Hey HT, I'm installing an MTX-D coolant/battery gauge in my car and I need to know the best location for the sensor proble.

I want to pick up the hottest coolant temp found in the motor for obvious reasons.

The probe is 1/8" PT and I can drill/tap the proper thread pitch/angle once I know where to put the probe.

The probe hangs into the coolant passage almost an inch, so I need a bit of room. I could tee into a coolant hose but I'd rather not as that would provide a new spot for leaks etc..

I will post a pic of the probe when photoufcket comes back online. The site GUI is currently offline and I don't have access to links of the pictures.

 

Outlet off the head, gives true engine temp

 

Retapping the bleeder screw below the arrow would interfere with the thermostat. uploading pictures of probe.

 

 

I drilled and tapped the piece that attaches to head for the upper radiator hose. Theres a nub on the side that is perfect to drill for a sensor

 

Get one of these hideous things then,
http://www.ebay.com/itm/Water-temp-g...39ea6d&vxp=mtr

 

Except that's not where the thermostat is

 

^^^I spit out coffee.

 

Are you referring to the bleeder nub? I could easily remove the bleeder and re-tap the hole for the sensor probe.

I'd like my sensor to be right in the hottest coolant. Which way does the coolant circulate through the engine? If I tap into the bleeder screw, I think that would be a false reading because the coolant is coming back into the head after being chilled down in the radiator.

Lol correct, that picture wasn't the thermostat housing. Glad to see that SOMEONE is paying attention. Here have another look.

 

The coolant is coming out of the head at the front of the engine, that will be the hottest coolant that has just passed through the engine and is on its way to the rad

I simply removed the bleeder and tapped it for 1/8NPT. Works perfect

There is about a 20 degree difference I notice in datalogs based on where the ecu gets its coolant temp from (back of engine on mine) vs my probe location. My ecu shows 186 while my probe shows 206-210

CrxCommunity love

 

Excellent information. The bleeder looks like a very easy place to tap in 1/8 PT for my sending unit.

So the coolant at the bleeder is coming OUT of the head on it's way TOWARD the radiator, correct?

Because if the coolant is re-entering the head after being chilled in the radiator it would yield lower temp readings than the ECT down near the thermostat.

Hopefully someone can verify.

damnit now I need to reprogram my gauge to account for the 20% hotter reading compared to the ECT numbers.

220*F @ the ECT = overheating.

which would mean +20% = 264*F on gauge would be overheating.

am i understanding this?

thanks

crxcommunity hell yeh

 

yes the flow of the coolant is INTO the water pump, OUT of the front of the head.

 

Nice. Thanks.

Damn I always thought the ECT value in smanager was the hottest coolant temp in the entire system.

Is there any downside to running my gauge off the bleeder screw apart from the obvious?

-no bleeder, duh
-hotter reading on my gauge

 

I think its the best spot to measure coolant temp. I was pretty amazed that my gauge was reading 225 before my fan came on aswell, when my datalogs showed my ect sensor was only showing 203.

My car mostly operates at 186 (180 thermostat) according to the ecu logs, but my gauge shows 199.

So ballpark 10% variance

 

Although reverse cooling would be optimal, as most of the heat is in the head, so logically you would want to cool it first

That's how I had my last ls/VTEC setup with my electric water pump

 

Any chance that the sensor would get heat soaked from the housing being connected to the head? My thoughts were having a section isolated by the hose itself would be a better reading. Think intake temperature sensors and heat soak. Yeah the air is 80 degrees but the sensor reads 110 because the head heats the manifold being metal on metal, thus heating the sensor.

 

Not really because the thermocouple is in the tip of the sensor... and the volume of water being moved through the housing will keep it at a pretty uniform temperature

 

Wow. Great stuff guys.

I'm working with a tuner who is used to the oem sensors and that's how he reads the datalogs. (Who doesn't?) Heat soak may be an issue - but it's uniform from one motor to the next. For example if the IAT sensor reads 110*F due to the heatsoak it doesn't really affect anything because the tuner is used to seeing 110*F ---- in other words I could possibly get a more 'accurate' reading, but it'd be useless because it's not what the usual numbers are when the tuner thinks of 'hot' or 'cold' temps. Hopefully that makes sense.

given the advice in this thread - I will tap the bleeder screw, or maybe drill/tap the little divot right behind the bleeder. Ignore the arrow and look at the divot. Tapping the sensor in there would retain the bleeder. I'll decide when I remove the piece from the head and have a chance to thoroughly inspect it.

 

And once I learn the temps that the motor runs at from this new ECT location - I can program the gauge accordingly to turn yellow when hot, red when dangerous etc.

I'm thinking of the gauge as a stand alone monitoring system - tuning will primarily involve the s300 oem ECT sensor data as that's what everyone is 'used to'. Might even be able to program a 'limp mode' if coolant temp rises above a certain temp.