View single post by Rick Willard
 Posted: 10-31-2014 06:37 pm
PM Quote Reply Full Topic
Rick Willard

Joined: 08-20-2005
Location: Broomfield, Colorado USA
Posts: 47
Hey Folks,

I'm scratching my head on this one, so I'm asking for some expertise from my fellow club members....  My JH is a real nice one that I just acquired last month.  One of the small issues I knew would have to be addressed is that the car is making a strange noise that actually comes and goes.  I'll try to describe it well, but will field any questions from those of you who might have a theory.  This is actually my 4th JH and I thought I had pretty much heard just about every bad noise a JH can make.  However, this one is a mystery so far.

The noise I'm talking about is a low wallowing noise that I/we initially thought might have been some sort of dry bearing...oil sump?  timing belt tensioner bearings?  water pump?  clutch-related?  gearbox?.  But the pattern is strange.  When you get in the car and drive it, the noise is non-existent.  Once it gets warmed up, you start to hear this noise that follows the RPM's and will slowly get louder.  It does not follow the speed of the car, and it doesn't matter if the clutch is engaged or not.  It follows the RPM's of the engine.  One footnote, you especially hear this noise coming from the passenger side.

One of the initial theories we had is a faulty exhaust at the center resonator (loose baffle vibrating and/or expanding under heat). That theory has been dispelled after we installed a replacement exhaust system (bottom of headers to the tail pipe). The replacement exhaust system was virtually brand new, so we know that's good.

The strange thing is that you can be very frustrated listening to this noise, and then...even when the engine is still just stops and goes for several more minutes without any noise at all.  One of the theories we have is that the noise is possibly the sound of "air pushing through a tube."  We're pretty convinced that the engine and transmission are generally very solid (running with 45mm Dellortos) and the receipt file that came with the car would confirm that it has been very well kept leading up to my purchase. 

If anyone here has any initial thoughts, I'm all ears.  Again, have heard our JH's make many noises over the years, but this is one I've never heard before.

Thanks in advance for your time and insights!