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BRAKE ADJUSTMENT
Some of you that have never adjusted your rear brakes may need to remove the 'knock-out plugs" that are contained in the lower section of the brake backing plates. The 'knock-out plugs" are removed by driving {punch) them into the drum area. Removal of the drums are necessary to remove the 'knock-out plugs". This will provide a slot for inserting a screw driver into the brake adjustment mechanism.
STEERING COLUMN GREASE
If you grease your own (or have it greased), have you ever wondered what's the proper technique for greasing the steering column shift assembly (the grease zerk between the two U-joints which is above the steering gear box)? Since grease never comes out the top slide surface. The grease seems to disappear or goes out the bottom near the lower U-joint. Here's a tip for proper greasing of the steering column. First of all, the column should be filed with grease to allow free operation and to keep out water. Water will run into the cavity and causes all kinds of problems if it stays inside. Filling the cavity with grease can be accomplished via grease gun and a properly placed finger. That's right! Place your finger at the bottom of the cavity (small hole in center) which is just above the lower U-joint. Press your finger over the hole while greasing the shaft zerk and eventually the grease will flow out of the top of the cavity. Now it's full and water can not enter! While you are at it, don't forget to grease the zerk in the center of the lower universal joint.
IN-LINE FUEL FILTERS
Several coaches have been observed that have been modified by placing a fuel filter between the Fuel Pump and Carburetor. The steel fuel line has been cut and a Rubber Fuel Line with an in-line Fuel Filter has been added on top of the Engine. Hose clamps have been used to secure the rubber fuel line. Several times I have placed my hands on the fuel line near the connections and noted wet fuel on my finger. The steel fuel line was placed on top of the Engine for a very good reason, to minimize fuel leakage on top of the engine (a definite fire hazard}. So, I advise everyone to inspect the fuel line and verify that no one has tampered with the steel fuel line between the fuel pump and carburetor. A recommended location for the addition of a fuel filter (if desired) is under the coach, between the frame (drivers side), just in front of the fuel transfer valve {between transfer valve and Engine). Maximum protection is provided in this location which already contains rubber fuel lines and makes fuel filter installation a snap. Don't help create a fire hazard !!!
STEERING DAMPER REPLACEMENT
If you haven't replaced your steering damper (looks like a shock absorber) lately, you may want to remove it and check for fitness. Most are worn-out and we don't know it! A good steering damper helps stabilize your steering while traveling down the road. We need all the help we can get. Replacement units are available from GM or from several after-market sources.
AIR BAG LEAK ISOLATION TIP
If you have a leak down problem which is predominately on one side, the following tip may be of interest for your Power Level and Electro Level I systems. Crossing of the air lines to the valves will isolate the problem to the air bag/lines if no change in leak down occurs. If the leak down goes with the lines (cross configuration), then the problem is within the valve area. Once you know where to look, finding the leak is much easier {air bag/line area or valve area). Operate in manual mode only with lines crossed and replace to original position before operating the coach. This is a trouble shooting aid only and is for a temporary connection.
DISTRIBUTOR LUBRICATION
The top bushing in the distributor can wear out. Prolonging
life involves properly lubricating the internal parts. Most handbooks
recommend GM Distributor Grease, but few vendors know what it
is.
The bushing is an oilite bushing and should not have worn
out at 94K miles unless someone had washed it with solvent. This
bushing should be only cleaned with engine oil. Also the six spaces
under the plastic seal should not be cleaned with solvent since
the sintered iron outside shell is porous also. Clean with engine
oil and fill with the grease below.
General Electric GL 622 should be used in the star wheel,
in the pole piece and plate center, in the space around the upper
bushing and inside the upper bushing. This is silicone dielectric
grease, a poor lubricant, but the only grease that will withstand
the ozone generated within the spark gaps.
If new oilite bushings are obtained somewhere, they should
not be lapped. If the fit is too tight, reaming with a very sharp
reamer is acceptable.
The handbook assembly instructions don't explain the gear alignment.
The end of the distributor cap mount that has square corners should
be aligned with the drive pin hole that is in line between two
teeth. If aligned the other way, the distributor will be turned
half a tooth when timed normally.
Everyone with an old distributor should check the upper bushing
for wear by trying to move the rotor from side to side. Some are
so bad that the star wheel wears off its tips and those of the
pole piece about .020 in. This can cause occasional backfiring
through the carburetor.
If the mechanical spark advance or the pole piece vacuum advance
motion are not completely free to rotate, the distributor should
be disassembled for the re-lubrication per the manual.
RADIANT HEAT
Everyone knows what a rainbow looks like, but do you know how
it relates to RV problems ??? Read on.
Water drops in the sunshine refract visible light into its
various colors so that we see the range of "visible', radiation.
Above violet, frequency-wise, is ultra-violet (UVA and UVB on
your sun-block bottle). Below red is, as the name implies again,
the infrared radiation band, radiant heat.
Radiant heat travels very much like light does. It passes
through clear glass and through a stream of rushing-by air with
very little loss. So what, you are thinking. Your exhaust system
is the hottest part on your RV and emits radiant heat all of the
time, about 2,500 degree F, that it also radiates visible red
light. No matter how much convection cooling air is rushing past
your manifolds they will send radiant heat into all surrounding
items. If you install headers, the instructions will advise that
you insulate certain critical components with reflective insulation.
Headers are larger than manifolds and can be closer to these items
than manifolds. Still, the same principle applies to manifolds.
One critical area apparently overlooked by the GMC designers
is the brake line to the right front brake. It runs just behind
both of the exhaust pipes below the manifolds. One solution is
to put reflective shields about 10" wide between this line
and each exhaust pipe. Brake fluid doesn't circulate continuously
like most other fluids do, and since Dot 3 brake fluid boils at
around 284 degree F (old) to 400 degree F (new), this is the most
likely spot, other then overheated brakes, to cause temporary
brake loss. The shields also protect the plywood "firewall"
behind the brake line.
There are areas all along the exhaust system that suffer from
radiant heat. Check above the mufflers, you might find the original
very thin aluminum corroded and the insulation behind it warped
and crumbled. Replace the insulation with 1-inch aluminum-clad
building insulation and the whole aluminum panel with shiny stainless
steel (all 3 bays is best).
The starboard side of both fuel tanks has a hot exhaust radiating
heat into a baffle. The baffle gets hot and radiates heat into
the fuel tanks. Another source of radiant heat into fuel tanks
is the highway, especially blacktop. As noted above, the rush
of air under the coach does not block this radiant heat. Besides,
the hot air from the engine contributes convection heating to
the tanks.
Radiant heat is also a consideration in where you park. Parking
on the bright side of a shiny metal or light colored RV will allow
it to reflect radiant heat into your rig when the sun is shining.
A light-colored wall will do the same. Walls, parking lots or
rocks that heat up during the day will continue to radiate heat
after sundown.
TRANSMISSION SHIFTING PROBLEM
Two serviceable items, external to our FWD Transmission, which
can cause erratic shifting are as follows:
1) Vacuum Modulator - the common failure is a ruptured diaphragm.
2) Governor - the common failure is a dirty or stuck piston or
a worn weight assembly which effects the entry and exhaust valve
opening.
Both of these items are easily removable for a periodic functional
test and cleaning. Condition of the Vacuum Modulator Diaphragm
can be checked by pulling a vacuum (hand pump with gauge) and
verifying that a vacuum seal exists. Also, inserting a pipe cleaner
into the vacuum connector pipe to check for the presence of transmission
fluid is a valid test. If transmission fluid is found or a vacuum
leak is detected, the Vacuum Modulator should be replaced.
Governor condition can be inspected after a thorough cleaning
in solvent. Air dry and blow out all passages. The valve piston
and valve sleeve must be free of nicks, burrs and scoring (free
valve piston operation). Disassembly and removal of the valve
piston may be necessary to verify condition (tap out the gear
pin, remove gear and valve piston).
An additional test is to verify the entry and exhaust valve
opening sizes (0.020" rain). A metal cover surrounds the
governor weight assembly on the GMC. Two screwdrivers or similar
objects can be used to move the weights completely inward for
the exhaust valve opening measurment. These tests can reveal a
governor in near-worn-out condition which can create shifting
problems.
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