Removing the thermostat will cause the engine to overheat.

The front side of the thermostat opens when warm to allow coolant to go into the radiator, if this were the only function it might be OK to remove it. But the rear side of the thermostat extends to block coolant from recirculating back into the engine, if you don't block that passage some other way the engine will overheat.

Put your thermostat in a pot of boiling water to make sure both sides work, then put it back in the engine

 

Interesting, is that in street driving under both stop and go and at normal cruising speeds? My oil temps in heavy stop and go can climb to between 80-90 C (176-194 F) after a long time but at cruising speeds below say 60 mph it will be about 70 C (158 F) and above 60 mph at around 60 C (140). On track it shoots up to 80-90 C pretty quickly and start to climb after 1-2 laps up to 115 C (239 F) when I start cooling it down (so I get about 15 minutes out of a session). I can manage longer if I don't redline every shift but my brakes are usually getting spongy after 15 straight minutes of hard stopping.

 

239 is pretty hot but as long as it's not extended period of time it'll be fine. my z on the track sees 240f+ on the regular and the damn thing don't even have an oil cooler lol. once it gets 240+ cool down lap and easy on the throttle low rpm speed

 

Your Z doesn't have coolant seals. From what I've read, 240 F. is probably about where they start to degrade.


All the temperature comparisons are interesting but probably have little to do with the OP's overheating problem. He was running no t-stat, has a big air block and heater in front of the radiator in the form of a FMIC and is running no belly pan. Change those things and I'm pretty sure the over heating goes away...if the coolant seals haven't been damaged.

 

I never knew this but it makes total sense. If the path of least resistance is flow through the engine, the coolant won't pass through the radiator to cool off and will just get hotter and hotter. Makes perfect sense.

 

It's pretty common knowledge that 245 plus will warp the aluminum housings. Iron and aluminum cool at different rates which causes the aluminum to warp which means ruined engine and two expensive housings needed etc... I've heard of z06 oil temps at 295 LOL. Different strokes for different folks. The FD or 13b cannot handle high temps.

Again it's the cool down problem that kills it. Ideally you'd wont to wind the car down slowly if you see anything over 115c (I don't think the PFC even registers over 117 which is around 240 and that's not good)) but these issues usually happen because of loss of coolant or some other coolant issue and it's game over.

I'm not sure what's going on with the OP but clearly there is a big issue and it's likely due to the rebuild. Something could be clogged not allowing proper flow, coolant is low and the coolant buzzer isn't working etc.... Very common for air bubbles to be in the system and lots of burping is necessary.

Easiest way to fill the engine with coolant. Disconnect the TB coolant line and fill until it overflows. Wait 10 minutes and repeat as needed. Once you have it full drive it. It will likely still need more. Take the top off when you park it and top off the fill neck after each drive for the next few days and you should be good to go.

 

I like how Flynn took two lines of text to say the exact same thing I said but needed 3 paragraphs...

 

LOL.........I first thought you were talking about my 3 paragraphs and felt like an idiot

Anywho thanks for the compliment and didn't realize you already ess-splained this one

 

u guy are great. this was the help I was looking for from the rotary gurus. I will test the t-stat tonight and put it back if it checks out

 

I did notice one thing. when the engine is warmed up, the top radiator hose was hot and the bottom was pretty cool. The radiator is brand new so i don't think it clogged. May be air trapped?

 

worst thing is you got a giant rat stuck in the lower hose lol

 

Consider the flow direction....

Hot coolant comes from the engine via the top hose and exits the radiator (after being cooled) via the bottom hose.

Thus, what you describe is normal.

 

The bottom hose should still be pretty warm. If its cool something is wrong.

 

I assumed cool was a relative term in comparison to the top one. But I agree, it should still be fairly warm/hot to the touch. Just coolER than the top hose.

 

i guess a better way to put it is that top is hot and bottom is warm.

 

One thing that has be baffled is that both hose seems like no pressure on it. When u squeeze it, there no pressure on the hose. On my daily, the hose are tight when the engine is warmed up

 

Your daily also has a thermostat in it I'm betting.

 

yes I tested the thermostat in hot water and installed it back

 

make sure that when you burp the system (purging the air out of the system) you turn on the heater as air can be trapped in the hoses. 2, make sure that you have the correct cap on the t-stat housing (the one with out the spring) and the one with the spring on the AST.

 

since the radiator hose is soft when i squeeze I'm thinking there is some kind of restriction. I order a new Mazda thermostat and start from there

 

I should have said purge instead of burp. You need to purge all of the air out of the cooling system. In order to do that you need to turn on the heater during the process. Do you have a Lisle funnel? This makes the job much easier.

 

So after waiting for over a week, the local Mazda dealer finally got my thermostat in. Today I pull the thermostat that come with a car (brand new in the box) and notice significant differences between the two. The back of aftermarket t-stat is significantly bigger than oem and wondered if it was not blocking bypass. Left is the oem and right aftermarket

 

after installation, went to 30 ride. car hit 95-105c. I do live in very hilly area so i that normal? also I notice that the radiator hose is still soft, any ideas?

 

Did you install an undertray as advised?

Also, if it were me I would reinstall the AST. It helps get any trapped air out (but is probably not directly attributable to your temps)

Another also, is your oil cooler working/adequate? That will help engine temps. Are you able to measure your oil temps?

 

undertray is there. I don't think AST will help because I bleed the system many many times