I would agree. Of course, thermostats are not high tech or difficult to manufacture. They are not a high cost part, attractive to counterfeiters. This stat is made in Japan, and that’s good. However, I bet that you could buy a high quality equivalent part made in China. Most of the Chinese stuff is good. It better be, that’s where most of your goods are coming from.

 

I have heard of others having trouble with thermostats not working properly that were sold at a high price at your local auto parts store. So it’s not all ways the same quality. Happened recently to a family member who installed a well known brand on a Civic. Had to do the job again with OEM and the problem was solved. There is a noticeable deference in what OEM looks like compared to others. Aisin looks closer to OEM.

This obviously is not…

 

$17.00 at Rock Auto vs. $53.00 for OEM at Cheaper Honda Parts.

If my Pilot keeps rolling long enough to get to another coolant drain, this seems like the way to go.

 

$17.00 at Rock Auto vs. $53.00 for OEM at Cheaper Honda Parts

Back in ’20 I bit the bullet and bought the $45 OEM thermostat versus $12 Gates. The OEM has a different build quality from the generic thermostat and I didn’t want any issues.

 

With how difficult the OEM thermostat is to access on most modern vehicles (and the fact that I don't want to handle plastic housings more than once) - I usually stick with OEM. High quality aftermarket like Aisin could be alluring but I'd likely go OEM like I have been.

 

My thinking as well. 🧠💡
Aisin being an OEM supplier of parts.

 

Ok, as promised, I’d report back with my experience with the Aisin thermostat THH-017.
The installation was not without a hitch. Although after a trip to a local auto parts store for the correct gasket, the thermostat is working great. So my advice is, if you buy the Aisin thermostat, be sure and research the gasket needed for your vehicle.
I was sent this….

I needed this…..

 

And this was part of the Aisin kit that was not correct or was it a separate item from the thermostat?

 

The gasket (1st pic) was in the box with the thermostat.
I guess the fact that the thermostat would work for my vehicle was enough for RockAuto to list it. It would have been nice to know before I ordered. I could have saved some time and money.

 

A little more research…
Aisin make a thermostat part # THH-009. It’s obviously the same exact thermostat as THH-017 with no gasket in the box.

 

A little more research…
Aisin make a thermostat part # THH-009. It’s obviously the same exact thermostat as THH-017 with no gasket in the box.

The OEM thermostat I got from Hondaautomotiveparts.com /majestic came with the correct gasket. Surprised to see that gasket supplied with the Aisin thermostat.

 

Aisin compared to old OEM thermostat that was removed. Looks like an exact match (except gasket).

 

when I did my cooling system overhaul the other year I did use the aisin t-stat and the aisin seal both from rock auto.
hard to trust parts from local auto stores ever since they sold me a radiator cap that caused the cooling system to over pressurize, blow a hose, crack 2 perfectly good radiators and cause enough coolant loss to cause the front head to crack!

do NOT cheap out on cooling system parts

 

I was extremely pleased with the quality of the Aisin thermostat itself. I’d believe it was made by the actual OEM manufacturer.

 

I replaced the thermostat in the 05 we got this summer using the Aisin THH-017 as well - same experience with the gasket. I did this when I replaced the timing belt and had everything apart when I ran into the incorrect gasket issue. The original one was still in good shape, so I just transferred the old gasket over to the new thermostat and ran with it - seems to be doing just fine (no leaks).

 

It's now June 2025 and Majestic Honda is currently charging a whopping $70 for the t-stat on the '05 Pilot....f that. I'd be willing to pay somewhere in the $40's for Honda OEM but I'm not willing to get raped for $70(plus s&h). Several months ago I was curious what they were charging for the rear stabilizer bar end links for my '98 CRV and I was astounded to see they were asking $110/each for them these days. I'll be going with the Aisin t-stat whenever I have to replace the current one. Thanks for the info, Nail Grease!

 

So just to consolidate the experience into one post. If ordering Aisin THH-017, discard the gasket that comes in the box. Order Aisin THP-509 or equivalent.

 

Or if you bought the Aisin thermostat in 2018 when you did your 2nd TB change, but were too lazy to replace it until it was weeping in 2023, the old part number had the correct gasket, and that thermostat was exactly the same as the OE thermostat, and was made in Japan as well.

 

Or if you bought the Aisin thermostat in 2018 when you did your 2nd TB change, but were too lazy to replace it until it was weeping in 2023, the old part number had the correct gasket, and that thermostat was exactly the same as the OE thermostat, and was made in Japan as well.

View attachment 183759

While the thermostat is the correct one, My research on THH009 has no gasket included. 🤷🏻‍♂️

 

ordered sometime last year but never got around to installing it. was going to hold off until maybe the next TB WP job.

 

View attachment 183760

ordered sometime last year but never got around to installing it. was going to hold off until maybe the next TB WP job.

So the correct gasket came in your box as pictured?