[x300] Spontaneous Over-heating

I have experienced twice what appears to be spontaneous over-heating
in which the two radiator fans fail to come on. The both times that this
has happened was during extensive downtown driving. They begin working
again after a day or two and give me no trouble until the next similar
scenario.
I automatically assumed it was the fan control module a.k.a.
glorified relay located in the front left hand side, behind the bumper.
So I went ahead and replaced it but just this past weekend it had
over-heated on me again.
I’m not sure what to pin it on now since I was certain it was that
relay module.
Both times I was able to safely drive it back home by turning on the
heater at the highest setting. That brought down the temp gauge to the
normal operating temperature immediately.
Any suggestions would be greatly appreciated!

Regards,
Tim
95 X300

In reply to a message from ZORAN1 sent Tue 19 Nov 2002:

Tim:

Your problem could be a questionalble thermostat. If you have not
changed yours, I would do it right away. They have a tendency to
fail over time.

Also, there is an X300 upgrade in that a wire jumper is installed
that enables the fans to run on low speed all of the time. A
pressure switch (that controls the function) in one of the A/C
cooling lines is removed, and a one wire jumper is installed where
the wiring harness from the pressure switch connected to the main
harness… This should take a dealer about 5 minutes to do.

There is some debate about this jumper, but it will solve two major
problems. 1) Eliminate the problem that the fan motors freeze up
from lack of use in the colder months and climates due to lack of
use. 2) In warmer climates it is a continual pre-emptive step to
prevent overeheating.

Now, if you are in Finland or some other very cold location, where
your problem is gettimg the engine up to temperature, perhaps this
fix is not for you.–
uncle
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Out of interest do you know how the fans tend to fail? My fans have stopped
working on low speed but work on high speed. On closer inspection only one fan
is actually turning on high speed so I assume on the low speed setting the
broken fan is stopping the working fan from spinning as there is no continuity.
I have tested the radiator sensor so it does not appear to be that.

Regards

Richard '96 XJ12

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Registered in England & Wales No. 2366970

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Registered in England and Wales No: 3407430

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It’s obviously not a fuse, so I would start on the input side of the control
module to see if the temperature sensor is telling the fans to come on. May
be a sensor problem, bad connection etc.

Cheers - Jez> -----Original Message-----

From: ZORAN1 [mailto:ZORAN1@Prodigy.Net]
Sent: 19 November 2002 06:24
To: x300@jag-lovers.org
Subject: [x300] Spontaneous Over-heating

I have experienced twice what appears to be spontaneous over-heating
in which the two radiator fans fail to come on. The both
times that this
has happened was during extensive downtown driving. They begin working
again after a day or two and give me no trouble until the next similar
scenario.
I automatically assumed it was the fan control module a.k.a.
glorified relay located in the front left hand side, behind
the bumper.
So I went ahead and replaced it but just this past weekend it had
over-heated on me again.
I’m not sure what to pin it on now since I was certain it was that
relay module.
Both times I was able to safely drive it back home by
turning on the
heater at the highest setting. That brought down the temp gauge to the
normal operating temperature immediately.
Any suggestions would be greatly appreciated!

Regards,
Tim
95 X300

Richard,

Have you checked the fan fuses? I know there’s fuses for both
parallel and series fan wiring.
Mine do not come on at all when they act up but when they start
working again they usually stay on at a steady low speed occasionally
alternating from hi to low.
I remember when I had to replace my fan relay module the first time
because the original had sustained physical damage, it would only switch
on the fans at high speed and only briefly, never on low. So you might
want to direct your attention to the fan relay.
Also, how’d you test this radiator sensor and where exactly is it
located? I think I should possibly check mine to see if it’s the cause
of my problem.

Regards,
Tim
95 X300

Richard.Mansell@pgen.com wrote:>

Out of interest do you know how the fans tend to fail? My fans have stopped
working on low speed but work on high speed. On closer inspection only one fan
is actually turning on high speed so I assume on the low speed setting the
broken fan is stopping the working fan from spinning as there is no continuity.
I have tested the radiator sensor so it does not appear to be that.

Regards

Richard '96 XJ12

___________________________ Disclaimer Notice __________________________
This message and any attachments are confidential and should only be read
by those to whom they are addressed. If you are not the intended recipient,
please contact us, delete the message from your computer and destroy any
copies. Any distribution or copying without our prior permission is
prohibited.

Internet communications are not always secure and therefore the Powergen
Group does not accept legal responsibility for this message. The recipient
is responsible for verifying its authenticity before acting on the
contents. Any views or opinions presented are solely those of the author
and do not necessarily represent those of the Powergen Group.

Registered addresses:

Powergen UK plc, 53 New Broad Street, London, EC2M 1SL
Registered in England & Wales No. 2366970

Powergen Retail Limited, Westwood Way, Westwood Business Park, Coventry CV4 8LG.
Registered in England and Wales No: 3407430

Telephone +44 (0) 2476 42 4000
Fax +44 (0) 2476 42 5432

Hi Doug,

To answer your question, I lost the coolant out the expansion tank
relief cap during operation. I had been driving it in traffic for quite
some time without realizing the temp gauge was redlining thus an
excessive buildup of pressure forced the coolant out the cap.
In fact that’s how I realized the car was overheating. I could see
the vapor rising out the engine compartment which compelled me to pull
it over and kill the engine, popping the hood open. I also ran the
heater with the egine off which brought down the temp very quickly.
If it were the thermostat would there even be any pressure out the
expansion tank?
I switched back to a pressure switch because I think it’s silly to
have the cooling fans spinning when you first start the car from a cold
start or during winter months and especially while you’re driving down
the freeway. It’s a waste of electrical resources and causes wear.
The fans don’t come on and off playing catch up ball. They just don’t
come on initially but once they do they STAY ON. If and when they need
to catch up they spin at a higher speed.
I’d like to do the thermostat but I just want to be certain the
symptoms I’m getting are characteristics of a failing one. I remember
changing the one on my XJ40 because it was stuck open.

Regards,
Tim
95 X300 48k

Doug Bernard wrote:>

Hello:

I would say the thermostat should be changed, and see what happens
afterward. On both of my Jaguars, I have had intermittent problems
with this component. One failed closed, resulting in overheating, one
stayed open resulting in low operating temperatures, and poor
heater/defroster operation. If this is the problem, it is the
cheapest and easiest one to fix.

When did you loose coolant? When you opened the cap, or did you loose
it in the course of operation? In some instances, excessive pressure
within the cooling system is and indication of other problems.

I do not think it is the water pump.

Regarding your change back to the pressure switch, why did you do
that? My thoughts are if you are in traffic, why not run the fans all
of the time, rather than playing “catch up ball” with the fans after
the engine gets a bit hot? Also, many XJ40 owners have fans that
freeze up due to lack of use.

Let me know if the T-Stat does the trick,
Doug

-----Original Message-----
From: ZORAN1 [mailto:ZORAN1@prodigy.net]
Sent: Wednesday, November 20, 2002 10:03 AM
To: uncle
Cc: dbernard@qts-inc.com
Subject: Re: [x300] Spontaneous Over-heating

Hi Uncle,

I was thinking it might be the thermostat but I’m not sure the
symptoms are in-sync with that scenario. The coolant in the radiator
definitely gets hot and the pressure is enormous as the first time it
had happened to me I had lost a considerable amount of coolant out the
expansion tank cap.

Also, on the freeway there is no problem, I can turn off the heater
and the temp stays at normal operating temperature.

Like I said, the two times that this has happened to me the
circumstances were the same. Long extensive downtown driving with an
occasional stop here and there. Perhaps it is the thermostat since I
believe it begins to happen after the engine has been stopped for
awhile allowing the stat to close.

Another list member suggested the water pump but isn’t there an
indicator if it’s failing? Like a drip out the front hole?

I’m aware of Jaguar’s so-called “fix” with the jumper cable.
My car already had it however I found that it was unnecassary to have
the fans on all the time regardless of engine status. SO I went ahead
and installed the original design pressure switch which appears to be
working fine. I doubt this is the cause of my problem as the engine
temp switch should be telling the fans to come on. Besides, from my
recollection a failed pressure switch would blow the fan fuses. I’ve
checked the fuses and they are fine.

Regards,
Tim

uncle wrote:

In reply to a message from ZORAN1 sent Tue 19 Nov 2002:

Tim:

Your problem could be a questionalble thermostat. If you have not
changed yours, I would do it right away. They have a tendency to
fail
over time.

Also, there is an X300 upgrade in that a wire jumper is installed
that
enables the fans to run on low speed all of the time. A pressure
switch (that controls the function) in one of the A/C cooling lines
is
removed, and a one wire jumper is installed where the wiring harness

from the pressure switch connected to the main harness… This
should
take a dealer about 5 minutes to do.

There is some debate about this jumper, but it will solve two major
problems. 1) Eliminate the problem that the fan motors freeze up
from
lack of use in the colder months and climates due to lack of
use. 2) In warmer climates it is a continual pre-emptive step to
prevent overeheating.

Now, if you are in Finland or some other very cold location, where
your problem is gettimg the engine up to temperature, perhaps this
fix
is not for you.

uncle
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Hi Tim

Yes I did check the fuses. Thinking about it, it was 4 months ago, what I
actually did was pull the connector off the sensor and short it out. Shorting
out the high speed side made the fans come on, shorting out the low speed fan
just caused a relay to click somewhere. So I haven’t actually proved that the
sensor works but it does seem to point towards the fan. Looking from towards the
front of the car, the sensor is on the bottom left hand side of the radiator.
The V12 makes space a premium under the bonnet so I had to push the release
clips from under the car whilst my wife was up top pulling on the connector.
Hopefully on the straight sixes it is a little easier.

For some reason the fan setup is different on the V12’s and I believe that the
only connector is behind the left hand wheel arch liner. As it is nearly winter
now I have lost the drive to try and fix it but I need to do something before
next summer especially as I have already fried one V12.

Is the fan relay module easy to get to and is it serviceable?

Regards

Richard

___________________________ Disclaimer Notice __________________________
This message and any attachments are confidential and should only be read
by those to whom they are addressed. If you are not the intended recipient,
please contact us, delete the message from your computer and destroy any
copies. Any distribution or copying without our prior permission is
prohibited.

Internet communications are not always secure and therefore the Powergen
Group does not accept legal responsibility for this message. The recipient
is responsible for verifying its authenticity before acting on the
contents. Any views or opinions presented are solely those of the author
and do not necessarily represent those of the Powergen Group.

Registered addresses:

Powergen UK plc, 53 New Broad Street, London, EC2M 1SL
Registered in England & Wales No. 2366970

Powergen Retail Limited, Westwood Way, Westwood Business Park, Coventry CV4 8LG.
Registered in England and Wales No: 3407430

Telephone +44 (0) 2476 42 4000
Fax +44 (0) 2476 42 5432