt
that is too tight will make noise and overheat the belt. A belt that is too
loose will vibrate itself apart. Remember, there is no such thing as an
automatic tensioner. Belt tension must be checked and maintained manually.
Cats
‘N’ Heat
This article I would like to
talk about what causes Catalytic Converters to fail and how to prevent this. The
most common causes of converter failure are misfires, lean or rich fuel mixture,
fouled spark plugs or bad spark plug wires, a bad ignition module, leaky
injector sand valve guide leaks which all cause the excess of hydrocarbons. A
slow acting Oxygen (O2) sensor can also cause the converter to fail. An O2
sensor’s reaction time decreases dramatically after around 60,000 miles. There
is a high probability of failure soon thereafter. Since 1995, up to four Oxygen
sensors and four catalytic converters have been added to exhaust systems to
monitor catalytic converter efficiency.
To prevent the failure of your
catalytic converter make sure to maintain a proper maintenance schedule and get
emission controls checked. You should also get your car checked out if it is in
poor running condition and immediately after the Malfunction Indicator Light
(MIL) comes on. Looking out for
these signs of failure and following these tips will help save you from the high
cost of replacing the Cat.
Head
Studs
This week we will discuss head
studs on Porsche 911's. All 911's have 24 cylinder head studs to attach the
heads to the engine. A broken head stud can cause many problems including loss
of power, oil leaks, blown head gaskets or worse. Every head stud needs to be
checked during every maintenance in order to help catch a broken head early on
before it can cause any serious damage. Head studs can fail at any time
regardless of mileage. We have seen failures on cars with less than 40,000 miles
on it. Old 911's and all 911 Turbo's are at the highest risk of a broken head
stud. Old 911's are at risk because the metal has been fatigued for many years
and Turbo's are at a high risk because there is more pressure in the combustion
chamber then a regular 911. Replacing head studs can be an expensive venture,
but it is much cheaper than a new engine! When we replace head studs we always
use Raceware studs, washers and nuts. They are strong and reliable, we have
never had a failure to date. Since there really is no way to prevent broken head
studs make sure those head studs get checked out!
Fuel
Tanks: Internal Corrosion
Recently
we have seen problems with internal fuel tank corrosion. If your car has a steel
fuel tank this may be a concern. In some models you can remove the fuel tank
sending unit and with a good flashlight you can see directly into the tank and
evaluate the condition of the internal lining of the tank. As sediment collects
in the bottom of the tank you may need to siphon, drain, clean or possibly
replace it to help prevent damage to internal fuel system.
Make
sure you change the fuel filter often. Before a car goes in for storage I like
to add Marvel Mystery oil, an additive that helps eliminate corrosion and also
helps keep fuel pump bushings lubricated and injector nozzles clean. As the cars
get older there seems to be more corrosion build up in the fuel tanks from
condensation.
Hydraulic
Clutch: Disappearing Fluid
If you find yourself adding brake fluid to your reservoir more often than usual
you might want to check your hydraulic clutch system for leaks. A leak in this
system will drain your brake fluid since it is both used for your brakes and
your clutch. The hydraulic clutch system consists of a clutch master cylinder,
clutch slave cylinder, connecting lines and a clutch hose.
These leaks
usually occur inside the car and are absorbed by the carpeting and padding,
which is why the leaks will not be noticed right away. A good place to start is
taking a look at the clutch master cylinder. You need to look at the push rod
that goes into the master cylinder. This push rod needs to be dry. Another place
to check is the clutch slave cylinder. Leaks occur near the mounting hardware or
transmission bell housing, depending on how severe the leak is. The last place
to check is the clutch hose (flex line). Take a careful look for fluid seepage
at the crimp fittings from the rubber hose to the steel line.
Keeping close attention to
hydraulic clutch leaks will prevent corrosion behind the carpeting. In severe
cases the clutch pedal will release itself with the pedal still pressed to the
floor or a total clutch failure and loss of fluid will occur.
Sway
Bars: Binding and Breaking
Lately we have seen many sway bar problems. On 911’s 1990 and
earlier the rear sway bar brackets have a tendency of tearing the sway
bar loose from the chassis. This may be noticed by a noise from the
rear of the car while driving over bumpy roads. These sway bars have
been updated from the factory with reinforcements. The brackets need
to be ground and carefully removed from the car. The new sway bar
brackets need to be accurately measured and welded to the car.
On
the Porsche 944, the stand off brackets (the brackets that hold the
sway bar in the center) is often bent because they are mistaken for a
towing point. Also keep an eye on the front bushings swelling up from
past or present oil leaks.
For
all Porsches, beware of aftermarket sway bar kits with rod end
bearings. This is an item that needs to be serviced often. Look out
for corrosion and binding. These are not designed to seal out moisture
and dirt.
Flex
Couplers
A
flex coupler is a rubber drive shaft dampener. It attaches the engine
to the torque tube in Porsche 944’s and 968’s. It is only on
automatic transmissions. When
they fail they make a loud clattering noise that sounds like the
engine is coming apart. Take a look in the inspection hole in the bell
housing. If you see rubber debris it means that your flex coupler has
failed.
The vehicle will still be drivable for a short period of time because
there are metal stops in the flex coupler. These stops will fail
quickly if driven on too long. If you find that your flex coupler has
failed get it checked out immediately. Flex couplers fail more
commonly on 968’s because they have the same part as the old 944’s
but they are heavier and have increased power outlet. There is no
telling when a flex coupler will go bad and there is no preventative
maintenance so listen for the noise and watch for the rubber debris.
Forgotten
Fluids: Gear Oil
One
of the most common fluid that is neglected is gear oil.
When the gear oil is not changed it carries small amounts of
gear and bearing material that contaminates the fluid. This
contamination causes excessive gear wear, bearing wear and
synchronizer wear. Gear wear and bearing wear cause fine metallic
particles to pack themselves into various small areas inside the
gearbox. After
disassembling high mileage transmissions there seems to be a lot of
excessive sludge and debris in hidden corners, detents and gear
bearings. The
manufacturer has no scheduled maintenance for gear oil changes. I
would recommend changing your gear oil at least every 30,000 miles to
steer clear of the sludge and debris build up.
Clean
Your Cores
It doesn’t
matter if you have an air-cooled or water-cooled engine; they all have
cooling cores such as a radiator, a/c condenser or oil cooler. These
cores can get blocked with road debris, leaves and many other things.
This blockage can cause higher temperatures in the cooling system that
can cause cars to overheat and premature engine wear. It can also
cause higher air conditioning discharge pressures, which may result in
premature failure to the hoses.
A careful
inspection of the air inlet of the core usually reveals the debris.
Spraying water through the back of the core will help dislodge and
debris caught in the cooling surfaces.
Some models such as 1990+ 911’s may require you to remove the
fender liner to expose the back of the core. Models that have
condensers in front of the radiator need to pay special attention to
the space between the two cores. Make sure to clean out with a
low-pressure water source such as a garden hose. No power washers!
High pressure can damage the cores.
Road debris is inevitable,
so cleaning out you core will help prevent higher temperatures and the
longevity of your engine and A/C system.
Sealed
Wheel Bearings
In
this article I would like to discuss sealed wheel bearings. Most
911’s have sealed wheel bearings in the rear, where 944/924 came
with sealed wheel bearings in the rear beginning in the year ’85.5+.
All wheel bearings, front and rear, have been sealed since the
birth of the C2/C4.
Now,
what is a sealed wheel bearing? They are bearings with a double row of
ball bearings and are not serviceable; if removed they must be
replaced. Non-sealed wheel bearings in the front are taper roller
bearings and rear non-sealed wheel bearings have a row of cylinder
bearings and a row of ball bearings (these are usually on 944’s).
Non-sealed wheel bearings are serviceable; they can be cleaned,
inspected and re-greased and it isn’t necessary to replace them.
Under
extreme conditions, such as track cars, your wheel bearing nut should
occasionally be re-torqued. The rear wheel bearings on all 911 turbos are a little
different. They have two taper roller bearings with a crush ring in
between to maintain torque and proper bearing pre-load. These are
serviceable and should be serviced once in a while.
If a
wheel bearing is going bad you can hear a moaning noise at road speed.
The tone and/or volume of this noise will change when you load the car
to the right or left. If you hear this noise on your car you should
have it checked out immediately. We have seen stub axles shear right
off when there was neglect to maintain torque or the wheel bearing was
not replaced.
Convertible
Tops: Water Leakage
Recently,
we've had a problem with a Boxster that had an incredible amount of
water damage, which caused the immobilizer to fail from moisture and
corrosion. The water entered the vehicle through the stow away
compartment for the convertible top.
There is a
liner at the bottom of the stow away compartment that channels water
to two drains at both sides of the car. This liner was torn and the
car was left outside for a long period of time. You can see the liner
when the top is partially open and the stow away lid is all the way
open. Check to make sure there are no tears in the liner and that the
drains are not plugged with leaves or debris.
While the car
was in the shop we took the seat out of the car, propped up the carpet
and left a blower on it and after 3 days it was still wet! Besides not
being able to start your car, you may need a new immobilizer and key
transmitter. This is not worth the grief and expense.
It
is really not a good idea to leave any convertible outside for a long
period of time. All Porsches have many control
units underneath the seats where water can collect. Convertible or
not, moisture is not a good thing, so keep it dry!
Heat
In
this article I would like to talk about problems with heat in the
first Porsche 911 up to the 1989 911.
The
System
Air is blown
though the alternator fan into hoses that go into the heat exchangers
where the heat is collected. Then the air goes to the heater control
box where it is either discharged underneath the car or to the inside
of the car depending on the cable position.
What
Goes Wrong
The usual
problems are the heater control boxes tend to rust out and bind, the
heater cable breaks or the cable guide tubes come apart. On automatic
climate control cars the control rod ball sockets to the cable pivot
also break.
How
To Check For Problems
If your
heat doesn’t work try checking the cables. They are located
underneath the car above both axle shafts on the chassis. Make sure
the control boxes and heater hoses are in good condition. Also make
sure the cables and tubes are in good condition and they work the full
range of the control boxes (from stop to stop). If the control boxes
are rusted out, they need to be replaced. If the cables are broken or
binding they need to be replaced along with new guide tubes.
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