[xj] Overheating SII

Hi guys-
I have finished the resurection on the ‘‘old kitty’’(74 XJ6L),
new paint, detailed engine, tuned, cleaned, and generally made it
as new as possible. However, test driving it prior to delivering
it back to my brother-in-law in North Carolina, it very quickly
pegs the temp gauge at ‘‘hot’’. Have done the following:

  1. balanced carbs (way off-got rid of miss)
  2. set timing at 0 deg
  3. checked vac and centrifugal advance
  4. checked thermostatic overheat protection valve
  5. new 160 deg thermostat
  6. flushed cooling system twice
  7. high pressure washed the radiator fins
  8. checked waterpump belt
  9. adjusted shiftdown cable and front trans band
    All of this did nothing to cure my overheat problem. I thought it
    might be the fan clutch but at 70 mph on the interstate, still no
    cooling. Now I’m thinking plugged cats(how do I check 'em)? or
    blown head gasket(tell me it ain’t so). After refilling the
    cooling system I do see large bubbles occasionally which I thought
    were the system gulping and expelling trapped air. I also see
    occasional ‘‘spritzes’’ of small bubbles which worry me a little bit
    more than somewhat.
    Temperature outside today is 93 deg F. Surely I don’t need to
    leave it parked because it’s hot out?
    Otherwise, it purrs like the kitten it is, runs 65 lbs. oil
    pressure and has 160 psi compression plus or minus a couple in
    every cyl (last time I checked 150 miles ago). Should I recheck
    compression now looking for blown gasket? At this moment it’s
    sitting in the shop puking water on the floor and is too hot to
    touch. Any and all help, condolences, encouragement, and advice
    will be greatly appreciated. I need to get this finished so I can
    start restoration of the vette.
    Thanks in advance!!
    Larry–
    Larry Skinner 74XJ6L 2000VDP 75VETTE RDSTR 78FERRARI308GTS
    –Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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In reply to a message from Larry Skinner sent Wed 26 May 2004:

Hello Larry!
I would replace the fan clutch anyway, and if you never had
the radiator out and given it to a radiator shop to really
core it out good, I would do that. Worked wonders for me,
now the gauge stays on the cool side all the time.
Does that timing of 0 deg. called out in your book?
Walter–
The original message included these comments:

  1. set timing at 0 deg
  2. flushed cooling system twice


69E / 78XJ6 / 73 VW Ghia
albuquerque/new mexico, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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In reply to a message from W. Schuster sent Thu 27 May 2004:

Hi Walter-
Yes, my Haynes manual says to set the timing at 0 deg at 650 RPM
with vacumn advance disconnected on 4.2 L North American engines.
The car has 43,000 miles on it and I have no way of knowing if the
radiator has ever been out or not. Does the bonnet have to come
off to remove it? Even at that, it looks like less hassle than
head gasket replacement but I have a hunch I will end up doing both.
I’ve read info in the archives on head removal until I’m bleary eyed
and not looking forward to it at all:(
Thanks for the reply!
Ya’ll Enjoy
Larry–
The original message included these comments:

I would replace the fan clutch anyway, and if you never had
the radiator out and given it to a radiator shop to really
core it out good, I would do that. Worked wonders for me,
Does that timing of 0 deg. called out in your book?


Larry Skinner 74XJ6L 2000VDP 75VETTE RDSTR 78FERRARI308GTS
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

===================================================
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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Larry Skinner wrote:

Hi guys-
I have finished the resurection on the ‘‘old kitty’’(74 XJ6L),
new paint, detailed engine, tuned, cleaned, and generally made it
as new as possible. However, test driving it prior to delivering
it back to my brother-in-law in North Carolina, it very quickly
pegs the temp gauge at ‘‘hot’’. Have done the following:

  1. balanced carbs (way off-got rid of miss)

  2. set timing at 0 deg

  3. checked vac and centrifugal advance

  4. checked thermostatic overheat protection valve

  5. new 160 deg thermostat

  6. flushed cooling system twice

  7. high pressure washed the radiator fins

  8. checked waterpump belt

  9. adjusted shiftdown cable and front trans band
    All of this did nothing to cure my overheat problem. I thought it
    might be the fan clutch but at 70 mph on the interstate, still no
    cooling. Now I’m thinking plugged cats(how do I check 'em)? or
    blown head gasket(tell me it ain’t so). After refilling the
    cooling system I do see large bubbles occasionally which I thought
    were the system gulping and expelling trapped air. I also see
    occasional ‘‘spritzes’’ of small bubbles which worry me a little bit
    more than somewhat.
    Temperature outside today is 93 deg F. Surely I don’t need to
    leave it parked because it’s hot out?
    Otherwise, it purrs like the kitten it is, runs 65 lbs. oil
    pressure and has 160 psi compression plus or minus a couple in
    every cyl (last time I checked 150 miles ago). Should I recheck
    compression now looking for blown gasket? At this moment it’s
    sitting in the shop puking water on the floor and is too hot to
    touch. Any and all help, condolences, encouragement, and advice
    will be greatly appreciated. I need to get this finished so I can
    start restoration of the vette.

But Larry, whatever that book says; my books say normal static ign
setting is 8 deg BTDC. Retarded ignition will certainly cause
overheating, and I have some difficulties accepting a prescribed
ignition setting at TDC with the engine ticking over. It’s certainly
unusual or a misprint for 10…? :slight_smile:

Of course there are other avilable causes as well, like a clogged
radiator or restricted exhaust etc etc, but you should certainly set ign
to static 8 deg…

Furthermore; if you top up the coolant, the system will automatically
eject excess to a suitable level, repeating the process as long as you
keep on refilling. It is, unfortunately not, the only way an engine will
spill coolant, though, but…
And as for the fan clutch; at speed the fan is basically redundant,
airflow alone is usually enough - which is one reason why some prefer
electric fans…

Another point; if you are constantly getting 65 psi oil pressure, hot
and cold - and even under overheating - the system is running at
pressure valve relief pressure. And you don’t even know if the engine is
receiving any lubrication. If you plug the oil outlet after the filter
you will still read 65 psi…

Apart from the plain overheating problem I think you should try thinner
oil to get a readable pressure…

Frankj
xj6 85 Sov Europe (UK/NZ)===================================================
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Larry, I timed our SII at 14 deg advance at 750 rpm with all hoses connected.
0 sounds a bit too retarded. Try advancing to at least 10deg.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

Larry Skinner wrote:

In reply to a message from W. Schuster sent Thu 27 May 2004:

Hi Walter-
Yes, my Haynes manual says to set the timing at 0 deg at 650 RPM
with vacumn advance disconnected on 4.2 L North American engines.
The car has 43,000 miles on it and I have no way of knowing if the
radiator has ever been out or not. Does the bonnet have to come
off to remove it? Even at that, it looks like less hassle than
head gasket replacement but I have a hunch I will end up doing both.
I’ve read info in the archives on head removal until I’m bleary eyed
and not looking forward to it at all:(

===================================================
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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Larry:

Yes, I would remove the bonnet (hood) to remove the radiator. I imagine you
can do the job with it in place, but your back and fingers will thank you if
you do. It’s a two person job and I would mark the area around the hinge so
you can put it back in the same place. Also, think ahead on where you can
safely store it.

When reinstalling the radiator, be certain to place the foam insulation
around to seal between the radiator and body (at least my S-1 had that).

Regards
Lou----- Original Message -----
From: “Larry Skinner” leskinner@msn.com
Subject: Re: [xj] Overheating SII

The car has 43,000 miles on it and I have no way of knowing if the
radiator has ever been out or not. Does the bonnet have to come
off to remove it?

===================================================
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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