rusty FC

iTrader: (7)

about 2 weeks ago i went to drive my rx7, and i thought i had all the problems taken care of. but i did not get even 1/2 mile from my house and its running hot so turn around and by the time i am home it is way hot not pegged out but up there so i turned it off and coasted up the driveway. get out, pop the hood put my hand on the radiator and the cap and its dead cold. so i think its got to be a bad thermostat. so i get a new thermostat put in go to test drive it and same thing again!

what could cause it to get that hot that fast?

i looked to see if the water pump is working at it appears to be just fine. i am going to take the radiator to the shop to have it tested, to see if it if flowing correctly. (will get an upgraded koyo to replace it )

anyone have any other ideas?

my car and mods are;
1988 turbo II
s5 turbo and manifold
s5 top mount intercooler
jdm non cat down pipe (2.25 inch)
2.5 muffler shop duel exhaust no cats
rtek 1.8 ecu with 750cc rc injectors primary and secondary
no emmissions (rats nest delete)
throttle body mod
a/c, p/s, and air pump delete

lduley

iTrader: (1)

Sounds like your on the right track, only question i have is, did you put the tstat in correctly?

welfare

are you sure that the reading is accurate? hit the waterpump with a thermogun to confirm

RotaryEvolution

iTrader: (30)

is there a lot of pressure being built up in the system within just a few minutes of starting the engine?

Jpk3200

Are you taking your readings from the stock gauge? If not, what is the actual reading from your aftermarket gauge?

My guess is that there could be a bad sending unit, bad connection from sending unit to gauge, or something with the gauge itself.

This happened to me before. I thought I was overheating because by the stock temp gauge (S5) read maxed out before I even left the driveway. Naturally I panicked and shut the car off immediately. Checked coolant levels, etc. Everything fine. Start up again the next day, same thing. Took me a while to realize it, but the gauge would climb on the cold engine without the car even being on, just with key to ON. It would climb faster once the vehicle was started, but nonetheless, it would max out with key to ON in about a minute.

I would check to see if your gauge behaves the same as mine did,. Either way, might be worth pulling the sending unit and testing as per the FSM.

rusty FC

iTrader: (7)

i did get the thermostat in correctly, that did cross my mind so checked to be sure.
i do not have an aftermarket gauge just the stock one. which one is the gauge running off of? i will just replace it to be sure.
i did hit the water pump with a thromo gun, think it was around 212f, but it could have cooled down some by the time i got the gun.

i pulled the radiator out but the shop was closed today, for the 4th weekend i guess. will drop it off monday.

anyone know were a good place to get a koyo-n-flow for an s4?
i looked around and i only see them listed for the s5

lduley

iTrader: (1)

Banzai has them, and you can make a s5 rad work, just need s5 brackets or make your own IIRC

rusty FC

iTrader: (7)

i thought of something while cleaning the up engine bay, mostly were its all apart.
i noticed that the fan belts are not as tight as i would like them to be. i would not say they are loose just not were i would like them to be. i have never had the belts squiel but i thought maybe when i drive the car the water pump is not turning as fast as it should. so when i am checking things out under the hood its all working fine but when i drive it starts to slip not enough to make a noise but still not circulating the water like it needs to.

does that sound like it could be whats going on?

i have a duel alt pulley and run two belts and they are some what new (look bran new)
i think i will buy that alt bracket banzai has so it stays tight

welfare

how much deflection does the belt(s) have?
not likely, if it's overheating as fast as you say. hit it with the thermogun when it's ocurring. you want to make sure the gauge is correlating to the true temp. 212* is not really that high

welfare

if confirmed, check the rad cap. the simple things are often overlooked. a system that is not allowed to build pressure is unable to raise it's boiling point. for every psi of pressure built, the boiling point is raised 3*f. so 16psi increases the boiling point 48*f! extremely common failure too. even right out the box. why i always test even brand new units

welfare

same thing goes for leaks. inadequate capability to build pressure=lack of boiling point increase

rusty FC

iTrader: (7)

i replaced the rad cap last year, the oem one was bad. i had a trd cap that i got for my supra but it did not fit the rad so never used it. fits the rx7 perfect, its a 1.3 cap.
does the oem temp gauge run off the sensor in the thermostat neck? i will get a new one just to be sure

RotaryEvolution

iTrader: (30)

no, it uses the single wire sensor under the oil filter.

welfare

you don't need to replace it if you just hit the area with a thermogun and confirm that it's reading relatively accurate.
also, the stock cap should be .9 bar. not 1.3

RotaryEvolution

iTrader: (30)

ive never seen a factory temp sensor for the gauge that ever was faulty. not that that can't go bad but in like, 3000 and not one faulty? unlikely that it is the issue.

besides, if you are reading 205F on the outside of the water pump after a short time then you already know it is running too hot and the gauge is probably accurate. i asked about pressure in the system because a faulty coolant seal can cause a major air pocket(a large pressurized air bubble in fact) in the cooling system which will cause the pump to cavitate and stop coolant from flowing through the block.

pressure is good for boiling point reduction, air is bad for coolant flow. there's a difference between the 2.

welfare

good call. and that is precisely why we don't just go ripping and tearing like a bull in a china shop. test and confirm PRIOR to disabling a system whenever possible. once it's back together, pressure test it for leaks. if it doesn't hold pressure, find the leak. the same tester should be able to test the cap using the appropriate adaptor. although, considering how rapidly it was overheating, it's more likely to be, as lyger mentioned, cavitation caused by an air pocket.

your symptoms will disappear, of course, after replacing the rad if the system is properly bled. but they will return in a matter of time if a leak is still present

rusty FC

iTrader: (7)

that's what i was worried about. the koyo rad and other parts i ordered should be in the end of the week or Monday. but i have some family coming this week and the first of next i think so it may be 2 weeks before i have a chance to get her back together. i will post when i start on her and let you know how it goes. i hope this will take care of everything but if not i guess i need to start saving and studying for a engine rebuild