rx7_

Ok guys, i've a really unknown overheating issue. My car started overheating today, well the weather was ****ing hot, but i dont think it'll cause my car to overheat. I'm using a Dc2 full aluminium radiator on my eg here in asia, i've no thermostat and i run my fan on a manual switch which i seldom off. My car started overheating on the roads while i was driving normally, no boost or anything, just normal cruising. When i stopped the car, i checked for leaks and such, couldn't find any leaks at all! Fan was still on as well! No white smoke on my tailpipe, no water in oil or oil in coolant as well. Im not sure bout coolant level though, it looks normal but i can't remember if it dropped or not. Well don't know if its relevant but today i found it hard to start my car too. Crank sounded slower and the car couldn't start unless i step on the accelerator to rev it up. When it starts it would sound like a boxer engine for few secs and then normal when the idle gets higher. Any inputs on this?


Another issue is, i have a pretty big FMIC, and my A/C is in front of my radiator, A/C fan facing the radiator. Well, basically my car runs fine without overheating(except today) without the aircon on, water temp will be good. However, when i switch the aircon on, my temp starts rising, and it wont stop rising. When A/C is switched on, i have 1 radiator fan, 2 A/C fans blowing towards my radiator, and it heats up like a bitch, even on the highway cruising, the temp does not go down. Temp would go back to normal when i turn the A/C off. I checked and all fans were working all the time, esp A/C fan was spinning strong so i don't get this issue. Even if my FMIC was blocking, the A/C shouldn't be heating up the radiator instead it should cool it down. Any inputs on this as well?

Seraph0

This just happened suddenly eh? How does coolant/oil look? Is your turbo water-cooled?

Nichelson_Performance

you should get airflow through you FMIC regarless of how big it is

have you changed your coolant or had any of the hoses or rad out lately.

sounds like you might have air pockets, but i can't really understand why the a/c would have anything to do with it

rx7_

Yes it just happened yesterday, last time i changed coolant was about 2 months back. Oil looks good, got about 1500km more to go as i change my oils every 5000km. As for the A/C part, it puzzles me too. I've no ****ing idea why it heats up when its on and whenever the weather is hot as hell i can't switch the a/c on. It pisses me off! Need some help here!

slowboy90

i had an issue with mine over heating without ac just cruising. Mine turned out to the me not having a thermostat in the car the coolant was staying inside the radiator long enough to get cooled properly.

hope this helps

rx7_

Im running a fan switch and its on most of the time so coolant gets cooled in the radiator im sure

95skunkedgsr

i would try running a thermostat and c if that clears it up .. i wouldnt rule it out of the picture just because your fan is always on , my buddy has his fan wired so its always on when the car is on and he haves a nice size rad and it still gets a lil warm

Nichelson_Performance

running a thermostat will make it heat up even more because it will stay shut until it reaches it's rated temperature, it will also restrict some flow.

what grade (weight) of oil do you run? too thick of oil will cause a overheating problem also

that is from my own personal experience of trying to run 20w50 lol

rx7_

Running on 10w50 oil. Main issue is the damn A/C i need it here in my country. Weather is ****in hot

Dee

WRONG!! Running a thermo will ensure that the engine reaches it's "normal" operating temp before water is circulated through the radiator (heat exchanger). A gutted thermo is better than no thermo at all because the semi-restriction caused by the gutted thermo will slow the flow of the coolant which will allow the radiator to do it's job of removing heat from the flow. No thermo = the coolant will pass through the radiator so fast that the radiator will not be able to "pull" the heat from the flow.

OP - Disable the manual fan switch and use the OEM fan switch. Go buy a brand new OEM thermo and install it. I ran a full-sized radiator with AC and an oil cooler during the Okinawa summers (95*+ heat with 90 humidity) without any issues. Do a compression check, check your ground wires (harness ground on the thermo housing, tranny side ground and battery ground), and check your plugs since you are having starting issues now.

crashsvg

sounds like the moto is being pressurized..when u took f the radiator cap did u hear a little 'poof' of air being released? if u that that would explain the hard start..its mostly caused by a leak in the head gasket ....even if there no oil n water mix .

jarven93

check your intake manifold gasket, i had my gasket go bad and ended up boosting into a radiator line on the manifold..... causing the car to over heat

Turbo-LS

iTrader: (4)

if the car is overheating without a thermostat in it , putting one in WILL NOT help anything. engines will run cooler without a thermostat period. you have a bad headgasket or a blockage of some sort

Nichelson_Performance

that's what i said but i was told i was wrong

a thermostat holds coolant in the engine until it reaches the temperature at which the thermostat is supposed to open at.

but like i said i was told i was wrong even though i've been working on cars and trucks my whole life and not to mention that is my occupation

Turbo-LS

iTrader: (4)

Yeah well its correct. Ive run my car no tstat and with tstat and i can vouch and so can datalogs that my car ran 20 degrees cooler in the winter and 10 degrees cooler in the summer with NO tstat.

I guess its probably something that could turn into a heated debate but i have living proof in my own car that it works that way LOL

Many engine builders even told me in the past dont run a tstat especially on a race car, they said try different sized washers aka diameter openings to regulate coolant flow to find the perfect spot and keep the coolant flowing through the engine and rad at all times.

ive found that using a stock thermostat withthe guts cut out of it seems to keep temps pretty well where they should be in most ambient temps here in new england. Im currently running a tstat but once it goes it will be taken apat and used that way

93supercoupe

your probably logging lower temps because the coolant is moving faster by the sensors.

I dont know about a stock rad., but the alum. ones will move the coolant too fast with out a tstat.

Thats why gutted t-stats are a common thing.There is no way a properly functioning tstat is making any engine overheat unless there are underlying issues.

Dee

I guess some of you guys skipped over my second sentence where I discussed the benefits of a gutted thermo.

Why did I suggest a compression test? To see if he has dropped cylinder but what I should have suggested is a leakdown test and checking for air bubbles/oil in the radiator.

Turbo-LS

iTrader: (4)

exactly, so if its overheating without a tstat it will certainly overheat with one because he has other issues. my car doesnt overheat it just runs hotter with the tstat in. And by hotter i dont mean really hot i mean like 198-202.

ahobbs

here's your problems. Go down this checklist
-radiator cap
-leaky hose, like the heater core hoses check all your hoses
-fan can not supply a good enough CFM to compesnate for the heat in the engine bay
-blockage in radiator or somewhere
-headgasket.
-coolant level
-air in system
Im going to bet is a air flow problem and too much heat in the engine bay

I cant think of anymore right now. But i promise - if you go down that list you will solve it

rx7_

Thanks for all the replies. Im suspecting a minor burnt headgasket though. Bled the air in coolant system, temp is normal now, but im still getting the hard starting of the car. Plus, i noticed coolant in the radiator has decreased, not drastically but a fair amount even after i topped it up. I'm just gonna continue driving till my HG gives way

ahobbs

the you risk messing up the block,