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1986 XJ700 Maxim overheating issue

Discussion in 'XJ DIY How-To Instructions' started by Longway, Apr 16, 2015.

  1. Longway

    Longway Member

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    Whilst out on my 1986 water cooled XJ700 Maxim X over here in the UK, today, I got stuck in very slow moving traffic and the temp gauge soon got worryingly high towards the red mark. The electric fan didn't kick in and to avoid overheating I kept hitting the kill switch, once on the move again the temp gauge soon dropped. Usually whilst on the move the gauge is well below what I would consider to be normal.
    I always wondered if the thermostat maybe stuck open with the engine appearing to run cool, now I'm wondering if there may be other issues with the fan switch or the fan itself. Any advise on how to proceed will be very much appreciated.

    Regards

    Longway
     
  2. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    You can jumper the fan switch to check both at once. If the fan comes on when the switch is jumpered then you can assume that the switch is faulty, since you know the fan did not come on when sitting in traffic.

    If the thermostat were stuck open you wouldn't have seen the engine get too hot.
     
  3. Maxim-X

    Maxim-X Well-Known Member

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    How clean is your cooling system. My experience was that after a while crud can accumulate in the bottom 1/4 to 1/3 of the rad itself, hence less cooling properties. Just a regular drain and refill just isn't enough.
     
  4. xHondaHack

    xHondaHack Active Member Premium Member

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  5. Longway

    Longway Member

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    Thanks for reply's, last year I changed the mechanical seal and in doing so flushed the system out and replaced with silicate free coolant, also only a few weeks ago I took the grill off radiator to stop a rattle and blew the radiator through with a compressor gun. I will test the fan and switch and look at the link for upgrading the thermoswitch.
     
  6. Longway

    Longway Member

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    I tried connecting fan direct to a battery today and the fan works OK,
    Not sure how to jumper the fan switch to see if that is OK, how do I do that?
    I have thought about wiring a manual switch through a relay to the handlebars, could be the cheapest fix giving me the control to switch the fan on myself
     
  7. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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  8. xHondaHack

    xHondaHack Active Member Premium Member

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    The fan thermoswitch has 12v power to it through the 15A fuse coming from the fuse box with the key on. It's the brown wire at the switch. When at the proper temp., it will provide 12v on the blue wire going to power the fan motor. The black wire on the fan motor itself provides the ground.

    Check for power at the switch with the terminal disconnected and with the key on. If you don't have power, check the fuse.

    Just keep in mind that it's less aggravating (no cutting up the wiring harness), more convenient (not having to switch it on and off), and not that expensive to replace the thermoswitch rather than patching a manual switch in.

    Tony
     
    Last edited: Apr 17, 2015
  9. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Not to mention that the thermoswitch does not require one to remember to turn it on.
    In case of concerns about another failure, it wouldn't be difficult to wire a manual switch in parallel with the thermoswitch.
     
  10. Longway

    Longway Member

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    Thanks for info, I will try that and let you know the outcome
     
  11. Longway

    Longway Member

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    Fuse checked OK, 12v power between brown wire and earth checked OK and brown to blue wire runs the fan no problem.

    Its appears the Thermo switch is the problem or just not switching on soon enough, I would like to upgrade the switch to the one that cuts in sooner but I'm not sure they are available in the UK, other than that it would be easy enough to wire in a manual switch without destroying the existing wiring
     
  12. xHondaHack

    xHondaHack Active Member Premium Member

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    Just do a search for wells sw519 . You should have some luck locating one.

    Tony
     
  13. Longway

    Longway Member

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    Thanks Tony, I've located a Wells SW519 switch from RockAutos.com which has now been ordered, also managed to source a spare thermostat housing with thermoswitch, temp switch, hoses and filler cap still attached from UK ebay which will be useful for spares. The thermoswitch has 105 stamped on, I assume that is the temp it is supposed to kick in. I still intend to fit the SW519 with lower switch temp.
    When working correctly would you say the standard switch works OK or is it normal to get a little too hot before switching the fan on, the other day when stuck in traffic, I was concerned the temp gauge was getting very near the red mark and the engine was smelling hot, the outside temp was approx. 55 - 60 degrees so I wouldn't have fancied it's chances in 80 degrees temp
     
  14. xHondaHack

    xHondaHack Active Member Premium Member

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    If the standard switch is working properly the fan will kick in just before the temp needle hits the red zone. The 105 indicates the temp (in Celsius) when the switch will close (make the connection) and turn the fan on.

    The SW519 specs indicates it should turn the fan on at 95C and back off at 90C. You may have to modify the connector or jumper harness to get it to work.

    Here's the link with all the Wells switch specs:
    http://www.wellsve.com/showall_ds_fans.php

    Tony
     
  15. Longway

    Longway Member

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    SW519 switch arrived today and I set about fitting it when I got home from work, nice straight swap and wires fitted without any cutting, once fitted I warmed the engine up and the fan kicked as the temp gauge reached the small gap in the line at the middle, once the fan was running the temp quickly went down and after a couple of minutes the fan switched off.

    I'm happy with that and I'd say that was a good result :):)

    Thanks for your Help Tony :):)
     
  16. xHondaHack

    xHondaHack Active Member Premium Member

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    Glad it works on your bike. Keep in mind that you will need to keep the idle up on hot days when stuck in traffic. That way it will keep you from draining the battery down.

    Tony
     

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