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coolant issues/overflow 700 1985

posted by  Rtilghman on  Thu Apr 11 11:30 CST 2002
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brickers:

having some odd issues with my coolant overflowing from the expansion tank and wondering if anyone has an idea why this might happen.

I popped the hood of my 745t after a quick run to town and found liquid all around the expansion tank. I first thought it was water that had splashed in from some large puddles I had come through on my way to the house, but quickly realized it was coolantgiven the location and area.

The top of the expansion tank was firmly tightened, but the coolant had apparentkly shot out through the cap. I'm guessing it came through a pressure triggered release in the cap itself... I don't know that the cap has this feature, but a glance appears to indicate it does and it would make sense to have a release to prevent pressure from possibly causing teh radiator to explode.

I'm currently living on a ski mountain in VT, and the drive back from town involves a 3 mile section up a fairly serious hill (maybe 30 degrees or so with some intermittent flats on the way). I generally take the hill at around 60mph, with some minimal turbo boost utilized.

As a test I checked the coolant this morning and repeated the trip while closely monitoring the temp gauge. The trip to town went fine, with the gauge needle staying around 11 oclock (its normal position). However, on my way back on the uphill the gauge climbed to 12 oclock and seemed to border on wanting to go higher. Since the only time it rises above 12 oclock is when it starts to seriously overheat this got me a little nervous.

Anyone know if there is a problem I should be aware or why this might have happened? I flushed the coolant about 4.5 months ago or so and haven'thad any trouble since despite the fact that I've driven a 3 hour, 200 mile trip 15 times with an average speed of 70mph or so. When I flushed it I checked the stat and it looked like new. The radiator has a pinhole leak that I used some radiator patching mixture to fix (the gunk you pour in the expansion tank, etc.). Yes, I know I need to replace the radiator and shouldn't use the goo, but I think it would have bugged out earlier if this was the source of the problem.

Any help or thoughts are greatly appreciated.

Thanks,
Rick








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    coolant issues/overflow 700 1985

    posted by  RAMontgomery on  Thu Apr 11 11:49 CST 2002
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    last visit: Sat Jan 12 00:28 CST 2013
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    Rick,
    That is a pressure cap, and they do go bad. When getting a new one, color matters. You probably should stick with the color you have now.
    --
    Richard Montgomery 83-244GL ; '90-780t; '92-940








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      coolant issues/overflow 700 1985

      posted by  Rtilghman on  Thu Apr 11 12:11 CST 2002
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      makes sense. mine is black... have to go order one now.

      I found some of the radiator patching gunk (white stuff) in the hole in the middle of the cap, so I figure it might have gotten in there and affected its performance.

      thanks,
      -rt








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    coolant issues/overflow 700 1985

    posted by  someone claiming to be mechanic on  Thu Apr 11 11:44 CST 2002 [RELATED]

    Sounds like you need to have the radiator rodded out and repaired. But it seems that has gotten expensive lately so for a bit more money you could buy a brand new radiator.

    In an older radiator that is beginning to see restricted flow, the gunk for radiator leaks finds a happy home and will plugg up the all ready clogged passages.








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      coolant issues/overflow 700 1985

      posted by  Rtilghman on  Thu Apr 11 12:10 CST 2002
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      yeah, I figure I'll just replace it with a new three tier one better suited to my 1875 745t when I have some extra dough to throw at it, but want to drain all the life out of the existing one first. Figure I can get another 20k or so at least out of this one... at 210k now.

      the radiator stuff is nasty, but its not as bad as I thought. When I flushed the coolant system 5 months ago I found some of teh material in places where it could hang up like the stat, etc. However, its incredibly fine and small, and it doesn't seem to cause any problems.

      amusing thing though... I flushed the car and then found the leak in the radiator. asked my dad (PO) and it seems he had done teh same before... I had simply washed out his patch in my attempt to clean out the nasty coolant.

      I found some of the gunk in the expansion cap (black cap). Is it possible the overflow left some gunk in the cap that affected its performance?

      thanks,
      -rt








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        coolant issues/overflow 700 1985

        posted by  someone claiming to be mechanic on  Fri Apr 12 03:26 CST 2002 [RELATED]

        Hheh got me. I would think it would plug up the cap and make even higher pressure but sort of doubt it. That is a fairly large area in the cap to become plugged,








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        coolant issues/overflow 700 1985

        posted by  someone claiming to be David Hunter on  Thu Apr 11 12:46 CST 2002 [RELATED]

        Sounds as if your cap did what it was supposed to do, that is release excess pressure along with some fluid due to mild overheat. Themostat cannot be deemed good by its appearance. Replace it, cheap and easy, see what happens. It may not be opening fully. Ultimately you may need a new rad.







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