my reference thread: https://www.rx7club.com/2nd-generati...1033485/page3/

well, I have changed the water pump, the radiator cap, converted to e fan (although with my old stant t-stat and e-fan it stayed at 1/4 unless idling or under heavy load on a hot day. so not e-fan problem). e'fan is hooked to ignition until this weekend when I have time to finally wire up my temp probe and relay.

genuine mazda oem thermostat for 86-88 cars. it is the newer version part # ending in -9u. My car now runs at half way up the gauge constantly. I have bled it a few times and it doesn't look like there are any more bubbles. its working and rock solid at 1/2 though. history: when I first got the car, it was also running at 1/2 up the gauge. When I replaced the t-stat, the old one looked oem (jiggle pin and the three legs on top side instead of 2 like most aftermarket). replaced it with 180 degree stant with 1/8" drilled hole in place of jiggle pin and ran at 1/4 on gauge. but stant sucks and apparently a few months later it was failing so mazda oem now. why is it 1/2 way up the gauge and is this ok to run?

 

I replaced mine earlier this year in my S4 and S5 with OEM. They too read about 1/2 way even after repetitive bleeding. Before replacement my reading was about 1/4 way on the gauge. I think this may be normal?

 

I'm not sure. I know that the part #'s ending in -9u are the newer style revamped mazda designs. the jiggle pin is closer to the center. I don't know if this is a problem on an s4. it was designed to run at 1/4 after all. s5 read 1/2 but the stock gauge is so slow to react its useless I hear.

I'm thinking that maybe the -9u models must be 190 t-stats and the old style was 180 on s4's but thats just a guess. as long as it doesn't go higher then half I can live with it I think. I believe that 1/2 on s4 is around 200 degrees if I recall. I think the engine can live with that. It's genuine mazda t-stat for 86-88 so if mazda thinks its ok then I guess its fine. it was running at 1/4 with that stant (other then idle and load overheat) so I know its not anything else unless its bleeding thats needed. I'll bleed it a few more times just to be sure though.

 

Although it is nce to stay stock I wouldn't trust the Temp gauge.It's like a dyslexic squirrel!..can't read right and it is half nuts!
If you have an Efan,then why you not got an aftermarket Temp gauge?
Cookies and milk..should have both..heh,heh.

 

did the e fan when I had idle overheat. just done recently and still not even wired to a temp switch. I have to do that this weekend. another temp sensor is on my list as well.

 

temp gauge with actual numbers will be the only way to tell if the gauge is crappy or the temp is getting too high

 

New t-stats dont have the jiggle pin anymore right? Drill a small hole and put it in the upper right corner of the housing (mounting bolt). Air is probably getting trapped causing a poor reading.

 

I had the same issue with a stant thermostat. S4's should only go 1/4 way up, S5's go half. Mazda was a lot more expensive but mine's been rock solid. I agree with styx, get yourself a temp. gauge!

 

I had that style in the pic origionally when it ran at 1/2. changed to stant with 1/8 drilled hole in t stat like you said but it failed with little more then 4,000 miles put on the car. the new style mazda oem t stat (# ending 9u) has the jiggle pin but its inside the center part of the t stat (under the "legs").

anyway, I may have found my issue. my thermostat housing is leaking between the seal. both bolt heads broke when I changed it to stant. had to drill and re tap them but the bolt closest to block is stripping out towards the end and not holding it tight enough I guess.

will a s4 t2 water pump housing work on my s4 na? I have one laying around but need to know.

 

nevermind, I'm gonna run the t2 housing and block some nipple that would go to a turbo.

 

I always convert my tstat housing neck bolts to studs. That way you can apply some real torque when changing stats without cracking or stripping.

 

Yes, +1.

 

^thats a good idea but the heads broke off the first time I changed my t stat. I'll do that this time. at least I have another housing that will work.

 

Before I replace the housing, I'm going to try and see if I can get a stud to thread in and hold in there. then the nut on the outer side would be pulling the torque. the bolt catches until the very end of its travel so it might work. then I just need to replace one gasket and a lot less work.

 

You did't swap the coolant temp sender did you?

 

No but I bought the car with 130k miles on it. my coolant reservoir was over by my engine bay fuse box which I don't think is oem? maybe it was on some models. I have a base/sport with the little black duck bill spoiler and no sunroof. I have no idea what could have been done. my 180 degree stant stat ran at 1/4 until it messed up.

anyway, I have that leak that may be letting air into the system. someone made a good point and im going to helicoil it and run the stud. Then when its all set I'll see where it runs. I don't expect much lower then half though as it is still rock solid there.

I did hear some other s4 owners running at 1/3 and 1/2 on stock gauge and they just run it that way. doesn't seem to pose a problem. Do I need an aftermarket temp gauge to run off the stock sensor or should I need an aftermarket sensor as well? I would assume both but just checking.

 

You'll need the sensor to match the aftermarket gauge.

 

managed to get a nut on the backside of the bolt for the thermostat cover and no more leak, gasket and rtv that has already set seem to be holding up.

temp on stock gauge has moved a splinter down after I bled it a few times to make sure. so its around 1/3 I'd say now but all the air is definately out. also wired my e fan to my temp probe. its a chili rainy day so I still have to adjust it. for now I drove the car for a while. stopped and let it idle for a while and turned my adjustment **** to where it just barely goes off. no more constant 30 amp ignition load on my system until the fan comes on. as I was told however, I will be needing a higher amp alternator. looking to get mine rewound instead of going taurus or FD.