New coach

[ol' jim hisself]

Sorry if this is a repeat, but I think my first message was eaten by
the listserver.

Anyway, I have found a '73 in running condition, for a relatively low
price. I was wondering if anyone could tell me of any GMC gotchas
for which I should be looking when I check this out.

This coach is from the last third constructed in '73 (#1011xx), and
is equipped with the double passenger seat, power levelling, a 6KW
generator, 3-way power refrigerator, and both side and rear dinettes.
I have yet to check for cruise, but I'll bet it is there.

I have not, as yet, run any of the accessories. I do know that the
brakes are spongy, probably from when somebody replaced a brake line.

Are there any ailments common to the GMC, or to RVs in general?

This will be my first motorhome, so I know a total of zip, zero,
nada!!!

TIA for any advice.

Ol' Jim, hisself

Jim and Ana Wallace Enjoyin' the Space Coast of Florida
hisself http://ddi.digital.net/~hisself

 

[ol' jim hisself]

> The rear axle swing arm pins and bushings need to be checked for
> looseness, excessive wear and end play.
>
> Jack up the rear of the coach and support with jackstands. make sure
> its stable. MAKE SURE you release the air pressure to the airbags as

How do I do this?? (I TOLD you I was a neophyte)!!

> soon as you have the coach supported BUT NOT jacked up.
> ( you don,t want to "hotdog" the airbags )
> Then check the pins and bushings for "slop" and endplay.

Then I continue jacking before checking? or do I just take the
load off the arms and leave the wheels lightly on the ground?

> The 73 rigs used a smaller pin than later models and tended to
> wear a little faster.
> Replacement of these pins and bushings could be considered a
> semi-major operation and costs $1000.00+ Labor intensive work
> and expensive parts.
> Rear wheel alignment is also important on the GMC and MUST be done
> if the pins are replaced, and is a good idea anytime to keep tire
> wear inline.

Now it begins to sound like my Corvette - trailing arm bushings
with carbon steel pins and alignment shims - rusted into a solid mass
which can only be removed by torch!

>
> The Brakes on the GMC are a real weak point, make sure they receive
> a extra good checkout and repair.

Anything specific, like shoes, pads, or just crappy in general?

> Front wheel bearings are on the weak side, and its worth the extra
> money for upgrades.

Is there any way to check them quickly? I don't know how much
checking this guy will let me do.

Thanks for the info.



Ol' Jim, hisself

Jim and Ana Wallace Enjoyin' the Space Coast of Florida
hisself http://ddi.digital.net/~hisself

 

[john szalay]

>Anyway, I have found a '73 in running condition, for a relatively low
>price. I was wondering if anyone could tell me of any GMC gotchas
>for which I should be looking when I check this out.
>
The rear axle swing arm pins and bushings need to be checked for
looseness, excessive wear and end play.

Jack up the rear of the coach and support with jackstands. make sure
its stable. MAKE SURE you release the air pressure to the airbags as
soon as you have the coach supported BUT NOT jacked up.
( you don,t want to "hotdog" the airbags )
Then check the pins and bushings for "slop" and endplay.
The 73 rigs used a smaller pin than later models and tended to
wear a little faster.
Replacement of these pins and bushings could be considered a
semi-major operation and costs $1000.00+ Labor intensive work
and expensive parts.
Rear wheel alignment is also important on the GMC and MUST be done
if the pins are replaced, and is a good idea anytime to keep tire
wear inline.

>Are there any ailments common to the GMC, or to RVs in general?
>This will be my first motorhome, so I know a total of zip, zero,
>nada!!!
>

The Brakes on the GMC are a real weak point, make sure they receive
a extra good checkout and repair. Replace the front wheel flexible
brake hoses, every couple of years, they appear to be subject to
failure on the inner hose wall, and can cause to disk brakes to lock on.

Front wheel bearings are on the weak side, and its worth the extra
money for upgrades.
The 455 exhaust manifolds tend to overheat and are subject to stress
cracks, We replaced ours with headers, and then had to replace the
oil cooler lines because of the higher radiant heat from the headers.
(there have been several coaches burned to the ground because of
failed oil cooler lines)

We really like our GMC, and feel its worth the extra effort to keep
it running and will continue our restoration effort.
We've had ours for a little over 9 years.

John & Brenda Szalay
Louisville Ky
GMC #51

 

[patrick flowers]

>
> The rear axle swing arm pins and bushings need to be checked for
> looseness, excessive wear and end play.
>
> The 73 rigs used a smaller pin than later models and tended to
> wear a little faster.
> Replacement of these pins and bushings could be considered a
> semi-major operation and costs $1000.00+ Labor intensive work
> and expensive parts.

The smaller swing arm pins are the subject of a recall being
administered by Cinnabar. Check with them for details.

> The Brakes on the GMC are a real weak point, make sure they receive
> a extra good checkout and repair. Replace the front wheel flexible
> brake hoses, every couple of years, they appear to be subject to
> failure on the inner hose wall, and can cause to disk brakes to lock on.

Also check the steel lines going to the rear wheels. They run along the
frame rails and can trap water and road grime causing rust. I got
lucky, mine blew out sitting in the driveway and not on the road.

> Front wheel bearings are on the weak side, and its worth the extra
> money for upgrades.

The Wallace hubs are expensive(IMO). I would just get the bearings from
Cinnabar(only way to be sure that it's the *right* bearing) and
replace(not service) them every 25,000 miles.

> The 455 exhaust manifolds tend to overheat and are subject to stress
> cracks, We replaced ours with headers, and then had to replace the
> oil cooler lines because of the higher radiant heat from the headers.
> (there have been several coaches burned to the ground because of
> failed oil cooler lines)

Personally, I don't like headers. I feel that they tend to increase
engine compartment heat and don't provide much performance improvement
at the RPM range that motorhomes operate in. Also the steel flanges are
more prone to warping than cast iron manifolds. Others will probably
disagree.

The oil cooler lines should be replaced if they're more than two years
old in any event. It's always suprised me that owner's change radiator
hoses on a regular basis, but not oil cooler lines.

> We really like our GMC, and feel its worth the extra effort to keep
> it running and will continue our restoration effort.

Yep, it gets in your blood.
Patrick
- --
Patrick Flowers
Mailtoatri63

The GMC Motorhome Page
http://www.gmcmotorhome.com

 

[john szalay]

>> The rear axle swing arm pins and bushings need to be checked for
>> looseness, excessive wear and end play.
>>
>> Jack up the rear of the coach and support with jackstands. make sure
>> its stable. MAKE SURE you release the air pressure to the airbags as
>
> How do I do this?? (I TOLD you I was a neophyte)!!
>

Support the chassis, then deflate the airbags, use the floor jack
to raise the wheels just slightly off the ground, you can remove
the tires if you want, but not required.( does help to remove wheels)
Use a lever (prybar or whatever) to move the arms back and forth
or up & down and observe the amount of movement at the pin, bushing
interface. I like to take the tires off, to remove the extra weight,
then I put pressure to try and work the swingarms to observe and measure
the amount of play or looseness of the bushings. On a coach with
tight bushings, there should be no movement at all, other than the
normal rotating action up & down with no slop.

[Also this is close to the recommended method for greaseing the bushings
it allows the grease to completely surround the pins, if you attempt
to grease the pins while they are supporting the coach, the grease will
not get to the surface contact areas.]

>
>> soon as you have the coach supported BUT NOT jacked up.
>> ( you don,t want to "hotdog" the airbags )
>> Then check the pins and bushings for "slop" and endplay.
>
> Then I continue jacking before checking? or do I just take the
>load off the arms and leave the wheels lightly on the ground?
>
covered above....

>>
>> The Brakes on the GMC are a real weak point, make sure they receive
>> a extra good checkout and repair.
>
> Anything specific, like shoes, pads, or just crappy in general?
>
crappy in general, IHMO: greatly undersized for the weight/mass.

NEVER allow yourself, when driving a GMC to get into a panic stop
situation. always drive defensivly. its a great driving machine
but I learned long ago, to allow plenty of space between me and
the vehicles ahead. there are disc brake mods available for the
rear wheels , and I am attempting to round up the parts needed
to convert our coach to all around disc braking.
(a friend just picked up the parts for his mod, this past weekend
on a trip to Tenn. I,m still looking for the rest )

>> Front wheel bearings are on the weak side, and its worth the extra
>> money for upgrades.
>
> Is there any way to check them quickly? I don't know how much
>checking this guy will let me do.
>
not really, most folks will tell you if they have the Wallace
bearing & hubs.

>
>Thanks for the info.
>
>
My pleasure, we have spent many happy miles & hours in our rig
and plan to spend many more. (even if the GMC is like the F-15 fighter,
27 hours of maint for 1 hour in flight, If the quote I,ve heard is correct. )
Its worth the effort.
John & Brenda Szalay
Louisville Ky.

 

[john szalay]

>
>The smaller swing arm pins are the subject of a recall being
>administered by Cinnabar. Check with them for details.
>
Too bad I just completely rebuilt mine. I,ll check and see what
is involved, just to be safe.

>Also check the steel lines going to the rear wheels. They run along the
>frame rails and can trap water and road grime causing rust. I got
>lucky, mine blew out sitting in the driveway and not on the road.
>
excellent point. I lost my brakes when the master cylinder seal failed
between chambers, do make for interesting times.

>> Front wheel bearings are on the weak side, and its worth the extra
>> money for upgrades.
>
>The Wallace hubs are expensive(IMO). I would just get the bearings from
>Cinnabar(only way to be sure that it's the *right* bearing) and
>replace(not service) them every 25,000 miles.
>
point taken. they are not cheap.

>> The 455 exhaust manifolds tend to overheat and are subject to stress
>> cracks, We replaced ours with headers, and then had to replace the
>> oil cooler lines because of the higher radiant heat from the headers.
>> (there have been several coaches burned to the ground because of
>> failed oil cooler lines)
>
>Personally, I don't like headers. I feel that they tend to increase
>engine compartment heat and don't provide much performance improvement
>at the RPM range that motorhomes operate in. Also the steel flanges are
>more prone to warping than cast iron manifolds. Others will probably
>disagree.

they do run hot. solved the "trapped heat" with two electric radiator
fans mounted close behind the front wheel wells ducted down and out,
really solved the excess engine compartment heat from getting into
the coach when coming off the road with the fans. We let them run for
a while when we park, helps to take the load off the air conditioner.
Keeps fumes out as well. no matter how well the engine access hatch
is sealed, some fumes seemed to get into the coach.

John

 

[patrick flowers]

>
> >The smaller swing arm pins are the subject of a recall being
> >administered by Cinnabar. Check with them for details.
> >
> Too bad I just completely rebuilt mine. I,ll check and see what
> is involved, just to be safe.

This is a *must* to get on the web page. I think it was detailed in a
fairly recent GMC Motorhome News.

> solved the "trapped heat" with two electric radiator
> fans mounted close behind the front wheel wells ducted down and out,
> really solved the excess engine compartment heat from getting into
> the coach when coming off the road with the fans. We let them run for
> a while when we park, helps to take the load off the air conditioner.
> Keeps fumes out as well. no matter how well the engine access hatch
> is sealed, some fumes seemed to get into the coach.

I've heard of this mod before, but never actually seen it. Sounds like
a great idea, especially for when you get stuck in traffic during the
summer months. Gotta remember that the engine compartment is basically
a plywood box. An article on coach fires by Jim Anstett in the August
'97 GMCMM describes lining the engine compartment with a ceramic
"paper"(?) material capable of withstanding up to 2300 degF(might also
make a good header wrap) which also sounds like a good idea.

Patrick
- --
Patrick Flowers
Mailtoatri63

The GMC Motorhome Page
http://www.gmcmotorhome.com

 

[john szalay]

At
>
>> solved the "trapped heat" with two electric radiator
>> fans mounted close behind the front wheel wells ducted down and out,
>>
>I've heard of this mod before, but never actually seen it. Sounds like
>a great idea, especially for when you get stuck in traffic during the
>summer months.

The fans work great, I run them anytime the engine is on and almost
always when we park, to help cool down the engine compartment.

I mounted mine one on each side of the engine access cover opening
they do not get in the way of any engine service, such as changing
sparkplugs, the fans are aimed on an angle down and out, we made
ducts that end just level with the bottom of the coach sides, so
nothing shows from the outside, the only way one knows something is
there, is the slight sound of the fans and the airflow around your
feet. I thought about the stainless air vents that are made for the
side of the coach, but I really hate putting holes in our rig.
it took me weeks to finally decide to cut the 14' opening in the roof to
mount the second roof air conditioner. I added a 7,000 btu unit to
the rear of the rig, that way the generator could handle both running
at once. its a little strain to handle 2 12.5 btu units up there.
but it handles a 12.5 and a 7 just fine.
We decided a second roof air was needed along with DARK tinted windows
everwhere except the windshield, after a long trip thru Texas and Okla.
several years ago.

John & Brenda Szalay
Louisville Ky.

 

[1]

John

I really like the mod you spoke of to get hot air out of the engine box.
Can you give anymore details. Pic maybe? Drawing? What size fan?
Where from? What size duct? Where to? ECT?

Take Care
Arch

 

[john nepper jr.]

>
I just replaced the fresh water tank on my '76 Palm Beach... I'm still
having several problems:
1) I assume that the drain valve which goes out the bottom floor should
be closed for normal opperation?

2) What about the smaller drain valve (with the 1/4" hose) that connects
to the same drain valve in #1, should it be closed for use as well?
What is the purpose of this valve?

3) Does the water pump shut off by it self when there is no call for
water, or do you need to turn it on as needed?

4) My toilet leaks around the floor... I'm assuming that the previous
owner had water freeze there???

Thanks for any help. John

 

[john szalay]

>>

>3) Does the water pump shut off by it self when there is no call for
>water, or do you need to turn it on as needed?
>

The water pump SHOULD shut off by itself IF the pressure switch is working
properly and there are no leaks in the system. That is known as a DEMAND system


>4) My toilet leaks around the floor... I'm assuming that the previous
>owner had water freeze there???
>
Most likely, yes, the valve body on the toilet, I believe is a plastic body
and cracks very easy, dispite the metal re-enforceing ring.
First check to see if the copper fitting on the supply line is snug, not tight
also check the copper supply line itself to see if it has swelled from freezing.
the valvebody itself can replaced as a unit, if the toilet is still in good
shape. else you might have to replace the whole thing, like we had to.
(Previous owner poured hot kitchen grease down the toilet, and warped it.
so a new one was called for.) We purchased ours from Camping World. bolted
right in.
BTW: I DO NOT work for Camping World, But I like their service and prices.
and they do have the items I am looking for.

Cant help you on the first two items on your post, on the water tank .

>Thanks for any help. John
>

 

[patrick flowers]

>

> >
> I just replaced the fresh water tank on my '76 Palm Beach... I'm still
> having several problems:
> 1) I assume that the drain valve which goes out the bottom floor should
> be closed for normal opperation?

Yes, all drain valves should be closed. I think you're referring to the
valve that drains the fresh water tank.

> 2) What about the smaller drain valve (with the 1/4" hose) that connects
> to the same drain valve in #1, should it be closed for use as well?
> What is the purpose of this valve?

IIRC, there is a check valve at the tank outlet that keeps the pressure
from the demand pump from leaking back into the tank. The valve that
you're referring to drains water from upstream of the check valve for
winterizing.

I believe John Szalay answered your other two questions.

Hope that helped,
Patrick
- --
Patrick Flowers
Mailtoatri63

The GMC Motorhome Page
http://www.gmcmotorhome.com