Funny logger temps.. Guru's Look here!

[JLangevin]

Ok, so because of another problem, I decided to start logging my car closely this past week when I noticed something odd. The ECU Coolant Temp readings are all over the place... but mostly very hight.

Here is some background; The car jumped timing about 10 months ago, and obviously had a new head (mine was toast) and gaskets all around. The temps this summer according to the dash gauge have been very nice, even with the A/C on and sitting in traffic on a 110* day. The temps never rose about the half way mark, and if they even started to move, the needle would drop quickly. Even when I would get on it, the temps would never really move, and sat most of the time just below half on the gauge...

So, when tracking my O2 this past week, I noticed the cars temps would read as high as 222*f WTF - Whats even more funny is that the cars dash gauge was sittle just below half when this happened. The logger has showed temps all over the place, from 199* to 222* and in a matter of 1-minute could rise 15* then drop back, and rise again. So, here is what I did.

-Radiator very clean, no deposits and only a couple months old
-Flushed coolant (was extremely clean, not a spec of deposits)
-Replaced Thermostat (factory 180*)
-Checked fans (both come on when AC is on)
-Pressure checked (Radiador cap was bad, replaced)
-Purged air from system
-Pressure cleaned the AC and radiator

So, yesterday I button it all up from the freshened system, and go for a drive, its rougly 100* outside, and the car rises to 203* in a matter of 2 minutes, and stays there, sometimes jumping to 206 or 210, then back to 203.... WTF WTF WTF - Ok, now Im pissed... why isnt the dash gauge showing this? Then I remembered that the ECU and gauge have their own sending units...

Is it possible that the ECU sending unit is bad? I had one go bad in my Camaro before and where as my dash gauge showed damn near 240*f at times, my Autometer showed 190*f. I know over time (11yrs) sensors can get out of spec. Does this sound like my case? Whether is 60*f outside (morning) or 105*f (way home from work) the temps show the same, 203-222. I dont get an engine lights for temps, and I do not have a thermal laser gun to test the water neck for temps.

Here are some pics from my logger. You can see in a matter of a minute, it has fluctuated quite a bit, and this is while on the freeway. Yet, the dash gauge never moved. On the logger pic, the low was 203 and the high was 222. AS you can see on the gauge to the left, in both pics, it wasnt reading the same temps.

 

[JLangevin]

Ok thanks. I will probably give it a shot tomorrow. I cant believe how many times I have drained and refilled this cooling system in the past 24 hours.

 

[JLangevin]

Ok so I used a Snap-On Thermal Laser Temprature gun on the thermostat housing on my car and here are the results..

Ambient Temprature: 100*f
Engine: Ran for approximately 20min of Highway and City Driving
Sitting idle for roughly 10min during test

So, the logger showed fluctuating between 217 and 222* at idle yet the temp gun showed 198-203* on the upper radiator hose housing (water leaving head) and 180-185* on the thermostat housing (water leaving radiator) - I would say the ECU is definitly not getting accurate readings... now to replace the sending unit.

 

[donmagicjuan]

Just be careful when ordering-- the part you want is actually the engine coolant temperature sensor. The sending unit is what drives the meter in the dash (separate component).

 

[JLangevin]

Right, my bad, but I do know the difference. Im going to go with a mitsu part, since I had nothing but trouble with autozone type knockoffs before, in another vehicle.