* THERMOSTATS ... GET THE RIGHT ONE! *

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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philip
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Location: Southern California, USA

* THERMOSTATS ... GET THE RIGHT ONE! *

#1

Post by philip » 14 years ago

There are a couple of thermostats that will physically fit the SDxx engine. Installing the wrong part will not cause problems in cold weather. But in warm/hot climates especially when you are hammering along in 4th and 3rd gears at full throttle, then the wrong design thermostat (one that does not close off the "bypass port" when the thermostat has moved off the full closed position) will permit a significant amount of coolant to bypass the radiator. Not desireable.

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When the thermostat is CLOSED, the bypass port is uncovered. This allows coolant to circulate around through the engine block, head, water pump, and the heater too (if the control valve is open).
ImageG.Guest)

As the thermostat opens to about mid travel, the bypass port is closed off completely which ... forces ALL coolant to route through the radiator to get back to the water pump inlet.
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Last edited by philip 13 years ago, edited 9 times in total.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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asavage
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#2

Post by asavage » 14 years ago

Very nicely done, Philip!

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asavage
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#3

Post by asavage » 12 years ago

Adding NAPA part Nos.

NAPA THM 139, 180°F
Dimensions:2.125" Flange Diameter
Limited lifetime warranty
It sells for about USD$9
Image


NAPA THM 239, 192°F
It sells for about USD$9
Image



NAPA THM 544080, 180°F
"SuperStat" line, it's a better-constructed unit, though the std ones are fine IMO.
It sells for about USD$14
Image



NAPA THM 544095, 192°F
It sells for about USD$14
Image


NAPA Beck-Arnley BA 1435081 "FailSafe" thermostat, 180°F
I have no idea what "FailSafe" means.
It sells for about USD$11
12 mo/15k mile warranty
It sells for about USD$24
Image

NAPA lists a couple others as well. The first four are "always" stocked.

Thermostat cover-to-housing gasket
NAPA BA 0390004
It sells for about USD$1
Image



Different gasket
NAPA THM 1073
It sells for about USD$1
Image



And the thermostat-housing-to-head gasket
NAPA NGA C24170
It sells for about USD$1.50
Image
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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philip
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Location: Southern California, USA

#4

Post by philip » 12 years ago

asavage wrote:NAPA Beck-Arnley BA 1435081 "FailSafe" thermostat, 180°F
I have no idea what "FailSafe" means.
FailSafe is ...

Notice the spring clip alongside the spring. There is one on each side. When the thermostat reaches WIDE OPEN travel, the clip pops inward around the valve edge thereby preventing from ever closing again automatically. You MAY be able to "reset" it manually or it may become a toss-away.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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asavage
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#5

Post by asavage » 12 years ago

New issue: my 1981 "Orting Truck" has an off-center counterbore for the thermostat to drop into, putting one bolt hole too close to the pressurized counterbore.

(click on image for larger)

Image

There is only about .045" material there for the gasket to seal. Without sealant applied to the gasket, and using a Fel-Pro gasket (that is not exactly a perfect rendition of the original hole size/spacing), I was getting coolant up through that bolt bore and quite a bit of it.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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philip
Posts: 1494
Joined: 14 years ago
Location: Southern California, USA

#6

Post by philip » 12 years ago

The first time I replaced the thermostat, one of the bolts broke off . I chose to remove the entire housing and take it to a machinist who torched it out. Even a "Time-Cert" would have been very close to coolant and gasket.

But I do love http://www.timesert.com/
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

User avatar
asavage
Site Admin
Posts: 5331
Joined: 14 years ago
Location: Duvall, Wash.
Contact:

#7

Post by asavage » 12 years ago

Tip for the future: triangular thermostat housing gasket is not symmetrical. Got to orient it correctly.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

User avatar
philip
Posts: 1494
Joined: 14 years ago
Location: Southern California, USA

#8

Post by philip » 12 years ago

I've been lucky every time? :wink:
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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