birdman2447

I just installed a summit digital water and oil gauge in my car. The oil pressure gauge seems to be working well. Stays around 40psi with an ls1 with ported oil pump. The water temp sender i placed in the pass head as the drivers head has the factory sender in it. The summit gauge displays a water temp around 40 degrees lower than the gm sensor when i scan it with HPtuners. I am unsure where the issue lies. I thought that i may have a bad sender, so i purchased another sender from them. This sender also produces the same lower temp. Any ideas on this, or are these just poor quality gauges?

baxsom

iTrader: (6)

what did you use to seal the threads? i have seen that teflon tape can affect a senders readings

birdman2447

i did use teflon tape, but the bung i used is drilled out to directly allow coolant to touch the sensor. I cant imagine that the tape on the side of the sender would make that much of a difference. Do you have a thread sealer that you recommend for sealing senders?

usafws6

iTrader: (10)

not sure if i would trust "summit gauges" spend the extra cash and get autometer.

soundengineer

iTrader: (16)

I can tell you from experience, that the stock sender and the values that GM have in the PCM are not correct...
I would trust your summit gauge more...but there is an easy way to test...
get a basic digital thermometer, cheapy one will do just fine...
check the temp according to any weather program on your phone, make sure the digital thermometer reads about the same... if they match, then look at your gauge...if it reads the same, then you know the gauge is correct..
you need to do this just sitting with the car cold not running, best to do it in the morning after the car sits all night...better if its parked indoors so you dont have to worry about temperature swings and you can let it sit for a full day..

My stock temp sender was off quite a bit from my autometer one...Like 20 degrees worth...
same thing goes for an IAT sensor... totally depends on which one you have on whether it really reads the correct data..

thankfully, with my Holley PCM, I can just enter the proper calibration and all is well...
My ECT, IAT ,passenger side ECT,Trans Temp from internal sender, and Autometer Trans Temp all read the same temp when cold...tested in winter at 20* and just recently at 70*
I've thermal checked the coolant temps with a heat gun and know they are correct at full temp..
and I know the internal temp sender is correct for my transmission, and my Autometer one matches, so I know that the calibration values for that type of autometer sender are correct...and its the same sensor in my passenger side head.

my passenger side is actually a little hotter than my drivers side as the coolant is picking up heat while moving thru the motor...

birdman2447

Thanks, I will take the car out for a spin tomorrow and report back. I will try checking head temp with a thermometer and a friend has a temp gun i will try as well

thanks

soundengineer

iTrader: (16)

not the head temp... the actual fluid inside the head temp...they will be different..

and do the initial check sitting still, engine cold, not running...

01ssreda4

iTrader: (96)

The sending unit converts an actual temperature into an electrical signal that the gauge can interpret. It does this (typically) as a varying ground resistance. The sending unit's body is it's ground connection....namely the threads as they are the only part that touches the actual metal of the car. When you wrap the threads in teflon, it is the same as a bad connection which could cause a faulty reading. Lots of sending units I have seen have coated threads and do not require teflon. That is why the guy asked if you used teflon.

birdman2447

Thanks, I will pull the sending unit out and install it without thread sealant as the brass pipe thread should seal the low pressure of the coolant system. I did a check with the temp gun and the gm sender when viewed through hptuners scanner reads around 10 degree hotter than the outside head temp, while the summit gauge displays a temp roughly 30 degrees lower than the scanner.

soundengineer

iTrader: (16)

you still need to go get a cheap radio shack digital thermometer and see what they both read at cold temps... its easier to get an accurate reading when the engine has been sittiig all night long..
if your heat gun measurements are that far off.. then you may have errors in your measurement or use of the heat gun...

birdman2447

After checking them again with a high end Omega thermometer i borrowed from college. The differences in readings are very similar to that when using the heat gun. I also properly installed the sender with out tape so it would be grounded. I am thinking i am going to purchase a better temp gauge/sender. Any suggestions on one to get?

soundengineer

iTrader: (16)

Autometer...preferably something that uses their 2 wire sender (it grounds to the gauge, not to metal on the engine)...which I think is any of their full sweep electrical gauges...
dead nuts on for me...

01cherryreds10

iTrader: (9)

I know it seems silly but does the gauge read in both celcius and farenheit? My trans temp gauge from Dakota does and requires you to change it over to farenheit before using it.

soundengineer

iTrader: (16)

hes only talking about a difference of around 30* so I'm fairly certain he's using his in Fahrenheit already...
otherwise 212F = 100C .....it would be over a 100* off if he was using the wrong scale

birdman2447

well it turns out it was a bad guage, bought a new one from summit, my old one read out 173, while the ecu read 202, my new gauge reads 203 at the same point after a short drive

thanks for the help, I am saving up to purchase a nice set of gauges.