cooling and overheating issues

[niSm095]

so I had a thread about my new radiator I bought because of some overheating issues and about both thermostats I've replaced the old one with, just trying to make a more concise question and answer thread here to help me out. my situation is as follows:

Brand new radiator, brand new thermostat, no kinks/leaks in the heater hoses, fluid level full, bled system four times, water pump has less than 4k miles on it.

Now whats happening:
On the interstate it seems the temperature is going up (on stock gauge), but when driving on "stop and go" temperature appears normal (on stock gauge)

Prior to replacing thermostat the second time, (just after the koyo install) onthe interstate the temperature needle was dropping down as if the car wasn't running at all, so I replaced the thermostat again, as I was not sure if the floating valve was installed upward facing.


My last guess is the coolant temp sensor and/or coolant temp sending unit. Anybody have any input? I got the wiring for the sensors off, but cannot get the coolant temp sensor off? The largest size deep well socket I have is an 18mm, is it a 19 mm? Anything else I need to know when changing the sensor?

[McRussellPants]

A) get a legit temp guage

B)Its probably because you didn't bleed it right.


get the air out and try again.

[niSm095]

i'm 99% sure its bled correctly. As I said, I've done it four times, i'm fairly certain all of the air is out of the lines. what can i be doing wrong with that.

I don't have money for an aftermarket gauge right now. 'about to graduate college' status.

[ladiesman8527]

the coolant temperature sensor doesn't have anything to do with the gauge. the thermal transmitter next to it is what your gauge reads from. use a deep well 10mm or 12mm socket i believe.

[niSm095]

by thermal transmitter I take it you mean the sending unit I spoke of?

[niSm095]

help, anyone?

[95Blue240sx]

Drive the car around again, get it to full operating temp. Make sure to have the heater on and then when it starts to overheat take it back home. let it sit on level ground and in the morning open the rad cap and check to see if it needs a fill, fill as needed. I have had the worst expeirence with cooling and this has worked for me in the past.

[Big Bronze Rim]

There are two sending units, one for the gauge the other for the ecu. The single pin is for the gauge, the two pin for the ecu. You really need to get a good temp gauge. I realize it costs money, but a toasted engine costs more. The stock gauge has 3 positions. Cold, middle and screwed. The gauge never really never moves unless the car is severly overheating. I don't recall specific values, but the center of the gauge ranges anywhere from around 160ish to almost 220. Once the gauge is near the hot mark, the engine is close to your-gonna-need-a-rebuild hot. The fact that its creeping up on the freeway with new parts is either the car isn't actually overheating, and the crappy gauge is giving a bad reading, or there is still air in the system, which even bled 20 times could still have air trapped in it. I'd spend ~$40 on a cheap temp gauge and try and rebleed the system.

[niSm095]

thanks for the assistance guys. It looks like I'll take some of the little money I have right now and replace the temp sensors. If that's not it, I'll get the temp gauge and go from there.

[niSm095]

and any other suggestions would be greatly appreciated

[DRFT180]

Check the ohm resistance of the transmitter. It will let you know if it's bad or not. Specs can be found in the FSM

[Realnez]

if its a KA they are know for BAD ASS air bubbles that are very hard to bleed. It could even be a pinhole leak in your headgasket that is causing air to come it to your system after you bled it.

[niSm095]

its an SR

msglngth

[codyace]

The sensor you need is a simple 10 dollar part that you can get at most auto stores (carquest/napa)...the cost isn't much more for the OEM one either.

If you still believe there MAY be an airbubble in there, just simply let the car idle with the rad cap on, but not fully locked on.

[niSm095]

Given that most everyone I've spoken with is saying 'sensor' rather than 'sensors', if I'm only able to replace one right now which would it be, the one that goes to the gauge or the one that goes to the ecu?

[niSm095]

I'm also going to try bleeding it again in the morning, see if that's the issue. If not, I will replace the sensors.

[DJ_Sunrise]

the one going to the gauge

[niSm095]

well, since of all the sockets i have i seem to be missing only the size large enough to remove the sensor to the ecu, i'll be changing the one going to the gauge tomorrow as well.

[codyace]

All you need is the one to the gauge...a simple 12mm IIRC 1/4" or 3/8" socket (or wrench) will do the trick....

[niSm095]

I'm going to spend the morning working on this when I get back from class. First up will be changing the sensor. Then the bleeding begins. First I will do the bleeding i know how to do - idling the car and opening the bleeder screw. (how long should I let it sit with the fluid bubbling out before I can say the system is good?) Then I will try the other method prescribed - closing the cap, but not all the way?

[PhopsonNY]

hi,

I had problems with this kind weird temp activity and it turned out I had a short in my rear cargo bay light. Once I fixed it, my temp issues went away.

Just an idea but it might help.

cheers

[niSm095]

well, i changed the sensor today and took it around, noticed no overheating, needle sat a hair above halfway like it used to. The car seemed to idle better as well.

[Big Bronze Rim]

Well it sounds like you got the gauge working and the system bled well. Glad its not overheating (or reading that its overheating) anymore. But words of wisdom - get a real temp gauge soon! Do NOT rely on the stock gauge as a true indicator of coolant temp.

[codyace]

Originally Posted by Big Bronze Rim

Do NOT rely on the stock gauge as a true indicator of coolant temp.

QFT (as said before too) Looking back on it, I was VERY DUMB for tracking my car without a real gauge....I love knowing now exactly where I'm at