[Lumps!] engine overheating

The 350 in my 76 XJ6 is overheating. It pegs the temp
gauge after about 4-5 miles. Here’s what I’ve tried
already: New thermostat, new water pump, rebuilt
heads/new head gaskets, letting it sit fer 2 months
while I cool off. Any ideas besides only driving it
3 miles?

Travis__________________________________________________
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Have you tried checking the radiator? How’s your fan/fan clutch?
Installing electric fans? Are your hoses collapsing from the
pressure/suction?

Most likely I’d say the rad and fan/fan clutch need replacement. Also
maybe your water pump isn’t working.–
-Ted
'82 XJ-S – 5.3L V12 '98 Volvo S70 GLT – 2.4L I5 Turbo
'93 GMC Vandura 2500 – 4.3L V6
New York City, NY AIM: FordCrusherGT Yahoo: Jag_Pushrod
Displaced in Terre Haute, IN for college!!

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Overheating?

What do you know about the condition of the radiator,
and what is it (3 row, 4 row brass, or???) I’d take a
look there. Usually though, the overheating takes
longer than just 3-4 miles. On the waterpump, what did
you put in?? There are generic Chevy V8 water pumps
that use a very cheap folded sheet metal impeller that
allows coolant to cavitate out the back side. Flow
Cooler (they adevertise in the hot rod magazines) make
a simple rivet on disc that supposed to cure this
problem, increase flow, and as a result, lower coolant
temps. As a matter of fact, all of the high flow and
truck pumps use a different impeller that is cast and
has a closed in back…

I will assume your AC condensor is not clogged with
road debris, etc.,… and limiting air flow…

Have you done a compression check- are they all up
and even?? You should also have a shop do a coolant
analysis- this is a test that looks for exhaust gases
in the collant (from a cracked head or block, or blown
head gasket). I’m assuming the heads checked out ok
when they were rebuilt??

You may want to also be concious of how you fill up
the coolant. There should be some sort of escape path
for air on the block as you fill it- usually the
thermostats have a small hole drilled in them to do
this (and allow some small amount of coolant to pass
so they will open when warmed). Sowthimes I even leave
a top hose connection loose or off to be sure the
coolant comes up that high (both radiator and engine.
If you have an air pocket trapped, that won’t help
pumping coolant at all… A good Jag cooling system
should probably take 3-4 gallons of coolant/water mix.
How much did yours take???

I had similar problems on a 76 XJ12 I ran some years
ago. It would only stay cool with a big crank driven
fan and a tight clutch. And that was with a 4- row
brass Corvette-style radiator. Flash forward a few
years and my 87 VDP (basically the same car) runs very
cool with the Camaro plastic/alum (1 row) radiator, a
17" OE Corvette electric fan, and one of my custom ABS
fan shrouds. Go figure…=====
Andrew Weinberg,
89 XJS convert-TPI 350; GR82B8
87 VDP-TPI 305; IHADAV8
67 XKE-302 GT; URT-007
Searching for an XJS-C


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The 350 in my 76 XJ6 is overheating. It pegs the temp
gauge after about 4-5 miles. Here’s what I’ve tried
already: New thermostat, new water pump, rebuilt
heads/new head gaskets, letting it sit fer 2 months
while I cool off. Any ideas besides only driving it
3 miles?

Travis

Radiator large enough in capacity, not clogged? How about airflow across
radiator, i.e., clutch fan (if applicable) working properly, fan shroud on
radiator (engine driven fan), electric fan(s) moving enough air?

These are basic ideas for further checking, my bet is on the radiator…

Colleen
79 XJ-S enhanced with TPI 350/T700 (running cool, especially with the fall
weather)

// list policy dictates that messages be trimmed----- Original Message -----
From: “lakookarancha” lakookarancha@yahoo.com
To: “jag lumps” lumps@jag-lovers.org
Sent: Sunday, October 13, 2002 3:00 PM
Subject: [Lumps!] engine overheating

Thanks to all who so promptly replied.
Here’s some more info on my problem: The engine
overheated on my wife on the way to the grocery store
2 1/2 months ago. This had not happened before. The
temp gauge always stayed at the same spot when warm
(the “M” of normal). The needle pegged the far right
of the gauge, steam, antifreeze on the road, etc… My
first thought was stuck thermostat, I took it out
(didn’t help). O.K. it’s the water pump, new water
pump (didn’t help). It’s obviously a blown head
gasket or cracked head then, besides I happened to
have some rebuilt heads and a new set of head gaskets
in the garage (didn’t help). I looked at and felt the
three or four cylinders walls that were exposed when I
took the heads off (no visible cracks). The block
supposedly had about six thousand miles on it and
looked clean with crosshatching visible. No oil in the
water, or water in the oil.
Today, after reading your replies, I traded fan
clutches with my suburban (the suburban fan clutch was
wore out, the fan would continue spinning 5-7 seconds
after engine was turned off) this should make the
overheating worse, and opened the manual heater hose
shut off (the stock vacuum controlled valve was
bypassed at conversion) I then drove the car apprx. 15
miles with only slight overheating (the needle stayed
on the “L” of normal. The heater was blowing hot, all
hoses were hot, but no steam. Was there air in the
system or did the heater core help that much? I was
afraid to drive it further tonight to see if it would
get hotter, but it obviously was better than before. I
now have hope. Any other suggestions are appreciated.

Travis=====
The Head Kook


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Hi Travis,
If it overheats after 4-5 miles I would guess something maybe wasn’t
installed correctly. I don’t think that most cars would get hot enough
to pop the thermostat after only 4-5 miles (unless its really hot out). On
my lump I suspect that the temp gauge is not really reading the true
temp. Buy a candy thermometer and stick it in the rad to check the temp. I
would pop off the rad cap stick the thermometer in there and start
the car and watch the temp. Do you see the obvious signs of fluid flowing?
Did you put your thermostat in backwards?
Daniel Neuman

The 350 in my 76 XJ6 is overheating. It pegs the temp
gauge after about 4-5 miles. Here’s what I’ve tried
already: New thermostat, new water pump, rebuilt
heads/new head gaskets, letting it sit fer 2 months
while I cool off. Any ideas besides only driving it
3 miles?

Travis

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Sizzle…sizzle…
Ditto on the radiator, Tedski! remember when I went about a year with a pin
hole in my original Camero 2 row. It had been fine for about 8months after
I’d put my '77 XJ-6L together, But soon even after realizing that I had
developed a nasty air bubble up at the highest point of where my upper hose
left the tank and coupled to the Moroso filler cap connector sleeve. If this
part is actually higher than any other part of your water circulation system
then you develop a air bubble which will cause the water in your cooling
system to overheat muprior to it even reaching the thermostsat. Also I
developed a small pin hole high pressure leak that really caused me a lot of
overheating problems simply because the water in the radiator would
litterally “peee” itself dry. But I solved all that when I bought and
installed the aluminum 4-row radiator! I also went for a brand new Hayden H-D
clutch fan. In my opionion the fan & the shroud (1975 Ford Granada) that
encases it are also very important! Because of the size of the engine and the
space under the bonnet you have to really work hard to keep the ambient
tempeture down to something thats normal…Good Luck! Hopefully your Jaguar
can stay as cool as it looks! It should never go higher than the “M” in
Normal, if it does you’ve got yourself some major problems,

Albert Escalante
1978 MGB;1977 Jaguar XJ6-Lump
Central Coast British Car Club (Ca.)

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In reply to a message from Aeseeyou@aol.com sent Tue 15 Oct 2002:

I am very sensitive to overheating!!

That is why my Jag is now getting ‘‘lumped’’!

I was in Stockton, Califpornia on a hot summer day. Knowing of the
over heating proclivities of DOHC Jags, I watched the temperature
very carefully! ON the freeway I noticed the needle start to
climb, then a miss, smoke and it quit!!! I cosated off the freeway.
it was hot and smoking. it would not turn over. I let it cool. I
put a lot of water back in!! I tried to start it. It would not!
Jagusr starters do n ot turn very enthusiasticaly! It came home on
a flat bed. I cleaned the plugs, blew it out carefully. No go. then
I trtied a compression test. O in all holes!!! It tried to fire a
couple of time. It fired in the crank case or in the intake
manifold. When I tried to turn it the last time, it would not.
When I stripped the engine to pull it out I lost no water. JAGCAD–
JAGCAD 94 Cadillac LT1 powered 83 XJ6
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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Whoa, you must have zero mechanical sympathy to seize up and melt your
pistons like that! Did you ever find out what was wrong with your
cooling system? Because they do work, if maintained properly.

Greg.-----Original Message-----
1 I cleaned the plugs, blew it out carefully. No go. then
I trtied a compression test. O in all holes!!! It tried to fire a
couple of time. It fired in the crank case or in the intake
manifold. When I tried to turn it the last time, it would not.
When I stripped the engine to pull it out I lost no water. JAGCAD

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Carl,
SBC motors don’t like running without water either. I live in So Cal. My
73 XJ6 ran fine, no cooling probs except once right after I got the car,
the PO had the timing set too late and it ran warmer than it should have
in summer stop-and-go traffic. After I set the timing, she ran great in
traffic or at 100MPH on the freeway.

My $0.02

– Dave Harvey
73 XJ12 Chevy 0/0 (no engine, no tranny , no overheating)
89 XJ-S 5.3L V12 Marelli (runnin’ cool)
Los Angeles, Ca.

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In reply to a message from lakookarancha sent Sun 13 Oct 2002:

I read all the info on your problem and what you have done. Two
things…your radiator is too small, inadaquate cooling fans. You
should need over 2400 cfm . I would suggest a 4 core Corvette
radiator or a Griffin Aluminium with 2 electric fans mounted in the
Jag Shroud, pulling the air through. You might take your car to a
radiator specialist and have the rad preasure tested… if you have
a pinhole you would never know but it would overheat. I had that
problem with my 79XJS /Z28TPI/700r4… pinhole made me nuts had it
preasure tested found leak and had the 4 core rad recored $500.00…
ran cool all the time. Note: the GM heat sensors have been bad
lately and not telling correct temps. Good Luck–
Brownjag
Cranston, Rhode Island, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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Len is probably right- it’s the radiator. But instead
of plunking big bucks down for a Griffin alum or
Corvette 4-row brass, buy the OE Camaro/Trans-Am
radiator- Modine 951. It has an alum core, and plastic
tanks. Fits the Jags perfectly- all you need to do is
cut a 3x3 hole in the header plate for cap access. It
will cool even the hottest 383. And what’s the best
part?? They are $130 brand new from carparts.com and
come with a lifetime warranty… Need I say more. Be
sure to get the Camaro hoses too- they fit the Jag
just as well…

Good luck

PS Len’s 4-row ZCorvette radiator is actually my old
one- I ran it for years before I saw the light…=====
Andrew Weinberg,
89 XJS convert-TPI 350; GR82B8
87 VDP-TPI 305; IHADAV8
67 XKE-302 GT; URT-007
Searching for an XJS-C


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Thanks, that’s what I needed to hear. I took the
jag to a radiator shop, and was told $70 (rod it) to
$1000 (new Jag radiator), depending on the problem.
My
radiator looks bad on the outside, and is full of
stop leak, so I figured it wouldn’t be on the $70
side of the spectrum. I was going to park it 'til I
found a cheaper solution, and here it is.From: lakookarancha <@lakookarancha>
Subject: Re: [Lumps!] engine overheating

— “Brownjag” len371@cox.net wrote:
I read all the info on your problem and what you
have done. Two things…your radiator is too small,

inadaquate cooling fans. You should need over 2400

cfm . I would suggest a 4 core Corvette radiator
or
a Griffin Aluminium with 2 electric fans mounted
in
the Jag Shroud, pulling the air through.

— Andrew Weinberg andrew_jag@yahoo.com wrote:
Len is probably right- it’s the radiator. But
instead
of plunking big bucks down for a Griffin alum or
Corvette 4-row brass, buy the OE Camaro/Trans-Am
radiator- Modine 951. It has an alum core, and
plastic
tanks. Fits the Jags perfectly-
They are $130 brand new from carparts.com


=====
The Head Kook


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In reply to a message from lakookarancha sent Sun 13 Oct 2002:

Fan and radiator must operate properly.–
daryl motes
kennesaw, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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Thanks, that’s what I needed to hear. I took the
jag to a radiator shop, and was told $70 (rod it) to
$1000 (new Jag radiator), depending on the problem.
My
radiator looks bad on the outside, and is full of
stop leak, so I figured it wouldn’t be on the $70
side of the spectrum. I was going to park it 'til I
found a cheaper solution, and here it is.

Kookie,

Find a radiator dealer in your area. I found the guy that sells to the
rad shops in my area & he sold me one for what he gets from the shops, which
was well under $100.

Donn
Mr. Badwrench

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