Forum Discussion

2000flair's avatar
2000flair
Explorer
Sep 12, 2023

Exhaust manifold question

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.
  • Sounds as if 1 or more spark plug wires may have burned. Check all your wires carefully. It helps to wrap them with high temp sheaths (8) from the end of the wire.

    Also check each of your exhaust donuts where the exhaust manifold meets the pipes. The donuts can burn up and you'll get excessive noise combined with power loss.
  • udidwht wrote:
    Sounds as if 1 or more spark plug wires may have burned. Check all your wires carefully. It helps to wrap them with high temp sheaths (8) from the end of the wire.

    Also check each of your exhaust donuts where the exhaust manifold meets the pipes. The donuts can burn up and you'll get excessive noise combined with power loss.


    Thanks, I’ll check the wires once more but they were replaced at the same time the manifolds were replaced the first time and they also added the temp sheaths.

    I think there may be a problem with the combustion that makes the engine shake and loosens the manifold. The shop that installed them will take in the rig in 2 weeks to fix under warranty but seeing that it’s the 2nd time it happens i’d like to find the root cause so there is nit a third.
    I will consider all the tips and advice everyone has given me and hopefully it’ll be corrected for good.
  • 3_tons's avatar
    3_tons
    Explorer III
    When you install a new exhaust manifold you have to use new OEM bolts…

    3 tons
  • Upgrade the manifold bolts with ARP bolts. Much better quality than OEM.
  • Thanks for the advice, I’ll ask for a replacement kit in those lines.