One Hot V8

[James M Dean <aes@idsi.net>]

A few weeks ago I noticed that my V8 would tend to run a little hot when
at idle. On the road everything was fine; running temp was around 80
deg. C. However, once the engine was sufficiently heat soaked and I was
in traffic or at a stop light, I noted that the temp would rise slowly,
but usually did not exceed 105 deg. C. This was occuring on hot days in
the summer so I blew it off to the hot days of summer. However, as
cooler weather approached here in ther northeast, I noticed that my V8
would tend to run hotter...faster while idling. Sometimes it would reach
110 deg. C. I checked the typical cast of suspects including sensors,
coolant level, etc.

All seemed to be fine, but I was still getting this chronic overheating.
Eventually, the overheating became more pronounced and more frequent.
Last week I was in the Pittsburgh area (500 miles from home, of course)
and the car was overheating above 110 deg. C every time I came to a
stop. As an emergency measure, I contacted two local dealers (arrrgh)
and one of them agreed to look at the car. After spending three hours on
the car, the Service Advisor notified me that they found the thermostat
stuck in a half open position??. That seemed a little odd to me, because
I thought that the car would overheat ALL the time if it were a
thermostat problem, but they convinced me that I had a thermostat that
was stuck in a intermediate position and that would cure the problem.
Then they calmly told me that it would be ONLY $268 to change it. I knew
I was getting raped, but what could I do.

After two more hours they finally finished with my car. The Service
Advisor then notified me that the NEW thermostat did not "TOTALLY" fix
the overheating problem. I asked what he meant by "NOT TOTALLY" and he
said, "well........it overheats when the car idles". I almost hit the
guy!!

I told him in no uncertain terms that was EXACTLY why I brought the car
in. After about 30 minutes of some vigorous discussions, he shoved the
service order in front of me and said, " sign HERE.......no charge". At
least I avoided a well overpriced thermostat, but still had my
overheating problem.

I was able to nurse the car back home to New York without much problem
(interstate all the way). After taking the car to my regular mechanic
(Greg Hayman @ Autofirme). he diagnosed the problem within 15 minutes.

As I understand it, the main cooling fan is operated on a clutch
mechanism which receives a signal from a bimetallic strip. The hotter
the car gets, the more the clutch is engaged. At approximately 105-110
deg. C the clutch mechanism is supposed to be fully engaged with no
slippage. We let the car idle and we were able to stop the fan
(carefully). Therefore, the fan clutch was not fully engaging and was
not cooling properly.

The fan clutch cost is $195, plus installation.

Thank the Audi Gods for mechanics that know what they're doing!!

--
James M. Dean (JD)
Applied Energy Services
P.O. Box 60, Fishkill, NY 12524
Tel (914) 486-4134  Fax (914) 486-4701
Pager: (888) 274-7281
e-mail: aes@idsi.net
http://www1.idsi.net/~aes