Rubber Thermostat Housing Gasket

[777Gage]

There are no cork OEM thermostat gaskets.

None.

Have you thought about going to a Toyota dealership and buying the correct part? (Which happens to be 90430-40058 for your 2 bolt thermostat housing)

Thanks for your insight Onur, always appreciate it!

Agree with you 100%, I didn't think there was a cork OEM gasket - then a cork gasket showed up in the mail, invoice marked OEM......

I did go the dealership route, but I'll explain what happened
Called Cruiser Outfitters first because of my previous order that included the Aisin thermostat above. They could ship me a correct gasket Monday - but it would be a Wed/Thurs delivery at the earliest. So they sent it out. (turned out to be cork - who knew?)
As soon as I got of the phone with CO I called my local dealership, they didn't have the 90430-40058 gasket in stock and according to their "warehouse" there was only one available, and it was 72 hours to get it. I wasn't too confident that the "one" existed or would be there when they placed my order or would it show up in 3 days.

So I called SOR, they had a gasket in stock, (post #11 above) drove the 40 min round trip, and installed it as soon as I got home.

I've driven it about 25 miles so far, and all is well!

 

[Bear]

Hmmmm. I'm wondering if there was a TSB at some time explaining what's going on here.

Of course genuine Toyota parts sourced from a Toyota dealer should be the final arbiter, but something as simple as a few gaskets should be able to be copied at least by an OEM supplier, and maybe simple enough even for our Chinese copycats. I don't think suppliers are simply throwing some generic gaskets into the parts bag, but......................

 

[S.CarolinaFZJ80]

2nd Update: The mail arrived with my Cruiser Outfitters gaskets.

They have a cork gasket for the top of the thermostat - CO Part # : RADOR40058 - invoice says OEM
Paper/Fiber gasket for the housing/hinge - CO Part # : RADH60020 - invoice says OEM

Picture below if of the gaskets again now with the cork (I installed the SOR rubber gasket pictured in the post above already)
From left to right
1. Original gasket I pulled out
2. Gasket that came in the box of the new thermostat - Aisan Part # THM-004 (thermostat part #)
3. Cork Gasket from CO - Part # RADOR40058

Again, the middle (#2) gasket is "almost" twice as thick and as the cork gasket.

In some ways this adds more confusion and more clarity, rubber vs cork discussion and why the 2 options, however, thinner gasket is correct vs thicker that may come with a new thermostat.. (and SOR gasket was $1.37 and CO was $5.50)

View attachment 2359527

View attachment 2359528

In the same boat here.

Removed a larger diameter upper thermostat housing rubber gasket. It fits the recess on the upper housing perfectly. The supposed correct Toyota replacement has the same ID but a narrower OD yet it's the same thickness.
Has any one else experienced any issues running the Toyota part #90430-43002 ?

 

[S.CarolinaFZJ80]

Also, looking to buy a replacement lower thermostat housing. 2/79 build date, US Spec, with two ports for vacuum valves.

Contrary to postings on Mud. If you get a seized/snapped bolt - DO NOT use a center punch and hammer to tap the broken bolt.

Based on a the copious amounts of sealant and a welded shut thermostat relief valve... a shade tree mechanic was in here before, so I suspect there was already a hairline crack that I wasn't aware of...

Anyway, if any of you have a lower housing laying around please message me. - Thanks

 

[matt19857]

There are no cork OEM thermostat gaskets.

None.

Have you thought about going to a Toyota dealership and buying the correct part? (Which happens to be 90430-40058 for your 2 bolt thermostat housing)

I am trying to finish a thermostat install on a 1976 CA spec FJ40 with the original housing. The original T-stat and gasket were discarded years ago during teardown of the project so I can't compare to what was there. There seems to be tons of threads of people having fitment issues and a gap in the housing, but nobody seems to have actually measured anything.

The depth of the top housing measures 25.5mm

I have an OEM gasket for between the lower and upper housing 1mm thick, and an orange paper Felpro 0.8mm thick as a reference.

The round rubber gasket for the top of the thermostat that I have is 2.45mm thick, 40mm ID, 52mm OD (looks like gasket #3 from post #12). I think this came with the OEM Thermostat but can't recall if it's OEM or not since this was bought over a decade ago. Do you know the dimensions of the OEM rubber gasket?

I've tried two thermostat options, and each one has a questionable issue:

1.) Toyota OEM 90916-03052 88 degree thermostat. I bought this by accident not realizing I want an 82 degree. This does not completely fit in the upper housing due to the shoulder where the rubber gasket sits. Some people seem to have milled out the top housing so this fits? That can't be right. The depth is 24mm to the flat part the gasket sits on and with the rubber gasket is 26.45mm. This seems close to ideal leaving a 0.95mm gap for the paper gasket. The issue is that the shoulder is around the same thickness of the rubber gasket, so I am worried I will crack the upper housing if the paper gasket compresses too much. It's also possible this is exactly how it was engineered assuming the correct rubber gasket and paper gasket are used. The thinner 0.8mm FelPro gasket would definitely not work.

2.) Aisin THM-004 82 degree thermostat. This fits fully in the upper housing without the rubber gasket since there is no shoulder, but it is taller with a depth of 24.75mm. Adding the rubber gasket the total stack height becomes 27.2mm which leaves a 1.7mm+ gap between upper and lower housing. This seems too big to close even once the 1mm gasket is installed in between and echos the issues many people seem to have.

I think a 1.75mm rubber gasket on top of the thermostat would be ideal here. Any idea what is the correct gasket for the Aisin thermostat and it's dimensions? I assume that a lot of these Aisin ones have been installed, so there must be a preferred rubber gasket to use. I just bought this brand new after being skeptical of the 88 degree OEM's fitment and there was no gasket in the box.

3.) I have not tried OEM 90916-03014 which is the 82 degree thermostat. My assumption is that this is the same in dimensions to the 88 degree version.

 

[matt19857]

Update: I grabbed a Murray Plus+ 3548 thermostat that Oreilly's had to try. This measures 24.56 tall and came with a 2mm gasket. This seems like a great fit, but the quality is terrible so I am not going to install.

The dealer wants $13 and pre-payment to order the OEM gasket part#90430-40058. Does anyone know the thickness of this before I pay them a 200% markup for a part that might not even work?