This is the way I'm going....

 

I prefer the Motorcraft replacement because it has a better/thicker gasket on it compared to the loose o-ring on aftermarket. They seal a little better. I still have the dieselsite aluminum housing though. And the riffraff lower inlet. Not a fan of the stamped steel parts that get rusty.

 

FLUID FILM stops rust, I spray it on every thing metal

Amazon 12oz can

 

UPDATE 10/21/25;
I believe the thermostat housing is now leaking. (This id the Motorad one that my mechanic installed brand new along with 192* thermostat itself) during the Motorcraft water pump installation.
I'm not 100% sure its the thermostat housing thats leaking but can see it seeping out from the area.
I'm not going to fool with it as I paid the mechanic to do the job-I;m going to take it back to him and ask that he fix it.
If it is the thermostat housing I will have him put my 203* DieselSite stat back in.
I know many years ago everyone was down on the factory stamped steel thermostat saying they wouldn't seal if installed a second time and most folks went with the Billet aluminum aftermarket units.
I GOT the billet unit from DieselSite probably 17 years ago and had a hell of a time getting it to seal up-ended up using silicone which I hated to do.
Every water pump installation since then has had a very hard time getting the darn billet housing to seal.
The LAST mechanic 5 years ago that replaced the water pump also had a real hard time getting it to seal and also resorted to using a heavy amount of silicone to do it.
My latest guy bad-mouthed the use of the silicone and now the Motorad stamped steel one he installed is leaking......

 

I'm using the 203* stat that I bought from RiffRaff,
probably a new stat housing, as the entire cooling system was replaced with the previous water pump seized up solid.

I just didn't feel good about any of it after that, new Radiator, hoses, belts, Gates water pump, etc.

got more than 5,000 miles on it now, and the temps are where they should be, mountains or down in the swamps of Georgia and Arkansas

 

UPDATE; The darn NEW MotoRad stamped steel housing is leaking!
I'm going to have my mechanic fix it. I'm also going to have him put my 203* stat back in.
So the stock setup is leaking, MY EARLY billet housing has always been very hard to get sealed and CANNOT be sealed w/o a huge amount of silicone which I know isn't right.
What the heck????

 

Ouch! But speaks well your mechanic will stand behind their repair.

Assuming he wants to I'd stick with the new stamped steel housing.

If it leaks again then insist on the billet housing.

 

What is the reason for using "MotoRad"?

It sounds like yet another cheaply made, market undercutting knock off brand of Amazon, whose leverage to create such brands overnight, and whose hubris to market these made up brands with names that knock off the genuine brand's name, just like unvetted products are knock offs of the OEM parts.

How about trying a Genuine Motorcraft RH63 / Ford F81Z-8592-AA stamped steel thermostat housing, new, whenever replacing the water pump or thermostat... as the Ford factory Workshop Manual instructs? No fuss. No mussy silicone. No Amazon silliness.

That's what I did. No Amazon. No knock offs. No problems. No leaks. Not even a drop.

New Motorcraft / Ford stock thermostat housing and stock thermostat. Done.

 

I honestly had no idea that my mechanic had replaced my DieselSite billet housing with the MotoRad stamped steel unit much less the 192* stat. I happened to see my old water pump on the floor in his shop with my DieselSite 203* stat still in it. I asked him about what thermostat he'd used and thats when he told me and showed me that he'd also installed the MotoRad stamped steel housing.
I had HEARD of MotoRad parts in the past but have NO experience with their products.

 

I posted more to point out that the MotoRad housing is not the "stock set up" because the housing isn't a stock housing.

It is an aftermarket facsimile that is made to simulate the stock set up at a lower price point, but is not the stock set up.

Readers of this thread in the future will benefit from understanding the difference, and knowing that truly stock set ups, using genuine Motorcraft parts, and without using any silicone sealants, are not likely to leak.

I also wanted to reiterate, especially in a thread about current thinking on thermostats, that Ford's service manual instructs to use a NEW stamped thermostat housing, and to discard the old stamped housing, even if the old stamped housing is OEM. The stock housing is intended to be replaced with each water pump change. It seems that a lot of folks over the years failed to do this, most likely because they did not have access to Ford's service instructions where they would learn of a service requirement that is not obvious in and of itself.

Bob Riley, owner and founder of DieselSite, was the first aftermarket purveyor of the aluminum billet housing. Every other vendor's billet housing is a "me too" copy of an idea that Bob was first to market with. I hadn't realized until your report that the first billet housings that Bob sold had issues that were resolved with a redesign. I had assumed that all of the billet housings had sealing issues, or required the use of RTV sealant, creating problems that Ford had already resolved by using a more ductile stamped steel housing... so I stuck with Ford's proven solution.

As for Bob's idea using a Non-Ford 203° thermostat, my engine gets hot enough to burn all the paint off of the center of the hood, despite (or perhaps because of) having an Excursion hood blanket insulation between the engine and the hood, so it seems like the engine gets hot enough to do what it needs to do. When and if it gets any hotter, the fan clutch kicks in, which robs a lot more horsepower than any imagined gain obtained by a delayed opening thermostat, IMHO.

If your mechanic agrees to redo the work to reinstall the old aluminum housing and put in a 203° thermostat, will you hold the mechanic responsible if the redo leaks?

If I were the mechanic, I would not have installed an aftermarket MotoRad part if a Motorcraft part were available, and I checked before posting... the Motorcraft housing and thermostat are still available.

 

I have a GREAT mechanic here locally for stuff I'm not comfortable with or cannot do at home.
I asked him in any case to please re-install my 203* DieselSite 203* Tstat.
He ELECTED to re-install my 15+ year old DieselSite Billet aluminum housing.
He said the mating surface of the factory style MotoRad stamped steel housing was completely flat and we needed a "ridge" in order for the O ring gasket/seal to seal.
He put it all back together and topped off the coolant, pressure tested the system and road tested it about 10 miles.
My cooling system is now leak free!!

For anyone locally that needs an HONEST, TRUSTED stand up mechanic;
-Jeff's Auto Repair
1063 Aurora rd.
Melbourne, Florida
321-752-0063

Jeff is a 1 man band and IMO darn good at what he does!! Highly recommend.