Is My Temp Gauge Lying to Me?

[rico05]

So here is the scoop:I have blown coolant hoses before. Twice. Empied the coolant system once, the other time I got it before it got bad. Since then, my temp gauge has shown that the working temp is higher than it used to be.

Ok, here is what I have found:-There is no coolant loss.-The coolant is clear-The oil is clean-There are no leaks-Radiator gets hot, but not overly so-Thermostat is new and working

Here is the issue:A few times in the last few weeks, the temp gague has been fine (resting about 1mm above middle on the stock gauge) then SUDDENLY (like in less than 30 seconds) the needle jumps to H. Now, when I have blown a hose, it has done this as quickly, but the needle goes past the H. In this circumstance, it stops at the H or a little before. It has done this 3 time. Twice, I was babying it (off boost, keeping it below 5k....how I normally drive) and once it happened right after I got on it (full boost, 7500RPM). All 3 times I have pulled over and snooped around to verify that there is no leaks, and after cool, I check the coolant level to see it 100% full and clear. So, since the coolant and oil are clean, I assume that my HG is fine. Also, since the motor never acts funny when this happens, I assume that since all coolant is accounted for, it must be the gauge that is wacky? Maybe the times I overheated the engine destroyed the sensor? Any thoughts? I need a few more supplies before my aftermarket water temp gauge goes on, but I have been meaning to ask this for a while. Thanks guys!

[Thrwnsprkz]

Air in the coolet system... theirs an article on how to properly bleed it, nissan's are a bia' to bleed...

another ex: some year celicas you gotta jack the car to a 45deg angle and runthe car for 30 min to get all the air out (nissans not this drastic, but its a pain, still havnt done mine yet)

[rico05]

No air in the system. Plus, CAs don't have a "bleeder" screw like SRs and KAs.

[sdtouge]

if oyur running a electrical water temp make sure you ground the sensor or it wont work rigth, it will read like 250 when its cold, just ground the sendor and its all good. i would say its probably just messing with you, just dont do anything too drastic until you get your gauge hooked up.

how do you bleed the cooling system onnthe ca then?

good luckmatt

[574-240sx]

I had this same problem in my last 240 with a KA. It would happen when it would get cold. I thought I had a bad thermostat. Turns out my temp sensor was messed up. Also on my KA-T I took the mechanical fan off and relied on the backup electrical fan. When I got on it during hot days when the radiator wouldn't get direct air flow the temp would shoot up quickly. Also on the earlier SOHC they used brass core radiators. They have a tendence to start to break down and melt inside into a big clump. This has happened to a friends car and a old SOHC coupe I was fixing up to sell. I though it was a hg a first. I replaced the hg and didn't fix it. Then I noticed the radiator was clogged when I ran a hose throught it. Hope this helps out.

[rico05]

Well, the temp sensor on there is stock, so I assume that since everything else is good and grounded that this sensor is as well. Also, I have a 91, so DOHC radiator. Furthermore I have flushed this radiator 4 times now, so I would like to think that it is a clean system. And the coolant is no more than 8 weeks old. And I run 70/30 water/coolant. I need to hurry up and get my aftermarket gauge in I guess.

And you bleed a CA by:-Opening the heater inside-Open the radiator cap-Start car-Watch rad. filler neck and fill as needed

Gotta love old school.

[WeldingHank]

i've had the same problem as you with my CA. my temp gauge being all screwy. i still have yet to install the temp gauge i have, to see whats going on. i just think its the old sensor playing tricks on me.

[rico05]

Indeed. One would assume that a fully filled and not overly hot coolant system that is not spewing fluid all over and overflowing the overflow bottle is fine and to blame the sensor.

But that is like chosing "E: None of the above" on your business math final.

[Bronze MFP]

has anything ever happened to the engine that might cause blockage in the coolant channels in the block or head? is the sensor wire grounded out? (not the ground wire, but the + wire to the gauge) just throwing ideas around here.

[rico05]

Damn. Did it again. Odd thing was, I was I cranked the heater (it was off before the "overheat") and it was cold for a long time. Like I drove with it all the way on and it took it a few minutes to get warm in the car then it didn't get too hot to keep it that way for upwards of 4-5 minutes. So if it was really running that hot, would it not be blowing out nuclear hot air?

Also, a few days ago it was 80 degrees out. Gauge showed that the car ran "cooler" on those hot days than it did this morning in a 40 degree commute...

[Bronze MFP]

you sure your thermostat is ok? it sounds f'ed to me

[rico05]

I installed a brand new OEM Nissan thermostat a few weeks ago.