[xj] Overheating 1978 XJ6L - what next / reverse flush?

The cooling system will only refill to about 10 litres - not
the 18 litres it should take. I have run the engine with
the heater on and the header tank cap off but it didn’t make
much difference. I am suspecting a blockage / buildups in
the water jacket. Any advice, please?

Can I reverse flush by feeding water in the heater hose as I
know the water rail is clear and I really do not want to
take out thermostat as I only just put all that in. Any
recommended chemicals/products to put into cooling system to
try to soak / soften gunk in there before flushing.

Any value in trying to fill the system and then pressurize
it by screwing a compressor line into one of the sensor
fittings on the water rail (I assume not too much pressure
or the old head gasket and any other seals may get blown.)

I have never done a reverse flush on any car before.

Thanks

David–
David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
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For Gods sake, pull that radiator and have it rodded and the tanks
cleaned. A Jaguar that old probably has half the radiator blocked and
the cost of a complete cleaning AND RODDING is peanuts compared to 3
hours on a hot afternoon walking home!!!

Jaguar recommended “Bars Leaks” once every year and that stuff end up
in the bottom of the radiator in a brick colored mass that is about
the consistency of a soft brick…crumbly and very much solid.

You can fart around for months with coolant changes, louvers in the
hood, blocking strange air bypasses, but in the end a $150 radiator
rebuild will fix it after you have spent a year worrying and working
on it. Save yourself all the anguish, GET THE RADIATOR RODDED!!!On Sun, Apr 5, 2009 at 3:04 PM, Dwomby davidawomby@aol.com wrote:

The cooling system will only refill to about 10 litres - not
the 18 litres it should take. I have run the engine with
the heater on and the header tank cap off but it didn’t make
much difference. I am suspecting a blockage / buildups in
the water jacket. Any advice, please?

Can I reverse flush by feeding water in the heater hose as I
know the water rail is clear and I really do not want to
take out thermostat as I only just put all that in. Any
recommended chemicals/products to put into cooling system to
try to soak / soften gunk in there before flushing.

Any value in trying to fill the system and then pressurize
it by screwing a compressor line into one of the sensor
fittings on the water rail (I assume not too much pressure
or the old head gasket and any other seals may get blown.)

I have never done a reverse flush on any car before.

Thanks

David

David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
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Jim Isbell
“If you are not living on the edge, well then,
you are just taking up too much space.”

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Have a look at the solution that worked well for my E Type:
http://forums.jag-lovers.org/av.php?633856l37

Craig

Dwomby wrote:>The cooling system will only refill to about 10 litres - not

the 18 litres it should take. I have run the engine with
the heater on and the header tank cap off but it didn’t make
much difference. I am suspecting a blockage / buildups in
the water jacket. Any advice, please?

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In reply to a message from Jim Isbell, W5JAI sent Sun 5 Apr 2009:

Jim (and others)

Sorry for not providing the full history. I have just
installed a rebuilt radiator, new thermostat (tested and
opens at 82C), rebuilt water pump, new hoses, new heater
valve. New gaskets on thermostat housings, water pump and
water rail (removed to get the thermostat housing apart).

So I don’t think it’s the radiator but I appreciate the
concern :slight_smile:

David–
The original message included these comments:

For Gods sake, pull that radiator and have it rodded and the tanks


David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
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It could be a buildup of minerals in the block. Did you check/replace
the fan clutch?

Craig

Dwomby wrote:>

Jim (and others)

Sorry for not providing the full history. I have just
installed a rebuilt radiator, new thermostat

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In reply to a message from Dwomby sent Sun 5 Apr 2009:

David

How bad is the overheating problem?

How warm does the radiator get?

Do you get hot air from the heater?

If you run the engine with the car pointing up hill and the cap
removed from the reservoir, does coolant get expelled, ever?–
The original message included these comments:

Sorry for not providing the full history. I have just
installed a rebuilt radiator, new thermostat (tested and
opens at 82C), rebuilt water pump, new hoses, new heater


al mclean '93 XJS 4.0 - '84 4.2 Daimler - '84 DD6
Telford, United Kingdom
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In reply to a message from Craig Talbot sent Sun 5 Apr 2009:

Craig

i tested the fan clutch and it seems OK. Stops spinning in
about half a turn when given a push by hand.

But, I can’t see how the fan would affect the amount of
coolant I can get into the system? That seems to me to
indicate a blockage somewhere in the coolant passages. I
read your post about the Kodak acid. May have to try
something like that.

David–
The original message included these comments:

It could be a buildup of minerals in the block. Did you check/replace
the fan clutch?


David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
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No, the fan wouldn’t affect the amount of coolant. When I did the flush
on the E Type after I drained the rad I was still able to get quite a
bit more coolant out of the block drain. With the waterpump in place the
block can’t drain much at all it seems.

It appears that XJ’s don’t have the drain tap that earlier cars do, but
I think it has a plug that will allow you to drain the block.

Craig

Dwomby wrote:>But, I can’t see how the fan would affect the amount of

coolant I can get into the system? That seems to me to
indicate a blockage somewhere in the coolant passages.

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In reply to a message from almcl sent Sun 5 Apr 2009:

Hello Al

The overheating is weird. According to the gauge it’s
getting too hot (way past ‘L’ in ‘normal’) unless the heater
is on. If heater is on, then it drops back to around ‘m’.
The radiator gets plenty hot (varies across it but about
65C) and the thermostat opens and the water rail shows ~85C
temperature using my infrared thermometer. Since the
temperature got higher at speed, I decided I would swap the
radiator for a rebuilt and all those other bits too as they
were probably overdue for replacement anyway. (BTW, I
discovered a 74C thermostat had been installed in the car).

I reassembled it yesterday and ran with water only in the
cooling system to test for leaks. There was NO difference
to the behaviour of the temperature gauge. I had just
decided it must be a gauge or grounding or voltage
stabilizer problem and refilled the car with coolant to try
out those electrical issues when I realised it wasn’t taking
more than about 10L and that the water I had just drained
out was only about 10L too. Hence the thought about blockage.

Haven’t time to run it facing up hill today but I did run it
for a while earlier on the level with the header cap off -
some gurgling but no overflowing although I did not check
what the temperature got to.

Getting a wee bit frustrating this one!

David–
The original message included these comments:

How bad is the overheating problem?
How warm does the radiator get?
Do you get hot air from the heater?
If you run the engine with the car pointing up hill and the cap
removed from the reservoir, does coolant get expelled, ever?


David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
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In reply to a message from Dwomby sent Sun 5 Apr 2009:

I’ve never manage to get all the water in even after doing a
pump simply because a lot of residual stays in the heater
etc. If you are getting 85c on the rail this is not abnormal
and so I would pull the temp sender from the rail and check
it out or just replace it.

there is a plug on the block near the bellhousing on the
exhaust side just by the dip stick and just below the line
of core plugs but to get 2 gallons of sediment !!

Check out the temp sender first.

Alex P

Alex P–
alex paterson
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In reply to a message from alex paterson sent Sun 5 Apr 2009:

When draining coolant, I just drained it through the plug in
the lower radiator pipe (a nice feature that apparently S3
models do not have).

Is it possible that the block is retaining coolant and that
is why I can only add 10L when I refill the coolant? Do I
need to open the drain plug on the cylinder block to get out
all 18L of coolant?

David W.–
David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
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Dwomby wrote:

The cooling system will only refill to about 10 litres - not
the 18 litres it should take. I have run the engine with
the heater on and the header tank cap off but it didn’t make
much difference. I am suspecting a blockage / buildups in
the water jacket. Any advice, please?

The only viable explanation is that 8 litres remained in the system,
Dave - there is no viable way the system will not fill properly…given
time…

As you have been doing some work like changing the radiator - which
principally should drain the system almost to the bottom, though the
full 18 liters is still unlikely to be drained off. Are you sure that
you have counted the refills properly. Ie, have you filled it in
forgotten instalments?

On another tack; are you soure that the vent lines are properly
connected and not obstructed? As yours is a 78 the cooling system may be
‘hybrid’ making precise advice dubious - but vent lines should go from
engine/radiator ‘high’ points to the expansion tank neck. As coolant is
filled air is forced out this way - preventing air pockets from forming.

Removing the header tank cap only will effect the same venting, of
course, but with a full system one would expect it to overflow as the
coolant heats up. Also, from cold; removing the temp gauge sensor aned
watch for overflow should similarely indicate that the system is full to
capacity - which should solve the ‘missing’ coolant mystery…:slight_smile:

Principally; after filling around half of the coolant the engine should
be idling with the heater ‘on’ while the rest of the coolant is added.
It’s not unusual that several cycles of heating/cooling is required
before the level stabilizes - though this doesn’t involve very large
amounts of coolant…

The level should be checked with the engine cold for consistency - and
left standing I cannot see anything preventing coolant from spreading
thoughout the coolant system given proper venting through the ventlines
installed. There are too many ways for coolant to enter the various
parts of the engine - I simply cannot conceive 8 liters of rust taking
the part of coolant…:slight_smile:

You can backflush through the heater hose at the end of the water rail,
but must of course also remove the lower radiator hose. This will
partially bypass the block - and ideally shod be donne withe the water
pump removed - but still…

As the system is nominally pressurized to some 15 psi this level should
be safe, but the merit of filling the system and flushing with
pressure…I don’t know if it is effective. The flush is more about
volume than pressure…

Frank
xj6 85 Sov Europe (UK/NZ)>Can I reverse flush by feeding water in the heater hose as I

know the water rail is clear and I really do not want to
take out thermostat as I only just put all that in. Any
recommended chemicals/products to put into cooling system to
try to soak / soften gunk in there before flushing.

Any value in trying to fill the system and then pressurize
it by screwing a compressor line into one of the sensor
fittings on the water rail (I assume not too much pressure
or the old head gasket and any other seals may get blown.)

I have never done a reverse flush on any car before.

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In reply to a message from Frank Andersen sent Mon 6 Apr 2009:

Indeed. 8 litres of corrosion deposits would fill the entire block -
possibly more. This appears inconceivable in an otherwise
moderately functional system.

One could imagine that if a thermostat without the pinhole were
used then filling would be laborious at best and incomplete at
worst. There can be somewhat simialr results if the pin hole is
present but not fitted at 12 o’clock. But several heating/cooling
cycles later things ought to have stabilised.

Frank–
The original message included these comments:

parts of the engine - I simply cannot conceive 8 liters of rust taking
the part of coolant…:slight_smile:


Frank Moore
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Dwomby wrote:

In reply to a message from almcl sent Sun 5 Apr 2009:

Hello Al

The overheating is weird. According to the gauge it’s
getting too hot (way past ‘L’ in ‘normal’) unless the heater
is on. If heater is on, then it drops back to around ‘m’.
The radiator gets plenty hot (varies across it but about
65C) and the thermostat opens and the water rail shows ~85C
temperature using my infrared thermometer. Since the
temperature got higher at speed, I decided I would swap the
radiator for a rebuilt and all those other bits too as they
were probably overdue for replacement anyway. (BTW, I
discovered a 74C thermostat had been installed in the car).

For comparisons with other gauges, David - the gauge needle straight up
assumes 90C, 1230 should be around 100C…so…?

The gauge should show rail temp as measured with the infrared at the
gauge temp transmitter - not all gauges are born alike. This should be
sort of calibration of the gauge, but can also be read at other temps as
the engine heats up for better comparisons…

It’s a bit difficult to get the infrared in the right positions for
pertinent readings. And the outer surfaces of various items may be
influenced by external temps in the engine bay/air flow - but it beats
other methods…

The top radiator hose should show thermostat opening or rail temps when
the engine is hot, as should the relevant part of the radiator. Which
should show an even drop-off in temps - while the lower hose should be
some 20 deg, or more, lower than the inlet hose. While this is
influenced by ambient temps the difference ‘in’ and ‘out’ indicates that
the radiator is cooling - ie; water is circulating through the radiator…

With the heater valve ‘open’ up to three circulation patterns may
emerge. >Water pump-engine block-water rail-heater core-water pump<.
With a cold cabin this may be sufficient for cooling the engine -
bearing in mind that a working AC will also cool the heater core. This
may be enough cooling to close the thermostat - at which state water
will also circulate; >water pump-engine block-water rail-thermostat
bypass-water pump<. Which will also will be ‘active’ with the thermostat
partially, but not fully, open. At which state the third pattern is
active; >water pump-engine block-water rail- thermostat-radiator-water
pump<…

The infrared is by far better to read the ‘true’ temps - the dash gauge
is simply not trustworthy in details unless verified…

If it is indeed overheating, by which we should mean that rail temps
significantly exceeds thermostat full open temps. Ideally temps should
never pass thermostat temps - thermostat fully open the system should
cool sufficiently. In fact; properly dimensioned the cooling system
should force the thermostat to an intermediate position to keep the
engine hot, leaving a ‘reserve’ of cooling capacity…alas…not that
much on the xk…

The questions still remains; too little coolant, or insufficient
circulation - or misreading instruments…?

Frank
xj6 85 Sov Europe (UK/NZ)>I reassembled it yesterday and ran with water only in the

cooling system to test for leaks. There was NO difference
to the behaviour of the temperature gauge. I had just
decided it must be a gauge or grounding or voltage
stabilizer problem and refilled the car with coolant to try
out those electrical issues when I realised it wasn’t taking
more than about 10L and that the water I had just drained
out was only about 10L too. Hence the thought about blockage.

Haven’t time to run it facing up hill today but I did run it
for a while earlier on the level with the header cap off -
some gurgling but no overflowing although I did not check
what the temperature got to.

Getting a wee bit frustrating this one!

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In reply to a message from Rickman74 sent Mon 6 Apr 2009:

I drilled a 1/8 inch hole in the new thermostat and definitely
fitted it at 12 o’clock position.

David–
The original message included these comments:

One could imagine that if a thermostat without the pinhole were
used then filling would be laborious at best and incomplete at
worst. There can be somewhat simialr results if the pin hole is
present but not fitted at 12 o’clock. But several heating/cooling
cycles later things ought to have stabilised.


David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
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In reply to a message from Frank Andersen sent Mon 6 Apr 2009:

Frank

I agree, 8 litres is way too much to be lost just to constricted or
blocked coolant passages but I am wondering if there is some point
that there is enough blockage to cause a big air pocket. To all
intents and purposes, the cooling system looks full when I have
only put 10 litres into it!!!

I definitely only put in less than 3 jugs of water/coolant
mixture. Each jug is labelled 1 US Gallon / 3.78 L. So that is
why I say around 10 litres went in. Also confirmed by measuring
the water that I drained out of the lower radiator pipe drain plug
which came to just over 2 of the above jugs.

I also know that the water rail was full because I pulled and
replaced the temperature sensor (for gauge, not the CTS) and it was
full to the brim.

The vent lines do run as you say from header tank to top of
radiator and expansion tank respectively. For what it is worth, I
noticed when engine was running and header tank cap was off that
coolant flowed from the top of the radiator line into the header
tank. I will check the line to expansion tank next weekend when I
get home.

I did not run engine long with header cap off, but although coolant
level came up maybe a 1/2 inch - it did not overflow.

I am away all week but should get a few hours to try things again
this weekend. I will run the engine longer with the header cap
off, re-exercise the heating system, try to raise the front end to
encourage ‘burping’. If that fails, I will get a flushing solution
and a flushing ‘T’ for the heater hose and maybe remove the block
drain plug too and hope for the best.

Until this ‘is it full of coolant or not’ issue is resolved, I will
leave alone the ‘why does the gauge read so high / is it really
overheating or not’ issue. One thing at a time - right?

David–
The original message included these comments:

full 18 liters is still unlikely to be drained off. Are you sure that
you have counted the refills properly. Ie, have you filled it in
forgotten instalments?
On another tack; are you soure that the vent lines are properly
connected and not obstructed? As yours is a 78 the cooling system may be
parts of the engine - I simply cannot conceive 8 liters of rust taking
the part of coolant…:slight_smile:
You can backflush through the heater hose at the end of the water rail,


David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
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In reply to a message from Dwomby sent Mon 6 Apr 2009:

David

From that snippet, I get the impression it wasn’t a Jaguar
thermostat but an equivalent? Are you absolutely confident that it
is, in fact, a direct replacement - the absence of the jiggle pin
makes me doubt this. It needn’t be ‘genuine Jaguar’ but it does
need to be correct length, shape and functionality.

http://tinyurl.com/cs97wh--
The original message included these comments:

I drilled a 1/8 inch hole in the new thermostat and definitely
fitted it at 12 o’clock position.


al mclean '93 XJS 4.0 - '84 4.2 Daimler - '84 DD6
Telford, United Kingdom
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Dwomby wrote:

In reply to a message from Frank Andersen sent Mon 6 Apr 2009:

Frank

I agree, 8 litres is way too much to be lost just to constricted or
blocked coolant passages but I am wondering if there is some point
that there is enough blockage to cause a big air pocket. To all
intents and purposes, the cooling system looks full when I have
only put 10 litres into it!!!

An eight liter air pocket defies credibility, David - and even deducting
coolant remaining after draining a large air pocket cannot be sustained.
As air is lighter than water it will be forced upwards and there are
simply to many ways of the air escaping to be trapped over time…:slight_smile:

I definitely only put in less than 3 jugs of water/coolant
mixture. Each jug is labelled 1 US Gallon / 3.78 L. So that is
why I say around 10 litres went in. Also confirmed by measuring
the water that I drained out of the lower radiator pipe drain plug
which came to just over 2 of the above jugs.

Water will be retained in the engine unless caps are removed to allow
air to enter. Any further loss due to parts removal…?

I also know that the water rail was full because I pulled and
replaced the temperature sensor (for gauge, not the CTS) and it was
full to the brim.

Which, if the engine is left standing indicates that the system is
indeed full - however strange…:slight_smile:

The vent lines do run as you say from header tank to top of
radiator and expansion tank respectively. For what it is worth, I
noticed when engine was running and header tank cap was off that
coolant flowed from the top of the radiator line into the header
tank. I will check the line to expansion tank next weekend when I
get home.

However the system is filled; it fills up from the bottom and up,
forcing air out through the various passages. Filling at the header or
expansion tank coolant flows ‘backwards’ through the pump and up the
radiator - air there being vented through the vent hose to the expansion
tank. While block air escapes via the water passages in the head into
the rails either though the header tank opening or vent hose there.
Other air back through the heater core via the open heater valve to the
rail. And water rail is vented through the vent hose at the header tank
to the top of the radiator and to the expansion tank. There is no place
for air to be trapped for any length of time…gravity wins…:slight_smile:

I did not run engine long with header cap off, but although coolant
level came up maybe a 1/2 inch - it did not overflow.

Nominally the coolant volume varies by around 1 1/2 pint between cold
and hot. Completely filled up this amount is forced out of the system on
the first heat cycle. So when the coolant again ‘shrink’ as it cools an
air pocket is left on top of the remaining coolant. To be compressed to
the normal system pressure as the coolant again expands - in this phase,
and during further cycling of the engine, the ventlines transfer coolant
and air internally, nothing is vented outside…

Thoughout the filling the thermostat remains closed, but as you can see
there is ample venting either side. The ‘jiggle pin’ hole allows
crossflow and ballances coolant distribution during normal cycling, but
another intent is to ensure that hot water rail coolant can ‘wash over’
the thermostat ensuring that it get the right idea about rail temps…

I am away all week but should get a few hours to try things again
this weekend. I will run the engine longer with the header cap
off, re-exercise the heating system, try to raise the front end to
encourage ‘burping’. If that fails, I will get a flushing solution
and a flushing ‘T’ for the heater hose and maybe remove the block
drain plug too and hope for the best.

Until this ‘is it full of coolant or not’ issue is resolved, I will
leave alone the ‘why does the gauge read so high / is it really
overheating or not’ issue. One thing at a time - right?

Right you are, David - the main point is not to be stuck with a fixed
idea of what is the fault…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)>The original message included these comments:

full 18 liters is still unlikely to be drained off. Are you sure that
you have counted the refills properly. Ie, have you filled it in
forgotten instalments?
On another tack; are you soure that the vent lines are properly
connected and not obstructed? As yours is a 78 the cooling system may be
parts of the engine - I simply cannot conceive 8 liters of rust taking
the part of coolant…:slight_smile:
You can backflush through the heater hose at the end of the water rail,

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The archives and FAQ will answer many queries on the XJ series…
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In reply to a message from almcl sent Mon 6 Apr 2009:

Admittedly it had no hole/jiggle pin but this is what I ordered and
it certainly looked like this:

http://www.motorcarsltd.com/item.wws?
sku=IN102507&mfr=BRITISH&cookieID=1928550112MG0EF8XM&drillid=12&clie
ntid=motorcarsltd.com&clientid=motorcarsltd.com

David–
The original message included these comments:

From that snippet, I get the impression it wasn’t a Jaguar
thermostat but an equivalent? Are you absolutely confident that it
is, in fact, a direct replacement - the absence of the jiggle pin


David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

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In reply to a message from Frank Andersen sent Tue 7 Apr 2009:

Thanks, as always, for the thoughts and suggestions, Frank. I’ll
let you know what I find when I get back to the car.

David–
The original message included these comments:

Right you are, David - the main point is not to be stuck with a fixed
idea of what is the fault…:slight_smile:


David Womby 78 XJ6L 5speed
Mount Dora, Florida, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

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