67 GTX 440 Engine Temperature With AC

1966 -1967 Mopars

  1. 67GTX440

    67GTX440 Well-Known Member

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    Okay, here is what I found out. Alternator wiring had a short that was causing overcharging. Electrical aftermarket temp gauge was moving up with volt meter under high RPM and was dropping when voltage dropped at idle. This is why it showed cooler at idle than on highway.
    Today was 80 degrees and here are temp readings from four sources after 20 minutes sitting at idle with AC on. Aftermarket dash gauge is obviously wrong. I understand they rarely work right and cannot be repaired or calibrated as per Redline Gauges. Hand held temp reading is from top of radiator and is same at thermostat housing. Radiator cap actually has a probe that reaches coolant.
    I think I am okay and have been chasing cooling ghosts. I guess that shows the issue may be in a less obvious direction than you originally thought. If I had stuck with my low reading dash gauge, I would have saved a whole lotta money. LOL
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    Last edited: Oct 20, 2016
  2. 67GTX440

    67GTX440 Well-Known Member

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    I spent money on water pump, radiator recore, fan clutch, hoses, water wetter plus all those temperature reading devices. A little over $500 or so total. At least I never ordered a new radiator! I am hoping four temperature sources are enough, even though I new my in dash repop gauge was reading real low since I bought it. My repop gas gauge is not much better. Two gauges where the needle moves but don't read accurately for $140 is not a great deal. The ones I had originally that quit working seemed to both be pretty accurate. I should have gone with repair rather than replace, but Redline wants the entire instrument cluster shipped to them, not just the non-working gauges. I will wait until I reinstall the factory tachometer they rebuilt for me and see how it works before I send that off.
     
    Last edited: Oct 20, 2016
  3. oldbee

    oldbee Well-Known Member

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    Finally a conclusion on the thread!!! LOL. It was definitely a brain teaser though. Glad it all worked out. Jeff
     
  4. 67GTX440

    67GTX440 Well-Known Member

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    I guess I should have called the remaining Tappet brother on Car Talk. LOL
     
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  5. 67GTX440

    67GTX440 Well-Known Member

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    Duplicate post.
     
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  6. 67GTX440

    67GTX440 Well-Known Member

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    Sorry for the duplicate posts. I was trying to post pictures from my dentist's chair on my cell phone.
     
  7. oldbee

    oldbee Well-Known Member

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    At least the motor is staying cool, that's all that matters.
     
  8. Ranger16

    Ranger16 Well-Known Member

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    So over charging was causing the electrical gauge to over read?
    That's why I like mechanical water temp & oil pressure gauges. They never lie.
    Glad you got it figured out.
     
  9. TxDon

    TxDon Well-Known Member

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    Sorry you went through all that and glad you figured it out. I have an SW mechanical gauge so I tend to trust it but they are all just taking a snapshot of the location the sender is in. I've done the larger fan, shorty fan clutch and hood to radiator seal and I've noticed definite improvement, so thanks again for all the info your post generated.
     
  10. 67GTX440

    67GTX440 Well-Known Member

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    Update. I finally bit the bullet and ordered a new $1300 correctly numbered and date coded Radiator from Glenn Ray. The one in the car I had recored was a 1969 26 " radiator for a 383 A body with ac.
    Car now runs a consistent 185 degrees. It was always running cool with ac on at idle, but getting progressively hot at high rpm until it peaked about 200 degrees with ac on on the highway. New radiator dropped it 15 degrees on the highway with ac on.
     
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    • themechanic

      themechanic Oklahoma is OK FBBO Gold Member

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      :thumbsup:
       
    • 67GTX440

      67GTX440 Well-Known Member

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      I put my old sending unit back in the car and that solved my problem of the factory gauge reading low. I thought it was the repop gauge I installed, but it was installing a new gauge sending unit alng with the new gauge. I though I was eliminating problem by replacing both at the same time. Sometimes new parts don't work as well as the old ones.
       
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