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Helpful ReplyHot!Stabilising water temp gauge reading

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sir_smeghed
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2017/12/22 22:58:23 (permalink)
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Stabilising water temp gauge reading

I have an SW20 with a honda F20C engine, this engine takes coolant returning from the radiator through the thermostat, does it's job then has an outlet on the passenger side of the block (I believe this is a similar setup the factory MR2 engine has).
 
The water temp sensors are all on the "to radiator" side.  I have an aftermarket gauge, and while driving the temp stays around 60C (coming out of the block, seems a bit cool realy) but when the car is idling and not moving the water temp can go close to 110C, the cooling fans make no difference at all to this temp, it only runs low while the car is being driven.
 
I need to make sure I'm getting good usable data from the water temp gauge, but shouldn't this output water temp be relatively stable?  Any suggestions would be greatly appreciated.
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    5SGTE
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    Re: Stabilising water temp gauge reading 2017/12/23 11:33:38 (permalink)
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    Owning a Honda I hope I can offer some sort of help.

    I find my cooling fans (Honda) don't come on without ac on before I shut it down at about 95. This is apparently normal and suggested they come on about 105, which IMO is too high. You can get switch with a lower temp.

    So I'm curious if yours uses the Toyota or Honda switch?
    #2
    sir_smeghed
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    Re: Stabilising water temp gauge reading 2017/12/25 00:19:21 (permalink)
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    I have checked the coolant temp coming out of the radiator going into the engine and it doesn't deviate much from 40C, which is great so no issues with that.  105C, thats pretty warm!  Boiling under pressure is 120C if I'm not mistaken so that doesn't leave a lot of room to move and seems consistent with what my temp gauge is getting up to but why such dramatic fluctuations?
    #3

    Reddtarga
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    Re: Stabilising water temp gauge reading 2017/12/25 22:41:17 (permalink) ☄ Helpfulby Dudeman 2018/01/01 01:29:55
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    "The water temp sensors are all on the "to radiator" side"
    Where exactly is your sensor located? That is important to know.
     
    The factory SW20 cooling setup has an engine quick warmup circuit that the thermostat controls, and the thermostat is 2 way in operation.
    When the motor is cold the thermostat forces the coolant to only flow through the quick warmup circuit and will not allow any coolant to flow to the radiator because it closes the inlet coming from the radiator back into the motor.
    Once the motor warms up, the thermostat closes the quick warmup circuit, and opens the inlet coming from the radiator back in to the motor. By cycling between the two positions the thermostat keeps the coolant temp inside the motor steady. 
     
    The stock coolant temp gauge sensor is mounted in the head outlet fixture right where the CSI and ECU temp sensors are located. They are inside the quick warmup circuit, so it moniters the actual coolant temp inside the motor, which is what you really need to know.
     
    I don't know if any of that helps, but good luck anyway in working out why your readings change so much.

    1990 ADM NA
     
     
     
     
     
    #4
    sir_smeghed
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    Re: Stabilising water temp gauge reading 2017/12/29 23:49:43 (permalink)
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    Thanks Reddtarga, I think you may be onto something there.  The F20C engine has a similar cooling system, there is a temp gauge mounted on the engine near the coolant outlet which feeds a signal directly to the Honda factory ECU.  My dash gauge and aftermarket temp gauge have the sensors located on the outlet pipe leading to the radiator.
     
    I will tap into the factory sensor and see if I can get a better reading.
    #5
    Reddtarga
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    Re: Stabilising water temp gauge reading 2017/12/30 10:10:58 (permalink)
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    The stock MR2 cooling setup has the temp gauge sender mounted in the housing close to the ECU temp sender.
    If installing an aftermarket gauge, the sender should be swapped over from the stock gauge sender, even if an adapter is needed. If you mount it in the outlet hose it's readings will be useless because it won't tell you what the temp is inside the motor.
     
    "I will tap into the factory sensor and see if I can get a better reading".
    I don't know what you mean by that, but probably not a good idea to interfere with the ECU wiring.
    Is there a hole in the housing somewhere close to where the ECU sender is that you could fit your gauge sender?
     
     
     
     
     
     

    1990 ADM NA
     
     
     
     
     
    #6
    sir_smeghed
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    Re: Stabilising water temp gauge reading 2018/01/03 16:18:55 (permalink)
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    Unfortunately the F20C has a single temp sensor feeding the ECU and all of the instrumentation is digital so it gets it's feed directly from the ECU.  There has to be some way I can get an accurate reading in the dash.
    #7
    5SGTE
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    Re: Stabilising water temp gauge reading 2018/01/03 21:20:27 (permalink)
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    My Honda has a 'diagnostic mode' where you can use the hvac display to show some vitals. I wonder if yours might have something similar, hopefully somewhere more useful to you than a hvac though. Might be worth checking out.
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    sir_smeghed
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    Re: Stabilising water temp gauge reading 2018/01/03 22:03:26 (permalink)
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    Thanks, I have put a query on a few of the honda forums.  I'm hoping that there may actually be a range of gauges that will be able to run directly off the ECU signal.  It would certainly make things easier.
    #9
    Mrskylighter
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    Re: Stabilising water temp gauge reading 2018/01/03 22:07:16 (permalink)
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    Does it have an OBD2 port connected up? Could just use a China bluetooth adaptor and an App like Torque?

    1989 AW11 Gen3 3sgte
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    sir_smeghed
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    Re: Stabilising water temp gauge reading 2018/01/03 22:23:08 (permalink)
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    Yeah, I have the ELM327 and several apps, Torque is my choice because it has the free racing dashboard.  
     
    This is ok, only problem is the signal and app response time is a little laggy.  Although this wouldn't be a real drama for water temp but it's just a bandaid, I want to keep my car looking as stock as possible and a couple of pillar mounted gauges are less noticeable than an LCD display.
     
    When I track the car I will use the App, but would really like to just mount a couple of analogue gauges.
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    Mrskylighter
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    Re: Stabilising water temp gauge reading 2018/01/03 22:47:41 (permalink)
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    Getting back to your original question about coolant temp.
     
    Could the thermostat be dodgy? Does it have an OEM Honda one fitted?
     
    I know using an aftermarket thermostat on the 3sgte sometimes leads to fluctuating temperatures.
     
    Edit: seems you can buy 60 something degree C F20C thermostats. Maybe that's what you have fitted? Hopefully not a band aid for a cooling issue. You mention it gets to 110 at idle which seems a bit high.
    post edited by Mrskylighter - 2018/01/03 22:52:47

    1989 AW11 Gen3 3sgte
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    sir_smeghed
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    Re: Stabilising water temp gauge reading 2018/01/04 10:56:05 (permalink)
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    I have put a brand new thermostat in it suitable for the F20C that opens fully at 70C as opposed to the factory 85C due to the fact that there are no heat soak issues with the radiator.
     
    The 110C is high but the radiator is dropping the temp down to 40C reliably and efficiently.
     
    This is what I now know:
     
    -  Coolant flows into the thermostat and has a similar temp regulation system as the SW20 MR2.
    -  Water temp returning from the radiator is a constant 40C.
    -  Water temp leaving the engine while car is being driven at speeds around 60km/h or higher is around 60C (low) and at idle slowly creeps up to approximately 110C (high).
    -  After market water temp sensors are located incorrectly.
     
    I think my next step is I have to tap into the ECU temp reading and see what the ECU is seeing.  The ECU has OBD2 wiring but it has not been installed so I will need to do this first, then I will use my ELM327 and App to check.
     
    I'm really getting a feeling that there is something wrong with this system for the output temp to get so high.
     
     
    #13
    5SGTE
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    Re: Stabilising water temp gauge reading 2018/01/04 11:38:11 (permalink)
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    What controls your thermofans?
    #14
    sir_smeghed
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    Re: Stabilising water temp gauge reading 2018/01/04 12:46:54 (permalink)
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    There is a temp gauge mounted on the radiator that triggers the thermofans.
    #15
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