What engine did the Jag XK-120 use? Was it the same engine as the
immediately postwar Triumphs (1800)????
Pete McHugh
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Subject: Skirted thermostats - Newly manufactured
Author: brooks@belcotech.com at Internet
Date: 8/4/97 4:18 PM
Recently a New Jersey Triumph Association club (& list) member, Bruce Hoppe,
discovered that a Jaguar restoration shop was producing a modern skirted
thermostat, which he thought was similar in size to those use in the
TR2/3/4's. This restorer commissioned a machine shop to produce these
thermostats for them. I saw Bruce's thermostat at a club meeting and was
satisfied with the quality. I purchased one, measured, tested and installed it.
The Jaguar thermostat is working well in my TR3A. It is a modern 160F
thermostat, which has been modified to include a skirt. The skirt is brazed
onto the thermostat in a very neat and clean manner. There is no
"bleed/vent" hole at the top of the thermostat flange.
This thermostat operates slightly different than the skirted thermostats we
are used to. The OEM thermostat has a skirt which is starts out behind the
bypass hole and moves forward, to block the bypass hole as the water
temperature rises. The Jaguar reproduction is just the opposite. The skirt
sits against the thermostat flange, in front of the bypass hole when it it
cold and moves backward, to block the bypass hole, as the water temperature
rises.
The dimensions I measured on the thermostat and my TR3A housing are shown below:
Dimension Thermostat My TR3A thermostat housing
Skirt Diameter 1.930 inch 1.967 inch
Skirt length 0.400 inch
Skirt movement @ 180F 0.320 inch
Bypass hole (from Flange) 0.375 inch
Bypass hole (diameter) 0.430 inch
If you "stack up" the skirt length and movement dimensions you will find
that the skirt moves almost exactly enough to cover the bypass hole.
On top of my stove, the 160F thermostat begins to open at 160-165, achieving
full open by 180F. It might have gone to full open at a lower temperature,
with more time, but I didn't realize this inadequacy in my test procedures
until after the thermostat was installed in my car.
I didn't measure the percent "open area" for water flow, but it was at least
as good as most thermostats I have seen.
Two downsides:
1. The thermostat costs $26.95 plus shipping.
2. The opening temperature is approx 160F, but full open does not occur
right away, so the normal operational temperature is somewhat above 160F,
more like 165F (electronic thermometer), but only extended idling (15+
minutes) will drive it above 180-190F.
As as aside, my cooling system (I think) was in pretty good condition before
I installed this thermostat. I use 70/30 water/antifreeze mix, w/water
wetter. Keep in mind, that no thermostat will cure cooling system
deficiencies and YMMV.
The source is XK's Unlimited, 800-444-5247. They are a reputable shop and
advertise in British car magazine. They have a site at www.xks.com
Tell them what car the thermostat is for, your TR, but the bottom line is
that their thermostat is designed for a XK120/140 Jaguar.
(TRF, Moss, Vicki Brit & others - did you catch the name of that source?)
I have no financial or other interest in XK's, although I wouldn't mind one
of their XK140 restored race cars (check out their site). I told them, if
it worked for me I'd be telling a few hundred of my closest friends, but
still couldn't get a freebie. (I'm only kidding, I didn't ask)
Also, From the SAAB list I learned about Mercedes-Benz anti-freeze. M-B
created it because they were experiencing a significant number of head
gasket and cooling system related failures. I have heard that it is double
buffered (against acid and base build ups). This is reputed to eliminate
the salt (white chalky deposits) and goop buildups some of us find in our
radiators and engine water passages. I have not yet tried this stuff
($10/gallon) but will by the end of the summer. Just another thought....
BTW - After replacing your thermostat let the system get hot (pressurized)
and check for leaks. A cold (unpressurized) coolant system test, done the
night before, may not reveal the substantial leak that a three mile jaunt
into town for bagels on a Sunday morning at 6AM will. You may not have
enough coolant left to make it home, unless you keep a gallon of water in
the boot. You may not have to put up with the smirk of a Porche Targa
driver as you run through a red light and begin coasting down the last hill
on the way to your home with the engine off. To quote others on this list
"How do I know this?" ;-)
Jack Brooks
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