With no more than 25# of pressure, I would be most concerned about bearings, and
with the knock, a rod in the process of letting go. John
> Well, it is with a heavy heart that I ask the following question. I'm
> concerned I know the answer before I hear it. I'm just hoping I'm wrong.
> While I am curious what the problem could be, based on everyone's
> experience, I am really looking for how to best eliminate different
> components as being the issue. Any suggestions as to how to proceed, and in
> what order? As always, I am most appreciative for your logical thinking
> PROBLEM: It developed this weekend while driving. When driving the TR6
> (approx 70K miles), there is a noticeable knocking (rat tat tat tat tat
> ....) that begins almost exactly at 2500 rpm. I seem to hear it most
> pronounced in the passenger foot well (but this could be compounded by the
> fact that the carpet is out of the car, and there is a 2 inch gap in the
> transmission tunnel cover where it is supposed to meet the bulkhead). While
> I can hear it when I quickly rev the engine above 2500 rpm, it is nowhere
> near as pronounced.
> POSSIBILITIES: I have thought about bad engine bearings, extreme valve
> noise, timing chain, oil pump, and just plain new rattles.
> PROBLEM WITH DIAGNOSIS: Other than never having dealt with a sound like
> this, when the bonnet is open, I cannot seem to discern where the problem
> is, and obviously cannot pinpoint the sound when I'm driving.
> SOME OTHER INFO THAT MAY BE PERTINENT:
> 1) Car had sat for 5 or more years without running - until beginning of May,
> 1999. Oil has been changed several times since starting it up in May.
> 2) In 90 degree weather, oil pressure tends to idle around the mid-point
> between 25 lbs and 0 lbs on the gauge, and at driving rpms, oil pressure
> tends to hover around 25 lbs. I use 20W-50.
> 3) I have not opened the engine yet. I've been hoping I could get another
> 25K miles on it before a rebuild.
> 4) I have not yet done a compression check. I'm thinking this might be a
> good idea, but am afraid to drive the car for the 10 minutes prior to
> compression testing to warm the car up.
> If I have left anything out, or need to be more specific, please write to me
> off list, and I can post the new information to the list for all to see.
> Thanks to all who read this,
> Eric Conrad
> Denver, CO
> 1976 TR6 CF52678U