New Member, Seeking Information on Servicing 1977 GMC Stored 6 Years! Next trip is 2500 Miles!

[slshearer]

Hello,

I've been an enthusiastic owner of GMC motorhomes for over two decades. Unfortunately, due to health issues, I am going to part with my coach. I am excited to know she is going to a good home, and I will be transferring ownership of my coach to my niece and her husband from Quesnel, BC. I currently reside near Atlanta, GA. My niece's husband, a seasoned truck driver and skilled mechanic with 35 years of experience is well-versed in handling HD trucks and similar machinery. I am compiling a checklist to ensure the coach is roadworthy before they take it over.

The coach has a rich history. I am its second owner; the original owner, Dale, had Golby remodel it twice, ensuring most parts, including the engine and transmission (replaced around 5,000 miles ago by a truck shop), are in top condition. My last journey was from Atlanta to North Chicago for a music festival, where the coach performed flawlessly and had no issues. It was stored in a dealership before I moved it to its current location in Buford, GA, at an RV storage park under covered parking.

As I prepare the coach for their trip to British Columbia, I welcome any advice on the following points:

1. Fuel System: Both fuel tanks were filled and treated with a gas preservative. The coach was last started three years ago without any issues. I'm considering replacing the gas filter canister and the carburetor. I would appreciate recommendations for someone who can rebuild the factory Rochester 4-barrel carburetor.
2. Tires: I've replaced all six tires with Firestone Transmode HT 16" 10-ply tires. To alleviate pressure, I've blocked the rear bogies. The coach is stored under a covered area, protected from the elements.
3. Brakes and Suspension: I've installed new airbags (I believe they're called Sully), serviced the brakes with new shoes, hardware, and wheel cylinders from NAPA, and used DOT 5 synthetic brake fluid. The coach also has a new master cylinder and proportioning valve.
4. Water System: The hot water tank has a leaky drain cock that doesn't seal well. I'm considering bypassing it to maintain some water capacity for travel. Does anyone know if the tank can be bypassed or replaced?
5. Air Conditioning: After converting the AC system to R134, the high-pressure hose burst during charging. Can this be sourced locally or custom-made?
6. Body Work: I need to replace a rear flare on the right side of the coach, lost due to a tire blowout. Information on the manufacturer or availability of the original design would be very helpful.
7. Generator: The rear Onan generator, which was recently replaced and has been used for about 500 hours, needs a fuel line flush and filter replacement. Any tips on the best approach would be appreciated.
8. Right-hand exhaust leak, Engine Has Headers, and the right header gasket is leaking! I can hear the ticking sound coming from the exhaust port; I am wondering what is the risk of changing the gasket as the AC compressor is in the way, and what about the bolts/studs?

I know this is a lot, but any tips or suggestions to ensure the coach is roadworthy would be greatly appreciated.

I appreciate your help!

Stewart
ibmsales@bellsouth.net
678-725-9566

 

[74_Coach]

Nice looking coach! It appears that we have the same model fridge - gas, electric & battery. I haven’t tested anything in my coach that uses propane since I purchased it in 2019. I know my floor heater was replaced back in ‘89 along with the fridge but the stovetop looks original.

Ed

 

[slshearer]

Nice looking coach! It appears that we have the same model fridge - gas, electric & battery. I haven’t tested anything in my coach that uses propane since I purchased it in 2019. I know my floor heater was replaced back in ‘89 along with the fridge but the stovetop looks original.

Ed

Actually, I had run it on propane, and it worked great, I think its a good unit and seems efficient even on battery

 

[pvfjr]

I just bolted in my headers last night. I did it from underneath, and the AC compressor was not in the way at all. The right-hand side actually had easier bolt access.

Granted, the coach was on a lift. But if you jack it up far enough, that shouldn't preclude you from replacing the gasket on the ground. Don't overlook removing wheel liners and the wheel either. It's not as much work as it seems, and it gives a ton of access to the sides of the engine.

 

[slshearer]

I just bolted in my headers last night. I did it from underneath, and the AC compressor was not in the way at all. The right-hand side actually had easier bolt access.

Granted, the coach was on a lift. But if you jack it up far enough, that shouldn't preclude you from replacing the gasket on the ground. Don't overlook removing wheel liners and the wheel either. It's not as much work as it seems, and it gives a ton of access to the sides of the engine.

Did you have studs or bolts? Also, did you use Locktite, and if so, what color? Thanks for the reply!

 

[pvfjr]

Did you have studs or bolts? Also, did you use Locktite, and if so, what color? Thanks for the reply!

I just used bare header bolts and Remflex gaskets (very nice gaskets). I'll try loctite if I see any problems with them loosening, but Remflex claims their gaskets rebound in such a way that loosening is less of a problem. We'll see.

 

[pvfjr]

I'm considering replacing the gas filter canister and the carburetor.

So it started 3 years ago without issue, and has had proper fuel treatment? What compels you to replace the carb? Are there issues with drivability now?

 

[pvfjr]

Air Conditioning: After converting the AC system to R134, the high-pressure hose burst during charging. Can this be sourced locally or custom-made?

Hoses can be custom made. Rural area mom&pop auto parts places often do things like this. Our local small-town parts house/mechanic shop does. They work on lots of trucks and tractors, but will make you any hydraulic or AC hose while you wait.

There are kits available that let you crimp your own hoses at home too. It just takes a bit of research/measuring to get the correct hose, the correct ends, and the corresponding crimper/dies. It's on my "someday" list, so unfortunately I don't have all the specifics prepared to share.

 

[pvfjr]

Body Work: I need to replace a rear flare on the right side of the coach, lost due to a tire blowout. Information on the manufacturer or availability of the original design would be very helpful.

Perhaps Michael Sadlon is making flares? He's picked up a lot of previous fiberglass designs for reproduction, and made some new ones. I believe he sells a lot of his stuff through Sirum:
Fiberglass News

They list front flares currently. You may have to reach out to Mike directly to find out more.
https://sirumvintagegmc.com/fiberglass-parts

 

[bdub]

What a terrific GMC! Golby did high quality refurbs.

Read Larry Weider's article on starting an engine that has been sitting a long time. https://www.gmcmidwestclassics.org/dormant_engine_start

Shouldn't need to rebuild the carb, but if you do, get with Dick Paterson at Springfield Ignition.

One moment, please...

Tires, it's the age that matters. If they're 5 years old, replace them. Don't matter how good they look. They will destroy part of your motorhome. Check the date code on them. https://cdn.wheel-size.com/filer_public/09/54/0954f172-f00c-420e-b0e5-472259fad1b6/dot-codes-6.jpg (this tire was made in the 35th week of 2011)

I installed a ball valve on mine that never leaks. It's a PITA to install. To bypass, get this: https://www.etrailer.com/Accessories-and-Parts/Camco/CAM35983.html
You need it when winterizing anyway.

A/C hose should be easy locally. Use DuraCool or equivalent refrigerant. Less pressure, larger molecules that won't leak as easily, and works better. http://www.bdub.net/Duracool_in_your_GMC.pdf

Sirum GMC sells all kinds of replacement fiberglass. They're the go to folks for tee skirts and flares. But don't install it without replacing old tires.

Generator fuel line? Shouldn't need to, but easily flushed with a Mighty Vac or even a short burst of compressed air.

Remove wheel well for easy access. Use Remflex gasket. Do Not torque the center bolt. Just snug it up.

Remflex HEADER Gasket SOLD IN PAIRS

We are a major supplier of GMC Motor Home, RV Parts. Serving GMC MOTORHOME owners everywhere.

www.gmcrvparts.com

While your messin with the Onan, install Gary Bovee's Electronic Ignition for it. Best thing you can do for your Onan. https://www.onanelectronicignition.com/

 

[slshearer]

So it started 3 years ago without issue, and has had proper fuel treatment? What compels you to replace the carb? Are there issues with drivability now?

 

[slshearer]

Hello. Due to my health, I haven't touched the coach for 3 years. I was told to drain the gas and dispose of it, and if I need to, I will have to find somewhere to take 50 gallons of fuel.

 

[LarryW]

As for #1 on your list, as Billy said, I would encourage you to please read this article on starting an engine that has not been run for an extended period of time.

https://www.gmcmi.com/wp-content/uploads/2020/06/weidner-starting-engine.pdf

 

[slshearer]

As for #1 on your list, as Billy said, I would encourage you to please read this article on starting an engine that has not been run for an extended period of time.

https://www.gmcmi.com/wp-content/uploads/2020/06/weidner-starting-engine.pdf

I saw that article I plan to remove the plugs and I will use some Mystery Oil and leave it for a couple of days and install some new plugs. The coach is stored in A covered storage for RV and boats. I will also turn the engine over several times before firing her up..
Thanks for your help

 

[Bhart]

Dot 5 brake fluid is a silicone base fluid. It is not compatible to dot 3, dot 4, or dot 5.2. Hopefully you flushed the brake lines and master cylinder before using the dot 5.

Stabil and Star-Tron gas additives are good up to 2 years. On the trip to Canada be sure to have plenty carburetor filters as the tanks might be rusty. Wix 33048, or Wix 33052 filters.
If the GMC starts to stumble or surge it is time to change the filter. You should have a metal supply line from the mechanical fuel pump up to the carb. If you can't totally remove the fuel line because of the close prominently of line to the thermoset housing from the filter housing, you will need to unbolt carb to get enough play to allow removal. Care must be taken when reinserting filter housing and metal line as not to cross thread them.

 

[slshearer]

Dot 5 brake fluid is a silicone base fluid. It is not compatible to dot 3, dot 4, or dot 5.2. Hopefully you flushed the brake lines and master cylinder before using the dot 5.

Stabil and Star-Tron gas additives are good up to 2 years. On the trip to Canada be sure to have plenty carburetor filters as the tanks might be rusty. Wix 33048, or Wix 33052 filters.
If the GMC starts to stumble or surge it is time to change the filter. You should have a metal supply line from the mechanical fuel pump up to the carb. If you can't totally remove the fuel line because of the close prominently of line to the thermoset housing from the filter housing, you will need to unbolt carb to get enough play to allow removal. Care must be taken when reinserting filter housing and metal line as not to cross thread them.

Hi, I had flushed the whole brake system as I had replaced all the hydraulic brake parts with new ones
I am not sure but I think there maybe a large fuel filter that takes a cartridge as well as the the inline filter to the carb. I will stock up on the filters, I know a HD mechanic told me to add some Heet to the gas to help remove the any water in gss tanks. Thanks for your time and help Stewart

 

[tmsnyder]

Exhaust manifold bolts on passenger side are not covered by the A/C compressor. If you remove the right wheel and the liner you will have easy access to that manifold.

The bolts can work loose with repeated heating / cooling cycles and are best retained using a factory style retainer from inline tube: https://www.inlinetube.com/products/inl10105

Also remove the fifth 'upper' bolt, or loosen it, bc it does nothing except cause leaks along the bottom of the manifold as it rocks the manifold up.

Tighten the other 4 bolts and it may quiet the leak.

And since the manifold is cooled by the head, if a gasket is used it should be a copper gasket from Dave Lenzi. Otherwise the manifold will be insulated from the head and will be more likely to warp or crack.

 

[Bhart]

Dip the exhaust manifold bolts in milk of magnesia.

Milk of Magnesia dries to a fine powder. This powder will not deteriorate with heat. Normal anti seize will deteriorate and disappear with time during extreme heat cycles.

 

[slshearer]

Dip the exhaust manifold bolts in milk of magnesia.

Milk of Magnesia dries to a fine powder. This powder will not deteriorate with heat. Normal anti seize will deteriorate and disappear with time during extreme heat cycles.

Well never heard that before but just my luck I have a bottle in the bathroom, Thanks again!

 

[slshearer]

Exhaust manifold bolts on passenger side are not covered by the A/C compressor. If you remove the right wheel and the liner you will have easy access to that manifold.

The bolts can work loose with repeated heating / cooling cycles and are best retained using a factory style retainer from inline tube: https://www.inlinetube.com/products/inl10105

Also remove the fifth 'upper' bolt, or loosen it, bc it does nothing except cause leaks along the bottom of the manifold as it rocks the manifold up.

Tighten the other 4 bolts and it may quiet the leak.

And since the manifold is cooled by the head, if a gasket is used it should be a copper gasket from Dave Lenzi. Otherwise the manifold will be insulated from the head and will be more likely to warp or crack.

Hi

I forgot to mention I have Doug Thorley headers!