Hello-

Why do people recommend against after market thermostats? I have heard alot of stuff about them. That they result in a 20-30% cooling loss, that they fail frequently, and that they will cause overheating.

Why is that? What differences between the OEM thermostat and aftermarket ones cause these things to happen? Are they more restrictive? Do they open up on a different temperature curve?

I have an aftermarket one in my car. It is rated to open at 180 degrees and i drilled a 1/16th hole for air to bleed through since it didn't have a jiggle pin.


Thank you.

 

So nobody knows?

 

you answered your own question.
The jiggle pin.
Plus the fact that the OEM is more dependable.

 

It's $21.00 bucks and change from a Mazda dealership for OEM. Why mess with ahving to worry that the after market is doing it's job when you know for a fact that the OEM will. Not worth the worry for the difference in price.

 

Always went OEM but heard the lack of a jiggle pin was one issue, and also problems with poor quality gasket/seals.
If you've got a thermometer and an old sauce pan, you could test whatever T-stat you get.

 

has any 1 ran without a thermostat?

 

I am running an 87 RX7,na.
No problems.The gauge stays around 1/3 of the way to center of the gauge.
I figure it this way,once warmed up,it stays open from either half open,to all open,anyway.
Especially here in Az.I have another person in town that does the same thing.

 

Many years of reported problems, including:
- No jiggle pin
- Bypass function does not work properly
- Wrong heat range

Yes, but this is not recommended for a street car. Since the thermostat is a bypass type, you need to plug the hole below the thermostat if you remove it. Otherwise, the engine may be subjected to heat stress that may not be indicated on the temperature gauge because the sensor is mounted above the problem area. You can read about the plugging process here, but again, it is intended for the track only:
Rotary Tech Tips: Water Cooling

About bypass type thermostats:
ARE Cooling (Aluminium Radiators & Engineering P/L)

 

Thanks everyone for replying. I am planning on getting the OEM one, but the one I have seems to be working fine. Runs normally around 1/4 and gets up to maybe 1/3 when I drive up the 1 mile hill to my house (~800 foot elevation climb).

A hole is basically equivalent to a jiggle pin, the only difference is that it will always allow coolant to pass (resulting in a slightly lower running temp, which actually should be mitigated by the thermostat itself), so I don't see that as a problem really with my non oem t stat.

The thermostat I have has the equivalent heat range of the OEM one (180) so that is not an issue unless the opening curve with respect to temperature is significantly different than the OEM one. (person at parts store told me that a 195 one would be fine, I told him to **** off)

I read the link you shared about bypass thermostats and that makes sense. My car usually warms up relatively quickly (~1 min idle + ~4 min of driving), and it doesn't seems to run hot, but does get hotter under load. Once I have the OEM one installed, I'll have to see if there is any improvement in temp under load. If there is no change, then I don't see anything wrong with using that t stat.


These types of things kinda annoy me. You will keep hearing the same warning over and over from people (which is probably a very real and important warning), but will never hear the reasoning behind it (at least specific reasoning). So if im stuck somewhere in a small town with no mazda dealer and no OEM rx7 t stat in there little auto parts store, I can't determine if an aftermarket t stat is okay to use to get me home. All I know is "NEVER USE AFTERMARKET THERMOSTATS CUZ THEY'LL MAKE YOUR ENGINE BLOW UP OR THEY'LL DIE AND GET STUCK CLOSED OR THEY'LL JUMP OUT OF YOUR ENGINE AND KILL YOU AND EAT YOUR CHILDREN"

Course when the wrong thermostat can be so damaging to an engine, I begin to understand the warnings that even the people who know what they're talking about post everywhere and spread around. It's very easy to not notice a stuck closed thermostat, and then blow your water seals..

For my engine though, it was actually the OEM t stat that got stuck closed.. lol

Now I'm more likely to crash into something that be caught not knowing exactly what that gauge reads..