I drove up from Richmond to Philly area today in the 95F heat that is a bit
uncommon for this time of year. About the time I got into Delaware, the
temp gauge began creeping up a notch and a half above the N. I watched it
and all at once, it began to retreat until it was just off the ‘N’. A bit
later it began the journey going up and then later back down. As time
progressed the rise proceeded closer to H, fully hitting the notch below
it, but later retreating. Nothing like this in the four years I have had
the car.
Any ideas? Could it be a bad ground? If there was no ground, would the
needle be fully ‘C’ or fully ‘H’? Are there two temp sensors? One for the
gauge and one for the ECU? Engine ran fine at speed. Coolant was full
last night when I checked before the trip.
Larry,
I would not assume the gauge has a problem.
I would assume the thermostat has a problem, or
the radiators are plugged up (outside and between).
Time to go through the cooling system in detail.
YOU HAVE BEEN WARNED!
Brett
1990 XJ6>
I drove up from Richmond to Philly area today in the 95F heat
that is a bit
uncommon for this time of year. About the time I got into
Delaware, the
temp gauge began creeping up a notch and a half above the N.
I watched it
and all at once, it began to retreat until it was just off
the ‘N’. A bit
later it began the journey going up and then later back down. As time
progressed the rise proceeded closer to H, fully hitting the
notch below
it, but later retreating. Nothing like this in the four
years I have had
the car.
Any ideas? Could it be a bad ground? If there was no ground,
would the
needle be fully ‘C’ or fully ‘H’? Are there two temp
sensors? One for the
gauge and one for the ECU? Engine ran fine at speed.
Coolant was full
last night when I checked before the trip.
I have to agree with Brett. Guage problems on any car are fairly rare. You might note what sort of driving you were
doing when it indicated a high temperature. First thing I would do is check the coolant level when the engine is cold.
Then I like to let it idle on a hot day while watching the guage.
if it starts to get hot under heavier loads (climbing hill etc) I’d suspect radiator blockage(internal and external) or poor
coolant circulation
if it over heats when moving slowly ensure that the fan is engaging.
changing the thermostat is a good idea. or at least check it. Remove it put it in a cold pan of water on the stove. Heat
the water and note what temperature it starts to open and at what temperature it is fully open at. Turn off the stove and
record the temperature at which it starts to close and at what temperature it is fully closed at.
The range should be fairly tight around rated temperature. I’ve had new thermostats which performed poorly.4/18/02 11:52:09 AM, Brett Gazdzinski brett.gazdzinski@wcom.com wrote:
Larry,
I would not assume the gauge has a problem.
I would assume the thermostat has a problem, or
the radiators are plugged up (outside and between).
Time to go through the cooling system in detail.
YOU HAVE BEEN WARNED!
Brett
1990 XJ6
I drove up from Richmond to Philly area today in the 95F heat
that is a bit
uncommon for this time of year. About the time I got into
Delaware, the
temp gauge began creeping up a notch and a half above the N.
I watched it
and all at once, it began to retreat until it was just off
the ‘N’. A bit
later it began the journey going up and then later back down. As time
progressed the rise proceeded closer to H, fully hitting the
notch below
it, but later retreating. Nothing like this in the four
years I have had
the car.
Any ideas? Could it be a bad ground? If there was no ground,
would the
needle be fully ‘C’ or fully ‘H’? Are there two temp
sensors? One for the
gauge and one for the ECU? Engine ran fine at speed.
Coolant was full
last night when I checked before the trip.
Thanks for the comments David. Brett has also offered several.
The first thing I’ll try is replacing the stat as the problem actually
started last year after putting in a new one and the 2-wire temp sender
simply as PM while changing the hoses and switching to the 5 year dexcool
coolant. So it could be a faulty stat. Could also have fouled up the rad
by switching to dexcool? There was a thread on this after I switched
either on modern or e-type. I flushed the system 3 times , but wouldn’t
you know forgot to turn the heater on. So I was concerned that I didn’t
flush that. But, I can’t find a heater valve where the factory manual
shows one to be - on the firewall. Is it possible on later cars although
91 is not all that late, with an AC’d car, the heater connected at all
times and simply the flaps direct the airflow to the heater when required?
It certainly seems that could be the case, from the factory manual’s
description on the heater/ac box. In that case, I would be less suspect of
a fouled rad.
Regards,
Larry
David Boarder
<dboarder@sym To: brett.gazdzinski@wcom.com, @larry.trom,
patico.ca> modern@jag-lovers.org
cc:
04/18/02 Subject: RE: [modern] erratic temp gauge
06:49 PM
Please
respond to
dboarder
I have to agree with Brett. Guage problems on any car are fairly rare.
You might note what sort of driving you were
doing when it indicated a high temperature. First thing I would do is check
the coolant level when the engine is cold.
Then I like to let it idle on a hot day while watching the guage.
if it starts to get hot under heavier loads (climbing hill etc) I’d
suspect radiator blockage(internal and external) or poor
coolant circulation
if it over heats when moving slowly ensure that the fan is engaging.
changing the thermostat is a good idea. or at least check it. Remove it
put it in a cold pan of water on the stove. Heat
the water and note what temperature it starts to open and at what
temperature it is fully open at. Turn off the stove and
record the temperature at which it starts to close and at what temperature
it is fully closed at.
The range should be fairly tight around rated temperature. I’ve had new
thermostats which performed poorly.4/18/02 11:52:09 AM, Brett Gazdzinski brett.gazdzinski@wcom.com wrote:
Larry,
I would not assume the gauge has a problem.
I would assume the thermostat has a problem, or
the radiators are plugged up (outside and between).
Time to go through the cooling system in detail.
YOU HAVE BEEN WARNED!
Brett
1990 XJ6
I drove up from Richmond to Philly area today in the 95F heat
that is a bit
uncommon for this time of year. About the time I got into
Delaware, the
temp gauge began creeping up a notch and a half above the N.
I watched it
and all at once, it began to retreat until it was just off
the ‘N’. A bit
later it began the journey going up and then later back down. As time
progressed the rise proceeded closer to H, fully hitting the
notch below
it, but later retreating. Nothing like this in the four
years I have had
the car.
Any ideas? Could it be a bad ground? If there was no ground,
would the
needle be fully ‘C’ or fully ‘H’? Are there two temp
sensors? One for the
gauge and one for the ECU? Engine ran fine at speed.
Coolant was full
last night when I checked before the trip.