I posted a few weeks ago about some issues with my recently
purchased XJS already lumped with a '95 LT1/4L60E, running pretty
good for $2500. Well, I’ve made some progress…
My ‘tested good’ t-stat wasn’t as it turned out, so a new
replacement fixed the no circulation problem. The only PITA is
trying to get all the air purged out of the system; the t-stat
housing is the highest point in the cooling system. This design
seems to be EXTREMELY sensitive to air in it; any air at all, and
the water pump seems to ‘vapor lock’, also killing any heat from
the heater. Not so sure I like this design. After all the work,
I’ve diluted the antifreeze to where I need to drain/refill.
Bummer…
And my heater problems seem to be at least semi-related. After
getting coolant moving correctly, I got the heater to at least work
intermittantly. There seems to be an electrical issue also as
during testing, something was giving out an electronic ‘whine’ (I
don’t know how else to describe this) under/behind the
dash/console. Now, if this gave voice, the heater didn’t work, but
if it didn’t, that still didn’t mean the heater would work. I can’t
tell where this is coming from, as it’s one of those non-
directional type sounds. Anybody ever run into this? Good news, it
doesn’t look like I have to pull the whole dash, just the console
to get to the electrical.
And as a side note, this car was rather ‘cosmetically challenged’
with it’s oxidized/weather-checked/faded paint (probably the main
reason for the low price). It appears to have been repainted with
the original ‘Sebring Red’ color, but the top/trunk/hood were more
orange than red. Well, while waiting for some manuals to get here,
I went after the paint (in between the rain deluges) to see if
anything could be done. After buying a 7’’ buffer and expending 2
1/2 cans of rubbing compound, it’s now pretty much red again.
Besides the cracks/checking, most of the problem was yellowed clear
coat. It looks better; now instead of having obviously bad paint,
you can’t really tell until you get within 10 ft… so it’s all
good, LOL! Cancel that trip to Maaco!–
Why?
Yelm Washington, United States
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In reply to a message from Why? sent Mon 20 Apr 2009:
‘‘the t-stat housing is the highest point in the cooling system.’’
No, it isn’t. Unless you have altered the system, the two
hoses/pipes at the front of the engine to the right of the throttle
body both have bleed ports. You need to bleed the air out from
these first while filling, and then with the engine running.–
lockheed
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In reply to a message from lockheed sent Mon 20 Apr 2009:
On this car, the t-stat housing IS the highest place to add coolant.
This swap was done (not by me) with a John’s Cars kit. It has the
heavy-duty 4-row radiator, but this unfortunately has no filler
neck on it. There’s one rad cap/fitting spliced into the driver’s
side hose, but it’s about 1’’ lower than the t-stat. My other choice
for filling is the original V-12 surge tank, which has been plumbed
into the fitting for the ‘main’ cap (twice), and also has a
pressure cap on it. This fill point is about the same level as the
stat housing.
Now, the inline fitting is done strangely; this cap/fitting uses a
newer style cap with the pressure seal and also has the neck seal.
On a ‘normal’ install, the neck seal would divert any overflow into
the surge tank, and when the car cooled it would draw the coolant
back out. But this fitting also has a tube out the bottom of it
that ALSO goes the surge tank, so the result is the cap is
pressurized from both sides. Sumpin’ ain’t right, now that I look
at it…
And the only ‘bleed point’ is the t-stat housing; any fittings on
any hoses are long gone, as this has standard heater hoses on it.
Now, this is a Corvette water pump, which is slightly different
than the F-body variety, but I don’t know if the 'Vette had a
fitting on that hose or not.
At some point this must have worked, but maybe it was always a PITA
to fill.–
The original message included these comments:
No, it isn’t. Unless you have altered the system, the two
hoses/pipes at the front of the engine to the right of the throttle
body both have bleed ports. You need to bleed the air out from
In reply to a message from Why? sent Mon 20 Apr 2009:
Why:
My XJ6 has an LT1 installation with a John’s kit by me. True, no
filler cap on the 4 row heavy duty brass radiator. I am not
enamored with the inline filler cap on the driver’s side hose.
Now, there is a bleed valve on the thermostat housing of my car.
The XJ plastic surge tank was not used. I sold it!!
My ‘‘overflow’’ is to the XJ tank behind the driver’s side outboard
head lamp.
I had no trouble filling this reverse flow system. It cools nicely,
and the heater will cook me, if called on!!
So, is it the bleed on the t’stat housing that is causing the
problem? I am not sure you have one?
Carl–
The original message included these comments:
On this car, the t-stat housing IS the highest place to add coolant.
This swap was done (not by me) with a John’s Cars kit. It has the
heavy-duty 4-row radiator, but this unfortunately has no filler
neck on it. There’s one rad cap/fitting spliced into the driver’s
side hose, but it’s about 1’’ lower than the t-stat. My other choice
for filling is the original V-12 surge tank, which has been plumbed
into the fitting for the ‘main’ cap (twice), and also has a
pressure cap on it. This fill point is about the same level as the
stat housing.
Now, the inline fitting is done strangely; this cap/fitting uses a
newer style cap with the pressure seal and also has the neck seal.
In reply to a message from Why? sent Mon 20 Apr 2009:
OK,
So, you are saying you don’t have the heater hose with the aluminum
section with the bleeder on the top to the right of the throttle
body just forward of the left side of the alternator? How about
the bleeder on the top of the radiator hose connection just below
the lower right side of the throttle body??–
lockheed
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In reply to a message from lockheed sent Tue 21 Apr 2009:
I have the bleed on the t-stat housing, that’s it. The bleed on the
factory heater hose is MIA, although I don’t know if the Corvette
even had that. That hose connection is different from the F-
body/Caprice/Impala pump.
With the fill point below the ‘top’ of the system, getting the damn
thing bled is a PITA. Open the cap to add water while bleeding, and
water comes OUT… not good. I tried ‘forcing’ water in via the
surge tank and by using my cooling system tester, with limited
success.
I’ve decided I’m going to redo the filler, putting another inline
fill point right near the t-stat, only up above the highest point.
The existing one I’ll leave as the pressure relief/connection to
the siphon (surge) tank. There’s room to do this right behind the
power steering pump. I’ll then convert the factory surge tank to
non-pressurized (plugging one of the hose connections) make-up
siphon use.
Once I do all this, gravity will do the bleeding for me.–
The original message included these comments:
So, you are saying you don’t have the heater hose with the aluminum
section with the bleeder on the top to the right of the throttle
body just forward of the left side of the alternator? How about
the bleeder on the top of the radiator hose connection just below
the lower right side of the throttle body??
In reply to a message from Why? sent Tue 21 Apr 2009:
Hey ‘‘Why?,’’
I had a terrible experience with the John’s Car kit when it
came to the cooling system on my 1987 XJS.
Without any good reason, the kit creates a Frankenstein
cooling system with that remote radiator neck and a separate
electronic control box with a whole slew of wires and hoses
in-between.
After the system failed on me twice, not to mention also
having multiple problems with leaks at that remote radiator
neck, I got fed up and junked the entire John’s Car cooling
setup.
It didn’t help matters that the folks at John’s Cars refused
to allow me to buy any individual parts from them to help
fix their monstrous creation. They insisted only on selling
me their entire kits.
Instead, I simply mated up the engine with the same radiator
that came with the LT1 in the 1995 Camaro donor car. As it
was intended by Chevy, the LT1 computer now controls my
cooling system directly.
It all fit well into the XJS with only minor cutting. The
result was a trouble-free cooling system controlled directly
by the LT1 computer with a lot less junctions and connectors
and less potential for leaks or filling problems.
Scotty said it the best when it comes to describing the
John’s Car cooling system:
In reply to a message from Neil24 sent Wed 22 Apr 2009:
Neil24:
What electonic box to control what in the cooling?
I am not enamored with the filler in line with the driver side
radiator hose. but, it works!!
my heater hoses come from the Jaguar heater to the GM pump direct.
Well, I did install a manual valve so that with the vacum valve and
it, I can isolate the heater matrix and as such get power
ventilation w/o the AC. the latter is not yet operational!!
My GM PCM contols the fans just fine with the after market harness,
not by John!
Carl–
The original message included these comments:
Without any good reason, the kit creates a Frankenstein
cooling system with that remote radiator neck and a separate
electronic control box with a whole slew of wires and hoses
in-between.
In reply to a message from Neil24 sent Wed 22 Apr 2009:
So this mess I’ve got may be ‘by design’? LOL
I’d already been warned about Johns ‘fees’, so it’s not likely
he’ll ever hear from me, or get my future business. I will say
Andrew has been very helpful when I’ve called, even with off-the-
wall questions.
I know I’m smarter than that car…–
The original message included these comments:
I had a terrible experience with the John’s Car kit when it
came to the cooling system on my 1987 XJS.
In reply to a message from Why? sent Wed 22 Apr 2009:
Carl,
You must have been lucky enough to have a different setup.
My conversion came with an electronic black box that
controlled the radiator fans. That box failed on me (mainly
due to a poor electrical connection).
If you’ve got yours setup through the LT1 PCM, then you’re a
smart and lucky man!
As for the remote filler neck, I never had problems filling
it up either. But it was made out of a very weak material.
After having so many problems with the cooling system, I was
constantly unscrewing the thermostat to check the fill
level. That’s a difficult task already because the remote
filler neck is free-floating and only supported by the
radiator hoses. Eventually the rim on the filler neck
warped and began to crack, so it leaked. John’s car would
not sell me a replacement. When that happened, I could not
find a direct replacement ANYWHERE.
So Carl, hard lesson learned. Be VERY careful with that
remote filler neck.
‘‘Why?,’’ Andrew’s a good guy and he’s only a mile or so away
from me. I switched my cooling system to the stock Camaro
system based on his advice, and I’m very thankful. He has
pictures on his website where he shows how to install a
stock Camaro cooling system into an XJS.–
Neil- 1987 Jaguar XJS
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In reply to a message from Neil24 sent Wed 22 Apr 2009:
My conversion has a similar cooling system, filler in the top
radiator hose etc, brass radiator. LT1 conversion and parts done
by??? But, I do have the drain screw in the T stat housing that
works well.
I am getting ready to change it all over to the stock GM suff and
it is just a matter of finding the time. I will be getting rid of
all that stuff - plus the 90 degree chrome intake elbow and K&N
filter that is inside the engine compartment. I am going to the
cool air/K&N air cleaner setup by Bob Loftus that brings in cooler
outside air directly into the throttle body.
Per Andrew, and my past conversion redos, I believe that using as
much of the stock GM stuff as is possible, is cheaper and as easy
and in the long run - much easier to find replacement parts. I will
be using the stock dual GM fans with the shroud that has the flaps
and it will all be controlled by the GM PCM to turn on the fans.
All the AC stuff will be stock GM stuff, it all works well together
and GM has figured out all the problems, why change that now?
Plus, the GM manual tells how to do everything pretty clearly. GM,
has made more cars, than have been converted by all of the other
conversion companies together.–
The original message included these comments:
level. That’s a difficult task already because the remote
filler neck is free-floating and only supported by the
‘‘Why?,’’ Andrew’s a good guy and he’s only a mile or so away
from me. I switched my cooling system to the stock Camaro
system based on his advice, and I’m very thankful. He has
pictures on his website where he shows how to install a
stock Camaro cooling system into an XJS.
In reply to a message from Roger Mabry sent Thu 23 Apr 2009:
Neil:
That filler neck in the hose is a Moroso product. I’ve seen it ion
a catalog somewhere.
The GM manual will ID the pin out put to fan 1 and 2. Green for
one and blue for the other, as I recall. Uses those to trigger a
relay for each fan. At least that’s my set up. A single fan set up
is probably similar in that the PCm will have a trigger pin for the
relay.
Andrew nd Bob Loftus helped me a lot as well.
Were I to do it again, I would do some things diferent. I like th
idea of using as much of the GM as possible. But, since I will be
80 in September and my shoulders are getting worse, it isn’t
likely. Now, I just enjoy it.
Still reading on aluminum v copper/brass radaitors. Good article in
this month’s HOt Rod.
Carl–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
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In reply to a message from cadjag sent Thu 23 Apr 2009:
Hi Carl,
It’s good thing you have your fans setup that way. It really
is the best way to go.
As for the Moroso filler neck, been there, done that. I
thought it was the same too, until I ordered it and realized
that it wasn’t. It didn’t have a third junction for the
return line. I tried to create a third one with miserable
results. The piece made by Moroso is aluminum, not brass, so
I couldn’t do a DIY weld unless I had the proper welding
equipment.
The brass filler neck is a John’s car part made especially
for their conversion kit and the bastards wouldn’t tell me
how to get a replacement one. So, again, be very careful
with it!–
Neil- 1987 Jaguar XJS
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In reply to a message from cadjag sent Thu 23 Apr 2009:
The Johns filler neck IS NOT a Moroso product (or any other I could
find, and I looked) but is something he apparently has built
for ‘his’ applications. Or at least the one I have is oddball; it’s
not a ‘homemade’ item.
The one on mine has TWO small hose connections, not just one like
all the available ones I saw. It has the normal overflow pipe barb
(such as you will find on any standard radiator and all the
aftermarket inline cap fillers) that is only in use when the cap
vents, but also has another connection opposite the cap opening
which is pressurized with the rest of the system. This barb is open
to the cooling system.
That’s part of my problem; both of these connections are hooked to
the original surge tank, which also has a pressure cap on it.
Because of the open connection into the filler neck, the tank has
to have a pressure cap to pressurize the system, but it also puts
the same pressure on the secondary radiator cap gasket. This gasket
in it’s intended design is only required to seal enough to prevent
leaks around it while it vents into a unsealed reservior when the
coolant expands and to maintain a seal to allow the system to suck
coolant back into the system when it cools to keep it full. But
here, it sees the full cooling system pressure and LEAKS at less
than the cap rating. Not good. So even if I could manage to get the
system full with the too-low fill point, I’ll lose coolant anyway.
I know what I need to do to fix it… just have to get the bits
and put it together–
The original message included these comments:
That filler neck in the hose is a Moroso product. I’ve seen it ion
a catalog somewhere.
In reply to a message from Why? sent Thu 23 Apr 2009:
Hey ‘‘Why?’’
I think we both posted at nearly the same time regarding the
Moroso product (see above).
You have perfectly described one of the problems I had
encountered with my old John’s Car setup. Because of that
setup and the pressure differential, I often would find that
the surge tank would fill up completely and then overspill
the coolant onto the ground after I drove the car for a
while and parked. That’s why I found myself constantly
having to add coolant to the system.
I didn’t understand why that was happening until your last
post. Bravo for figuring that out!
It just proves how vulnerable that Frankenstein setup is.
Here’s Andrew’s description of how he put in the stock GM
radiator system on one of his Lumped XJS-LT1s:
In reply to a message from Neil24 sent Thu 23 Apr 2009:
HM,
Perhaps I am halucinating about the inline filler thing. I still
recall a pic of one that appeared to be brass in some catalog.
But, if all that is missing in the aluminum version is a spigot,
there are two possibles. First, eliminate the flue of coolant into
the throttle body. Then, you don’t need that extra spigot as a dump.
Second, drill and tap for a bsrb or have it tg’d in.
As to it making the inlet of the radiator vulnerable. plce it very
close to the neck and reduce the levered load on it.
As I recall, my Achieva had no filler on th radiator tank. It was
replaced at the resevoir. Although my Jeep has a cap on a tank, I
rarely open it and check level at the resevoir and top off there if
required, which is very rare.
But, I lean to the GM replication, it looks neat and is very well
tested.
Carl–
Carl Hutchins 1983 Jaguar XJ6 with LT1 and 1994 Jeep Grand
Walnut Creek, California, United States
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