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Coolant temperature sensor bad?

Discussion in 'General Tech and Maintenance' started by autox19, Jul 18, 2017.

  1. autox19

    autox19 Member

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    hopefully easy question. still fighting the over heating issue, but I have the stuff for the head gasket replacement I am doing after vacation.
    Can a sensor fail and give the wrong signal? let me explain. from what I can see on the all knowing google world, when a temperature sensor fails, it drops to -0 ohms. I am not seeing much that shows that when it fails it shows that it sends a signal that the real temp is hotter than what it really is. Everything I can find (so far) says the sensor either works, or it sends 0 ohms all the time.
    Because my temp (form the ECU, not the gauge) shows the temperature climbing, not spiking at extreme hot, I would say my sender is fine. My laser reader puked so I cant verify the head temp vs what the ECU is reading.
    Would it be worth changing out the sensor? or is this just wishful thinking that I wont have to do the head gasket.
    I really have no other symptoms of a head gasket failure, no smoke, no oil in the coolant, no coolant in the oil, no erratic idle or running. Just the less than 5 minutes to 200+ degrees even at idle.

    Odie
     
  2. autox19

    autox19 Member

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    found the resistance chart, going to check this afternoon.
     
  3. autox19

    autox19 Member

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    weird. temp sensor is reading .331 when the ECU is saying its 167. the chart I got says 176 is .4 and 212 is .4 so the ecu should be saying its between 176 ands 212 right?

    meat thermometer says coolant is 167. thinknig the chart is off.

    Odie
     
  4. Megalodong

    Megalodong New Member

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    Hopefully you have it solved by now.
    With Honda engines the strongest sign of a headgasket breach is coolant loss in the radiator combines with coolant gain in the reservoir. The best method of testing is similar to a Leak-Down test with the exception of not using a leakdown tester...just inject 150 psi of air into each cylinder at TDC with the radiator cap removed. If there is bubbling in the coolant sytem then there is a head gasket breech. Another less effective method is a Block Test: a block tester is a free rental at autozone or o'reilly's and test fluid is $10..if there's exhaust emissions in the coolant system the blue test fluid will turn yellow or green.

    Run your engine from cold start with the climate control at max heat, recirculate mode, fan on 1. Stick a thermometer in the radiator neck and record temps 10 minutes past opertating temp. Test the ECT as shown in the video:

     
  5. CAFROG

    CAFROG Honda Minion VIP

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    I know you've been worried about the engine temp and the gauge reading for a while now. Would it be too much hassle to temporarily wire up a different gauge and test?
     
  6. autox19

    autox19 Member

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    Update: Head gasket. leakdown proved it. We did the leak down after 10 days of purging the coolant, driving around the block (about a mile) and when I got back I had to purge again because there was air each time. So we did the leakdown. We did a leak down originally, but it was only about 3%. well the last leak down was, well, WAY more. so it just got worse. Took insurance off and moved it into winter project mode. My wife made me as I was starting to band aide rather than fix. There was other things I wanted to get done as well. like switching the rod linkage to cable.
    So the latest, we are pondering the following possibilities:(I currently have 2 b16's. (A)one with spun bearings that I drove the car it came from for 100 miles from where I bought it no major issues, and (B) one that I bought as a mule, never started it until it replaced (A) after (A) spun bearing in the fiat, currently blown head gasket) possibility 1. Easiest, Buy "new" JDM b16 and be done. 2. rebuild (B) with new head gasket/ARP studs/oil pump/Water pump/make sure block and head are straight. 3. Buy B20 and do a Frankenstein all motor, as I already have 2 b16 heads. 4. rebuild B16 with turbo. either way I do it, I have until next april to do it. Keeping in mind, this car at 2000 lbs, was a blast at 75 HP. so extreme HP isnt the goal.

    Other stuff.. tested sensor (thanks for the vid!!!) it tested right. Trying to figure how to wire the coolant fan relay. Still trying to decide if I am going ot use the fiat switch in the radiator, or the honda. Which I find a little perplexing. I have a connection from the rywire harness called "fan switch" the connector is a 2 wire small circular connector. I ran that to control the relay and it didnt work. so I think that isnt it. From what I google, there is a switch in the rear of the block with 2 bullet connectors. the size of it looks like it is a full poser switch not a relay feed. but cant confirm.

    thanks for all the help!


    Odie
     
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