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Overheating on the Highway

Discussion in '70-Series Tech' started by Rotac, Aug 29, 2006.

  1. Rotac

    Rotac

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    I'm running an 85 BJ70 with 465,000 km and have had the rad flushed and changed the thermostat twice now but she still heats up once I get over 110 km/hr. The truck is stock (3B) and the rad appears fine. I drive it all year round and even pull a trailer with it a couple times a year but as long as I keep under 110 it won't over heat. Is this common or should I be looking at a new rad or water pump? How can I tell which may need replacing first.
    Ken
     
  2. Tapage

    Tapage Club 4X4 Panamá SILVER Star

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    If your water pump aren't leaking .. it's fine. I check your fan clutch ( or you have fixed . ? ) coz at hight speed maybe is more wind that you can get from your speed than your fan .. in this case your engine ( stuck fan clutch or fixed fan ) are fightinh with the wind that comes throught rad ..

    Other nice idea are check you compresion values ..

    Other idea is check your EGT and diesel inyector .. coz at hight speed maybe you are pushing more diesel than your engine can burn.
     
  3. roscoFJ73

    roscoFJ73

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    Ken I would keep it under 110klm and get a few more years out of it.
    When diesels or any engine gets high klms they tend to run hotter.
    If your radiator was no good it would probably overheat earlier;)

    Take it easy and let the old girl die gracefully:D
     
  4. crushers

    crushers post ho SILVER Star

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    do real good flush of the cooling system including running water out the block drain above the starter...
     
  5. Rotac

    Rotac

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    Thanks guys for all the great suggestions. I'll try the suggestions and I only hit the highway about 6 to 10 times a year. It's just fustrating on the 401 here in Ontario when everyone else is going 130 km/hr and I'm having to stay at 100 to 110 km/hr. I ran it to North Carolina and back in May at 110 the whole way and she's still running like a charm.
     
  6. crushers

    crushers post ho SILVER Star

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    so take the slow lane... oh yah, there is not slow lane on the 401...
     
  7. lshobie

    lshobie

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    Is your rad dirty? spray water (not too high a pressure) from inside the engine out through the rad to wash out the dirt and bugs. Also, might you have an air pocket in your cooling system? With the vehicle cold drive it up a steep bank - and work any air that might be in it out - ie. increase angle on one side - check for air - then other side and check for air etc etc. open up the rear heater switch to let the air out etc.

    good luck.
     
  8. UpsideDown

    UpsideDown

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    I would have to say that your problem is probably a plugged rad, given the vintage. You can check it by spraying a fine mist of water on the rad when the vehicle is up to temperature and the thermostat is opening up. Where the water evaporates quickly is where the rad is clean(ish) inside, and where it stays wet... it's blocked.

    If your rad is not too old, you should try to get it rodded out at the local rad shop (find a good rad shop to do this) to clear out sediment.

    Ontario water is quite hard, depending on where you are, so use distilled water when you refill your system or buy pre-mixed coolant.

    Using chemical flushes is generally contraindicated, most of these flushes do more damage than help as they remove the corrosion protection coating that coolants leave behind as they do their job.
     
  9. Island Moose

    Island Moose

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    110km/hr in my rig is like encountering an unstable warp field...


    [​IMG]

    "I've no more pewer ta give ya Captain!"



    Much happier at 90, in love with 80.
     
  10. knorrena

    knorrena

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    Yeah, I suspect the rad is blocked too. I had this happen on another vehicle. From the outside the rad looked near new. When the guy at the rad shop showed me the guts it was amazing how much crud was in there. The new rad was much lighter than the old one too, but I dont know if this was due to crud buildup or not.

    Originally I thought about flushing with clr. After all it is supposed to remove this stuff. I have read a few posts on doing this, and most concerns surrounded the effect of clr on aluminum. As far as I know, there is no aluminum in the cooling system of an 85 bj70 so I think you should be able to try this trick though I accept no liability :). My plan is to try it myself before winter hits calgary.

    Karl
     
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