DaleClark

iTrader: (55)

Hey guys -

Trying to figure this one out.

As some of you know, I cut my teeth on FC's and TurboII's. The hard and fast rule back in the day was ONLY use a Mazda thermostat. Saw parts store thermostats fail time and again, either out of the box or a month or two down the road. Mazda T-stats always treated you right.

When I first bought my FD I put in a good Mazda thermostat along with a flush and fill, just good general maintenance. I rebuilt my motor around 2 years ago and put a new t-stat in again with a new seal and everything. The T-stat came from Mazdacomp.

Well, this weekend I went to flush/fill the coolant - it's a REALLY good idea to do this once a year. I went ahead and checked out the thermostat while I was in there.

Sure enough, the rubber seal inside the thermostat had badly degraded. Most of it was missing. Mind you, my car NEVER overheats, runs 80-90 deg. C all the time, and has very few miles over the past 2 years.

On Mazdatrix's page, they list the OEM thermostat but state "Note: We have had several problems lately with the OEM 89-95 thermostats due to their rubber seal failing. For this reason, we sell the Stant thermostat for this application."

This is exactly what happened to mine. I'm looking to run a Stant thermostat, but I'm really leery of it.

BTW, here's another thread on Mazda thermostats where some people have discovered that Mazda has changed around their part numbers and stuff -

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/aint-got-no-jiggle-642855/

Attached are pics of my thermostat. You can see the missing rubber seal inside. The outer sealing washer was chewed up, but that might have been from removing it from the car, I'm not worried about that.

What do you guys think?

Dale

Mahjik

iTrader: (1)

Sard FTW

arghx

iTrader: (3)

I have heard similar things as well. I have used a stant thermostat and drilled a small hole in it in lieu of a jiggle pin used in the OEM one.

DaleClark

iTrader: (55)

I'm leaning towards using a Stant with a drilled hole. Might have to check into a SARD for long term, have a feeling that won't be cheap .

Anyone else have any experience with this? Big thing is I don't want the thermostat to go out on me at Deal's Gap!

Dale

SonicFD

iTrader: (17)

Make getting a Sard, Billion, Stant, etc one of your reliability mods. Don't buy OEM because Mazda's cooling parts are not worth buying lol.

MOBEONER

iTrader: (18)

sard Cooling Thermostats (93-95) Mazda FD RX7 (FD3S) $95.00....ouch!!!!

last winter My buddy's FD was over heating. We went and bought an OEM thermostat and i drilled two small holes in it. He drove it all last summer with no problems. Now i am tempted to tear down his thermostat housing to see what we discover. Now i am paranoid.

MX722

iTrader: (1)

Dale,

The Mazda thermostat never caused you any over-heating issues, correct? Merely just the issue of the rubber seal falling apart.

Why not just replace the seal and keep the thermostat as opposed to replacing the entire unit?

Basically, what makes the aftermarket company thermostats any better/effective than OEM?

grimple1

iTrader: (1)

because it's inside the thermostat. It's not the seal that's lying beside the thermo in his picture.

The aftermarket question is one that you can ask about anything... what makes an after-market radiator better than Mazda's OEM? well, a lot actually.

Scrub

iTrader: (25)

Has anyone had problems with the seals degrading while using NPG+ coolant? I'm installing a new filler neck in the next few weeks, kinda interested to see what the seals look like.

That is quite concerning.

DaleClark

iTrader: (55)

Did some looking, and the SARD thermostat is available for around $80ish or so. My big beef with it is the low temp - it opens at 68 degrees C or something. Might be good for track use, but not for a daily driver or street car.

The good thing is if the rubber seal fails I believe it will just keep the two halves of the thermostat from sealing, so the car will actually run too COOL instead of too hot. My old Nissan Quest van (the one with the horns ) had this exact problem when I bought it. Took forever to warm up, pulled the thermostat and the rubber seal was damn near gone.

Really, it's a case of using the wrong type of rubber for the job. A proper rubber seal that can take the heat and deal with coolant immersion would work fine. There's nothing here that's special for a rotary - the coolant temps and pressures the thermostat sees are identical to any piston driven car out there.

Regardless, it's disheartening that Mazda has changed something in the thermostats that makes me question them. This has been one of my "pillars" for a long time - you could at least feel good that putting in a Mazda tstat would result in zero problems for years to come.

I drilled a hole in my Stant thermostat last night and I'll be installing it hopefully tonight - I also have all the belts off the car, doing my last round of cleaning and preventative maintenance before DGRR.

Dale

futureshock

is there any downside to running the FD without the thermostat. I live in trinidad and its really hot most of the year. thank you

AzEKnightz

iTrader: (24)

increase in emission, LONG warm up time, fuel consumption, might also causes your fans to not operate correctly due to the "cooling" stays cool for MUCH longer and doesn't get up to tempt.

However it would be great during cruise and higher speeds.

I dont suggest removing the T-stat completely.

-AzEKnightz

DaveW

Dale, do you have any idea when these problem thermostats started to be used by Mazda? I replaced mine in 2005 and have not noticed a problem.

Natey

iTrader: (19)

I put a t-stat from Kragen into my FD, then read all the horror stories of them going bad.

I've really been watching my gauges, and in my experience, the generic one opens sooner than the OEM Mazda one (that had countless miles on it). I'll get back to you on it's durability, but so far, so good.

nashman69g

iTrader: (3)

I'm starting to wonder about mine...I'll try to remember to pull mine and report my results back after I finish my bathroom remodel.

Marshall

Speed of light

iTrader: (8)

You guys don't think SARD actually makes the thermostat do you? It's someone else's part re-badged/re-boxed and sold for big bucks. You can go ahead and make the resale guys rich.

I have had the rubber inner valve seal fail on the OEM thermostat and get pinched in the valve (look closely at the pics). The OEM part is unnecessarily complicated....a thermostat is a decidedly low-tech device. Carquest does list/sell the original style OEM part number with rubber valve seal, if you want it.

The revised OEM replacement, which I bought from Ray, was different in that it didn't have the seal or jiggle pin, however; it FAILED OPEN after about two years of use--motor would not warm up. I think it was a Beck-Arnley part.

So I just replaced it with a Stant, which works fine. While they don't look impressive, I've used Stant occasionally for more than 30 years with otherwise good results. FWIW, I have a 30 yr old Stant thermostat in my '68 Plymouth that still works, and which appears to be of the same design as current models. *What you likely don't want is a Chinese or off-shore knock off of unknown quality*.

DaveW

I wonder if some coolant flush or other aromatic solvent/oil that got into the cooling system caused that to fail - it looks decidedly swollen, as if it had been soaked in gasoline.

Dave

futureshock

thank you for the info.

My fans are hooked up directly @ the moment and they help alot when i cruise around(88*- 90*) but the moment i step on the highway my temps go up to 96* and even then, when i slow down and cruise on the highway it still remains @ 96*.
I have a koyo radiator, FMIC and i'm also single turbo(400hp) and also have a apexi AST and i also use texaco coolant. I was wondering if i remove the thermo, if it would help out a bit. thank you

Tripple 7's

The last one I got from Mazda was a re-boxed MotoRad http://www.motoradusa.com/ProductImages/322.jpg p/n 322-180. On there web page they even list a high flow one is available.

jkstill

iTrader: (11)

The tstat in my FD is one I got a couple years ago from MazMart.

It is a Mazda tstat modified to open earlier than stock.

So far no troubles with it - no leaks.

BTW, they seem these tstats seem to be in perpetually short supply.
I owe one to someone and MazMart never seems to have one.

FDSeoul

iTrader: (8)

+1 I am running the ARC(same manufacture) but i think i paid like 85usd for it!!!

DaveW

Geez - I meant 2005...

mdpalmer

iTrader: (24)

Hm... I put a Mazda "OEM" t-stat in a few months ago when I put my w/p in. Haven't had any problems yet (about 3k miles), water temps have been around 80-90*C in SoCA roads, mountains, and auto-x. It did NOT have a jiggle pin in it... I just drilled a hole in it. My old t-stat's rubber was actually in pretty decent shape, had about 20k miles on it. Here are some pics:

old:



new:
see gallery

Speed of light

iTrader: (8)

Dave,

That's a good observation. I know factually that nothing other than coolant/water was intentionally run through it for the 10 or 11 years it was in service--it went in with a motor and came out with it. Since I've always owned the car, I know that there was never any flush in there, nor would there have been contact with any solvent that I know of. The system was always maintained and is/was still clean. Additionally, the motor was running (@104k+ miles) but pulled due to a coolant seal failure, which is an interesting link in and of itself. What I have wondered about is the possibility that mid 90's dexcool compatible a/f may have been run in there and if that was a factor. Interestingly enough, I did have an original radiator cap that also exhibited swelling on the pressure sealing washer. However, no other cooling system elastomeric components, including some of the original hoses, showed any unusual deterioration when I finally replaced them 3 years ago.

I am puzzled by the need for that seal. A standard metal poppet valve doesn't seem to leak any appreciable amount.... Nevertheless, I wonder if this was necessitated as part of the factory's quick warm up scheme(?).

Joe

Speed of light

iTrader: (8)

Problem is that there is nowhere for your engine's heat to go and the FMIC is likely your culprit. Many, if not most, FMIC configurations I've seen are incapable of allowing adequate airflow to the radiator, and therefore, cooling is marginalized. By contrast, I have a super-efficient, properly ducted v-mount that holds temps exactly at the point where the thermostat opens regardless of ambient conditions, A/C use, speed, load, whatever.... it doesn't matter. And that's with a smaller Fluidyne radiator. It's all about airflow through the radiator.

If you want to improve you cooling system performance, you will need to get more air through your radiator, either by ducting, partially bypassing the FMIC, or by ditching the FMIC all together. It's not likely that playing with the thermostat is going to make much of a difference for you--except to maybe delay the inevitable.