Author Topic: overheating  (Read 1355 times)

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Offline MadMax78

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overheating
« on: May 27, 2020, 07:51:14 pm »
1978 RC with 400, recent radiator flush and fill.  Can let the RC idle all day and temp gauge reads normal, as soon I drive for about 10 to 15 minutes the temp gauge starts to climb when I come to a stop.  It does not climb rapidly but after several close stops its to the high end.  It will slowly move back towards the cooler side of the gauge the more driving without stopping I do.  I have bleed the system as best I know how and checked coolant and oil for discoloration, which none is present.  Heater blows hot and fan clutch feels tight coolant level stays the same.  Not sure if this would be a thermostat issue or what is going on.  Engine is stock and not sure what issues it could be.  Any suggestions would be great. 

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    Offline 712edf

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    Re: overheating
    « Reply #1 on: May 27, 2020, 08:29:27 pm »
    Did this problem begin after the radiator flush, or all along?

    If you get in it & drive it at highway speeds, does it ever get above normal, or only when stopping?

    Automatic transmission?

    Does it otherwise run fine?

    Are you running 50/50 water/coolant?

    Bucky
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    Offline dodge82273

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    Re: overheating
    « Reply #2 on: May 27, 2020, 09:10:04 pm »
    custom bumper grill guard ?  air flow around radiator rather than through it , plastic cover between rad and radiator support on top AND bottom rubber in place ?   fan clutch ? fan shroud ?
    78 to 93 parts trucks
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    Offline DODGEBOYS

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    Re: overheating
    « Reply #3 on: May 27, 2020, 09:57:23 pm »
    did you just flush the Rad or the whole system and did you back flush it //  l,ve had it happen to me dozens of times where you "think" yer do'in a good thing and you end up filling the heads with crap from the sediment at the bottom of the water jacket 
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    Offline dodge82273

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    Re: overheating
    « Reply #4 on: May 28, 2020, 02:46:20 am »
    cold water flush , the t stat is closed....
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline MadMax78

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    Re: overheating
    « Reply #5 on: May 28, 2020, 07:11:29 am »
    Its an automatic, issue started after the flush.  Stock rad, shroud and fan with clutch, nothing in front of radiator that shouldn't be and no bumper or grill guard.  Flushed with cold water and let the engine warm up and ran water through the system.  Would a T stat be an issue even though its fine at idle and temp stays in middle just when I start driving does it go up.  Would air in the system cause this?

    Offline Mad Max

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    Re: overheating
    « Reply #6 on: May 28, 2020, 08:38:33 am »
    t-stat stuck open?  Possible the coolant is flowing through the system/radiator too fast and not enough heat being removed from the coolant when under load, but okay at idle?
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    Offline 712edf

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    Re: overheating
    « Reply #7 on: May 28, 2020, 11:31:47 am »
    I would check the t-stat, even go ahead replace it. I like 160 degree ones. While it's true that hotter running engines have better emissions & less cylinder wear, this should be a moot point with a 40+ year old motor.

    A lower t-stat won't fix an overheating issue, just delay it, which sometimes is all you need.

    Bucky
    1975 W600   318  NP540  T223Rockwell tcase, Rockwell front & rear axles, 6.8 ratio

    Offline dodge82273

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    Re: overheating
    « Reply #8 on: May 28, 2020, 03:16:29 pm »
    when "flushing" a  system with cold water , the T stat closes , the gunk never gets FLUSHED out . see dodgeboys comment above about gunk in heads . I'd remove the lower rad hose , and the t stat , run water from garden hose into heater hose outlet in manifold .. do what I could to wash out the engine , THEN wash out the radiator .. install a new stat .
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline RCCADMAN

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    Re: overheating
    « Reply #9 on: May 28, 2020, 05:46:03 pm »
     {popcorn} {popcorn} {popcorn}
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    Offline 86w250

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    Re: overheating
    « Reply #10 on: May 29, 2020, 05:36:48 am »
    What is the temperature when you say it gets up to the high side and are you using an aftermarket gauge or the one in the dash that says C------H?
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    Offline Elwenil

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    Re: overheating
    « Reply #11 on: May 29, 2020, 06:15:15 am »
    Before I did anything, I would verify that the cap is holding pressure.  Easy to test and you don't have to tear anything apart and it would be a cheap fix.  Very common problem with older vehicles.
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    Offline MadMax78

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    Re: overheating
    « Reply #12 on: May 29, 2020, 08:33:40 am »
    The Rad cap is new and I have a new t stat coming.  Will drain and flushed as mentioned above with the removal of old t stat and lower Rad hose.  Its the stock gauge was replaced with a nos one this winter.  Stays in the middle of c___h all day in driveway at idle when driving and making several stops after about 10 mins it will eventually make it all the way to the H on stock gauge. Going somewhat down when I drive on the open road.

    Offline dodge82273

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    Re: overheating
    « Reply #13 on: May 29, 2020, 03:23:22 pm »
    ahhhh , important question : did it do this before you changed the gauge , or right after ? sometimes the gauge and sender are not compatible , why did you change the gauge in the first place ? so it has not puked ? 
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline Canadian country boy

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    Re: overheating
    « Reply #14 on: June 9, 2020, 02:53:15 pm »
    Before I did anything, I would verify that the cap is holding pressure.  Easy to test and you don't have to tear anything apart and it would be a cheap fix.  Very common problem with older vehicles.
    I agree. 7 - 12 lb cap is ideal. Also make sure you have a spring in the lower hose to avoid collapse at rpm.
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    Offline Elwenil

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    Re: overheating
    « Reply #15 on: June 9, 2020, 05:11:47 pm »
    I am reasonably sure a Mopar needs 14-16 PSI of pressure to cool correctly.
    L.Clemons

    1988 Ramcharger AW450-318EFI-NP435 4 speed-NP205 Transfer Case-Dana 60s-Braden Wormdrive Front Winch

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    Lord of Storms am I,
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    I am the Father of the War,
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    Offline ToxicDoc

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    Re: overheating
    « Reply #16 on: June 9, 2020, 06:57:41 pm »
    I am reasonably sure a Mopar needs 14-16 PSI of pressure to cool correctly.

    And that's pretty typical of most American engines of this type.
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    Offline Canadian country boy

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    Re: overheating
    « Reply #17 on: June 10, 2020, 08:52:06 pm »
    I've always ran a 7lb cap with no issues but I did switch to a 16lb cap and I notice my truck runs hotter. I have a 195 high flow thermostat with an 8 blade pump and a brand new radiator with the 16lb cap, the engine runs around 210/215 degrees in traffic when it ran cooler with the 7lb cap at around 190. I've left the 16lb cap on as a hotter engine has lower emissions and less cylinder wear.
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    Offline Jeffy45

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    Re: overheating
    « Reply #18 on: June 12, 2020, 05:02:31 am »
     When ya flush remove t-stat. Also remove both  block drains poke around in there w/something cause they are usually blocked w/ sediment. Take off both heater core hoses from engine. If there is a heater valve inline open it and back flush heater core in reverse flow direction. Put every thing back together w/ no t/ stat. But leave the block drains out. Make sure ya got flow out the block drains and run it w/ water hose in radiator.       Also don't trust a new cap
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    Offline ToxicDoc

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    Re: overheating
    « Reply #19 on: June 12, 2020, 07:04:58 pm »
    I've always ran a 7lb cap with no issues but I did switch to a 16lb cap and I notice my truck runs hotter. I have a 195 high flow thermostat with an 8 blade pump and a brand new radiator with the 16lb cap, the engine runs around 210/215 degrees in traffic when it ran cooler with the 7lb cap at around 190. I've left the 16lb cap on as a hotter engine has lower emissions and less cylinder wear.

    That's unusual and maybe just a coincidence. Hot spots in the head can make the coolant boil/enter the gas state. So higher pressure coolant is beneficial there, keeping the coolant in the liquid state in a larger temperature range.
    '85 W150 SB, 408 stroker, Magnum manifolds, Performer RPM, 670 Truck Avenger, HEI ignition, Auburn LSD 9.25 and '82 D44 (non-CAD) with 3.55/3.54,  NV4500/NP241

    Offline dodge82273

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    Re: overheating
    « Reply #20 on: June 12, 2020, 08:00:01 pm »
    unusual ..... yeah to put it politely . higher pressure MAKES it hotter ? , hummmm ....
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline Canadian country boy

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    Re: overheating
    « Reply #21 on: June 12, 2020, 10:12:11 pm »
    It could be a coincidence and i found it strange but as soon as I put a 16lb cap on my rad my temp gauge reads hotter. It used to sit at 180 in traffic and now it reads as high as 215. I don't get it either. The entire system is new. Maybe I should put the 7lb back on and see what happens.
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    Offline ToxicDoc

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    Re: overheating
    « Reply #22 on: June 12, 2020, 11:19:53 pm »
    That would be an easy way to tell for sure.
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    Offline dodge82273

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    Re: overheating
    « Reply #23 on: June 13, 2020, 04:17:09 am »
    warmer weather happened ?
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline Chilly

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    Re: overheating
    « Reply #24 on: June 13, 2020, 05:44:30 am »
    t-stat stuck open?  Possible the coolant is flowing through the system/radiator too fast and not enough heat being removed from the coolant when under load, but okay at idle?

    If the water is flowing too fast to remove the heat then how did it get so hot as to overheat?  Or is only the metal hot while the water stays (relatively) cool?  How does the heat get to the temperature sensor?  If I move the water fast enough will it never boil over?
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    Offline Mad Max

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    Re: overheating
    « Reply #25 on: June 13, 2020, 08:29:08 am »
    it's just one possible scenario, but the basic premise is the engine block makes the heat and the radiator removes it, most demanding under loads, and if it flows through the radiator too fast then not enough heat is removed and 'everything' gets hot, but when the engine load decreases the heat decreases and then more heat is removed going through the radiator - the thermostat really just slows down the coolant flow.  The conditions have to be just right but it is possible {noclue}
    « Last Edit: June 13, 2020, 08:41:44 am by Mad Max »
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    2007 Cummins Ram 3500 Megadually 4x4, 5.9/G56
    1952 Willys M-38 "Poncho"

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    Offline Killerbee

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    Re: overheating
    « Reply #26 on: June 13, 2020, 08:14:13 pm »
    I don't see anything about timing in the thread yet... so....  Timing.  Too much advance can cause it to run hot.

    Also, the distributor might be connected to the wrong port on the carburator, which would also cause issues with timing too.

    Both would not be evident at idle, but would appear even just slightly off idle.

    $0.02,
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    Offline dodge82273

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    Re: overheating
    « Reply #27 on: June 14, 2020, 12:50:43 am »
    just so ya know , too much retarded will make it run hot too ...faster than advance ....
    78 to 93 parts trucks
    91 w250 318 518 44/60 single 9 foot driveway plow locked
    87w150 44/corp727 kandy w/ ghost bats/summer
    86-D/W100 44/corp/318mag/carb/4500/aka shit box/winter
    93w150short/44/corp/360/le/mag "caddie"
    93w250LB51844/60posi 318"New Truck"
    93w350 6 tire CC 60 c/a flat bed dump

    Offline Canadian country boy

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    Re: overheating
    « Reply #28 on: June 14, 2020, 01:49:27 am »
    Yes, if your ignition is too far retarded your exhaust can go glowing red from heat and ping and vapour lock like crazy.
    Dodge boys have more fun!  Get with the adult toys from Dodge!
    '79 Macho Power Wagon.

    I support American made  🇺🇸

    Love Jesus with all your heart. Satan is the greatest deceiver.

    TRUTH IS NOT A CONSPIRACY THEORY.
    STOP GLOBALIZATION!!! STOP THE UNITED NATIONS!!! #WEDONOTCONCENT

    Offline Jeffy45

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    Re: overheating
    « Reply #29 on: June 14, 2020, 05:45:05 am »
    Couldn't resist 🤣🤣🤣                                                                     https://youtu.be/1Y3FzVQi-R8
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    Offline Chilly

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    Re: overheating
    « Reply #30 on: June 14, 2020, 08:26:06 am »
    it's just one possible scenario, but the basic premise is the engine block makes the heat and the radiator removes it, most demanding under loads, and if it flows through the radiator too fast then not enough heat is removed and 'everything' gets hot, but when the engine load decreases the heat decreases and then more heat is removed going through the radiator - the thermostat really just slows down the coolant flow.  The conditions have to be just right but it is possible {noclue}

    I've read that theory more than a few times on the interweb.  It's contrary to thermodynamic laws, however.   I'e operated nuclear reactors in very dynamic conditions on a fast attach sub.  Unlike a power station plant, a fast boat experiences many transients: power levels up and down, hot rodding the main engines, shifting reactor coolant pumps often to give sufficient cooling at the slowest (least noisy) speed allowed for reactor conditions.

    If running without a t-stat causes boil-over then there is at least one other reason.  Coolant moving too fast 100% certainly isnt it.  What it could be is that the restriction of a t-stat increases the pressure head at the pump.  Running without may be just enough drop to allow localized cavitation and air binding in the pump.

    Running coolant more quickly through the radiator does zero for heat generation OR heat removal up to a point.  The pump simply moves hot stuff from where it becomes hot (engine) to where it gets cooled (radiator).  The heat sink that actually DOES remove heat is the air moving through the radiator.   So the AVERAGE coolant temp (avg of hot leg and cold leg) doesnt change much based on coolant speed.  If the coolant moves slow the hot side gets hotter (each "piece" of water spends more time in the engine) and the cold side runs cooler (radiator has more time to cool each "piece" of water).  Conversely, if water moves quickly the avg temp stays same but less temp difference across the thermostat.

    So flow doesnt really matter until the hottest point in the engine reaches the boiling point.  Then a runaway boiling event begins.  First, tiny steam bubbles form and collapse at the metal surface. That becomes a skin of steam, which is a terrible conductor of heat, causing temps to tocket.  Boil-over ensues.   
    92 Ramcharger
    360 TBI, auto, 241 t-case
    44F, 9.25R posi, 3.54 gears (yeah, I know)
    Skyjacker 4", 33x12.5