93 240sx weird overheating problem, pls help!

[TheConstipated]

Well, maybe not so weird but I'm stump and I've tried searching to no avail.

So..a few days ago my S13's rad cracked and had to be replaced. It was working perfectly fine before.

Fast forward later and I've replaced the rad, t-stat, and water pump (cause you should and it was about time anyway).

Now, the problem. It idles fine but when I drive..it starts to overheat in about a few minutes or so. I check the hoses for temp, upper is hot, lower is cold indicating the t-stat is not opening (I did bleed and burp the system, yes).

I've checked the t-stat using the boiling water method and it opens up. So I put it back...and same thing. I also try turning heater on to see if it helps lower the temp but doesn't work

BUT, BUT! after letting the car sit off for a few minutes...I can feel the lower t-stat housing and lower hose getting hot. T-stat now opening? I turn the car back and drive again...overheat. Check hoses, upper is hot, lower is cold. Let it sit off for a few minutes and lower gets hot. WTF.

So the only thing I can think of is a faulty t-stat...but i'm not too sure. I haven't tried running the car without the t-stat to eliminate that possiblity yet. Fucking ballz man.

[Nategreat923]

What kind of t-stat? If aftermarket it could be failing, always use an OEM one. Is the jiggle valve facing up at the 12 I' clock position?

[TheConstipated]

Originally Posted by Nategreat923

What kind of t-stat? If aftermarket it could be failing, always use an OEM one. Is the jiggle valve facing up at the 12 I' clock position?

It's the cheapo one I got from o'reilly and I did make sure the jiggle valve was facing 12 o'clock.

http://www.oreillyauto.com/site/c/de...rd=thermostats

[TheConstipated]

Again, just earlier, I bled and bled at more than a 80 degree angle! Car still overheats. Upper rad hose gets hot and lower still stays cold during operation. Only after it is off that the lower gets hotter. I'm stumped.

Any suggestions?

*EDIT...I do notice that the coolant doesn't flow during idle. Sign of another problem?

[srstan]

ditch the shitty thermostat and buy a Nissan/Nismo one.

[KevinEdgar]

If you don't have a temp gauge your car will never overheat

[zombiewolf513]

Bad coolant temp sensor?

[TheConstipated]

Does the coolant not flowing mean bad water pump? I did buy new, though.

[cotbu]

Now, the problem. It idles fine but when I drive..it starts to overheat in about a few minutes or so. I check the hoses for temp, upper is hot, lower is cold indicating the t-stat is not opening (I did bleed and burp the system, yes).

You can't bleed the coolant system, if the thermostat doesn't open. There's probably air not water behind the thermostat. That makes temp sensors read high usually.
What you can try is remove one of the sensors and makes sure water is there, get a temp gauge real temp gauge and monitor the thermostat housing, you can let it get to 85c-90c and still be good, if it doesn't open then replace the tstat or drill holes in it.
Your problem is you can't cool your engine, fans should be off until about 85c hopefully the thermostat opens.

Does the coolant not flowing mean bad water pump? I did buy new, though.

NO, where's the water flowing? I'm sure you spun the water pump by hand as every does before it even makes it to the engine.

what temps did you record for overheating? 220f 185f or needle on H

[TheConstipated]

Originally Posted by cotbu

You can't bleed the coolant system, if the thermostat doesn't open. There's probably air not water behind the thermostat. That makes temp sensors read high usually.
What you can try is remove one of the sensors and makes sure water is there, get a temp gauge real temp gauge and monitor the thermostat housing, you can let it get to 85c-90c and still be good, if it doesn't open then replace the tstat or drill holes in it.
Your problem is you can't cool your engine, fans should be off until about 85c hopefully the thermostat opens.

NO, where's the water flowing? I'm sure you spun the water pump by hand as every does before it even makes it to the engine.

what temps did you record for overheating? 220f 185f or needle on H

I don't have a temp guage so I wouldn't be able to do it at the moment.

What I did earlier, though, was replaced the t-stat - oem from nissan. Overheating still occurs but it fluctuates, it never goes to H but about 1 bar from the middle then goes back down. I immediately felt the t-stat housing and it feels warm. So I think it's opening... Drive again and temps still fluctuate. I do several times and the t-stat housing is a hit or miss on temp (sometimes cool, sometimes warm).

I will try removing one of the sensors and report back. Thanks.

[zombiewolf513]

What radiator are you using?

If you remove the single prong one, youll just be unplugging the gauge, basically. Id suggest replacing the single pronged unit with an autozone replacement and see if it continues to spike. Ive had an autozone gauge sensor for about a year and a half, they work fine. The sensor with a connector i would get oem, and an aftermarket water temp gauge.

[JDMBart]

go to oreileys and say that the item is defective and they will exhange it for you. It is possible that the thermostat is flawed

[accoupe]

I have always had problems in 240's with aftemarket thermostats. I would get an oem t-stat and get a spill free funnel. These funnels attach to the radiator and become the highest piont in the system. These have always worked great for me. Also make sure to use the bleeder screw on the engine.

[superwowfactory]

Originally Posted by accoupe

I have always had problems in 240's with aftemarket thermostats. I would get an oem t-stat and get a spill free funnel. These funnels attach to the radiator and become the highest piont in the system. These have always worked great for me. Also make sure to use the bleeder screw on the engine.

I agree 100% with this.

Get an OEM or NISMO Thermostat and a "Spill Free Funnel" like this.



Best $30.00 we have ever spent. You can fill the system and bleed without having the car at any type of incline.

Make sure to remove your bleeder screw when filling.

When a steady stream of coolant comes out, put the filler screw back in and tighten it.

Fill the overflow tank until the Max line.

Then fill the spill-free funnel about halfway and start the car with the heater on full blast.

Run it for 20-30 minutes and make sure you feel the heater get hot.

Remove spill free funnel and install standard cap.

You should be good to go.

[anti tyler]

If you're having overheating issues instead of spending money remove the thermostat and run the car for 24-48 hours without one and see if it still overheats.

If it does then it's time to replace the waterpump my friend.


Lets try to solve the underlying issues before suggesting the OP spends money on stuff.


If you're driving and it's dropping and such, I would check your belt and belt tension

There are only so many possible reasons for the car to overheat... The thermostat has nothing electrical so it's not like anything is restricting the t-stat from opening.


Burp the system and run it without a thermostat for a few days. just make sure you run the car 5-10 minutes before you take it for a drive. Wouldn't want to drive around with the car still bone cold.

[TheConstipated]

So, I feel like a dummy and somewhat not. Cause well... it was air. I've read and read but the problem still persisted but I kept on trucking with the "bleeding."

And I'll look into that no-spill thing in the future. Anywho....

For future references or anyone looking for a different method on what I did to solve the problem.

1. I did the usual bleeding...park at incline, loosen the bleeder screw with rad cap off and heater on full blast. Did this for like a whole day. Still overheated.

2. I used a different method which seemed to help solve it in the end.
-I parked car at incline (my driveway).
-loosen the bleeder screw half-way (rad cap still on).
-turn car on and rev to 2-3k a few times and turn off.
-wiggle upper rad hose (lots of bubbles). Then I squeezed the rad hose all the way while closing the bleed screw.
-and last step I did...loosen bleed screw half-way and turn car on and let idle. I did not turn the heater on nor did I remove the rad cap. I let the car idle until I couldn't see anymore bubbles from the screw - only water/coolant. Then I closed it and turned the car off.
-Took for a slow drive, no overheating. Drove normally on faster streets, no overheat. Freeway drive, no overheat. Took home and felt upper rad hose - hot. Then felt lower rad hose, warm (T-stat working). Drink a beer for job well done.