WARNING: Mishimoto low-temp "racing" thermostat failure

[ATL BRZ]

Update: Mishimoto have reached out to me with a sincere apology for my experience and I agreed to send the failed unit back to them for analysis with their engineering team.

I'm still not going to swap thermostats on this car ever again unless the OEM unit fails on me, which hopefully never happens.

I was one of the first to order the Mishimoto cooling package last year on Amazon for a ridiculously low price when there was a major pricing error, and they ended up honoring the price and they shipped it to me and several others before they fixed the price. The package included their big aluminum radiator, coolant hoses and their low temp (76 C) thermostat. I installed it all in January 2015 and have since tracked the car hard over at least 4 times and driven the car on the street all summer and winter long. I don't daily drive the car anymore but once or twice a week in cold weather on the highway the car would throw a CEL for coolant temp below threshold because the temps wouldn't get high enough when cruising in 6th gear at part throttle, but I could remedy it by leaving the car in 5th gear.

Now that spring has sprung I am getting the car ready for this track season. Yesterday I installed my 17x9 wheels with fresh track rubber on them and went on my routine drive down the street to fill up with E85 and decided to hit the highway on my way home for a run around a tight on-ramp to get a feel for the grip from the new tires. The car ran fine and temps were good up until this point. I pulled 2nd gear hard and 3rd gear at par throttle before getting back into 5th for my cruise home about 3 exits down the highway.

About 3 minutes later when I was about 1 mile from my exit I see the CEL trip and I look down to see my coolant temperature gauge pegged in the red.

I get off the highway at my exit and limp the car home another half mile and immediately shut it down and found it spewing coolant out of the reservoir and the fans in high speed mode. It didn't take much diagnosis to see that it was the thermostat that had failed and stuck closed allowing no coolant to circulate. There was no milkshake in my coolant and the oil was clear and at the right level. Nothing else leaking from anywhere as the car continued to idle fine when I tested it after it cooled down. I realized that I was very lucky to not get stranded or have a catastrophic engine failure.



Back on jackstands last night for emergency surgery, which happened today.

My findings...



OEM (88 C) thermostat on left, Mishimoto (76 C) on the right

The pin at the bottom of the Mishimoto thermostat worked its way out of the assembly and as a result the thermostat was stuck closed and overheated the engine very quickly. I found that pin sitting in the bottom of the thermostat cover piece.

I put the OEM thermostat back in, filled the system back up with coolant and bled it properly at both ends and thankfully after a test drive all is well. Crisis averted. My BRZ lives to see another day.

I am posting this thread as a warning to other owners who may currently have or are considering purchasing this thermostat. I highly recommend leaving your OEM thermostat or swapping it back on. I will not be using the @Mishimoto lifetime warranty on this part. I have heard from several owners with these and different cars that failures with both the Mishimoto thermostats and the radiators (pinhole leaks) are common. Caveat emptor.

[Anthony]

Such a tiny thing that could potentially cause such catastrophic problems.

[Ro_Ja]

I was very lucky to not get stranded or have a catastrophic engine failure . . . I have heard from several owners with these and different cars that failures with both the Mishimoto thermostats and the radiators (pinhole leaks) are common.

Quoting for emphasis. I know too many people that experienced quality issues with Shittimoto products. Total junk. "It was cheap" or "I only want to spend $___" is not a justifiable reason to mess with critical components on the car. Do it once, do it right. And do your research too. Sometimes, sticking with OEM can be the best bet in a situation.

[2ZZW30]

Far from the first time I've heard of this failure. Their rad caps are not known for reliability either.

[OkieSnuffBox]

This is why none of the Miata track guys have bought Mishimoto for years.

The only people I see buying them on a regular basis are the cheap E30/E36 BMW guys.

[DJCarbine]

Originally Posted by OkieSnuffBox

This is why none of the Miata track guys have bought Mishimoto for years.

The only people I see buying them on a regular basis are the cheap E30/E36 BMW guys.

Had a mishimoto on my e36, leaked from where the bars went into the endtanks. Too many people having issues so I decided not to use the warranty just to have to do the job again sometime down the line.

Radiator fans didn't mount to rad correctly either, the mounting brackets on the rad were not correctly welded/placed. Drain plug was plastic and never sealed correctly. They did honor the warranty, I just decided not to use it.

That being said, I just purchased a mishimoto IC for my wrx and am pretty happy with it as far as fitment... but a leaky IC is a lot different than a failed thermostat or radiator

[JazzleSAURUS]

My Mishimoto radiator for my Forester XT failed and they were prompt about replacing it, but a welded aluminum radiator should not have pinhole leaks at all.

After 4 caps failed I put an OEM cap on and the problem was resolved.

I won't buy their products in the future.

[brzaapi]

Well just to share another experience. I installed the thermostat on my 2nd BRZ in August 2014. It failed April 2015.

I have since stayed OEM on thermostats. Luckily the BRZ/FRS coolant system seems to run pretty good on its own.

Oil, now thats another story.

[ATL BRZ]

Update: Mishimoto have reached out to me with a sincere apology for my experience and I agreed to send the failed unit back to them for analysis with their engineering team.

I'm still not going to swap thermostats on this car ever again unless the OEM unit fails on me, which hopefully never happens.

[Mishimoto]

Originally Posted by ATL BRZ

Update: Mishimoto have reached out to me with a sincere apology for my experience and I agreed to send the failed unit back to them for analysis with their engineering team.

I'm still not going to swap thermostats on this car ever again unless the OEM unit fails on me, which hopefully never happens.

Thank you for working with us on this and for giving us the opportunity to further investigate the concern. As noted in our PM, we truly apologize for the failure you experienced. Product failures are taken very seriously here at Mishimoto and we intend to identify the issue, inspect our product design, and make any changes needed to ensure this never occurs again. We have offered this thermostat for quite some time and have numerous customers utilizing it without issue. Our assumption is this unit was defective in some way or improperly manufactured. If this is the case, we will determine how this occurred and develop a solution to assure this does not happen to any future users.

Again, we apologize for the inconvenience and poor experience. We will be reaching out shortly with further details regarding the acquisition of the failed component.

Thanks
-John

[DrWill]

Originally Posted by Mishimoto

Thank you for working with us on this and for giving us the opportunity to further investigate the concern. As noted in our PM, we truly apologize for the failure you experienced. Product failures are taken very seriously here at Mishimoto and we intend to identify the issue, inspect our product design, and make any changes needed to ensure this never occurs again. We have offered this thermostat for quite some time and have numerous customers utilizing it without issue. Our assumption is this unit was defective in some way or improperly manufactured. If this is the case, we will determine how this occurred and develop a solution to assure this does not happen to any future users.

Again, we apologize for the inconvenience and poor experience. We will be reaching out shortly with further details regarding the acquisition of the failed component.

Thanks
-John

a truly professional response from a conscientious company with customer satisfaction and safety in mind. thanks Mishimoto for doing what is right.

[Wayno]

Originally Posted by DrWill

a truly professional response from a conscientious company with customer satisfaction and safety in mind. thanks Mishimoto for doing what is right.

Truly professional would be to not make shit products worse than oem in the first place.

[DrWill]

Originally Posted by Wayno

Truly professional would be to not make shit products worse than oem in the first place.

there is literally no company that manufactures parts of any sort that has not experienced a failure of some sort. it happens. its how the company deals with it when it happens that defines them

[ST-A]

we had the exact same problem on our kraftwerks boosted project!
we installed the low temp mishimoto thermostat to gain some extra cooling, after only 3000km the thermostat failed like yours, leaving us with 2 blown headgaskets!

we now also have back our original thermostat in it.

after that issue happened i had a supra mishimoto thermostat on order for a 900hp project, when it arrived it wasn't flat on the mounting service, it was bend where they are pressed together. so we did not use it.


don't think i will use them again, my confidence is gone after 2 parts gone wrong in one week....

if they want to rectify this problem, they can contact me direct for pictures, the GT86 project we had to pull the engine, replace gaskets and bolts, had to resurface the heads, .... because a stupid new "racing" thermostat failing!! $$$ very costly mishap.