Rattle at High RPM/Load

[Jay Laifman]

My car has a rattle at full throttle/high RPM load. Schneider Autohaus rebuilt the engine a number of years back. The noise happened before the rebuild and after. They said it was not pinging and thought it was something rattling. And since they did the full engine, they didn't think it was anything they touched. The only thing they didn't touch was the muffler. So since I trust Schneider completely, the process of elimination leads me to suspect perhaps something inside the muffler is loose and making the sound.

I have separate posts recently to learn about the factory muffler now available from Porsche. I'm just about ready to pull the trigger and buy one. But before doing that, I thought I'd see if anyone else has had this issue. Again, full throttle/high RPM, will get this rattling. It does not happen at low rpm. It does not happen if I give the engine too much load at lower rpm.

And I also thought I'd see if anyone might have a muffler, any muffler, that I could borrow to put on for a short drive to see if the rattling goes away. For this test, it doesn't have to be a factory muffler. It could be a heavy Dansk or Bursch or anything else that would fit without hitting the body of course. I'm in So Cal - so local for me to swing by and pick up would be best. I'm also happy to pay rental for borrowing, or even buy it if it is inexpensive enough. I put an ad up in WTB for this part of the question.

[Haasman]

Jay- curious did you determine the source of the rattling?

[Jay Laifman]

Not yet. I did end up buying a new Porsche Classic Muffler. I had planned on installing it this weekend, but didn't get a chance. I might try next weekend, but I think it will have to wait until the weekend after that. I will certainly circle back and report. (and either I have a good '74 factory muffler to sell, or a bad one to give away. I'm hoping for the latter).

[Jay Laifman]

Well, I have a perfectly good 1974 911 Leistritz muffler to sell.

I put on the new Porsche Classic. The rattle is still there. So there is nothing wrong with the Leistritz - other than it was the wrong year for my car.

I did knock on the heater encasing around the header pipes and they did have a little rattle. I don't know if that simply gets rattling at those higher rpms. But when the sound occurs, it usually is under load, not just high rpm - at least I think it does. So I would think it was more than just those header pipe encasings.

[raspy2point2]

I would say it is the heat exchangers is my guess