OEM Dash temperature gauge: position vs temp

Discussion in '80-Series Tech' started by e9999, Jul 24, 2005.

  1. e9999

    e9999 You want to do what...? Moderator

    Messages:
    16,632
    Likes Received:
    520
    Joined:
    Sep 21, 2003
    Location:
    US
    it's been well established alredy that the OEM dash temp is highly non-linear and gives very misleading information on the temp of your engine (see for ex the great info by our friends here who generated curves of resistance vs temp and discussed this before).

    Well, now that I've rigged a coolant temp probe, I wanted to see how bad this gauge's indications really are in my case.

    Here is what I saw:

    Needle at lowest position : engine temp 98 F
    needle at "0" / 107
    1/8 : 112F
    1/4 : 117F
    3/8 : 125F
    1/2 : 132 - 221F with no change seen in needle position over that range.
    Didn't go above 221F.

    This is eyeballing the positions of course.

    I didn't think it would be this weird.

    What on Earth were they thinking? :confused:
     
  2. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

    Messages:
    22,365
    Likes Received:
    6,746
    Joined:
    Mar 27, 2003
    Location:
    Land Cruiser Heritage Museum broom closet
    I just installed an Isspro gauge and the sender is in the upper neck. I observed today that the "middle" of the OEM gauge ranges from about 140 degrees to at least 210 degrees.
     
  3. Cobra Jet

    Cobra Jet

    Messages:
    123
    Likes Received:
    0
    Joined:
    Jul 11, 2005
    Location:
    Southern NJ
    CDan - what is the stock OEM thermostat rating? (190*, 185, 200, etc)

    I know with the Mustangs, the OEM stat is supposed to be a 195*, but, we always use a 180* in place of the 195*, it helps out with the cooling system.

    Another thing too for those in hotter climates, if you were to use more water than antifreeze (regardless of what type or brand of antifreeze), the cooling temps will actually be LOWER, than using the predetermined mix of 50/50. You can get away with 75% water and 25% antifreeze in climates that see consistent "summer temps" without any detrimental effects at all. For those who experience 4 Season climates, if running a 75/25 mix in the summer, one HAS to switch back to 50/50 to avoid any possibibility of the fluid freezing in the cooling system.

    I run a 75/25 mix in the summer and the temps on my Cobra run at exactly 180* with the 180* stat. I'm also running a mechanical Auto Meter temperature gauge, in which the probe is also tapped directly into the intake for accurate readings.

    If the OEM LC thermostat is "hot", try running a lower temp thermostat and see what differences you pick up on the readings while dirving your normal routes.

    Also, are you still running the mechanical fan on yoru Cruiser, or have you removed it and installed an electric fan in it's place?
     
  4. e9999

    e9999 You want to do what...? Moderator

    Messages:
    16,632
    Likes Received:
    520
    Joined:
    Sep 21, 2003
    Location:
    US
    OEM stat: 176-183F opening/closing range.
     
  5. flintknapper

    flintknapper

    Messages:
    5,020
    Likes Received:
    1,791
    Joined:
    May 22, 2004
    Location:
    Deep East Texas
     
  6. Cobra Jet

    Cobra Jet

    Messages:
    123
    Likes Received:
    0
    Joined:
    Jul 11, 2005
    Location:
    Southern NJ

    exactly... it's a well known fact among those who race (drag race, road race or auto cross) that running less antifreeze will keep the cooling system temps down, more so than running a 50/50 mix OR those who even run more antifreeze than the 50/50... Running a 75/25 mix has no adverse or detrimental affects at all on the cooling system.

    I too have always run 75% water and 25% antifreeze on all the prior Mustangs I've owned, I also did it in my prior 95 BMW M3 and way way back, did it on a Jeep Wrangler 4.0.... I've never had any issues, also never had any major cooling issues as what I have been reading recently on this forum....


    If the OEM stat for ALL FJ80's is the same as what e9999 has posted, then drop down a grade below the factory specs for better cooling too.

    Also - one other thing to know - when doing ANY cooling system flush/fill - always use distilled water - never use "tap" water... Tap water causes the blockages in the cooling system (radiator, heater core, coolant passages in engine block, etc) due to all of the minerals found in tap water. Distlled water can be purchased at any or most supermarket/grocery stores AND PEAK sells bottles of distilled water for use in vehicles. Using tap water is BAD for any cooling system, regardless of vehicle make or model.
     
  7. hobbes

    hobbes SILVER Star

    Messages:
    664
    Likes Received:
    150
    Joined:
    Feb 2, 2002
    Location:
    Naples, FL
    I have a GN that likes a cooler thermostat. One thing to keep in mind, however, is that all engines are designed to run within a certain temperature window. This is especially important for computer controlled cars that have to pass emmissions. I'm not sure that dropping to a cooler thermostat will keep a Cruiser from overheating. High performance street cars are generally pushed for power for a relatively short period of time. If a Cruiser is overheating at a stoplight, a properly operating thermostat is not the problem. I do agree about the antifreeze and have heard nothing but good things about WaterWetter.
     
  8. Bob_Garrett

    Bob_Garrett

    Messages:
    1,195
    Likes Received:
    4
    Joined:
    May 17, 2003
    Location:
    Irving, TX
    That's much the same as I saw when monitoring the temp via the OBDII port. Didn't check it as far down as 140 degrees, but I know that the gauge needle on my 95 didn't move at all while the OBDII reading varied from 180-210 deg.

    Bob
     
  9. MH_Stevens

    MH_Stevens

    Messages:
    691
    Likes Received:
    20
    Joined:
    May 24, 2005
    Location:
    Bonsall, California
    I run one and a half gallon jugs of the red in my system, the most I could get in, and this gives about a 40:60 mix. I'm wondering if there is a link between using too much antifreeze and the HG failures.
     
  10. parabola

    parabola

    Messages:
    316
    Likes Received:
    0
    Joined:
    Jun 27, 2005
    Location:
    Austin, TX
    +1 on this. I ran anywhere from 80/20 to nearly 100/0 (+ water wetter) on my Supra and not once had cooling system issues, even at it's peak (750+HP) output. Of course I live in Central TX so freezing isn't much of an issue.

    Nothing stresses a cooling system like 25psi of boost in a 3L motor with runs up to 170+mph in 100 degree heat. Yes, we'd do that with no overheating.
     
  11. flintknapper

    flintknapper

    Messages:
    5,020
    Likes Received:
    1,791
    Joined:
    May 22, 2004
    Location:
    Deep East Texas


    Sounds like a fun vehicle to drive out 2222 on the way to Lake Travis. Used to run that in my 69 XKE.
     
  12. parabola

    parabola

    Messages:
    316
    Likes Received:
    0
    Joined:
    Jun 27, 2005
    Location:
    Austin, TX
    2222 is a blast. :) Lime Creek is also a ton of fun when there isn't traffic. The decreasing radius, negative bank turns can catch you off guard though.

    XKE?! Wow, what a beautiful car. I'd be scared to bang that thing up out there.
     
  13. cary

    cary

    Messages:
    3,124
    Likes Received:
    52
    Joined:
    May 7, 2003
    I'm still waiting for one of our electrical engineer gurus to reverse engineer the factory guage and come up with a mod to make it read in a linear or semi-linear way. Is it possible by using a resistor to make the guage start to move from the middle at say 215f? Even though it would be useless after that, it would give an early warning, and then the A/C cutout would provide the final warning.
     
  14. e9999

    e9999 You want to do what...? Moderator

    Messages:
    16,632
    Likes Received:
    520
    Joined:
    Sep 21, 2003
    Location:
    US
    cooler thermostat?

    you guys been smoking weird stuff? Our OEM stat is fully open at 185F or so. Considering that I measured my coolant temp to be always at 185 or more with engine hot, how is having a cooler stat going to help since the stat is already fully open when the engine is hot, and for sure overheating?

    A cooler stat would simply keep the engine a bit cooler longer before it reaches steady state temperature. Once the engine is warm, how is that going to make a difference?

    One could argue that a thermostat that is more "streamlined", i.e. offering less resistance to flow might help increase the flow rate a bit but that would be a miniscule difference.

    Or what am I missing?


    add: btw, did you read the post about the rad that exploded cuz of a bad aftermarket stat? No thanks!
     
  15. e9999

    e9999 You want to do what...? Moderator

    Messages:
    16,632
    Likes Received:
    520
    Joined:
    Sep 21, 2003
    Location:
    US
    might be interesting to try out the 25/75 approach and test it in the summer against a good temp gauge, admittedly, but with the apparent connection between cooling systems being off (sludge and all) and HG failure, I would tread very carefully.
     
  16. landtank

    landtank SILVER Star

    Messages:
    19,283
    Likes Received:
    1,566
    Joined:
    Mar 27, 2003
    Location:
    Groveland MA
    You're Right E, regardless of what rating the t-stat is if the cooling system can't disapate the heat generated fast enough it will overheat.
     
  17. sjcruiser

    sjcruiser

    Messages:
    834
    Likes Received:
    3
    Joined:
    Apr 3, 2003
    Well, for an average Joe (like me), this would prevent (countless) panic stops on the road just because the temperature needle glitches above the middle range. My old MBZ does this and it's very annoying - think about false alarming :doh:
     
  18. e9999

    e9999 You want to do what...? Moderator

    Messages:
    16,632
    Likes Received:
    520
    Joined:
    Sep 21, 2003
    Location:
    US
    bah, you could have a red zone. Basically, it would give more warning if it creeps up.

    As it stands, it seems like if you're overheating the needle will go from "normal" to red in a very short time. If you don't check the gauge frequently, you'll miss it. With a more linear gauge, you could see the progression towards overheating, when climbing for example...
     
  19. parabola

    parabola

    Messages:
    316
    Likes Received:
    0
    Joined:
    Jun 27, 2005
    Location:
    Austin, TX
    Well, you are not going to get worse cooling going with more water. Water cools far better than anti-freeze.

    Basically, we have a few things to worry about with cooling mixtures.

    1. Corrosion protection
    2. Lubrication
    3. Heat transfer
    4. Boiling point
    5. Freezing point

    Most anti-freeze products improve 1,2,4, and 5 at the expense of 3. Higher percentages of coolant increases the effects. Pure water is best at providing 3. Adding a cooling lubricant such as Water Wetter can provide 1 and 2 for you. Some regions don't need 5. 4 is the big question. Our caps are .9 bar (right?) or about 13 psi. I don't have the figures for the boiling point of distilled water at 13psi but I'd bet it's around 230F, too close for comfort for the temps our trucks run at. I'd feel most comfortable (for my region) with a 80/20 and maybe add some Water Wetter to provide more 1,2 and 3.
     
  20. Darwood

    Darwood

    Messages:
    1,957
    Likes Received:
    8
    Joined:
    Oct 8, 2003
    Location:
    Z.O.W.I.E. Headquarters
    This is a good thought. Seems kinda silly to have two temp guages. Does anyone know if it's in the instument cluster that this dead spot occurs or is it closer to the senesor that it occurs. The further from the cluster the easier it will be to modify (unless it's done at the ECU).
     
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.