1979 401 cooling issue

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  • Ristow
    • Jan 20, 2006
    • 17292

    #16
    It came with a clutch fan and that’s what you need. Flex fans are a joke as wont pull enough air. Very likely that is the problem.

    The fab is always in play. There is no ram effect on these, the fan is needed to create a low pressure zone behind the radiator. This forum has had multiple threads from guys that thought they could throw electric fan on and make power and mileage only to have the same problems you are.
    Originally posted by Hankrod
    Ristows right.................again,


    Originally posted by Fasts79Chief
    ... like the little 'you know what's' that you are.


    Originally posted by Fasts79Chief
    I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!

    It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...

    Comment

    • 440sixpack
      327 Rambler
      • Jul 21, 2016
      • 612

      #17
      The right fan could really help. all A/C rigs had the big fan and clutch.

      Is your condenser so plugged up it's blocking air flow to the radiator ?

      Ground speed won't push enough air through to do much good. it has to be pulled by the fan.

      Comment

      • rang-a-stang
        Administrator
        • Oct 31, 2016
        • 5466

        #18
        Originally posted by Ristow
        It came with a clutch fan and that?s what you need. ... Very likely that is the problem.
        Chuck McTruck 71 J4000
        (Chuck McTruck Build Thread)
        79 Cherokee Chief (SOLD, goodbye old buddy)
        (Cherokee Build Thread)
        11 Nissan Pathfinder Silver Edition 4x4
        09 Mazdaspeed3 Grand Touring
        00 Baby Cherokee

        Comment

        • gpcl16
          232 I6
          • Apr 02, 2016
          • 121

          #19
          The fan clutch will also prevent your fan from turning too fast. Having a regular fan bolted directly to a spacer is a bad idea. The fan can actually spin too fast at high RPMs causing very odd airflow characteristics. Not to mention sapping power and causing your engine to work harder than it needs to. In my experience, fan clutches were standard on many larger American cars and trucks going back to the early 60s.
          1988 Jeep Grand Wagoneer
          4" BDS Suspension Lift
          Tru-Trac Rear
          Howell GM TBI with Custom Tune

          Comment

          • gpcl16
            232 I6
            • Apr 02, 2016
            • 121

            #20
            Fluid dynamics is some really complicated . Air behaves in ways that are sometimes very unexpected. There's way more to it than "put a bigger fan on" or "make the fan spin faster so it moves more air." Sort of like how most pickups get better gas mileage with the tailgate up than down.
            1988 Jeep Grand Wagoneer
            4" BDS Suspension Lift
            Tru-Trac Rear
            Howell GM TBI with Custom Tune

            Comment

            • rapom
              232 I6
              • Aug 10, 2016
              • 35

              #21
              Reply

              I have a similar issue with my 79 chief. I have a new radiator, thermostat, and a clutch fan that seems good. Mine will also overheat, but only at idle or very slow speeds. I even installed a 14? spal pusher fan on the condenser which gives me nice and cold a/c sitting in traffic. It stabilizes the temp. But I still think it runs to hot.

              The 360 has about 130,000 on it and the water pump looks original, so my next idea is to install a flowcooler water pump and a Robert Shaw thermostat to get my idle water circulation up.

              In your case you may what to try adjustable homemade front spoiler under your front bumper.

              A heavy duty fixed blade fan is another option.

              A four core radiator from champion, may be better. May have to source one from an old mopar application.

              Water wetter in your antifreeze is supposed to help.

              I bet the front spoiler would work but would take away your stock look. A lot of oem?s use them because cars now have smaller grills and need that extra low pressure in the engine compartment at higher speeds.

              Comment

              • Ristow
                • Jan 20, 2006
                • 17292

                #22
                the flowkooler pump is a joke. it usually scars up the timing cover with the rivets on the gimicky backing plate,so you put 2 gaskets on which i leak maker.


                if your motor won't cool with a standard issue water pump and thermostat you need to find the reall reason why.


                all the spoiler does on these is hide the front shackles. the spoiler wasn't used until later years.


                the fan creates the low pressure zone.
                Originally posted by Hankrod
                Ristows right.................again,


                Originally posted by Fasts79Chief
                ... like the little 'you know what's' that you are.


                Originally posted by Fasts79Chief
                I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!

                It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...

                Comment

                • 68glad
                  350 Buick
                  • Jun 01, 2006
                  • 1043

                  #23
                  Originally posted by Ristow
                  Flex fans are a joke

                  100% agree especially wheeling offroad. Fan thinks your going 65mph and blades flatten out but really only going 5mph. Never again.
                  68 gladiator- 455/400/20 r.i.p.
                  78 wagoneer- 401, drw60, drw70, 203/205, 38's, oba, obw, hydroboost, dual p/s pump, bla bla bla

                  "If you don't stand for something, you'll fall for anything."

                  Comment

                  • AZChief
                    230 Tornado
                    • Aug 16, 2018
                    • 17

                    #24
                    Ok, so I finally had time to look at things a bit. I moved the trans cooler out of the way just to take that out of the picture, because the previous owner had it mounted in front of the condenser at an angle, meaning it was leaning forward. I was afraid it was creating a deadspot right behind it that was affecting airflow into 1/3 of the radiator (its a big cooler). I test drove it with the cooler out of the way, and no change. I did notice that the previous owner did put a flex fan on there, so I am now looking for a stock-type non flexible fan to mount, with the addition of a fan clutch. Anyone have any ideas on where to look for a stock fan? Im going to look at a few FSJ websites soon.
                    Im still suspicious though, as to why there is such a fast and drastic climb in temperature once I turn on the A/C. The compressor clutch isnt working all that well, as I recently noticed. It appears to be getting stuck sometimes when I switch on the A/C. I know it cycles on and off, but there is a constant scraping noise coming from it, and like I said, it stopped several times and I had to tap on it to release it so it could spin again. Maybe the compressor (the original one bolted back on after the motor swap by the previous owner) is on its last legs in addition to the clutch not working well is causing a lot more resistance than it normally should?
                    So for now Im looking for a factory style fan to which I will attach a clutch to, and looking at a new A/C compressor clutch.

                    Comment

                    • gpcl16
                      232 I6
                      • Apr 02, 2016
                      • 121

                      #25
                      The compressor putting extra load on the engine could have something to do with it. Do you notice a big drop in RPMs at idle when turning the AC on? Assuming you're running a carb, the idle speed would drop quite a bit if there was a heavier than normal load from a faulty compressor or blockage in the AC system. A slight drop 50-100 RPM would be normal.

                      Also just how much hotter are we talking here? Are you running an aftermarket gauge that shows you the actual temp or just a stock gauge with no numbers? Oftentimes stock gauges do not have a linear movement of the needle, in other words, there might be little difference between 180-205 then suddenly it climbs much faster after 205. You might only be running 5-10 degrees hotter which I would think is normal when running AC on a hot summer day.
                      1988 Jeep Grand Wagoneer
                      4" BDS Suspension Lift
                      Tru-Trac Rear
                      Howell GM TBI with Custom Tune

                      Comment

                      • AZChief
                        230 Tornado
                        • Aug 16, 2018
                        • 17

                        #26
                        I havent really noticed what kind of an RPM drop there is, whether its at idle or cruising. Thats something I'll have to watch for.
                        While tooling along with the A/C off, it stabilizes at 195-200, and that is with the interior (stock) gauge at the 3/4 mark, and the aftermarket underhood gauge giving me that reading of between 195-200. I installed the underhood gauge so that I could get some actual numbers. Once I switch on the A/C, the A/C works just fine, but the coolant temp very quickly rises to 220, then continues to climb to 230. Yesterday I was testing things out again after moving the trans cooler out of the way, and as it was sitting in a parking lot at idle with the A/C still on, the underhood gauge climbed to about 240 in about 5 minutes. So at that point I just turned it off and let it sit until it cooled off.
                        As soon as I get a day off here coming up, I want to do a compression check, check the timing, and make sure the carb is set decently. But mostly I want to check the compression to ensure there isnt a leaking head gasket.

                        Comment

                        • wiley-moeracing
                          350 Buick
                          • Feb 15, 2010
                          • 1430

                          #27
                          can you place a box fan in front of the radiator while running with the a/c on and see if the temps drop or stabilize. That will show if its a airflow issue or something else. will help to narrow it down. Is your radiator cap functioning correctly?, I feel your pain here in phoenix area.

                          Comment

                          • babywag
                            out of order
                            • Jun 08, 2005
                            • 10284

                            #28
                            Originally posted by AZChief
                            I did notice that the previous owner did put a flex fan on there, so I am now looking for a stock-type non flexible fan to mount, with the addition of a fan clutch. Anyone have any ideas on where to look for a stock fan?
                            Not a FSJ fan but I have an 18? 7 blade fan off a roadmaster.
                            IIRC the stock FS Jeep fan is 19??
                            I stole/used the clutch on my Jeep so it should work/bolt up.
                            Shoot me a PM if you?re interested.
                            Tony
                            88 GW, 67 J3000, 07 Magnum SRT8

                            Comment

                            • AZChief
                              230 Tornado
                              • Aug 16, 2018
                              • 17

                              #29
                              I dont believe its an airflow issue at this point. I had the grill assembly off when I relocated the trans cooler out of the way, so I was able to clearly see the condition of the fins on the radiator, which were great because it was just recored (3-cores). The A/C condenser fins were in good shape as well, very little debris to clean out, and I straightened a few of the fins that needed it, and none of the fins seemed brittle or corroded, so Im ruling that out.
                              Aside from replacing the mechanical fan and adding a fan clutch, and replacing the A/C compressor clutch as well, Im going to look into the basics first, to include a compression check to ensure that I dont have combustion leakage into the cooling system, as well as a check of the ignition timing and fuel mixture.

                              Comment

                              • letank
                                AMC 4 OH! 1
                                • Jun 03, 2002
                                • 4126

                                #30
                                Time to get an infra red thermometer, also known as non contact thermometer and measure the temp difference between the input and output of your radiator hoses.
                                If the engine is really cooking the coolant, you may need a better cooling system for those bored over 401...
                                21" fan from a dodge RV with 9 blades can be in your future, I read that it seems that the flow is not restricted, but in the end it is how much heat can the radiator extract, and how much flow to remove heat is designed in a specific system


                                Otherwise if it is really running lean, time for an oxygen sensor and have real data at various rpm.


                                Too much advance while crusing will increase the temp of the engine, and as usual always look for the cheapest solution to solve a problem!


                                post a pict of your shroud and fan combo please


                                I am running a 9 blade 17" fan and fan clutch out of a 560SL mercedes, FSJ fan on left side. Why, it is aluminum and 1 lbs lighter... more HP for my dinosaur.




                                and the result



                                and the bottom view, you need the opening to prevent a vacuum effect that will impede the airflow


                                Last edited by letank; 09-01-2018, 04:15 PM.
                                Michel
                                74 wag, 349Kmiles on original ticker/trany, except for the rust. Will it make it to the next get together without a rebuilt? Status: needs a new body.
                                85 Gwag, 229 Kmiles. $250 FSJ test lab since 02, that refuses to give up but still leaks.

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