Stock radiators are crap. The plastic parts always end up cracking.

 

My 86 FC still has the original plastic ended radator, not a single problem, had a thermostart issue earlier in the year but that was an unrelated. I've only heard of a stock radiator failing but never seen it, i live in AZ where you'd think it would have died long ago . . .

EDIT: oh yeah, my 88 TII ALSO has the original stock radiator too

 

my koyo leaks as well from some where on the fins. It's a small one so I don't bother getting it fixed. I just top off evry couple months.

 

My stock radiator cracked along the plastic part. My car was completely stock at the time. I've got a friend whose radiator cracked at the same spot. The radiators are good, but eventually the plastic part will fail.

 

I may do the electrolysis test tonight

 

Aluminum alone, yes. However, it is my understanding that once the aluminum has oxidized, and formed itself a layer of aluminum oxide, which is far less reactive, the zinc becomes the sacrifical anode.

Having examined the slight pitting on an installed zinc anode, it would seem that the theory holds true.

My aluminum outboard engine also uses a zinc anode. Where the paint has been scratched off and bare aluminum has been exposed for years, no corrosion has taken place to the aluminum, while the zinc is badly corroded.

 

How/where did you install/attach the anode?

 

TIG a bung on somewhere accessible.

 

People regurgitate info all the time. Doesn't mean it's right.

Most NA owners don't make nearly enough power to need a radiator upgrade. Capacity-wise the stock one is fine. Even mildly modded turbos (which use exactly the same radiator remember) don't have problems in normal duty. Track work might be a different story though.

The stock radiator is crap because the plastic parts fail at 20-odd years old? Show me plastic radiator parts that don't. Welcome to the real world. Like any other part, if it fails you replace it, and you can expect another 20-odd years of service.

Upgrades aside, the only real advantage an all-aluminium replacement radiator has is that they tend to be cheaper because they're not OEM.

 

just a FYI, I got my stock rad off radiators. Its all brass as far as I know, and painted black. Works damn near perfert even without the belly pan.

 

Anyone out there with a Koyo notice the water temps are too low this time of year??

I'm pretty sure my thermostats are stock, and I ASSUME they are 180* thermostats, but the water temps are in the 160* range. Two cars, both with Koyo, same temp readings this day.

I'm thinking of blocking off part of the radiator front surface with????? piece of paper, cardboard or the like to get the temps up to 180*.

 

^I was thinking the same thing today.

I was on the highway doing 80 and it barely was hitting 175 after giving it more load.

 

I'd check them. If you don't know what they are, they somebody else must've put them in, so who knows what they are.

With a functioning thermostat, a radiator can't overcool an engine. If the coolant temp is below the thermostat's opening temp then there's no coolant flow through the radiator. Blocking it's airflow won't do anything.

 

Yeah. It defies common sense. I shoulda kept my mouth shut. Now I've gotta pull a thermostat and put it in a pot of heated water to find out. Both, in fact all the thermostats I have are from Mazdatrix, and I ASSumed stock and 180* thermostats.

Then again, If I blockoff a good portion of the radiator and the temps stay up above what I've been seeing, then that proves they are not shutting all the way or are the wrong temp thermostats.

 

The opening temp should be stamped on the thermostat. If it's the wrong temp, replace it. It it's the right temp, test it.

I'd be surprised if Mazdatrix gave you the wrong temp thermostats though. They don't list anything other than the correct one.

 

Pointless to do that test since they are so cheap to get.

 

Nope. I've got three from Mazdatrix and NOT buying another.

No numbers on the thermostats as seen the the attachments.

Got a pot of water at 160 degrees steady. Put the thermostat in it. The thermostat cracks open. Not all the way, but cracks open. It won't fully open til ? around 180 degrees.

I'm convinced that the kOYO cools enough with the thermostat just cracked to keep the internal water temp at the 163degrees I see when driving at a steady speed. It's not like the thermostat will just pop wide open when you hit 180 degrees and stay closed below that figure. Thermostats open gradually til wide open IF the water gets hot enough.

Go to the store. Temp is 163 before shutting off. Go shop. Come out. Key just to ON. Temp is 174 degrees. Start up and drive for a quater mile....temp 163 degrees again.

Outside air temp is 40 degrees.

OR does a 180 degree thermostat START cracking at 180 degrees?

 

OEM thermostat is supposed to START opening around 180 and be fully open at around 200

I have a 180 degree thermostat, with my aftermarket stock rad my temps will be at 180 +/- 5*F in 10*F weather.

Its obvious when your water temp goes below 170 that the thermostat is opening to early. You could have 5 koyos in series and the water temp should still be 180*F with the right thermostat.

 

oh.

Then they don't sell 180 degree thermostats at Mazdatrix. Never bought one from anybody else.

I did notice in the past the little white box they came in had no writting on it plus the lack of numbers on the thermostats. Had a jiggle pin though.

Cardboard on the Koyo coming soon.

 

They are definitely not the right thermostats for our engines. I'd replace them with new ones from Mazda. The ones I bought from them have "82degC" marked on them and open up right when they should. Perhaps you should have Mazdatrix on about it too.

Personally I wouldn't half-*** around with cardboard to make up for incorrect parts. Too random, too hit-and-miss...

 

Fluidyne FTW, first of all. No quality issues with mine.

As far as the thermostat... I've noticed in the winter that my car would hover around 160 or so as well unless I start to boost it. The previous owner said he put in a Mazda thermostat, but it may be from Mazdatrix.

Can anyone confirm that Mazdatrix does not actually sell OEM thermostats?

 

Their website says the S5 ones are from Stant...

 

Ahhhh. Your no fun. Let's see. One size cardboard for forty degrees, another size for fifty and on and on.

Yeah. Just kidding. Someday, someday I'll go to the local dealer, order one that they won't have, wait three weeks and have them tell me it's coming from Virginia, wait another week whereupon they'll tell me that can't get one. I've had similar experiences with the local Mazda dealer plus their three hundred percent markup.

I might even waste a buck or two calling Mazdatrix.

Series four cars all.

I used Stant on my first generation and I had no problems, unlike the stories told on this second gen forum, which are all negative about Stant. PepBoys, here I come.

 

I have been using thermostats from the auto store for a while. I can't remember which brand or brands I used that didn't last long, regardless of what people say I don't think its due to the "rotary engine", just the quality of the T-stat its self. The one I have in my car right now has laster for about 1.5 years so far and got it from AdvanceAuto Parts. Might be stant. can't be for sure though.

 

Just use one piece. Mark lines at 10deg intervals and fold over as required...

Man your dealers suck. All the parts I've ordered from Mazda were either in stock (including the thermostat!), same day or next day from the warehouse, or one week from Japan!

Yeah but most 1st Gens make about half the power of an FC Turbo...

Hey, are we off-topic?