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  1. #1
    Join Date
    Mar 2018
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    Macon GA
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    96

    Default Water Pressure switch

    One of my buddies melted down an engine because his radiator got punctured and he ended up losing most of the water. The problem is, water temp looked normal because it was normal before there was no water left.. I want to put a water pressure switch in so that I have an idiot light turn on if I lose all the water. What is the best way of doing this? I was thinking buy a 4 PSI pressure switch (https://www.quickcar.com/4-psi-fuel-...switch-61-730/) , weld npt bung in radiator or thermostat housing, then wire the switch to the idiot light on the Water temp on the gauge cluster. Would this work?

  2. #2
    Join Date
    Nov 2014
    Posts
    379

    Default

    Why not put a water pressure gauge in the car?

  3. #3
    Join Date
    Mar 2018
    Location
    Macon GA
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    96

    Default

    A: no room for more gauges B: does it really matter what the pressure is? as long as its not 0. lol

  4. #4
    Join Date
    May 2007
    Location
    Kansas
    Posts
    1,416

    Default

    Quote Originally Posted by Burke1118 View Post
    A: no room for more gauges B: does it really matter what the pressure is? as long as its not 0. lol
    An idiot pressure light is very very common almost everyone I know runs one. The way your doing it is fine, I like a little more pressure then 4# but that should work

  5. #5
    Join Date
    Mar 2018
    Location
    Macon GA
    Posts
    96

    Default

    Thanks BBC

  6. #6
    Join Date
    Oct 2017
    Posts
    742

    Default

    we use the oil temp dummy light. And it doesn't matter where you put it in the system it will work no need to weld anything special in the radiator. Top of the water pump or the intake works just fine. If you run water lines to the back of the intake most thermostat housing spacer plates have a spot right in the center that works well

  7. #7
    Join Date
    Nov 2014
    Posts
    379

    Default

    Is there some sort of bypass for a pressure switch upon first startup when the pressure is low that will allow the car to start? Or does the water pressure build that quickly to 4lbs? That's the reason I asked about the gauge was because i was unsure how long it would take to actually crank the car if the pressure build was slow.

  8. #8
    Join Date
    May 2007
    Location
    Kansas
    Posts
    1,416

    Default

    Quote Originally Posted by Punisher88 View Post
    Is there some sort of bypass for a pressure switch upon first startup when the pressure is low that will allow the car to start? Or does the water pressure build that quickly to 4lbs? That's the reason I asked about the gauge was because i was unsure how long it would take to actually crank the car if the pressure build was slow.
    It doesn't hook to the ignition or anything, just a light on the dash. Light is on when no pressure, so it will be on until the cooling system builds to 4# then goes off. If it comes on when racing, you know you have a leak and the water is running out or gone at that point.

  9. #9
    Join Date
    Nov 2014
    Posts
    379

    Default

    Gotcha. I have a low oil pressure switch on my car that will shut it down below like 15. With a bypass button I can mash to make it start initially. When the word switch was used I assumed it meant it would switch the power off below a certain pressure. Not just a warning light.

  10. #10
    Join Date
    Jul 2014
    Posts
    365

    Default

    Can't say I know of anyone that doesn't have at least a light.

  11. #11
    Join Date
    May 2007
    Posts
    257

    Default

    I use a adjustable fuel pressure switch for my water pressure sensor and it works fine. I have mine in my goose neck housing and I have a big idiot light so it can be seen a mile away lol. Been running this set up for about 12 yrs with no problem I just replace the switch every year so I know it's good. You also want to start your motor and let it get up to temp then set the switch at operating temperature.
    Last edited by racinrocket1; 05-13-2020 at 03:28 PM.

  12. #12
    Join Date
    Nov 2010
    Posts
    110

    Default

    Longacre sells this setup in a kit for like $25

  13. #13
    Join Date
    May 2007
    Posts
    1,016

    Default

    After reading this and not knowing these could be bought I purchased kit. Wired to ignition toggle switch and other wired to sensor. Let car warm to over 110 degrees and light still on. Obviously no leaks. How long does it take to build pressure? Let run for 10mins approx.

  14. #14
    Join Date
    May 2008
    Location
    outside
    Posts
    67

    Default

    old chevy oil pressure sending unit works great

  15. #15
    Join Date
    Oct 2017
    Posts
    742

    Default

    Quote Originally Posted by Jim11h View Post
    After reading this and not knowing these could be bought I purchased kit. Wired to ignition toggle switch and other wired to sensor. Let car warm to over 110 degrees and light still on. Obviously no leaks. How long does it take to build pressure? Let run for 10mins approx.
    It varies but you were probably real close to having the light out mine is out before 140 but it can vary with how much room you leave in the radiator for expansion

  16. #16
    Join Date
    May 2007
    Posts
    1,016

    Default

    Much appreciated. Told guys I'll try Saturday and if don't go out I'll disconnect for night

  17. #17
    Join Date
    May 2007
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    Well light never went out. I've got the tall thermostat housing and that's where mounted it. Used reducer to fit. Car was 180 and light still on. It did flicker around the 140-150 but when on throttle brightened right back up. Any thoughts?

  18. #18
    Join Date
    May 2007
    Location
    Kansas
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    Default

    Quote Originally Posted by Jim11h View Post
    Well light never went out. I've got the tall thermostat housing and that's where mounted it. Used reducer to fit. Car was 180 and light still on. It did flicker around the 140-150 but when on throttle brightened right back up. Any thoughts?
    Jim, here's a couple ways to test what's wrong or if you have a bad sender

    1. Unplug wire from sender, the light should go out. If it does then the sensor either is the wrong pressure rating or just just bad and not breaking the continuity to ground at the 4 PSI.

    2. Use or go down to O'reilly's auto parts or etc and borrow/get a radiator system tester to pump up the cooling system. With light on and no pressure in system, pump up the cooling system and watch light at around 4 to 5 PSI on pump gauge it should go out. If not, you can pump up higher and see when it does and that would be the rating PSI of senor (maybe you got a 20# low oil sensor, by mistake).

    If it's not wired correctly (#1) then most likely you have the (#2) a bad sensor or wrong one.

  19. #19
    Join Date
    May 2007
    Posts
    1,016

    Default

    Thanks billet I'll try that. It's all new so was kinda leaning toward wrong sending unit. Wiring nearly impossible to mess up

  20. #20
    Join Date
    Nov 2012
    Location
    Wisconsin
    Posts
    2,902

    Default

    How about the old school light? I rubber hose coming from the radiator overflow to the RF A-pillar. When you see steam you know your getting hot.
    Member of the Luxemburg Speedway Hall of Fame
    Class of 2019

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