Stant Co. is still around but they Sold aftermarket division to MotoRad that quickly killed the brand.

MotoRad makes many "Store Brand" caps for years so many use their rad caps but never knew it.

But their T-stat covers had problems because of rubber seal is too wide and won't fit in some cars.
87 & up "dukes" have an Updated T-stat Tube and I've tried MotoRad in the past and refuse to install.
Current MotoRad T32 on their site seems to be Stant cap but buying one may get the old one that's had the problem just said.
IOW look @ motorad.com/motorad-catalog...ocator/part/?pid=T32

old MotoRad rubber filled the cap and no margin like above pic.

Note: While MotoRad shows above pic & listed as Stant part in other sites. Don't believe that pic = to the part you get. Most Vendors do not have "NOS" Stant parts & even if label as Stant, is a MotoRad part & may not fit you car. I'm not sure even the pic below is actual current MotoRad part.

I knew some months back but I'm posting this because just a T-stat cap leaking and may need to use my spare Stant cap.
I had it off replacing the Intake Manifold Gasket and dripped a few days after reusing the cap. I cleaned more carefully and coat w/ Brake Grease and so far seem that solve the leak.

⚠️ Warning: While Stant covers are made to swivel so easy to install and remove... The rivet in the T-stat cover center can rust and stop this.
Coat the rivet w/ Silicone Oil to keep out weather etc attacking the top when on the car.
Similar reason to coat the tube lip etc w/ brake grease to prevent rust that often locks the cap to the tube.
Silicone and Permatex brake grease won't wreck the rubber seal. Do Not use other oil or grease.

Stant SuperStat® Thermostat is likely gone... Quick search 195° 45819 is not found at most places now. This T-stat type slows or stops temp gauge bouncing that many see in Fiero in cool/cold weather because of 14+ quarts of coolant to heat.
I doubt MotoRad is making this under new number or maybe only making as base model...

]⚠️ Watch buying New Radiator caps... MotoRad and thus many store brands Does Not list a non-vented cap for Fiero. vent/non-vent caps had a letter at end of some PN. Even w/ that data seems have renumber(ing) the radiator caps.
So for Fiero... A few cross ref 1008-16 as Stant 10231 or Motorad T16V vented caps.
By cross ref Stant 10230 not Year etc of car here. For MotoRad and many "store brands" T16.
Note that both T16 are "locking caps" that you pull up the lever... I never like this type even from Stant because locking pin often leaks air so recover/overflow tank doesn't work right.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 11-07-2023).]

Thanks for the warning ogre. I just ordered a bunch of spare radiator caps and thermostats (the less desirable 13819).

You're right about the temperature swings with the Stant 13819.

Here is a datalog of a drive of my car (equipped with Stant 13819) from cold.

In the lower pane, we see the trace of the coolant temperature. Once the coolant reaches operating temperature, it oscillates somewhat.

[This message has been edited by pmbrunelle (edited 11-09-2022).]

I guess that "oscillation" looks fine. I would be surprised if such a simple, mechanical control system could regulate any better at this scale. Even modern digital control systems will always have some error that would be corrected up or down in some way.

Assuming the Coolant Systems is 100%... (So skip crush Fiero pipes etc. for this...)

Yes, you see coolant temp swings on most vehicles but often not as much as Fiero.
Nearly all cars and Light Trucks, even some labeled as Heavy Trucks, don't have 14+ quarts of coolant to equalize for whatever distance to drive.
Many only have 6-8 quarts including many w/ "Big Block" V8...
When Fiero Engines are in FWD cars, those cars also have far less coolant to get a "stable" temp and often use same Thermostats.

Very dirty, Not digging under car car to actually measure them. The Fiero pipes and long hoses for D-side uses > 1 gallon to connect engine to the rad just to to fill ~ 18 feet of pipes and hoses. Math: 1.25" diam = 1.23in² area x 216in {18'} to get 207.07in³ convert to get 4.59 quarts. that's w/o adding V6 cross pipe adds ~ 2 feet of pipe or 0.5 quarts more. (And I'm allowing some Fiero rubber to = out FWD hoses.)

So most just don't have a Temp Gauge etc that Bounce like Fiero can at different weather temps. Even then many "High $" models had ways to smooth out the gauge reading before was simple program for PCM or BCM controlled dashes so Driver never sees this.

Example: In my 87 duke... At certain weather temps and engine started cold... Temp Gauge would see warm up as normal but after driving ~ 5 mi and stop at a traffic light then gauge and ECT would often swing to 220+ and run the rad fan then would "slam" OEM type T-stant Open and slug engine w/ cold coolant and temps drops and fast. I mean can see it happen in cycles that last seconds to < 1 minute if stopped for a long light.

Super Stant really helps Fiero because open/close more slowly vs normal types. Just adding that years ago, the car doesn't have that issue but all senders/senders still swings some and follow coolant temp but you have to idle for a longtime to see the fan to turn on. In normal driving, the rad fan almost never turns on and 87/88 Duke's ECM switch on @ ~ 220°F... (this ECM supports 2 speed rad fan but never used for Fiero.)

Even when a vehicle have a Temp Gauge most never had numbers partly because the numbers aren't very accurate and people have No Clue what the numbers mean anyway. Many have nothing but red area. Some have that + C/Cold & H/Hot text. As long as gauge isn't in the Red area, most people see nothing wrong. At that's w/ same type of wiring and sender behind the gauge.
Fiero and a few has number and since then you hear the engine runs "hot" because of same problem and "vendors" love stupid people that hype the Fake Problem so buying whatever to make run "cooler."

Side Note: When scanning the ECM, Watch O2 Ready and Loop Flags to see actual time before run an engine in Close Loop. 87 Duke w/ Bosch O2 can go Close Loop in Seconds after starting cold even in the Winter. Other can take a bit longer because O2 is farther down the E-pipe to heat up to operate but very often is Not affected by Coolant MAT/IAT and other sensors.

Update:
I found a pic of old Motorad T-32 "mislabeled" as a Radiator Cap showing bottom view of T-stat cover at amazon...
https://www.amazon.com/Moto...or-Cap/dp/B000C5I9OW
Notice the rubber fills the whole cap...

(pic is 1390x1409 and easy to see the rubber nearly hits the sides at full size. DL a copy if needed as PFF auto zoom make hard to see when "zoomed out.")

This is the one that didn't fit the "updated" T-stat tube on 87 & newer Dukes. Didn't had older T-stat tube to see if fits them or not.

Note: Even this pic may not be = to current MotoRad cap.

[This message has been edited by theogre (edited 11-07-2023).]

It didn't fit my '85 duke. Had to use a wrench to get it on and off.

OGRE, I've been using Robertshaw T-stats in my 2.8 before converting to 3800sc. I never experienced any issues or swings in temperature that would raise my curiosity. Do you have an opinion on that brand or if they're still available. Memory not what it use to be, could of been R-shaw cap.

With the 3800 the T-Stat is on the driver side of the engine bay and I can monitor when the stat begins to open using a digital laser gun aimed at the metal coolant pipe behind the rear tire. For troubleshooting this removes the coolant sensor, wiring,, ecm and shaky gauges from the diagnostics. as far as what the t-stat is doing. Also good for checking for any pinched hoses or piping along the way.

ps: https://www.summitracing.co.../pontiac/model/fiero


Spoon

------------------
"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut

[This message has been edited by Spoon (edited 11-11-2022).]

quote Originally posted by Spoon: OGRE, I've been using Robertshaw T-stats in my 2.8 before converting to 3800sc. I never experienced any issues or swings in temperature that would raise my curiosity. Do you have an opinion on that brand or if they're still available. Memory not what it use to be, could of been R-shaw cap. With the 3800 the T-Stat is on the driver side of the engine bay and I can monitor when the stat begins to open using a digital laser gun aimed at the metal coolant pipe behind the rear tire. For troubleshooting this removes the coolant sensor, wiring,, ecm and shaky gauges from the diagnostics. as far as what the t-stat is doing. Also good for checking for any pinched hoses or piping along the way. ps: https://www.summitracing.co.../pontiac/model/fiero

Robertshaw Co is still around and make Some Automotive parts but I believe not in aftermarket parts for years now. I used their car T-stat too.

Using IR meter on T-stat house is covered in my cave... IR thermometer
You can't use them while driving.
Can use Thermal Couples and Themistors connected to whatever... standalone meters to "ardiuno" projects like thread "Fiero Engine bay vs Heat." https://www.fiero.nl/forum/Forum2/HTML/141784.html
Reading/Attach to a T-stat house should about = coolant temp but if read/attach to the head or block then often won't = to coolant temp and can be much hotter or colder depending exact location for any type of probe.

GM and ACDelco hasn't made parts in nearly 20 years when spin off Delphi that went Bankrupt 2x or more then sold and now a Brand of BorgWarner Inc. Even when GM made parts, Didn't make All parts. T-stats and Caps for many things were made by Stant and others. Many times years ago OE GM & Ford caps had a small Stant S logo somewhere on them...

As to Big Temp Swings in Fiero and others...
Even w/ OE engines Many people never see them because how/where you drive and weather maybe too warmer or colder to "trip" this problem.
If I took the interstate to work, is about same distance but never stopped at a lot of traffic lights and speed is never drops < 30-40mph.
I take surface streets because if one way is block have several other ways to get A to B.
Swapped setup can have same problem or never for same reasons plus many change the thermal loads and heat up coolant system faster so have a smaller window to have the problem if they ever show this.

Sim issue for DTC that only happen at Idle and/or certain weather conditions. Example: See my Cave, DIS Ignition MAT section. Took Weeks to find a Iffy MAT because only trips DTC 45 at idle and only when air temp and moisture is "just right" even after replacing O2... Worse because Haynes and others say Dukes don't have a MAT/ACT ignoring DIS etc too.

Well done theogre...

Spoon

------------------
"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut

Update:

MotoRad site & likely others T-stat cap is not listed when lookup some or all Fiero. Does show when run PN T32.
Page changed & edit first link & pic showing "stant style" cap.

i installed a new moto rad 195 tstat two months ago ang its already stuck open.i even put it in the freezer overnight out of curiosity.its still open.im going with autozone because at least its easy to get them to replace them.

quote Originally posted by richard in nc: i installed a new moto rad 195 tstat two months ago and its already stuck open...

⚠️ Some MotoRad PN are "Fail Open" by design.
Before replacing them, check for crush pipes etc in cave.

"Fail-Safe Thermostat" PN start w/ 7. Example: 7211-195 195°F Fail-Safe Thermostat for Fiero etc.

"Store brands" made by MotoRad may have same PN or older PN or store number system & stores may have "Fail-Safe" units or not w/o saying.