Exhaust manifold stud breaks-falls out

[RVnUSA]

A stud broke and fell out of the right exhaust manifold. My motor home has about 16,000 miles on it and had been parked in the same location for about a month. I had been starting it once a week letting it warm up.
This week I moved it out of its parking place, maybe 20' washed it and moved it back. (it was not running while I washed it)
A couple days later I was walking up to the MH and notice a stud lying under the MH.
Picked it up and said to my self "self that looks like an exhaust manifold stud". Sure enough with a flash light I could see that the rear stud had broke and fallen out. The threads on the stud were rusted so bad there was hardly any left. I had told my wife just this week "it was just a matter of time until the right manifold studs fail". I sure am glad I found this before our trip next week.

What would cause this to happen???

This same thing is what caused most of my spark plug wire problems last year on the road, except it was the rear of the left side manifold. I am on my third left exhaust manifold.
I have had the air vent kit installed, but of course it does no good if you're not moving.

I have had no more spark plug wire problems since installing the Taylor wires with the insulators installed on the wires. "KNOCK ON WOOD"

I am headed for the Workhorse service center to get it repaired. It is still under warranty.

[RVnUSA]

A stud broke and fell out of the right exhaust manifold. My motor home has about 16,000 miles on it and had been parked in the same location for about a month. I had been starting it once a week letting it warm up.
This week I moved it out of its parking place, maybe 20' washed it and moved it back. (it was not running while I washed it)
A couple days later I was walking up to the MH and notice a stud lying under the MH.
Picked it up and said to my self "self that looks like an exhaust manifold stud". Sure enough with a flash light I could see that the rear stud had broke and fallen out. The threads on the stud were rusted so bad there was hardly any left. I had told my wife just this week "it was just a matter of time until the right manifold studs fail". I sure am glad I found this before our trip next week.

What would cause this to happen???

This same thing is what caused most of my spark plug wire problems last year on the road, except it was the rear of the left side manifold. I am on my third left exhaust manifold.
I have had the air vent kit installed, but of course it does no good if you're not moving.

I have had no more spark plug wire problems since installing the Taylor wires with the insulators installed on the wires. "KNOCK ON WOOD"

I am headed for the Workhorse service center to get it repaired. It is still under warranty.

[Thudman]

A TSB was issued on manifold stud stress. Workhorse should know if it applies to your chassis.

Thudman

[RVnUSA]

The WH Service Center replaced the right exhaust manifold, studs, nuts, and gaskets. They also replaced the starter; I didn't even know there was a problem with it.

If anybody in the Oklahoma area needs to have work performed on the WH I would strongly recommend City Chevrolet in Oklahoma City.
They started to work on my MH when they said they would, I had them overnight the parts which I paid for the shipping. They started on it Monday morning and it was ready around 2:00 on Tuesday.
It is refreshing to have a SC that will work with you.

[Bigdaddy]

I just looked at my rusty manifold bolts! Some have rust and others have not. My question is. Did just the threaded part fail or did the entire stud fail? And what can be done to prevent any more rust from forming. If they are just replaced with the same type of stud, the rusting problem will contunue. I do not have a spark plug problem with 27K+ miles. I have seen other manifold stud rust, but they were larger size. Does anyone have any suggestions????

[RVnUSA]

Bigdaddy,
To answer your question...the stud just broke off flush with the head and fell to the ground while the motor home was setting in a RV park.
Luckly I spotted it before we left.
Last year I had two studs on the other side break and fall out while traveling.
The WH service center replaced all of the studs and manifold. There were bolts broken off in the manifold that holds the heat sheild.

I don't know how you would prevent this.