|
|
|
|
The first issue of Tech Center will cover service. We have
many new GMC owners in the club who have not had the benefit of
a basic service schedule. It's also a good idea for the "veterans"
to brush up once in a while. The whole idea behind service or
preventative maintenance, is to catch small problems before they
become big ones and leave you stranded somewhere. Speaking of
being stranded, make sure that whatever towing coverage you have
covers motorhomes. Too many members have had to pay several hundred
dollars because their auto policy did not cover their motorhome,
and they found that out in the middle of nowhere.
We are going to cover the factory recommended service and
several other items which are not mentioned by the factory, but
are of critical importance.
It's a good idea to have a complete set of service manuals
for your coach, they can really be of help when you need service
and cannot find a mechanic who is familiar with the GMC. They
are also a must if you plan to do any work yourself. Manuals are
available from Cinnabar Engineering at 415-948-2618, Monday-Friday
8: 00am-5: 00pm Pacific time.
Every 3,000 miles or 3 months:
Oil and filter change and chassis lubrication, changing the
filter every other oil change puts a quart of dirty oil back into
the system. The $5.00 it costs for an oil filter is cheap insurance
against oil contamination.
While you (or your mechanic) are under the coach, check the
oil lines which run from the oil filter bracket to the radiator.
The lines carry high pressure oil to the oil cooler inside the
radiator. These lines will wear with age and eventually fail.
If they fail while you are driving you will lose oil pressure
and there is a great risk of fire if the hot oil contacts the
even hotter exhaust manifold. If the lines have never been replaced,
or if you don't know if they have been, it's worth the effort
to do it. Any good hose/fitting shop can duplicate the lines.
In some cases the fittings on your old lines can be re-used. If
the lines look good, make sure they are not rubbing on the frame
or the engine. Make a point of checking them each time you change
the oil.
A second item to check while you are looking at the oil filter
is the filter bracket itself. It tends to loosen up after several
tighten and loosen cycles of the oil filter. If its gets loose
enough you will have a messy oil leak and possibly loss of oil
pressure. Once the oil filter is removed you can tighten the nut
which holds it to the engine block. If the gasket between the
bracket and he engine is worn out, take the gasket from the oil
filter you just removed and use it as a replacement, it's the
same size.
Also check the lower radiator hose and the hoses running to
and from the power steering pump. Look for cracks or places where
they are rubbing against something else. Now is the time to correct
any minor problems you might find.
Check all your fluid levels including; transmission, power
steering, windshield washer, batteries (both engine and living
area), brake fluid, coolant, and generator oil level. This is
also the time to poke around the engine compartment and the under
carriage to check for any loose wires, holes, or vacuum hoses
which might be cracked.
After checking the engine, turn your attention to your air
suspension system. Drain the water from your air compressor wet
tank. Check to make sure the drain valve is not clogged and leaking.
If it is, replace it, this will keep your compressor from running
constantly leading to early failure. If your air system still
has the original brass check valve on the air tank, it needs to
be replaced. The all brass valve won't seal properly causing the
system to leak once it has been turned off. Replace the valve
with an updated type which is available from most of the after-market
GMC Motorhome parts suppliers.
Every 6,000 miles or 6 months:
Repeat the 3,000 mile service, plus, rotate the tires,
while you have the tires off, check the tires for any uneven wear
pattern. Check the front disc brake pads. You don't have to remove
any parts, there is a little cutout on the back of the brake caliper
where you can look in and see how the pads are wearing. The pads
have a groove cut down the middle of them. If you look in the
cutout and can still see the groove then they are OK. If you cannot
see the groove, they will be somewhere between one eighth and
one sixteenth inch thick and need to be replaced.
Check the rear drums for any weights that might be loose or
have fallen off. A lost weight can cause an annoying imbalance
that can drive you crazy if you keep taking the tires and wheels
to get balanced but still have a vibration. A good welding shop
can reattach the weight.
While your checking the brake pads, check the steering linkage,
grab the steering rods and try to move them. They should be tight
with no noticeable play. Check the drive axle constant velocity
joint boots. The axle connects the final drive unit with the front
wheel on each side. The boots should not be torn. They contain
vital lubricant for the joint, if they are torn they should be
replaced immediately. If you are on the road and notice a split
boot, most auto parts houses carry a temporary sealer you can
use. The boot needs to be replaced as soon as possible.
Every 12,000 miles or 12 months:
Repeat the 3,000 and the 6,000 mile service plus, change
the transmission and final drive fluid and clean the outside of
the radiator with a garden hose flushing toward the front of the
coach. Replace the engine air filter, fuel filter, and spark plugs.
Check the spark plug wires for cracking or fraying. Carefully
check the distributor cap for cracks, carbon tracking, or terminal
corrosion. Replace it if you find any of these conditions. If
you have a 1973-1974 coach with conventional ignition, replace
the points and condenser as well as the distributor cap and rotor.
You will need to check the timing after replacing the points.
Check the fan belts for wear and proper tension.
Remove the rear brake drums and check the linings. The basic
rule-of-thumb is if the lining material is as thin or thinner
than the backing it's attached to, then they need to be replaced.
After re-assembling the drums. Take the coach on a road test.
Adjust the rear brakes by stopping firmly a couple of times while
rolling backwards at about 5mph. A nice empty shopping center
or church parking lot is perfect for this. Once the brakes are
adjusted, test the holding ability of he parking brake on a small
incline. You can make minor adjustments by turning the knob on
the end of the parking brake lever. The parking brake is important
because the coach can get locked in park if you stop on an incline
and it rolls backward while the transmission gearshift is in park.
It's good driving practice to set the parking brake before you
put the transmission in park.
This is also the time to check all your interior appliances.
Make sure the furnace works properly, check the stove and oven,
and check the stove vent, and the refrigerator for proper operation.
Check all interior lights and fans for proper operation.
Every 24,000 miles or 24 months:
Repeat the 3,000, 6,000, and 12,000 mile service plus, Replace
the front wheel bearings and repack the rear wheel bearings. The
front wheel bearing service is best left to an expert if you are
not familiar with the process. The bearings need to be pressed
off and on the hub. In addition, they must be measured precisely
and fitted to the hub. They are sold in matched sets and cannot
be mixed. Several club members perform this service as well as
all good GMC Motorhome service facilities. This bearing replacement
is critical because the bearings are the same ones used in the
Oldsmobile Toronado from which most of the Motorhome front end
was borrowed. The bearings can carry the weight of the Toronado
for 100,000 miles, but when you triple that weight on a Motorhome,
the bearings wear out much faster. It' s cheaper to replace them
every 24,000 miles than to repack them and risk failure a few
thousand miles later.
The rear wheel bearings can be checked, cleaned, and repacked.
Make sure you use new grease seals and set the bearing preload
properly, always use a new cotter pin when you reassemble the
hubs.
Check your air suspension system for cracked hoses, leaks
(use a soapy water solution), and missing parts. The fittings
should be tight but not so tight that they distort and leak, this
is especially true for the plastic AMP fittings. Look at the air
bags, they should not be peeling or "hot dogging". Periodic
rotation of the air bag can eliminate the "hot dogging"
problem.
Don't neglect your generator, now is the time to change the
oil and filter, clean the air filter and replace the spark plugs.
Lubricate the throttle linkage. Check the unit for any loose wires
or hoses. Make sure it will be ready when you need it.
City Water Entry valve Information:
The original equipment city water entry valve and pressure regulator is made by Shur-Flo and is made of brass and plastic assembled using screws and rubber gaskets. It is very easy to take apart, however, Shur-Flo does not carry replacement service parts for it anymore. The model was discontinued about six years ago. The only model they make is a standard all plastic one which uses no common parts and cannot be taken apart. The original valve has a pipe fitting on the side of the unit to connect it to your plumbing system. The interior closet wall (on side-bath models) is right against the valve. If the valve fails and you replace it, the new all-plastic unit has the pipe fitting on the end. You will need to use some adaptors to get your plumbing to connect to the new valve. Save the 1/2"-to-3/ 4" adaptor from the old valve, you will need it to connect to the motorhome plumbing. The closet wall might have to be moved to accommodate the pipe fittings. This appears to be the configuration on the side-bath 26 foot models.
Air Suspension Update:
This is for those of you who have installed the air suspension
upgrade kit from Cinnabar Engineering or a similar kit and are
having trouble finding a leak. Check the polycarbonate bowl and
filter on the air line which runs from the compressor to the wet
tank. What appears to be a leaking schrader valve could also be
a cracked bowl. If you look carefully you may be able to see hairline
cracks where the valve screws into the bowl. If you are on the
road, a piece of chewing gum, urethane, or "plastic rubber"
sealer put down inside the bottom of the bowl will seal it until
you can replace it.
|
|
|