AF: Coolant leak (300m 3.5L) - what could be source? | Allpar Forums
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Coolant leak (300m 3.5L) - what could be source?

Discussion in 'LH: Large Cars, 1993-2004' started by MoPar~Man, Dec 29, 2019.

  1. MoPar~Man

    MoPar~Man Member

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    For the better part of the past year, my '00 300m has been leaving about a teaspoon of coolant on the garage floor overnight on most days. A few days ago I finally got around to replacing what I thought was the source - the upper rad hose (I thought the leak was happening at the top end of the hose where it connects to the engine). Turns out this is not where the leak is coming from. From under the car, I can see some drip points on the back-edge of the sub frame and the front edge of the oil pan (not sure how it can drip from both locations given the air-gap between them). All rad connections look clean and dry, as does the upper rad connection. So what gasket or seal could be causing this?
     
  2. ImperialCrown

    ImperialCrown Moderator
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    Leaks will usually blow back and down from road draft and gravity. Turbulence under the hood can blow it around and be misleading as to the source.
    The water pump under the front cover is a common leaker. It is driven by the timing belt.
     
    valiant67 likes this.
  3. valiant67

    valiant67 ...

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    But, rent, or borrow a coolant system pressure tester. You’ll be able to trace the leak better than finding after the car has driven and some evidence of the trail may have evaporated.
     
  4. chuzz

    chuzz Well-Known Member

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    Sometimes a loose hose clamp can drive you crazy. I'd check all of them too.
     
  5. MoPar~Man

    MoPar~Man Member

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    I had the timing belt and water pump changed back in I think it was 2012, at a chrysler dealership, and I asked for the old pump and belt so I'm reasonably sure the work was actually done. So I've never seen myself what it looks like behind the timing belt cover but in looking at the manual and the videos it seems that that area is sealed off from the oil sump so it should be bone dry. My first question is:

    If the water pump gasket / ring leaks, where does the coolant go? Is there an escape path from the timing belt area?

    Second question: The thermostat housing and the lower rad hose connection (and the other smaller pipe coming off the other thermostat housing where another hose is connected to) is hard to see. Is this the likely area for the coolant leak?

    Between the water pump o-ring and the thermostat housing (and the connecting hoses) where else would the coolant leak from and drip from somewhere at the front of the engine? A head gasket?
     

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