[xj-s] Need suggestions for Another cooling system issue

First I want to say that this site has been a tremendous
resource for addressing all the issues I have had with my
90 xjs convertible. With that said, I hope to get a
little more assistance with an ongoing cooling issue I
have.

I recently had a new aluminum radiator, twin electric
fans, new hoses, new expansion tank, 82 degree
thermostats and air and coolant temp sensors replaced. The
car has roughly 38k miles on it, but did sit unused for
nearly 2 years. The problem is as follows:

The engine comes up to temperature (barrel gauge needle
just below the ‘‘n’’) after 6- 10 minutes of use. Temp
gauge stay relatively constant for next 10-15 minutes,
but the begins to slowly creep up to middle and then
ultimately at the top of ‘‘n’’ in regular stop and go
driving. When I get up to speed, gauge does not come down
and will even creep slightly higher. Gauge has not
increased much past there, but my expectation is that at
speed, gauge should return below the ‘‘n’’ . I am not
losing coolant, fans are working appropriately and with
all the replacement parts I am relatively comfortable
that the system is working, just not cooling as
efficiently as it should.

My question is should I continue to look at cooling
system issues or are there other more likely causes(
timing, etc) causing the gauge to read higher than it
should and not cooling at speed? After reading this forum
for several hours today, I now think that my idle RPM s
might be high (1100 RPMs in park)or I could have other
ECU issues. If anyone can recommend a good Jaguar/ V12
mechanic in the North Atlanta, GA area, that would be
greatly appreciated as well.

Thanks in advance for any assistance–
Don Ashley
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Don,

I think the general consensus is that the Jaguar gages are just not

that accurate or reliable.

I recommend that you get an inexpensive infrared thermometer (Harbor

Freight carries them) or an aftermarket digital temperature gage and get a
second opinion on the temperature before doing anything else.

You car has the Marelli ignition and you can't really do much with

the timing. Do you have the air dam/spoiler installed under the front of
your car? If not that can affect the airflow and reduce the efficiency of
your cooling system.

Coventry West has a great reputation and they are located in

Lithonia, GA. I know that is south east of Atlanta, but thought I should
mention them.

Regards,

Paul M. Novak

1990 XJ-S Classic Collection convertible
1987 XJ6 Vanden Plas
1985 XJ6 Vanden Plas (parts)
1984 XJ6 Vanden Plas
1969 E-Type FHC
1957 MK VIII Saloon
Ramona, CA
P.M.Novak7@gmail.com-----Original Message-----
From: owner-xj-s@jag-lovers.org [mailto:owner-xj-s@jag-lovers.org] On Behalf
Of 90 xjs
Sent: Sunday, July 03, 2011 2:26 PM
To: xj-s@jag-lovers.org
Subject: [xj-s] Need suggestions for Another cooling system issue

I hope to get a little more assistance with an ongoing cooling issue I
have.

I recently had a new aluminum radiator, twin electric
fans, new hoses, new expansion tank, 82 degree
thermostats and air and coolant temp sensors replaced. The
car has roughly 38k miles on it, but did sit unused for
nearly 2 years. The problem is as follows:

The engine comes up to temperature (barrel gauge needle
just below the ‘‘n’’) after 6- 10 minutes of use. Temp
gauge stay relatively constant for next 10-15 minutes,
but the begins to slowly creep up to middle and then
ultimately at the top of ‘‘n’’ in regular stop and go
driving. When I get up to speed, gauge does not come down
and will even creep slightly higher. Gauge has not
increased much past there, but my expectation is that at
speed, gauge should return below the ‘‘n’’ . I am not
losing coolant, fans are working appropriately and with
all the replacement parts I am relatively comfortable
that the system is working, just not cooling as
efficiently as it should.

My question is should I continue to look at cooling
system issues or are there other more likely causes(
timing, etc) causing the gauge to read higher than it
should and not cooling at speed? After reading this forum
for several hours today, I now think that my idle RPM s
might be high (1100 RPMs in park)or I could have other
ECU issues. If anyone can recommend a good Jaguar/ V12
mechanic in the North Atlanta, GA area, that would be
greatly appreciated as well.

Thanks in advance for any assistance


Don Ashley

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Are you sure that the proper coolant fill procedure was followed? The nose of the car should be raised when filling to help get the air out of the system.

A.J.On Jul 3, 2011, at 5:25 PM, 90 xjs wrote:

I recently had a new aluminum radiator, twin electric
fans, new hoses, new expansion tank, 82 degree
thermostats and air and coolant temp sensors replaced. The
car has roughly 38k miles on it, but did sit unused for
nearly 2 years. The problem is as follows:

The engine comes up to temperature (barrel gauge needle
just below the ‘‘n’’) after 6- 10 minutes of use. Temp
gauge stay relatively constant for next 10-15 minutes,
but the begins to slowly creep up to middle and then
ultimately at the top of ‘‘n’’ in regular stop and go
driving. When I get up to speed, gauge does not come down
and will even creep slightly higher. Gauge has not
increased much past there, but my expectation is that at
speed, gauge should return below the ‘‘n’’ . I am not
losing coolant, fans are working appropriately and with
all the replacement parts I am relatively comfortable
that the system is working, just not cooling as
efficiently as it should.

// please trim quoted text to context only

In reply to a message from A.J. Simpson sent Mon 4 Jul 2011:

AJ,

Thanks. I believe that Any air has been bled from the
system. When I checked coolant level the car was on a
significant incline and there are no air bubbles
releasing at either the crossover or the expansion tank
fill holes.

While the gauge hasn’t got past the Top of the N by very
much, my concern is that with the 82 degree thermostats,
that gauge reading is pretty hot. (assuming a properly
functioning sender and gauge).

I think my next step will have to be to test the gauge
itself and perhaps add another gauge somewhere else in
the system to confirm temps.

Appreciate the response.–
Don Ashley
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In reply to a message from 90 xjs sent Mon 4 Jul 2011:

Before getting all worked up over your gauge readings you
should figure out what temp your car is running at. Get a real
gauge and then compare temp readings to your factory gauge.
You may find you are ok.

Also lower temp thermostats do nothing to cure an overheating
or hot running car.–
Greg 1985 XJS HE DANA rear
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In reply to a message from 90 xjs sent Sun 3 Jul 2011:

Mistakes are common??? I also have the alum rad, elec fans, 82’s
etc. I crossed the wires when I installed them. I had one fan
pushing & one pulling!!! Did the same thing yours is doing, Check
to make sure both fans are pulling the outside air through the
radiator.
This ‘‘fix’’ brought my temp (91-5.3-barrel gauges) down to the
bottom of the N in 90 degrees. As far as your above 30mph, I don’t
know.
Larry
91 XJ-S 12cyl 5sp
95 VDP 6cyl–
The original message included these comments:

First I want to say that this site has been a tremendous
90 xjs convertible. With that said, I hope to get a
little more assistance with an ongoing cooling issue I
I recently had a new aluminum radiator, twin electric
fans, new hoses, new expansion tank, 82 degree
thermostats and air and coolant temp sensors replaced. The
car has roughly 38k miles on it, but did sit unused for
nearly 2 years. The problem is as follows:
The engine comes up to temperature (barrel gauge needle
driving. When I get up to speed, gauge does not come down
and will even creep slightly higher. Gauge has not


Larry Hartman
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

// please trim quoted text to context only

In reply to a message from 90 xjs sent Sun 3 Jul 2011:

If it overheats at speed you have a coolant flow, ignition
timing or mixture issue.

You can rule out the fans at any speed above 20 MPH or so.
If it is running lean or your timing is off it can do this.
I think your car has Marrelli so that rules out timing. Is
your cooling system clean? The bleed pipe not clogged? Is
there no air in the system? Does the heat blow warm?

As I said before, what is the temp of the engine when you
are concerned. Maybe your gauge is not exactly the same as
others. The IR thermometers are not really good for getting
a real reading. The can be good for checking the radiator
across the core to see if it is working. You should have
more more then 10-15 degrees difference from inlet to outlet
anywhere on the core. If you do your radiator is not doing
it’s job. Possibly clogged with debris. Some say that a new
radiator will clog right away if you don’t use filters. If
that is not the case then you don’t have good flow. Maybe
water pump impeller? You need to take things apart and make
sure everything is working and clean.

If you have to take things apart a few times. Instead of
wasting coolant. Just use water. Once you get it working
then put the proper mix in. When I say straight water I mean
only for a day or two while you diagnose the system. Not
weeks where it can corrode the system.

Also you can use one of the vacuum fill setups for the
cooling system. They work very well and make it easier to
refill after repairs.–
Greg 1985 XJS HE DANA rear
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In reply to a message from Greg Edge sent Mon 4 Jul 2011:

For next to nothing at the wreckers, you can get an XJ6 round
gauge calibrated in degrees C which works fine with the XJS
sender. Just keep it level. A SPDT switch lets you select
between them.
Somewhere in these archives I listed the correlation between
C-N-H and degrees. IIRC, one needle over N was OK but near the
edge, two over was at the edge and above that was bad.–
Joe Bialy, ’ 87 XJ-S
Grosse Ile, Michigan, United States
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In reply to a message from JaguarJoe sent Mon 4 Jul 2011:

I guess I missed it if the prospect of installing an additional
temp gauge has been discussed here. This sounds like an excellent
idea. I’d like to have a reliable, accurate temp gauge mounted
under the hood … maybe on the firewall. If I thought the in-dash
gauge was suspect I could pop the hood and check the temperature.
Anyone know what gauge to get? Where to put the sender? … etc.

Jack Skeens–
1996 XJS 4.0 Drophead aka ‘Black Beauty’
Camden, Arkansas, United States
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In reply to a message from 90 xjs sent Sun 3 Jul 2011:

Don;
Your car is normal…Typical…about what you can expect.
If you want the needle lower and don’t want to smash the
glass over the gauge and bend it lower (a little frustration?)
You can use the earlier thermostat. (1980& earlier, not
sure it will fit)
But it will cost you slightly worse fuel mileage. (a
warmer car gets fractionally better car than a cooler car…)
For added insurance you can do the Lutz modification which
will cost you next to nothing and ensure that the hot
stagnant coolant in the back of the engine circulates rather
than allow the coolant at the front of the engine to short
circuit…–
MGuar
Wayzata Minnesota, United States
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In reply to a message from jackark sent Mon 4 Jul 2011:

Instead of mounting a gauge under the hood, buy a semi-
inexpensive ($25) digital multimeter than can measure
temperature. Permanently mount a thermocouple compatible
with the meter (probably type K) on each side of the engine.
Now you can use the meter for other Jaguar problems and
still be able to measure temperature whenever you want.

You can use thermistors that are a lot cheaper than T/C’s
and would only require a simple ohmeter to read but their
accuracy is not so great.

I don’t have much faith in cheap IR thermometers. Just
because they flash a bunch of numbers doesn’t make them
accurate.

I saw an instrumented Windstar van at Ford one day. It had
yellow T/C wire everywhere.–
The original message included these comments:

Anyone know what gauge to get? Where to put the sender? … etc.


Joe Bialy, ’ 87 XJ-S
Grosse Ile, Michigan, United States
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