1997 Mercury Sable leaking coolant 1997 Mercury Sable

Tiny
RICH120865
  • MEMBER
  • 1997 MERCURY SABLE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 165,000 MILES
Car runs at normal temperature and everything is fine when idling but if I drive just down the road it begins to run hot. When I lift hood coolant is coming from under the coolant recovery tank cap. I bought a new cap and a new coolant recovery tank and had coolant flushed but the same thing still happens. What is causing this?
Wednesday, May 19th, 2010 AT 3:38 PM

8 Replies

Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Is radiator cooling fan working properly? Also remove and test thermostat to ensure its opening and closing right.
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Wednesday, May 19th, 2010 AT 4:47 PM
Tiny
RICH120865
  • MEMBER
  • 12 POSTS
Yes fans are coming on but if thermostat isn't working properly wouldn't it overheat during idling? I let it run in park for 30+ minutes with no overheating. Someone suggested a bad head gasket, can that be?
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Wednesday, May 19th, 2010 AT 5:54 PM
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
No not necessarily, thermostat only opens once coolant reaches certain temp. Normally around 185F.

A failed head gasket will normally cause engine to idle slightly rough and you may also find coolant mixed into the engine oil. Easy way to check for cracked head gasket is to remove radiator cap WHEN COLD, then start motor and if coolant shoots up out of radiator cap opening then most likely head gasket is bad.
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Wednesday, May 19th, 2010 AT 7:06 PM
Tiny
RICH120865
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But why doesn't it overheat while idling in park?
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Wednesday, May 19th, 2010 AT 7:21 PM
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Takes a long time for engine to reach 185F or higher when just idling.
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Wednesday, May 19th, 2010 AT 7:30 PM
Tiny
RICH120865
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  • 12 POSTS
But I let it run for over 30 mins. Also when you say to remove cap and coolant shoots out do you mean right away or when it gets to temp?
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Wednesday, May 19th, 2010 AT 7:33 PM
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Coolant will blow out soon as you crank engine because there would be pressure pushing coolant out since the pressure is not sealed in by the faulty head gasket. When the engine is at idle the water pump is slowed way down so the coolant has time to transfer the heat off to the cooling fins of the radiator. Also there is no load on the engine while idling. I'm almost positive that you have a faulty thermostat.
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Wednesday, May 19th, 2010 AT 7:37 PM
Tiny
RICH120865
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You're right. It does not blow out so apparently its the thermostat
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Wednesday, May 19th, 2010 AT 7:45 PM

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