Thermostat Housing: Why they leak and permanent fix

[Paul Fithian]

I have posted this on some other forums and wanted to post here for fellow Sport Trac owners. Bottom line is you are wasting your time and money on anything other than a Simmons aluminum thermostat housing.

While on a recent trip to Florida, the tensioner pulley seized, destroyed the belt, and caused overheating. This also split the seam on the nylon thermostat housing, which required replacement to get home, more than a thousand miles away. A local NAPA store was great at getting one in from Jacksonville that day, Part No S4402AT by Motorad. As a side note, our local NAPA store stocks these in our town of 30,000 people, indicating high demand.

This new plastic thermostat housing started leaking ~ 1,500 miles after I installed it shows evidence of weld line separation and where it leaked.

Of most interest are the date codes on these parts, they were molded several months apart before welding. This is key to understanding the failure.

These parts are molded from glass filled nylon, which will absorb moisture from the air. Nylon parts should be welded together immediately after molding to prevent moisture absorption. This moisture absorption has a great effect on weld strength, as documented in DuPont's literature regarding best practices for welding nylon:

" b. Effect of Moisture on ZYTEL. Nylon resins absorb somewhat more moisture from the air after molding than most other plastics. When released from joint surfaces during welding, moisture causes poor weld quality. For best results, parts of ZYTEL should either be ultrasonically welded immediately after molding or kept in a dry-as-molded condition prior to welding. Exposure of 1 or 2 days to 50% relative humidity at 23°C is sufficient to degrade weld quality by 50% or more . . ."

So to fix this, I installed an Austekk aluminum thermostat housing. This also started to leak after ~ 1,000 miles.

This great video explains why:


If you want to do this difficult job once and have it last, an aluminum Simmons Autosportz is the only one I recommend. Check https://simmonsautosportz.com

 

[swshawaii]

Had to be a reason the Simmons is almost 3x the price of the Austekk. Thanks for your thorough research Paul.

 

[Paul Fithian]

My pleasure! The difficulty of replacing this, especially on a Gen 1 Sport trac, totally outweighs the cost differential.

Perhaps another member can have a look at the date codes on other failures and confirm the time difference between when the parts were molded.

 

[Todd Z]

All the plastic sucks, its a bad design, and durability of plastic is not there.....
ALSO the bottom seal, sideways ring, not even an o ring, is CRAP !!!! the aluminum is not machined clean so its planned obsolescence at its best !!!!!

Apply a thin layer of Ultra copper between the housing and block OR use the paper gasket and youll never change it again !!!

Been doing this since the aluminum one came out.... Ive installed about 20.....

 

[Paul Fithian]

It's not that the material sucks, glass filled nylon is used in a lot of underhood applications. Radiator end tanks, power steering reservoirs, coolant reservoirs, intake manifolds, fan shrouds, and fans are some examples. I used to do a lot of this type of automotive development work for one of the big nylon suppliers. Nylon can be used with great success, but the rules for part design, molding, welding, fastening, and sealing have to be followed.

If these were made in a production cell where the parts were welded immediately after molding, using a vibration instead of ultrasonic weld joint, it would last.

 

[Todd Z]

Exactly my point.... Everything you named fails on the ST... LOL.......

 

[Paul Fithian]

If they fail, one or more of the rules I listed were violated.

All cars made in the past 20+ years use nylon for these parts. It enables cost and weight savings. For intake manifolds, it increases engine HP and torque due to smoother interior walls and colder air charge.

 

[EddieS'04]

I bought the simmons for my Trac....
I also didnot like the way the other were made.

 

[Todd Z]

I bought the simmons for my Trac....
I also didnot like the way the other were made.

Eddie, I thought you ran the Austekk on yours ?? Forget it, It was Mark....

 

[Todd Z]

Doing a little research on this.... the Aluminum housing posted above IS NOT the Austekk one !!! its the knockoff a (Tom) or some one else is peddling..... The Austekk housing has Austekk Molded in the top cover and the part number on the RED hose In the box is not ATX its ATK....

SO be careful what you buy !! it could be cheep knock off and screwing a good product !!!

 

[EddieS'04]

Eddie, I thought you ran the Austekk on yours ??....

Todd, I liked the one piece main body, plus I trusted the forged nipple. In the old days of sheet metal type nipples. I have had them to rust rot. If they were screw in type from SS or bronze. They held up, and when they did get thin. They were easy to screw out of the cast iron. For replacment. With the correct coolant mix, they lasted forever, almost. Most of the old style were NPT threads. I have used pipe nipples in a pinch.

 

[EddieS'04]

IMO, the best use of the plastic nylon, is the intake manifolds. Other than some at the TB throat. The runners usually are supported of more HP than the metal runners. They dont have to be extrude honed. Runner ID is generous and smooth, and less heat soak. Port matching is good for OEM also. Ford did have some early 4.6L lowers that cracked though.

 

[Todd Z]

Ok I understand about that, I just doing research like I said above and it seems some one is doing "bad business" practices and using other knockoffs to slam a company.... I despise that coming from small business my self....... Don't always believe what you see on the internet.....

 

[Todd Z]

THIS is the real Austekk, has their name in it from what I have found.... any other not having this is the knockoff....
I wish Mark would chime in on what he got.....

 

[Paul Fithian]

That is also the one with the real leak.

 

[K Thomas]

I have posted this on some other forums and wanted to post here for fellow Sport Trac owners. Bottom line is you are wasting your time and money on anything other than a Simmons aluminum thermostat housing.

While on a recent trip to Florida, the tensioner pulley seized, destroyed the belt, and caused overheating. This also split the seam on the nylon thermostat housing, which required replacement to get home, more than a thousand miles away. A local NAPA store was great at getting one in from Jacksonville that day, Part No S4402AT by Motorad. As a side note, our local NAPA store stocks these in our town of 30,000 people, indicating high demand.

This new plastic thermostat housing started leaking ~ 1,500 miles after I installed it shows evidence of weld line separation and where it leaked.

View attachment 715

Of most interest are the date codes on these parts, they were molded several months apart before welding. This is key to understanding the failure.
View attachment 716
View attachment 717

These parts are molded from glass filled nylon, which will absorb moisture from the air. Nylon parts should be welded together immediately after molding to prevent moisture absorption. This moisture absorption has a great effect on weld strength, as documented in DuPont's literature regarding best practices for welding nylon:

" b. Effect of Moisture on ZYTEL. Nylon resins absorb somewhat more moisture from the air after molding than most other plastics. When released from joint surfaces during welding, moisture causes poor weld quality. For best results, parts of ZYTEL should either be ultrasonically welded immediately after molding or kept in a dry-as-molded condition prior to welding. Exposure of 1 or 2 days to 50% relative humidity at 23°C is sufficient to degrade weld quality by 50% or more . . ."

So to fix this, I installed an Austekk aluminum thermostat housing. This also started to leak after ~ 1,000 miles.
View attachment 718

This great video explains why:


If you want to do this difficult job once and have it last, an aluminum Simmons Autosportz is the only one I recommend. Check https://simmonsautosportz.com

I have posted this on some other forums and wanted to post here for fellow Sport Trac owners. Bottom line is you are wasting your time and money on anything other than a Simmons aluminum thermostat housing.

While on a recent trip to Florida, the tensioner pulley seized, destroyed the belt, and caused overheating. This also split the seam on the nylon thermostat housing, which required replacement to get home, more than a thousand miles away. A local NAPA store was great at getting one in from Jacksonville that day, Part No S4402AT by Motorad. As a side note, our local NAPA store stocks these in our town of 30,000 people, indicating high demand.

This new plastic thermostat housing started leaking ~ 1,500 miles after I installed it shows evidence of weld line separation and where it leaked.

View attachment 715

Of most interest are the date codes on these parts, they were molded several months apart before welding. This is key to understanding the failure.
View attachment 716
View attachment 717

These parts are molded from glass filled nylon, which will absorb moisture from the air. Nylon parts should be welded together immediately after molding to prevent moisture absorption. This moisture absorption has a great effect on weld strength, as documented in DuPont's literature regarding best practices for welding nylon:

" b. Effect of Moisture on ZYTEL. Nylon resins absorb somewhat more moisture from the air after molding than most other plastics. When released from joint surfaces during welding, moisture causes poor weld quality. For best results, parts of ZYTEL should either be ultrasonically welded immediately after molding or kept in a dry-as-molded condition prior to welding. Exposure of 1 or 2 days to 50% relative humidity at 23°C is sufficient to degrade weld quality by 50% or more . . ."

So to fix this, I installed an Austekk aluminum thermostat housing. This also started to leak after ~ 1,000 miles.
View attachment 718

This great video explains why:


If you want to do this difficult job once and have it last, an aluminum Simmons Autosportz is the only one I recommend. Check https://simmonsautosportz.com

So tell me, why does it look like the supposed leaking part doesn't look like it was installed? Maybe you are Simmons, or a buddy and just trying to bad mouth a better product....DON'T TRUST THIS GUY'S POST.

 

[Paul Fithian]

Both were installed and leaked. The Austekk one is still on the truck, and leaking. Waiting for the Simmons part to arrive before I remove the leaking Austekk one.

I rinsed off the NAPA one before I returned it to them for a refund.

 

[swshawaii]

Doing a little research on this.... the Aluminum housing posted above IS NOT the Austekk one !!! its the knockoff a (Tom) or some one else is peddling..... The Austekk housing has Austekk Molded in the top cover and the part number on the RED hose In the box is not ATX its ATK....

SO be careful what you buy !! it could be cheep knock off and screwing a good product !!!

These are the "tomautoparts" kits Todd is referring to:

https://www.ebay.com/itm/NEW-ALUMIN...S-FOR-02-10-EXPLORER-MOUNTAINEER/223214837870

https://www.ebay.com/itm/NEW-ALUMIN...T-FOR-02-10-EXPLORER-MOUNTAINEER/223214846817

https://www.ebay.com/itm/NEW-ALUMIN...S-FOR-02-10-EXPLORER-MOUNTAINEER/223214829726

 

[K Thomas]

Todd, I liked the one piece main body, plus I trusted the forged nipple. In the old days of sheet metal type nipples. I have had them to rust rot. If they were screw in type from SS or bronze. They held up, and when they did get thin. They were easy to screw out of the cast iron. For replacment. With the correct coolant mix, they lasted forever, almost. Most of the old style were NPT threads. I have used pipe nipples in a pinch.

Forged "nipples" is a weak spot that will likely crack sooner or later, the Austekk has machined aluminum double sealed, and won't leak regardless of what Simmons buddy Paul (or maybe simmons himself" says.

 

[K Thomas]

Both were installed and leaked. The Austekk one is still on the truck, and leaking. Waiting for the Simmons part to arrive before I remove the leaking Austekk one.

I rinsed off the NAPA one before I returned it to them for a refund.

So in other words, by your own words your are a scammer "rinsed off for refund" WOW....Anyone that reads your posts should take note, NOT HONEST!