[xj-s] Multiple 95/96 AJ16's overheating

XJ-S
41

Anybody with a facelift XJ-S (even 6.0L model) can help Mark. It
appears that all 92 - 96 models used the same temp gauge sender and the
same round gauge. So the more the merrier (and more helpful). You
don’t have to have an AJ16.

BTW, I’m not sure 220F is overheating when ambient temp is ~ 100F and
you are in stop & go traffic with the A/C on. Anything much more than
that (230 & up) would cause me concern.

George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: George Balthrop <@GBalthropXJS>

Why don’t you guys with AJ16’s help each other out and do measurements
of (1) temp gauge sender resistance, (2) gauge position, and (3)
infrared thermometer readngs (pick one, C or F for uniformity) at the
thermostat housing where the gauge sender is located. If 3 or 4 people
did that for various housing temps from 190 to 220F, you could get some
roughly reliable data where you could tell if (1) you had a bad sender,
(2) you had a bad gauge, or (3) you were really overheating (whatever
you deem that to be).

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42

In reply to a message from Veekay sent Fri 22 Jul 2011:

I forgot to add that after (exhausting) online searches I have come
up with a couple of 95/96 owners who posted on other forums about
the same issue, but most importantly how they fixed it with a new
gauge–
95 AJ16 4liter 6cylinder, Houston TX
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43

Hi Mark.

I don’t have an XJ-S, but I do have an X300 with the 4.0.

Here is another thought, 1995 MY is supposed to have OBD-II, although
not required in the US until 1996. One of the parameters (PID) you
can get with an appropriate scanner is the coolant temperature. This
may be of use because this will tell you what the ECM thinks the
temperature is; regardless of what the gauge says.

Just a thought.

  • Mark, 1995 X300 4.0

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44

In reply to a message from Mark Pilant sent Fri 22 Jul 2011:

Mark, that’s a great idea…so can I see what the temps are as I
drive the car and what not??? if so,where can I get this machine???–
95 AJ16 4liter 6cylinder, Houston TX
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45

Hi Mark.

so can I see what the temps are as I drive the car and what not???

Yes. Depending on the scanner, you should be able to monitor all
manner of parameters. Another which comes to mind are the O2 sensor
parameters.

I do it all the time when cashing down problems.

Caveat here… I have not yet used it on my 1995 X300. I have used
it with success on the 1996 X300 I used to have and our 2001 Volvo
V70XC.

if so,where can I get this machine???

There are a number of places to get one. Although you may have to
check to make sure it is capable of doing more than just reading the
MIL/CE codes.

I have an Actron CP9180 that I picked up at Sears, because I was in
a bit of a hurry. It was in their (auto) tools area. I’m sure you
will will be able to get something comparable at just about any good
auto parts store. I think even AutoZone, VIP, and Pep Boys carry
them.

  • Mark, 1995 X300 4.0

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46

In reply to a message from Mark Pilant sent Fri 22 Jul 2011:

OK, from what I understand, the 95 XJS has the OBD-1 (yes,
there was a 1) which has limited reading capability.

The 96 was the first XJS to come out with the OBD-2.

I have a 96, so I am extremely interested in this. I think
this is a great idea.

I have a wireless OBD2 reader, I just never downloaded
software to pick it up (I have a Mac, most freeware seems to
be PC oriented) I will definitely look into this further.–
1996 XJS 2+2 Convertible with 4.0L AJ16
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47

In reply to a message from Veekay sent Fri 22 Jul 2011:

Veekay,95 does have obd2 as well.

I am going to look for this machine Saturday–
95 AJ16 4liter 6cylinder, Houston TX
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48

In reply to a message from Mark Janzic sent Fri 22 Jul 2011:

That is good to know regarding your '95. I think the V12s
then were only OBD-1. I don’t think the v12s ever got to
OBD-2.

I am going to invest in an application for a laptop. I
think its the best bang for your buck. The attachment
machines do not all let you read everything, I believe the
laptop apps do.

Since I have a Mac, I am limited to a program called Movi,
by Yhasi. A quick Google should get you all the info you
want.

I’m sure PCs have a bunch of options. I think iPhones and
Androids might as well. (I still carry the Blackbery…)

I’ll keep everyone posted what happens. I happen to be away
this weekend, so I won’t get back with any results this
weekend.–
1996 XJS 2+2 Convertible with 4.0L AJ16
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49

OK, from what I understand, the 95 XJS has the OBD-1

Well… mostly :slight_smile: :slight_smile: How’s that for an answer :stuck_out_tongue:

1995 (at least in the US) was something of a transition year. I
believe most makes were indeed OBD-I. However, there were a small
number of makes which had ODB-II… sort of. I say sort of because
while the connector and data exchange met the ODB-II spec, some of
the codes appear to have been from a draft because they changed for
1996. I think Honda and Toyota also had ODB-II in 1995. I’m not
sure about any US manufacturers (Ford, GM, etc.)

I actually have a copy of the 1995 XJ-S OBD-II Jaguar factory manual.
I got because a number of the systems are shared with my 1995 X300.
I also have copies of the Jaguar X300 '95 & '96 Technical Supplements.
These do show different “P” codes for the '95 and '96 for the same
problem. (This is the big reason I believe the '95 was done to a
draft version.)

In any event, driving around with a scanner hooked up can be very
enlightening.

  • Mark 1995 X300 4.0

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50

In reply to a message from Mark Pilant sent Sat 23 Jul 2011:

Well I don’t have an lap top anymore just a pc and ipad and
iPod…and I can’t find any apps for obd monitoring.
:frowning:

I will probably have to buy the device itself–
95 AJ16 4liter 6cylinder, Houston TX
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51

In reply to a message from Mark Janzic sent Sun 24 Jul 2011:

Well I did find an app for the ipad…but the reviews suck.

Hopefuly someone had used something that has worked on their aj16
xjs–
95 AJ16 4liter 6cylinder, Houston TX
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52

Hi Mark.

While you can get hardware/software which will interface the OBD-II port
to a computer, you may want to check out the hand-held devices. The
Actron I have is hand-held, and will allow you to monitor various PIDs
real time. I think there are somewhere around 40 for my X300 (although
I haven’t checked the exact number for a while). Oh yes, I believe mine
will also record values to be later downloaded to a PC; although I have
never used this feature.

There are several varieties of hand-held scanners. They range from fairly
simple read and reset MIL codes to read, reset, and monitor PIDs real-time.
Some of the more sophisticated units will also graph monitored parameters.

At the time, about 3 - 4 years ago, mine cost about USD $180 at Sears.

I’m sure there are other units available which will do the same thing, I’m
just more familiar with the Actron as I have one :slight_smile:

  • Mark 1995 X300 4.0

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53

In reply to a message from Mark Pilant sent Sat 23 Jul 2011:

I’m pretty sure one can parse what was OBDI & OBDII in '95 by
saying that none of the US spec. '95 XJS V12 cars were OBDII.
There were no US spec. '96 V12 XJS’s. All the '95 & '96 AJ16 4.0
XJS’s are OBDII.–
lockheed 92 XJS Cpe/97 LT1 Miami FL/ 96 XJS Cv 4.0 Austin TX
Austin, TX, United States
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54

In reply to a message from lockheed sent Sun 24 Jul 2011:

Alright, I had a wireless OBDII reader (works over
Bluetooth) that I ordered from eBay months ago for about
$20. (yes, its Chinese) I made sure it was ELM27
compliant…whatever that is.

I finally got it paired with my Mac Laptop and the Movi
software from Yhasi works great! (I don’t know if the iPad
will work with it) I can definitely read what the car is
being told is the coolant temp.

I will drive to work tomorrow with the AC on and see what it
reads. I will borrow an IR temp gun and see if I get a
similar reading from the radiator.

Should be above 90 all week. Plenty of time to get
readings.–
1996 XJS 2+2 Convertible with 4.0L AJ16
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55

Unless you’ve added some new temp sensors for your OBDII reader, it
only has 2 to choose from: (1) temp gauge sender (single spade), or (2)
CTS (Coolant Temperature Sensor for EMS which has two spades). It
probably uses the CTS output to the EMS. Both of these sensors have a
resistance that varies with engine temperature at the thermostat
housing where they are mounted. If whichever of those sensors it uses
(or its wiring) is bad, the Reader temperature number will be bad.

So if you want to confirm the readings, don’t measure anything at the
radiator (where temperature varies ~ 30 degrees from top to bottom, but
measure at the thermostat housing where the sensor is located.

Now we are back to what I suggested days ago, which is measure
thermostat housing temps with an infrared thermometer, temp gauge
resistance with ohm meter and record corresponding gauge position for
temps between 190 & 220F. Get data from a number of people with
facelift cars, and you have something reliable to use (assuming a
specific method is adopted for use by all participants so ALL the
readings are obtained in the same fashion).

All you’ve done with the OBDII reader is add a new variable (which
you’re having to confirm with an infrared thermometer). You don’t even
know what sensor output you are measuring unless you pull the connector
to each alternatively and see when the temp readout stops. The
software of the Reader has to convert the resistance to a temperature.
What’s the number of degrees variation from actual in that software
conversion?

Technology is great, but unless you understand what it is really doing,
it can simply be bells & whistles, giving data that you assume is a
certain thing, and accurate, when it may be relying on a defective
sensor or wiring in the vehicle, and giving an entirely different data
point from what you assumed, which is inaccurate.

George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: Veekay valde@verizon.net

Alright, I had a wireless OBDII reader (works over
Bluetooth)…
I will drive to work tomorrow with the AC on and see what it
reads. I will borrow an IR temp gun and see if I get a
similar reading from the radiator.

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56

Just to continue the discussion :slight_smile:

Unless you’ve added some new temp sensors for your OBDII reader…

While there may exist OBD-II readers which have external connections for
additional sensors, the one I have simply reports what the automobile’s
system “thinks” it is seeing. It doesn’t have to convert resistance, as
the appropriate PID is already in degrees.

As you say there are probably two temp sensors. If the one for the
FI/EMS system is correct and the gauge is still reading high, then it
may be the fault lies in that portion (temp gauge) of the circuit.
Although it could be anywhere from the sensor itself to the gauge.
Some possibilities are:
1) Bad/marginal grounding/earth (corrosion on the threads) of
the sensor.
2) Bad/marginal connector to the sensor.
3) Bad/marginal wiring to the instrument cluster (connector).
4) Bad/marginal connection from the instrument cluster to the
gauge.
5) Bad/marginal grounding/earth of the instrument cluster;
necessary to provide a “return” for the gauge.
6) Bad/marginal supply voltage to the instrument cluster.
7) And so on…

(One reason I dislike electrical problems… they can be very time
consuming to resolve as you need to be real methodical so nothing gets
overlooked.)

I only brought up the topic of a OBD-II scanner because I expect most
folks will have one of them rather than a IR temp sensor. (Me, I have
both, as well as a lab grade unit which will measure to 1500C, great
for measuring exhaust temperatures, but I’m a tool junkie :slight_smile: In
addition, a scanner is useful for other things such as pulling codes
when the MIL/CE light comes on.

Although even the IR temp sensor must be used correctly. If it is not
held the proper distance from the source, the readings may be suspect.
(Although, truth be told, the difference probably won’t be very great.)

Technology is great…

Yep. But like a lot of things, it is just another tool to be used. The
skill comes in knowing how to use the (appropriate) tool and how to
interpret the result(s).

  • Mark 1995 X300 4.0

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57

In reply to a message from Mark Pilant sent Sun 24 Jul 2011:

I have not confirmed these readings with the IR yet.

When the needle was halfway (or a bit more) between the N and the
H, I got a solid reading of 210 degrees from the OBDII.

When I stopped the car and let it run, it rose to 212, with an
occasional blink to 215.2, but it never sustained it.

The intake air temp on the highway stayed at 113 this morning (once
I turned the AC off, it sank to 109) On the slow roads, the intake
temps got up to 160 degrees.

Ultimately, I no longer believe there is a lot to worry about. It
seems that once it hits the red part of the H, it will probably
exceed 220, which begins the danger zone.

When the needle was standing right over the N, I was getting 190
degrees. When it was at the very end of the N, I was reading 200.
If the needle is touching the N in any way, you are probably below
the 200 degree marrk.

It’s worth noting that the middle to end of the N has a spread of
10 degrees. The distance between the end of the N and the midpoint
between N and H carries another 10 degree spread, even though the
distance is much larger.

I’ll do a check on the way home and back it up with the IR.–
1996 XJS 2+2 Convertible with 4.0L AJ16
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58

In reply to a message from Veekay sent Mon 25 Jul 2011:

Mark P, Veekay, thanks for keeping the topic alive.
I hope it ends with both Veekay and me reading at N under all
conditions.

in regards to the sensor gauge suggestions posted earlier, all that
has been done (on mine at least)

I have posted some pictures in my album, hopefully they will show
by today, The reading is 186 right at the middle of N. The pics
speak for themselves.–
95 AJ16 4liter 6cylinder, Houston TX
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59

Veekay wrote:

The intake air temp on the highway stayed at 113 this morning (once I
turned the AC off, it sank to 109) On the slow roads, the intake
temps got up to 160 degrees.

Your radiator fans are either inadequate or nonfunctional. 160 is
too hot, you need to get more air flowing through that engine
compartment at standstill.

– Kirbert

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60

In reply to a message from Kirbert sent Mon 25 Jul 2011:

The fan is definitely working, both of them.

On a 100 degree day, 160 is the hottest reading I got.

I will do the same thing on my 2000 Ford Taurus and see what
readings I get from it either tomorrow (the coolest day of the
week) or Wednesday.

It should make for a good comparison. Coolant temps and incoming
air. Remember, the Ford has the dummy temp gauge, that thing never
moves.–
1996 XJS 2+2 Convertible with 4.0L AJ16
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