Neil Beasley wrote:
> I finally got the lbc on the road (legally--inspected, registered and all) in
> Texas heat(100 F). Here's the problem. As it heats up while driving(max temp
> running about 3/4 of the way to gauge max), the rpm at idle speed increases
> from about 1000rpm to about 1200. I know 1000 rpm may be a little too high to
> start with but I'm not sure how well the tach is calibrated. When I stop and
> need to shift to reverse, it won't shift --just grinds. When the engine is
> cooler, there is no problem getting into reverse.
Hmm. This sounds like a real stumper to me. I can't think of any
logical problems that could cause this sort of behavior. (So, I'm
going to grasp at straws, instead...)
Are the clutch hydraulics in good shape? Is the fluid in the clutch
actually hydraulic fluid? (One speculation is that the fluid in the
clutch hydraulics may be heating up enough to reduce clutch travel due
to a slipping seal???) Do you have any problems shifting at any other
times, in any other gears?
Another thought is that this may have something to do with play with the
thrust washer. Any body else have more ideas along this line?
> In regard to heat, I notice the oil pressure runs about 75 psi on
> start up and drops to about 15-25 after heating up. I'm using
> 10W-30 weight oil. Is this much drop normal?
That much of drop between cold and hot sounds normal. I would be
somewhat concerned with oil pressure dropping to 15psi at idle, unless
the engine had been driven at high RPM for an extended period.
Switching to a thicker oil will help keep oil pressure up by reducing
thinning of the oil as it heats up, particularly in the searing heat.
I found that last summer on the few 95-100F days we had here in New
Hampshire, that after my afternoon 45-minute 65MPH (~3250rpm) drive on
the highway, that my oil pressure would only be about 20psi while
idling (~800rpm) at the toll booth immediately at the end of such a
run. (The temp gauge would hold at its normal position "just above
center" throughout the drive.) I seem to recall that a "rule of
thumb" for minimum oil pressure to keep oil on bearing surfaces is
approximately 10psi per 1000rpm.
I am running 20W50 in my TR6 for the summer. At the temperatures you
are combatting in Texas, I would personally suggest switching to a
20W50 oil, at least for the summertime, and possibly backing off to a
lighter oil for the winter. I don't think you'll do any significant
damage using a lighter oil -- the biggest problem would be that you'd
be more likely to burn it off, and thus may need to top it up more
frequently.
For what it's worth, I used 5W-30 in my TR6 two winters ago, so I
could take it out on those gorgeous January/February days when the
roads were clear of salt, the sky was bright blue, there wasn't a
cloud in sight, and it was only 15F out. (I didn't dare use anything
heavier,
Kenneth B. Streeter | EMAIL: streeter@sanders.com
Sanders, PTP2-A001 |
PO Box 868 | Voice: (603) 885-9604
Nashua, NH 03061 | Fax: (603) 885-0631
|