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Installing thermostat

Tiny
MIKE R RINEHART
  • MEMBER
  • 1997 MERCURY MOUNTAINEER
  • 5.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
No heat it blows, car dose not get very hot.I know all about blend door cut hole through glove box. Fixed door warm air then was shown a diagram showing the thermostat going in backwards. I could not believe it. So I took out the thermostat and put new one in backwards I had to snip off the little brass deally to make it fit then my heater got hot air and my car warms up then cools back down like it supposed to. No one believes me it has been a while and it got replaced again by a mechanic. I told him everyone in there shop laughed and now no heat car stays cool and they want to charge money to fix problem the only problem is the thermostat looks right but it is backwards?
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Tuesday, May 1st, 2018 AT 5:04 PM

6 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
I would show them the problem, have them remove and replace it the way you said, and then show them it works properly.
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Tuesday, May 1st, 2018 AT 6:44 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
Thermostats are always installed with the bulb end facing the hot water side. On the 302 engine it should be inside the intake with the pointed end facing the radiator. If it is installed backwards but seems to work then you have an odd issue.
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Wednesday, May 2nd, 2018 AT 6:02 AM
Tiny
PATENTED_REPAIR_PRO
  • MECHANIC
  • 1,853 POSTS
There is a special note. Caution: It is critical that the water thermostat be correctly aligned, to provide coolant flow to heater.
To prevent incorrect installation of the water thermostat, the thermostat housing contains a locking recess into which the water thermostat is turned and locked. Install the water thermostat with the bridge section in the thermostat housing. Turn the water thermostat clockwise to lock it in position on the flats cast into the thermostat housing.
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Wednesday, May 2nd, 2018 AT 8:17 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
Yep, and the bridge section is the end opposite the wax pellet and return spring. With the 5.0 in question they have very weak heater core flow and if the spring seat support is in the wrong place it blocks water flow to the core enough that you will get "no heat" complaints.
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Wednesday, May 2nd, 2018 AT 10:27 AM
Tiny
MIKE R RINEHART
  • MEMBER
  • 1 POST
The odd reason is this one goes on opposite no odd issue. First thermostat I bought had a little brass bobble thing I clipped off to make it fit snug only after I saw diagram of backward installation. They have corrected the problem new thermostat has no brass deal and it fits snug. I saw diagram of it going in backwards.
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Tuesday, May 8th, 2018 AT 1:06 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,002 POSTS
I do not see how it can even work if it is installed the wrong direction. That is what the warning note is about. The wax pellet/spring has to face the engine. If it does not the hot water which comes up to the thermostat cannot actuate it because it will be in cold water on the radiator side.
Can you post or take a picture of the diagram you saw talking about this?
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Tuesday, May 8th, 2018 AT 3:25 PM

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