/6 running hot - what are your temperatures?

Heating / Cooling / AC

  1. Loggato

    Loggato Well-Known Member

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    Hey guys and gals. My '74 duster (which has been sitting many years) has reached the point where I cant drive more than 10 minutes without it getting too hot. As in, puking as soon as I shut it off. I've replaced the 22" radiator with a 24" (from A/C car), with fan shroud and also a 17" 6 blade fan. This thing should COOL. I have no thermostat and a 16# cap

    So taking some temps yesterday with the gauge just shy of 250, I get:

    1. Thermostat housing - 240
    2. next to temp sensor - 235
    3. upper radiator hose - never exceeded 220
    4. lower radiator hose - never exceeded 190

    I couldn't check the radiator temps because of my condenser, but it had good air flow.

    What difference do you usually see between the radiator hoses?

    Thanks.
     
  2. 340doc

    340doc Well-Known Member

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    Sitting many years. Did you flush the block good before you hooked up the new rad? If the rad you put in is used it might need cleaned. Have you tried a thermostat? Some will run cooler with one. Also is your cap verified good?
     
  3. toolmanmike

    toolmanmike FABO Staff Staff Member FABO Gold Member

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    Put in a 180° thermostat and make sure you have a new cap. You may have a head gasket or crack problem but never overlook the simple things.
     
  4. Bad Sport

    Bad Sport HALF A BUBBLE OFF Staff Member FABO Gold Member

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    That's where I'd start. Without a T Stat how is the system supposed to slow down the liquid flow long enough to be cooled while in the radiator?
     
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    • Loggato

      Loggato Well-Known Member

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      It's a good place to start!

      I'll get a T-stat and new cap. While that thermostat housing is off, I'll see if I can see any debris inside the block.

      It was flushed out pretty extensively, but it's turning the water brown pretty quickly. Right now it's soaking in cooling system flush.
       
    • TrailBeast

      TrailBeast Slightly Twisted Member

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      Water pump impeller vanes can rot away causing no circulation.
      The vane hub can also come loose (rust loose) from the shaft.
      Common on engines that sat for a long time.

      Puking only after shutdown isn't a head gasket, (not saying it isn't possible) but usually puking after shutdown is a weak cap or rising temps after shutdown when hot already, like yours sounds.
      Your temps look like little or no circulation.
      (at least pull and check the water pump)
       
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      • Loggato

        Loggato Well-Known Member

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        Water pump is brand new! So is the V-belt and all radiator hoses.
         
      • TrailBeast

        TrailBeast Slightly Twisted Member

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        So much for that theory.:D
        Still though, with 240 at the T stat housing and 220 at the top hose points to low/no circulation.
        You can check this with the cap off since you don't have a stat. (which you should)
        A 180 is fine.

        Example:
        I have a mechanical temp gauge and a thermostatically controlled electric fan controller is in my top hose right at the radiator.
        The fan controller is set to turn the fan on at 210, and when the fan comes on my mechanical gauge in the intake shows exactly 210.
        The point here is that the temps should be really close to the same at the T stat housing and the top hose at the radiator.
        This is why I suspect circulation.

        You don't have a reverse direction fan by accident do you?
         
      • Loggato

        Loggato Well-Known Member

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        It's a stock exhaust fan from an older dart. I made sure it was the same direction.

        My guess is the block is heat soaking a lot more than the hose, which will cause it to be slightly different. I also ran my garden hose through the radiator and it appeared to flow well. Looking at the temp of the lower hose shows that it is cooling fine, but that doesn't prove that it's flowing fine.

        Keep in mind, this is the 2nd radiator Ive tried and have the same issues, first one "seems" to flow fine with the garden hose as well.
         
      • TrailBeast

        TrailBeast Slightly Twisted Member

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        In my own opinion 190 at the bottom hose is too hot.
        I'll keep thinking on it and let you know if I come up with anything else.
        In the meantime try to get that stat in there and see if by chance that solves the problem.
        It very well could.
         
      • motorpirate

        motorpirate serial mopar owner

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        don't overlook retarded timing...
         
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        • Loggato

          Loggato Well-Known Member

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          I've heard that option too... Thing is: every time I read that, it wasn't the actual problem. but maybe this time it is!
           
        • motorpirate

          motorpirate serial mopar owner

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          I had it once myself..
          Wouldn't have believed it otherwise!!
           
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          • trapster

            trapster Well-Known Member

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            Or lean Carb
             
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            • Loggato

              Loggato Well-Known Member

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              How did you figure it out? was it happening all the time, even at idle? or was it more of a failing vacuum advance?
               
            • motorpirate

              motorpirate serial mopar owner

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              Used 360 I bought with an unknown cam.
              Turned out to be more of a "race" motor than I thought it was.
              Ported heads, Crane Blazer cam, 273 rockers and a manual choke Thermoquad.
              I set it at 10 degrees and after its first road test it boiled over as soon as I shut it off.
              Tried all that you have except the radiator because the 318 I took out never overheated.
              Finally advanced the timing A LOT.
              Like 20 or 25 more degrees.
              Had a ton more power and stopped overheating. I kept advancing it until it pinged then backed off a little.
              I suspect the balancer ring had slipped but never took time to check.
              Ran for many years after that with no more problem, even towing!!
              It was in a '72 3/4 ton pickup.
              Kind of miss it, it was a POS but my friends swore you could see that big hood suck down in the middle when those secondaries opened!!
               
            • AJ/FormS

              AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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              Well it ain't yur rad, cuz its showing a 30* drop from top to bottom which should be adequate.
              If your 6-blade is the narrow bladed one without the air-foil tips, then throw it away. Go get something with all-steel high attack-angle blades with the anti-vortex tips on the end, and make sure is not off a serpentine, reverse rotation system,lol. In your case I would shop for a 7-blader.
              Now you got yurself a freaking fan.
              Now the diagnoses can begin.
              But if your 6-blader does have a similar hi-attack, etc; then go find a regular 8.5x11 sheet of writing paper. Then put the carb on fast idle around 1800-2200 rpm, then paste that paper onto the condenser, off center. Next; grab a corner and attempt to slide it in any direction except towards the center. If yur fan is working right, that thing should want to tear, if it doesn't flat out shred.
               
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              • Loggato

                Loggato Well-Known Member

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                Mine was off a 66 dart with A/C. It's definitely pushing more air than the 4-blader. I have a gut feeling that the rad is good. It's got good suction even through my condenser. When I hosed it out, There wasn't even a spec of dirty water.

                it's funny you mention the high idle, because when I was holding it at 2000 RPM in the driveway, I could keep it from getting hotter, but If I let the idle fall or drive it, it just keeps creeping up.
                 
              • pishta

                pishta I know I'm right....

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                I poked a lb of crap out of my 67 when I had the freeze plugs out. Open the rad and start the cold motor and watch the coolant flow. if its a stat issue, youll either see no flow (until it opens) or youll see flow off the bat which is not good either unless the bypass is showing you a little ancillary flow. Id check the pump again, rebuilt stuff is hit or miss sometimes. Does it run well outside the temperature issues? Valves adjusted .010/.020? Here is an online reference for an Aussie Slant but all the specs are legit, 'cept the Bosch distributor!
                Chrysler 225 Slant 6 Engine Rebuild Manual : Free Download, Borrow, and Streaming : Internet Archive
                 
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                • AJ/FormS

                  AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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                  What does that tell you? What it tells me is that whatever air is coming thru the rad at lower rpm is either not at ambient, or there is not enough of it coming. Maybe the hot air is just going round and round and round........ Or if the stat was out, the water was not circulating properly.
                   
                • TrailBeast

                  TrailBeast Slightly Twisted Member

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                  He said he doesn't have a stat in it.
                   
                • Loggato

                  Loggato Well-Known Member

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                  my mechanical senses are telling me that there is just too much heat being generated by the engine. As I'm standing there measuring temps, I'm thinking "ok, radiator is showing good temps, it's pulling air through it, the lower hose is running cooler.. but It just isn't keeping up!

                  these are just my gut feelings. Maybe I'll make a video.
                   
                • RustyRatRod

                  RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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                  With the engine running and the radiator cap off, rev the engine. If the coolant comes out of the radiator badly, the radiator is probably stopped up. You don't want to do this with the radiator slopped full to the top. Do it with the radiator filled just enough that you can see the top of the flues.
                   
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                  • Slantsix64

                    Slantsix64 Well-Known Member

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                    i would do a compression test and go from there.
                     
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                    • Loggato

                      Loggato Well-Known Member

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                      Small update.. I PROMISE I will get to the rest of the stuff after this week.. but last night I drained what was in it.. the water came out medium brown in color - not as bad as I thought. So my heater core hose has a T-fitting with a cap half way to the firewall. I unscrewed that only to find it LOADED with gunk. I pulled off both hoses from the block and rinsed out some seriously nasty stuff. My guess is the Heater core was housing some of my problem. I ran a small bypass hose and am now running with no heater core.

                      So the test drive: It took a lot longer to warm up this time - I thought it was almost fixed til about 10 minutes in. then it got hot FAST. Like it hit a threshold. As I got home, the bypass hose that I made for the heater core was whistling, so I apparently did not get that tight enough.

                      more to come.
                       
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