Noise from the Engine Bay
Joe Angell
My car had gotten louder in the last year or so, which was odd since it had only been on the road for about two years since I did the engine swap. Turns out there were a few problems, and all easy to fix.
Loose Exhaust Tip, Driver’s Side
The exhaust pipe that going from the muffler to the exhaust tip on the driver’ side was loose and rattling. This was just a matter of unbolting the old clamp, pulling out the pipe, sliding on a new clamp and tightening it down (with a new clamp). It’s quite possible to do from the ground, but much easier on a lift. I did this while I was waited for the oil to drain from an oil change.
Tightened up (with the old clamp) and no longer rattling.
Rattling Exhaust, Passenger Side
A higher-pitched rattling was coming from the passenger side of the exhaust, like something was bouncing around inside the pipe. It thought the silencer was loose, so I went to remove the pipe to check. Actually removing the pipe was not that easy. The exhaust clamp had been tightened so much that the muffler’s pipe was itself compressed around the exhaust pipe, and I couldn’t just slide them apart. I had to hammer on it with a rubber mallet for a few minutes before it finally popped out, which was made harder due to the exhaust hangers dampening my hammer blows.
The silencer turned out to be just fine, but the cap I had crudely tack-welded on the end had come off and was rattling around in the pipe. I just took the cap out and left it off, since it wasn’t important. That, and I wasn’t going to get the silencer back out at this point, and there was no way to get in there to weld it back on.
To reinsert the pipe into the muffler, I first used a pipe expander on the muffler side to widen it, and then slide the pipe in, securing it with a new clamp.
Engine Cover Rattle
For months I was trying to track down a kind of rattle or repeated bang from the engine bay. Everything seemed to be securely bolted down, and I couldn’t figure out how the engine cover might be loose when closed, and it seemed to be resting properly. The clip strips holding the engine cover grills in place seemed secure as well.
When checking the transmission fluid I noticed a notch worn into the top of my air intake pipe. It turns out that when the engine cover was closed, the pipe was rubbing against one of the engine cover clip strips. I must have twisted the segmented air intake pipe (which is a series of metal pipes connected with flexible silicone joints) such that it was sitting too high and hitting the cover. I gave it a strong push, which slid the pipe against the joint clamps and causing it to sit lower, clearing the engine cover and fixing the rattle.
The notch worn in the air intake pipe (bottom) and in the cover strip (top) from vibrating against each other.
A closer view of the notch worn into the air intake pipe.
Exhaust Leak
All of that still didn’t solve my noise issues. A persistent noise had been coming from what sounded like the exhaust, but I couldn’t pin it down. Eventually it evolved into a fluttering — clearly an exhaust leak, and definitely coming from the driver’s side. When the header was removed, the problem became clear: the welds on the DPI exhaust header had failed. These were the welds that hold the round pipes onto the trapezoidal engine block mounts. In effect, the pipes were rattling freely against the engine, leaking exhaust as they did and making a lot of noise.
My friend’s brother could weld stainless steel and was able to repair the headers for me. After reinstalling it with new studs (as long as I’m in there…), the rattle and noise was gone and the car was notably quieter.
Those header pipes (left) are supposed to be welded to the holes in those blocks (right).