Over heating when AC is on???

[BadazzSr20]

hey guys,

i have a 97 240sx with a sr20det in it. im having a problem when i have the AC on the car starts to over heat slowly but it creeps up to where im not feeling safe.

i have a FMIC on the car so i was thinking this might be stoping alot of the air comeing in to cool the condencor. i removed my front bumper and got on 95 and did about 65 70mph. after about 30mins driven the car started to over heat alittle not as much as it does with the bumper on.

i got off 95 to return home again drving 65 70mph and this time i left the ac on. the temp im reading is the stock temp gauge. the temp the whole way home the was at the line before the H. if you have a 97 gauge cluster you will know what im talking about.

that seems to be running hot to me. im running Flex-A-Lite fan in the car right now and i dont no the cfm that they run at. i was thinking to get bigger cfm fans hoping this will stopt he over heating problem.

i had 5 diffrent proformance shops look at this and everone is stomped on this. i spoke to enjuku and they said this is commen problem for the 97 sr20s. i was told by 2 diffrent people to run a 2nd set of fans inbetween the rad and intercooler pushing out.

i would like to try and fix this with that route. if theres anyone out there that has or had this problem please help me fix this. the florida sun is just killing me.

i also removed the thermostat out of the car and still no luck. i want to put my thrmostat back in once i fix this problem. anyone please can help im be here listening cause im going crazy.

i think my next step will be to remove the intercooler and see this that stops the over heating problem. if it does then i know my intercooler is to big and blocking all my air folw.

thanks all.

[Prime]

You've got to remember, all of those items (intercooler, AC Condenser) are just radiators, really. You've got three of them inline, and the one handling your coolant is the furthest back. So you've put heat into the charge with each step. Sounds like your AC condenser is bleeding enough heat to tax the radiator, and with the additional load on your pulleys slowing cooling even more... So, either move something around to get some virgin air to the radiator, or take your chances with something like "Water Wetter" or whatever that stuff is.

[GroundPerformance]

You should just run a good aftermarket radiator with the original AC fan and stock shroud /w clutch fan. I've seen some issue when using e-fans only and has no shroud setup and not a good reliable way of controlling them. Just keep it basic and often times it gets the job done.

[BadazzSr20]

im run a mishimoto rad. so i think the rad is fine. i had a few people tell me to try and run watter wet i have 50/50 collent int he car now so i just add that bottle of water wet into my rad with the 50/50 coolent that already in there?

is that going to be anought to keept he temp low aough to where i can use my ac?

[inopsey]

can you feel air being sucked threw the condenser when you put your hand on it?

[omgRWDgoodness!]

Try bleeding your coolant system? Or maybe your water pump/something else is leaking? That happened to me, I'd be driving along and would notice my temp gauge creep up at stoplights. Looked under the car when I got home and saw coolant dripping onto the floor. Checked everything out and saw the top of my crank pulley was wet, so I replaced my water pump and haven't had any problems since. The water wetter is also a good suggestion, especially with the summer temperatures down here right now.

[JDMwannaBE]

Try bleeding your coolant system? Or maybe your water pump/something else is leaking? That happened to me, I'd be driving along and would notice my temp gauge creep up at stoplights. Looked under the car when I got home and saw coolant dripping onto the floor. Checked everything out and saw the top of my crank pulley was wet, so I replaced my water pump and haven't had any problems since. The water wetter is also a good suggestion, especially with the summer temperatures down here right now.

I agree, try bleeding the cooling system, or maybe even a total flush and fill + water wetter. Also check your radiator cap and make sure it's not worn. I had both issues and was overheating. Fixed those and fixed the problem. Both are relatively cheap so it's a good place to start. good luck.

[BadazzSr20]

can you feel air being sucked threw the condenser when you put your hand on it?


great question i didnt even think about this ill check now.

[BadazzSr20]

also im thinking about going to auto zone or pepboys and get a 12" pusher fan tommrrow and installing that and trying that. the ac is blowing not to cool so im thinking it not geting anough air flow.

ill need to do a flush tommrrow and try this water wetter you all talking about. how to i use this water wetter do i flush the system and add the water wetter and then fill it the rest oft he way for 50/50 coolent?

i never used water wetter so any info on this will be great thanks!

[chituntang]

Make sure your temp sensor is the one form the usdm chassis, or use a aftermarket temp sensor to rule out wrong reading from stock cluster...

Happened to me...

[naw_speed]

My buddy is havin the same problem. His 96 240sx will only start to get warmer when you drive at 65-70 mph. if you turn the AC off it will cool down or if you slow down. At idle the temp is fine… motor is stock has fmic, elec fans, and aftermarket Rad. This is what we have done so far-
Changed the coolant temp sensor…
Removed the coolant fans and drilled extra holes in the shroud
Removed Rad and did a flush, even probe it with a mini cam to see if it might have been clogged
The next step is to install the OE shroud and clutch fan. Then we’ll see how that works. We monitor the temp with a modis scanner. The temp is runnin 200 up to 240 before we shut it down. My s13 never gets any higher than 200.

[Razi]

I had the same issue.
I plugged in my stock A/C electric fan and that fixed it.

I think the stock A/C fan on the radiator is supposed to kick in when the A/C is on, to prevent the engine from overheating.

Figure out a way to wire up a second fan to your A/C fan harness, or just go back to the reliable stock setup.

[BadazzSr20]

so i installed a 12" pusher fan on the condensor and still over heats like before. im going nuts i dont understand why it keeps overheating. i would think a 12" fan on the condensor would have fix this problem but it didnt.

i guess ill flush the rad tommrrow and see maybe theres a bubble in the system i dont no.

really upseting that i had this car for a year and i cant run my ac!! pissed off!

[Def]

Is your cooling system bled properly? Open the bleeder screw with the car cold and the radiator cap open and you should see coolant come out. Add coolant until it is coming out the bleeder screw, then fill up radiator all the way. You can check this after running the engine some more and it will bleed the air out (or let it idle out, but that tends to not get all the air out).

Secondly, ditch the Flex A Lite fans - they suck. They don't move anywhere near their rated CFM.

Get some Altima fans or a Taurus fan, those will definitely keep your car cool.


If your water pump impeller is really pitted it can really affect coolant flow, so consider replacing this. It's cheap, and they do wear out so think of it as preventive maintenance.


Don't keep running your car to where it is overheating, you will warp the head.

[BadazzSr20]

Is your cooling system bled properly? Open the bleeder screw with the car cold and the radiator cap open and you should see coolant come out. Add coolant until it is coming out the bleeder screw, then fill up radiator all the way. You can check this after running the engine some more and it will bleed the air out (or let it idle out, but that tends to not get all the air out).

Secondly, ditch the Flex A Lite fans - they suck. They don't move anywhere near their rated CFM.

Get some Altima fans or a Taurus fan, those will definitely keep your car cool.


If your water pump impeller is really pitted it can really affect coolant flow, so consider replacing this. It's cheap, and they do wear out so think of it as preventive maintenance.


Don't keep running your car to where it is overheating, you will warp the head.

thank you very much ill try the rad tommrrow. the bleeder screw is the nut oat the bottom of the car where u drain it? i dont no where this bleeder screw is i have a mishimoto rad.
thanks

[Def]

Christ.. I hope you didn't install the radiator then...


The bleeder screw is on the water outlet coming off the head of the engine. It's on the driver's side of the engine bay at the front of the motor. It's a 10mm head hex bolt. Look at the FSM before you do this.

[BadazzSr20]

Christ.. I hope you didn't install the radiator then...


The bleeder screw is on the water outlet coming off the head of the engine. It's on the driver's side of the engine bay at the front of the motor. It's a 10mm head hex bolt. Look at the FSM before you do this.

Ya i got it already i open the screw and coolant came out there was no air. I dont no what to do at this point. Im so pissed off about this its not even funny.

[Def]

Replace your fans with ones that actually move air!!!

[Vernal]

make sure theres airflow through the condensor otherwise unclog it but you might need an accessory pusher fan if not also a high cfm puller

[bladetech8]

Please go back to the mechanical fan/fan clutch setup.. It moves like ~3500 CFM's and there's a good reason why Nissan engineers put it there in the first place. Nothing performs as effectively and efficiently as a good mechanical fan/fan clutch setup.

[DRIFTERS14]

I had the same problem koyo rad & twin 12in flex-a-lite , and ran redline waterwetter to change boiling point and on I-95 temp slowly went up so I changed to clutch fan with oem Sr20 shroud and I am also using the a/c fan that came stock on ka. Setup no more problem I can drive with a/c on all day no problem

[SnakeKack]

Do you have one fan or two? From the factory the clutch fan cools real well with the shroud but there is an electric fan designed to turn on when you kick the A/C on to dissipate the extra heat. If you are running only one electric fan then it's not enough when the A/C is on.

And it looks like you are down in South Florida like me so yeah it's hot as shit out right now.

[mad-ass]

check the fins on your condenser! if there are a lot of them bend, straighten them out and clear out any thing that's tuck in there[bugs/rocks/leaves]