Quest for a Coolant Sensor Location
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Thread: Quest for a Coolant Sensor Location

  1. #1
    1000+ Posts bowie's Avatar
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    Default Quest for a Coolant Sensor Location

    Sooooo I have a nice little gauge that will read the temperature, and give it to the ignition ecu, of a sensor I jam somewhere.

    Now the thinking goes, I want it before the thermostat, and as close to the head as possible, So what about the heater exit that I've since plugged up?

    I could nearly tap and drill into the water pump, but since I have an outlet plugged I might as well get a aluminium or etc blanking plug and tap the sensor into that?

    That's a good enough position (for a 30yr old POS) to take a reading as it leaves the head surely? Any issues with flow or crap circulation that could crap the reading in that Cul-de-sac?

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    I'm tempted to drill and tap into the radiator inlet from the car, but then again if the Thermostat gets shut I'll happily melt everything without even the slightest of bother.

    Works: 1999 Volvo S40 T4, (has Choo Choo's)
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  2. #2
    1000+ Posts driven's Avatar
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    Sensor has to be on head, anywhere else nil value, just for decoration if feeding into ECU

  3. #3
    1000+ Posts bowie's Avatar
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    Default

    Ok fair enough. Ok I'll look at the plate with the existing sensor on the back, er front.

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    Too many posts! JohnW's Avatar
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    The R16 had the sensor fixed to the cylinder head. By this I mean fixed to the metal in a key place, not reliant upon coolant being in contact. So if coolant drains, the head heats up PDQ and the guage would respond fast. I always thought this the best option. The R8/10 series had the warning light attached to the metal too.

    So, I reckon that is a slightly different paradigm. My R8 has the sensor in the top hose so I can see the thermostat opening but I reckon it is a surrogate for what you really want to know, i.e. the head temperature.

    Just my two bob's worth.
    JohnW

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  5. #5
    1000+ Posts REN TIN TIN's Avatar
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    You shouldn't put a sensor on the water pump, that the 'cold' side of the cooling system.
    Just before the thermostat is the 'hot' end of the cooling system so would be better or where the temperature sensor is now on the end of the head.
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure. Mark Twain"

  6. #6
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by REN TIN TIN View Post
    You shouldn't put a sensor on the water pump, that the 'cold' side of the cooling system.
    Just before the thermostat is the 'hot' end of the cooling system so would be better or where the temperature sensor is now on the end of the head.
    The R8/10 light switch is indeed at the end opposite the water pump! Good point. I can't remember where the 16 one was bolted on.
    JohnW

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  7. #7
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    Not sure about the 16 but interestingly the R15 and R17TS/G have them at the opposite ends. The 16 and the 17TS/G both have electric fans so may be the same as the 17TS/G that has both of them at the front away from the water pump where as the 15 is at the water pump end before the water goes into the water pump. I said both on 17TS/G because one is for the injection computer one for the gauge. The sensor for the electric fan is almost at the bottom of the radiator nearer to the cold water outlet. On a Sierra motor most people weld a socket into the end plate near the fire wall or over the bell housing on an 8/10. On the 17TS/G there is a third sensor for the computer on the opposite side of the head but up near the water pump end. Now ain't all that confusing.
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  8. #8
    1000+ Posts bowie's Avatar
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    Yeah I'm thinking I'll take that temp sensor plate off and tap directly into that, or just replace the stock sensor with something of similar size.

    Works: 1999 Volvo S40 T4, (has Choo Choo's)
    Playing: R12, SuperPos, thinks It's a race car.
    Previous: SuperGrumpy fuel spitting 504ti(ish), SuperComfortable 505 STI, SuperDoper carried my groceries Mi16
    Wanted Ye old K4J / K4M Click!

    "More and more of less and less" - Marina Abramović

  9. #9
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by bowie View Post
    Yeah I'm thinking I'll take that temp sensor plate off and tap directly into that, or just replace the stock sensor with something of similar size.
    The sensor should be in an area of high coolant flow with coolant flowing directly past the sensor.
    Don't put the sensor in a dead end.

    You'll end up with two sensors, One for the dash gauge and one for the modern whizzbang gadgets.
    Renault will have probably put their Dash gauge sensor in a high flow location.
    Jo

  10. #10
    1000+ Posts schlitzaugen's Avatar
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    The R12 engine head had a removable plate on one end (don't remember which one) where there were all sorts of sensor bosses. I think it was at the g'box end. What you want is to be as close as possible to the exhaust side of the head, because that is really reflective of the temperature inside the cylinder. Gauges and fan and all else can be anywhere you want (not really, but close) but the computer feed needs to know what's goin' on inside the engine. I would have the gauge sender in the head near the exhaust end anyway, simply because that is the hottest point and that's where gaskets/heads can fail. Rad fan can be on the radiator.
    ACHTUNG ALLES LOOKENPEEPERS

    Das computermachine is nicht fur gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitssparken. Ist nicht fur gewerken bei das dummkopfen. Das rubbernecken sightseeren keepen hands in das pockets-relaxen und watch das blinkenlights.

  11. #11
    1000+ Posts Frans's Avatar
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    My is as follows.

    The water coming out of the top of the waterpump is a good indication of the average temp of the engine. The back plate at the opposite end of the head that we are talking about will be probably the hottest spot of the engine and is the best to use.

    The cooled water that enters the bottom of the pump is forced straight into the block at no.4 cylinder (opposite side of flywheel) and then it makes it's way to the other cylinders and then through the holes in the head gasket into the head where it then returns to the outlet of the pump. That far end where the plate is that we are talking about must be the hottest part of the engine because it will get the hottest water from the block and I'm sure the slowest flow as well. I think that can be a reason why the factory bolted the heat switch on that spot as well.

    Apart from that my next question is going to be...... is the computor going to change the settings between the 80 degrees flowing past the thermostat and the 90 degrees at the back of the head? Is it so fussy that it will make a difference?

    That was the original question wasn't it?

    Frans.
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    Young enough to do it anyway.

  12. #12
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    From what I recall about your setup, you are running a carb so I assume the computer uses the info from the sensor to control ignition timing and maybe an electric fan. It would therefore be good risk management to mount the sensor to read the hottest water. The computer can then make adjustments just in case the driver isn't watching the gauges.

  13. #13
    1000+ Posts bowie's Avatar
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    Yes it seems very clear now, I'll be taking it from near enough the stock sensors location.

    Thank you everyone

    Works: 1999 Volvo S40 T4, (has Choo Choo's)
    Playing: R12, SuperPos, thinks It's a race car.
    Previous: SuperGrumpy fuel spitting 504ti(ish), SuperComfortable 505 STI, SuperDoper carried my groceries Mi16
    Wanted Ye old K4J / K4M Click!

    "More and more of less and less" - Marina Abramović

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