A while ago we had a big exhaust leak on my 2000 Flair, Workhorse 7.4L. We took it to the shop and they replaced both manifolds.2 days after we got it back, we went on the road and after 20 minutes the problem came back on the drive side only. We took it back to the shop and they fixed it under warranty, they said the manifold they installed was defective. We drove it a couple of times, about 500km each time without a problem.Last Friday we went out again and at some point the engine started stuttering, then vibrating hard enough that the steering wheel was shaking some. I slowed down and the vibration went away but the RV lost a lot of power and it started smelling like gas inside. I pulled over turned the engine off and looked around but didn't see anything abnormal (I am definitely not a mechanic but I tried all the same).I started it again and went back on the road. The driving was better but the tapping noise from the manifold started a couple of minutes after that. Not very loud at first but by the time we reach our destination it was like the first time we had the problem.I imagine the heads are not the problem since the shop replaced the manifold twice and never mentioned that to be a potential issue. Is it possible that it's coming loose? Does anyone have an idea of what may be causing this to occur?Thanks.

Could be an ignition issue. When was the last time you had your spark plugs and wires replaced?

Definitely possible for the manifold to be loose.

I suspect you may have a catalytic converter that is not flowing freely.That will cause the exhaust manifold problems and power loss.Richard

IB853347201 wrote:Could be an ignition issue. When was the last time you had your spark plugs and wires replaced?They were replaced the first time the change the manifolds in July.

jimh406 wrote:Definitely possible for the manifold to be loose.I have a feeling that may be it but I'm only learning all of this so I appreciate the input of more experienced people. https://www.rv.net/SharedContent/cfb/images/smile.gif

Exhaust manifold question | Good Sam Community

IB853347201
Nomad
Sep 12, 2023
Could be an ignition issue. When was the last time you had your spark plugs and wires replaced?
jimh406
Explorer III
Sep 12, 2023
Definitely possible for the manifold to be loose.
RLS7201
Explorer II
Sep 12, 2023
I suspect you may have a catalytic converter that is not flowing freely.
That will cause the exhaust manifold problems and power loss.

Richard
2000flair
Explorer
Sep 12, 2023
IB853347201 wrote:
Could be an ignition issue. When was the last time you had your spark plugs and wires replaced?

They were replaced the first time the change the manifolds in July.
2000flair
Explorer
Sep 12, 2023
jimh406 wrote:
Definitely possible for the manifold to be loose.

I have a feeling that may be it but I'm only learning all of this so I appreciate the input of more experienced people. https://www.rv.net/SharedContent/cfb/images/smile.gif
2000flair
Explorer
Sep 12, 2023
RLS7201 wrote:
I suspect you may have a catalytic converter that is not flowing freely.
That will cause the exhaust manifold problems and power loss.

Richard

good point, is there a way for me to check that or is it something they must do a the shop?
fyrflie
Explorer III
Sep 13, 2023
I recently had my manifolds resurfaced. I installed them exactly to factory torque specs. New studs, nuts, etc.
After several hundred miles, I found two nuts that were loose. Retorqued to factory spec and so far no more issues.
Did the shop check the new manifolds to make sure the surfaces were flat ? Just because they’re new doesn’t guarantee anything.
Good luck and let us know how it all turns out.
RLS7201
Explorer II
Sep 13, 2023
2000flair wrote:
RLS7201 wrote:
I suspect you may have a catalytic converter that is not flowing freely.
That will cause the exhaust manifold problems and power loss.

Richard

good point, is there a way for me to check that or is it something they must do a the shop?

A pressure gauge in the O2 sensor port would tell a lot.

Richard
2000flair
Explorer
Sep 13, 2023
fyrflie wrote:
I recently had my manifolds resurfaced. I installed them exactly to factory torque specs. New studs, nuts, etc.
After several hundred miles, I found two nuts that were loose. Retorqued to factory spec and so far no more issues.
Did the shop check the new manifolds to make sure the surfaces were flat ? Just because they’re new doesn’t guarantee anything.
Good luck and let us know how it all turns out.

Thank you, I'll ask them to check for that.
2000flair
Explorer
Sep 13, 2023
RLS7201 wrote:
2000flair wrote:
RLS7201 wrote:
I suspect you may have a catalytic converter that is not flowing freely.
That will cause the exhaust manifold problems and power loss.

Richard

good point, is there a way for me to check that or is it something they must do a the shop?

A pressure gauge in the O2 sensor port would tell a lot.

Richard

Will take a loot at that for sure. Thanks

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