Thermostat replacement...
 

Hello all!!!

I ran into some considerations the other day, that is, if I upgraded or downgraded my cooling circuit. :lol:

So here it goes... I changed the old 82C (180F) thermostat that was drilled peripherally all over with a new 75C (167F) thermostat.
I didn't new it was drilled by the time I took it out (I am new to rotarys and thought that those LOONG warming up times were normal lol). It had approximately 14 holes, 2mm (0.0787inches) each! But still, I replaced it with the 75C unit...

I get the same readings with both of them. Only thing that's changed is that warming up now doesn't last for 30min. :lol:

Did I do any good with the 75C or the multi-drilled 82C thermostat was better?

Marios

The new one is probably technically "better", but you should still be using a 180F thermostat.

Not only that the non-OEMs are failure prone and often restrictive too. Head down to your Mazda Dealer or order one online from mazdatrix.com or rx7.com. Ya that old one was pretty screwy. It is bad for engine wear to drive the car hard before it has warmed up. My car takes maybe 5 minutes if that.

Thanx for the quick replies! :)

I installed this one at a Mazda dealer. :scratch: I tend to treat the right pedal with a little heavier foot than the middle one :blush: :lol: so I thought a lower thermostat would be better (also here in summer it's way too hot lol). I also take my car to trackdays, circuit or drifting.

So if the lower thermostat will cool better than the drilled original I'll be ok. That's what I wanted to know... :)

Yeah it was annoying to wait for about 30min before I could step on the gas. Especially if other "wanna-beat-RX7 drivers" came across me during warm up lol.
Now 10mins and I'm good to boost hehe.

Oh and something else... Is the stock temp gauge accurate? In case of an imminent overheating will it respond? Or when it does it will be just to say "Game over"?

Thanx a lot!!!
Marios

:)

This ultra long warmup confuses me.
Even in subzero weather my car hits nominal temp in just a few miles/minutes using a stock thermostat.

The S4 gauge is generally considered more responsive than the S5 unit, but they are both inferior to an aftermarket part.

Clokker thanx for the info!
Yeah, cause my stock thermostat was drilled all over its periphery... :icon_tdow :lol:
That's why I'm wodering if that one was more effective than the new lower I installed... :scratch:

Weird that the dealer would have that temp on a thermostat. Maybe it was designed for another Mazda car. The motor will function ideally at the recommended operating temperature, but the t-stat you have should be close enough. If you want improved cooling make sure all the air is directed at the radiator: foam or other blocking of side passages is in place and plastic undertray is in place. Make sure the fan has some resistance like peanut butter is inside when you try to spin it manually. Change the coolant and thermostat every 12-18 months using distilled water + antifreeze and OEM thermostat, inspect hoses and belts on schedule.

And ya, the slower warmup was bad. Not good to push the engine hard while cold, so that one made you wait longer or else increased engine wear.

the dealer t-stat is differnt from basic aftermarket designs, it works correctly for the rotary engine and the others do not PERIOD!

I wasnt a beliver it untill i had a extra $20 laying around, went down and gotta stat, threw it in and the rest is history. running at the correct temperature for what the engine is tuned to makes all the differnce.

Thank you very much for the advice!!!
Ericgrau thanx a lot for the tips! :) I even fabricated levers that keep the license plate inclined and use it to direct air into the cavity from the lower side. :icon_tup:

So I should maybe switch to an OEM thermostat... In the past I was experiencing several fuel cuts, which now carry on with the new t-stat... I thought it was due to possible faults to the exhaust system (boost creep), so I put an FCD just to check. The fuel cuts persisted... :(

Is there also any fuel cut mechanism when the engine is colder than operating temperature? I ask cause if there is, the thermostats could be responsible for my fuel cuts. :scratch:

Thanx again and let me apologize if I cause you headaches or annoyance with my terrible posts...

Bye! :)

I had a stant thermostat work perfectly for over 3 years and 60,000 miles. It just went bad (stuck closed) a few months ago and I replaced it with an aftermarket one. You can tell a crappy one from an OEM quality one by looking for the jiggle pin and the overall design. My temps were exactly the same between the two, the new one being an OEM quality one.

Nippon is the same as OEM (jiggle pin and all) but otherwise you could easily run into trouble if you don't get OEM. You could get lucky, but why gamble? I've had a Stant partially fail within a month, and a major headache stuck in the middle of nowhere for a few hours (had to walk to get more coolant) from another a previous owner put in. Changing the thermostat and coolant every 12-18 months is a very conservative schedule - you may get away with less often - but given that overheats are the number one cause of engine failure in NAs it is warranted.

The Haynes manual should describe the ECU consequences of running without a t-stat (or running with one that likewise doesn't quickly warm up the car, I'll bet). IIRC it forced the car to stay in open loop causing the loss of 2 mpg. I don't think fuel cut is related, though maybe the s5 is different. An s5 owner could tell you. s5 is 1989-1991.

Infernal,
If your 75 C thermostat is a good quality one you should have no problems with it. I would not go lower than 75 C though. So keep it and there is no need to change it.

Thanx for one more time for the replies!

Well, my intention was to prevent an imminent overheating cause usually my rear wheels spin a lot more than the front ones... (You know, basic stuff like burnouts, slides, drifts and the like.) That's why I chose to put a lower thermostat - not the OEM one. To deal with the "unusually less" air flow to the radiator... :blush:

If the only main drawback is fuel consumption, that's a price I can live with in favor of my engine's health. :nod:

Thanx RHDturboII! I think it is of good quality cause I paid 120 euros for it! :lol:

if your fan is working corrcetly, you'll be fine with a stock thermostat

I'm sure the OEM one is the better choice, but I've had one stick closed on me causing an almost blown coolant seal. So they have their problems as well.

Ya I think OEM is better b/c at best the aftermarket one will be as reliable. But as said 75 is close enough so you might as well leave it in if it's good quality. I doubt it'll have much effect on your actual operating temperature several seconds after the vigorous driving starts. All a t-stat does is cut off coolant flow when you're too cold; it's not like it can make the coolant move faster when you're too hot.

Oh well, I think I'll "test drive" the now t-stat and push the limits to see what happens. It's getting hot here in Greece so I'll give it a shot. I hope the stock temp gauge will respond in case of an imminent overheating... :blush:

I think a lower t-stat has a lower threshold at the point it fully opens, so coolant will start to flow earlier than with an OEM one. :scratch:

Ya that's possible, though an overheat doesn't happen until 250ish anyway and "possibly too hot" is over 200. Probably a minor difference.

The 1986-1988 temperature gauge is pretty good. 1/4 is normal, about halfway is 200 degrees, 3/4 is hot (215-220?) and 7/8 is overheat. The 1989-1991 gauge stays in the middle and barely moves most of the time so it doesn't give much of a warning of an overheat. If you do ever overheat pull over within 30 seconds to prevent engine damage; don't wait for the exit.

Regular scheduled cooling system maintenance according to your owner's manual (or a lot more often to be safe), making sure all the cooling system ducting is in place - foam preventing air from going around the radiator and the plastic undertray - and making sure the fan resists attempts to turn it manually like there's taffy inside are the real ways to keep your temperature in check.

Thanx a lot ericgrau! I got an S5 and yeah, I haven't seen the needle ever move during driving, after the warmup... :( :( :(