i have a rb25det in my s13. isis aluminum radiator. dual isis 12" e fans. 300zx 170* tstat. and my prosport water temp gauge says it is 220* while driving normal.
i know thats way hotter than it should be but i dont know why. i have flushed the radiator and engine 5 times over the past couple months and it has made no difference. im using a 50/50 prestone antifreeze water mix. system has also been properly burped after each flush. and i have a circuit sports surge tank/swirl pot aswell to get any excess air out.
so im basically looking for input as to what could be the cause. or if anybody elses rb runs this hot. temperature has also been double checked with a laser temp gun.
thanks

 

oh yea i forgot to mention that even at 220* there is no pressure in the system. you can open the radiator cap and no coolant shoots out. just a very small amount overflows. and you can squeeze the radiator hoses with the cap on and they are soft and have no pressure.

 

Did you make sure the tstat is actually working? Is it OEM or autozone?

 

Its a stant t stat from advance auto. And no i didn't check it. But I took out a nissan oem one that had about 4k miles of use on it. And it had the same issues with that one in there.

 

let me guess, this started at the same time it started running "sluggish"

coolant temp sensors will cause that problem.

well, there are a few things that could be happening.

you could be over boosting, which is causing a lean burn situation in turn causing excess heat.

your injectors could be taking a shit, causing the same situation

fuel pump and or FPR could be taking a shit causing the same situation

or you forgot to change your oil and that is allowing for extra friction

Or you have some gay e-fan thing going on that doesn't move as much air as it should

or your radiator itself is clogged up (I know you said you flushed it, but you never said how, so I'm assuming you poured in a bottle of flush and ran it for a bit then drained it out. which won't clear clogs)

or you didn't really get all of the air out

or your temp gauge is wrong

or you "think" it should be lower than 220 degrees when that might actually be closer to what it should be. Have you gotten the FSM yet to find out what operating temp should be?

BUT
most all of that gets thrown out the window when you say the system never pressurizes.

That is impossible at 220 degrees.
That would lead me to believe that it is possible that your water pump is taking a shit.
And/or your radiator cap doesn't work.

what happens when you just run the engine with the cap off? It should start to over flow once it starts getting hot.

at 220 degrees, with a functioning cap, it should erupt when you take that cap off.

 

no this just recently started happening. it has always been under 180 at the hottest. not overboosting. wastegate spring is 8psi, boost gauge says 8psi, wideband never reads higher than 12:1 at wot. fuel pump and fpr are good. set at 38psi base pressure. and pressure rises linearly when revs are increased. oil has been changed once every 2 months with valvoline sythetic blend 10w30. the e fans arent as strong as i would like but they are rated at 800 cfm(1600 combined) and are supplied 13.9 volts when the car is running. ill have to double check the fsm to find the right operating temp.
and if you idle the engine with the cap off water evenually makes its way out of the radiator but not with any force it just drips out. when the engine is reved the water level drops into the radiator and when it idles it comes back up to the radiator fill neck. i also thought it was a cap but ive been through 3 caps(one nissan, one stant, and one circuit sports) with the same result from all. i also pressurized the system with a mac tools cooling system pressure tester and it held 16psi.

 

i have also checked the temp with a snap on solus scanner and the stock coolant temp sensor reads within 10* of the prosport gauge.

 

ok, so what I could find, 80-85* C is normal, up to 90* C is acceptable.
So most people run between 175 and 185 degrees F and you can get up to 195* before you have a problem. but that should only be on hot days, at idle.

I say it is the water pump.
maybe get a long extension and/or screw driver, stick it to the pump and listen. You'll probably hear some nice grinding noises.
You've probably gotten away with it for the last several months because it has been cold enough to just pull the heat off. and I'm sure you have some water moving around in there. just not enough.

So my money is on water pump and probably needing a new radiator cap since, even with the pump dead, the heat alone should pressurize the system some.

I'd also bet that getting the temp back down where it should be will fix that sluggish problem you have.

 

yea idleing it sits under 190 but after a minute or so of driving it climbs up to around 220.
and i have been hearing a very feint noise recently. sounds like a wahh wahh wahh. almost like timing belt whine. so ill have to check and see where that is coming from.
so i guess ill get a new water pump and hope for the best. ill keep this thread updated on whether or not it fixes the problems

 

your water pump prob looks like this...