JaySam Posted June 14, 2023 Share Posted June 14, 2023 (edited) I recently had a new motor installed in my Sunrader and when I did I had the mechanic add an Auto Gauge Water Temp gauge so I could monitor temps a little more closely. When he installed it he just replaced the factory temp sensor with the auto gauge one so the dash gauge no longer worked. I wanted to re-hook up the dash gauge so I could have 2 gauges and more closely monitor the temp and when I might be treading into dangerous territory. Today I installed a temp sensor into the block drain plug location and reconnected it. The gauge works but is reading extremely high, almost into the red even though the actual temp on the auto gauge is only 180. I'm guessing this is because of the location of the sensor but I don't know, would this be the case? Could the exhaust be heating up the sensor or wire maybe and making it read high? Or is there a better location for a secondary temp gauge sensor? I have the upper radiator hose manifold kit to install the sensor there and had it there but it read hot as well and only kicks on after the t-stat opens so i was hoping for a spot that would read the block temp. Edited June 15, 2023 by JaySam Quote Link to comment Share on other sites More sharing options...
WME Posted June 15, 2023 Share Posted June 15, 2023 Original Toyota sensor? Quote Link to comment Share on other sites More sharing options...
linda s Posted June 15, 2023 Share Posted June 15, 2023 Your engine block temp is always going to be far hotter than your coolant temp. That temp difference is why your coolant can work. I can't imagine how this would help you in any way. Linda S Quote Link to comment Share on other sites More sharing options...
fred heath Posted June 15, 2023 Share Posted June 15, 2023 (edited) You can double up the output from the factory water temperature port on the engine with a “T” type fitting. I’ve attached a photo of my oil pressure sender configured to run the factory idiot light as well as my Auto Meter supplemental gage. A similar setup could be used for water temperature. Fitting is dirty, but gives you the idea. Edited June 15, 2023 by fred heath Quote Link to comment Share on other sites More sharing options...
JaySam Posted June 15, 2023 Author Share Posted June 15, 2023 (edited) I don't understand why the coolant temp in the block would be so much hotter than the coolant temp at the intake, but maybe part of the temp is coming from the block itself? The reason I'm trying to install a secondary gauge is because twice now the auto gauge sensor hasn't kicked on until after the t-stat opened and it gave me concerns about it going out so I wanted to add a backup. It's a new sensor I bought from LC Engineering. I've thought about adding a t at the intake port but it'd be nice not to drain and refill the coolant system again haha. I guess I'm still just confused on why the temp sensor on the block would read so much higher than the temp sensor on the intake. Is the coolant that much hotter in the block before it gets to the intake? Edited June 15, 2023 by JaySam Quote Link to comment Share on other sites More sharing options...
WME Posted June 15, 2023 Share Posted June 15, 2023 Segal's Law.. A man with 2 watches never knows what time it is. The block is the coolest part of the cooling system, the head is much hotter, the upper radiator hose is the hottest place in the cooling system. Quote Link to comment Share on other sites More sharing options...
JaySam Posted June 15, 2023 Author Share Posted June 15, 2023 lol well now that's a new one to me! that's what I thought so I'm confused why it would read so much hotter at the block than the intake? could the exhaust manifold be a contributing factor? still need to learn how to leave well enough alone i guess Quote Link to comment Share on other sites More sharing options...
extech Posted June 15, 2023 Share Posted June 15, 2023 un calibrated sender? Quote Link to comment Share on other sites More sharing options...
WME Posted June 15, 2023 Share Posted June 15, 2023 Very BASIC check on the temp sensor...http://schematicsdiagram.blogspot.com/2012/03/toyota-coolant-temperature-sensor.html do it on a cold engine Yes the exhaust heat could effect the sensor. An old trick is a 1/8" hole in the thermostat flange will let some water circulate and reduce the wild readings on an engine that is still warming up. Some stats have the hole from the factory Quote Link to comment Share on other sites More sharing options...
JaySam Posted June 15, 2023 Author Share Posted June 15, 2023 Can you calibrate the temp sensor? I thought it was just a passive sensor and nothing you can adjust or calibrate on it I'm not getting wild readings while warming up, the pic is showing the gauge after fully warming up and driving around for a few. It maintained itself where its at I just figured it would be sitting in the slightly-below-halfway mark like it always used to instead of up near the red line like the pic shows. I'm going to try shielding the sensor from the manifold heat and see if that changes the reading at all Quote Link to comment Share on other sites More sharing options...
IdahoDoug Posted June 15, 2023 Share Posted June 15, 2023 Was the block sensor you installed for the factory guage the proper one for the factory guage? A sensor sends an output based on the temp it is experiencing, but different sensors have different output ranges. So, I'm thinking your sensor is not a good match with your original factory guage - unless LC Engineering specifically makes it for your original guage, which would negate my concern. Quote Link to comment Share on other sites More sharing options...
extech Posted June 15, 2023 Share Posted June 15, 2023 temp sender is a thermister. resistance to ground changes with temp. less resistance= higher gauge reading. the sender has to match the gauge Quote Link to comment Share on other sites More sharing options...
extech Posted June 15, 2023 Share Posted June 15, 2023 you could experiment with adding resistors to the circuit to get the reading you want Quote Link to comment Share on other sites More sharing options...
JaySam Posted June 15, 2023 Author Share Posted June 15, 2023 This is the sensor I installed in the block https://www.lceperformance.com/ProductDetails.asp?ProductCode=1067001 I think it's for the dash gauge but maybe I'm mistaken? Would teflon on the threads mess with the grounding and throw off the resistence? Quote Link to comment Share on other sites More sharing options...
extech Posted June 15, 2023 Share Posted June 15, 2023 if the resistance increases, the gauge reads lower Quote Link to comment Share on other sites More sharing options...
JaySam Posted June 16, 2023 Author Share Posted June 16, 2023 Ok well a heat shield didn't change anything but I did swap out the wire to a smaller gauge and that seemed to get it more into line. I may try the resistors as well but for now it's usable. Thanks everyone for the help and information! Quote Link to comment Share on other sites More sharing options...
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