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Thread: 7MGE Supra 1986 Manual MA70 OVERHEATING - After Full Rebuild

  1. #16
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 7MGE Supra 1986 Manual MA70 OVERHEATING - After Full Rebuild

    From your description I am guessing that the fans are along the lines of these...

    And that they attach to the radiator with zip ties or similar (no mounting plate). If so
    their effectiveness will be limited to the percentage of the radiator actually exposed
    to the airflow from the fans. This will help cooling at low speeds and when stuck in traffic,
    but will not have a lot of effect at highway speeds.

    Factory electric cooling fans have a switch that turns the fan on when the temperature
    of the coolant goes above the thermostat control temperature indicating that extra
    cooling is required. In my experience, it is unusual to have a thermo fan turn on at
    highway speeds. Mechanical fans with a viscous clutch also turn freely when cool and
    only engage when there is insufficient airflow through the radiator to cool the clutch
    housing. Viscous clutch fans with the factory shroud do a good job and the only reason
    I would change to an electric fan is if there is not enough room for the factory setup.

    Nevertheless, fans of the above type do not present much of an obstruction to airflow
    and should push a bit more air through the radiator if they turn on at highway speeds.
    There is a fair amount of science involved when comparing 1, 2 and 3-core radiators
    based on the number of tubes, fin spacing and construction details. Adding extra cores
    does not mean that you get twice or three times the cooling, as adding cores makes it
    more difficult for the air to pass through. Hopefully you will get enough extra cooling to
    keep the engine happy

    Cheers... jondee86

  2. #17
    Forum Member 1st year Apprentice
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    Default Re: 7MGE Supra 1986 Manual MA70 OVERHEATING - After Full Rebuild

    Thank you. Just waiting on the new shrouds now and ready to go with the 3 core radiator. Does anyone know what PSI the cap should be rated to for these? Thanks.

  3. #18
    Junior Member Backyard Mechanic
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    Default Re: 7MGE Supra 1986 Manual MA70 OVERHEATING - After Full Rebuild

    Quote Originally Posted by SlotCar84 View Post
    Thank you. Just waiting on the new shrouds now and ready to go with the 3 core radiator. Does anyone know what PSI the cap should be rated to for these? Thanks.
    According to the Toyota 7M-GE, 7M-GTE Engine manual:
    Radiator Cap Relief valve opening pressure:

    Standard:0.75 - 1.05 kg/cm (10.7 - 14.9 psi 74 -103 kPa)
    Limit: 0.6 kg/cm 8.5 psi 59 kPa

  4. #19
    Forum Member 1st year Apprentice
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    Default Re: 7MGE Supra 1986 Manual MA70 OVERHEATING - After Full Rebuild

    Thanks �� appreciate it

  5. #20
    Junior Member Backyard Mechanic
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    Default Re: 7MGE Supra 1986 Manual MA70 OVERHEATING - After Full Rebuild

    I have owned two Cressida cars with 7MGE.

    First thing that comes to mind is, are the electric fans running in the right direction?

    Assuming the engine & radiator is not clogged, the standard system will be ok.

    One of the previous writers is correct about thermostats. Aftermarket thermos are poor compared to OE. However, you can buy 'Heavy Duty' aftermarket ones with a larger opening although they appear to have a similar opening as the OE. On a Mitsubishi we owned the OE thermo was cheaper than the aftermarket.

    Is the thermo upside down and/or the jiggler located correctly?

    I think there is a method of bleeding out the air bubbles as they can cause overheating.

    If an aftermarket head gasket is used, was it checked to see if it had all the same water holes punched in it. I have come across gaskets where this was not done.

    Was the engine or radiator sealed off with a piece of rag during the repair process and it was forgotton to be taken out.

    If you have to remove the head again, its much easier to replace the welsh plugs with brass plugs plus there is one that can only be replaced with the head off. One of the rear ones behind the starter motor rusts through first

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