Question about 1999 Mercury Cougar

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1999 mercury cougar 2.5 still runs hot . 240 . New thermostat, new radiator, new temp guage, new water pump. Runs great otherwise. No noticeable fluid contamination.

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  • aremueller Oct 12, 2010

    Had fans checked at a local shop and was informed that they were working properly.

  • aremueller Oct 13, 2010

    It was about 70 degrees out when I drove it a few days ago. It took about a 5 mile hiway drive to get to 240. I changed the temp sending unit and water pump and flushed the system with a garden hose in 3 orfices until clear water came out.

  • aremueller Oct 13, 2010

    I don't know if you are familiar with the cooling system on the 2.5 but it is the oddest conglomeration I have ever seen! More coolant hoses than 3 engines should have! Not sure how to go about flushing this thing with chemicals, but maybe I'll try it in a day or two. I need to find out if this engine has any particular overheating characteristics. I think Ford used it in the Contour as well as the 99-02 Cougar. How many days am I allowed to keep chatting with you?

  • aremueller Oct 13, 2010

    I think I mentioned how strange this cooling system was. The thermostat is mounted in a little "pod" between two hoses, not in the block like others I've replaced over the years. Could this thing be turned the wrong way?

  • aremueller Oct 13, 2010

    Sounds like you looked at the cooling system diagram. Have you ever seen such a mess of hoses? I assume that the spring end of the thermostat points toward the firewall.

  • aremueller Oct 29, 2010

    Thought I would bring you up to speed on the Cougar running hot. Did everything you mentioned and nothing changed. Took it to Ford dealership where they hooked it up to computer and let it run for over an hour. They said that the fans kicked on at about 210 according to the laser thermometer. It never got any hotter than that. Said that the sending unit on the O'Reilys gauge was bad and causing it to read 35 degrees hotter than their laser thermometer. Installed a new sender, went for a drive , 245 !!!!!!!!!!! Original sending unit, replacement from NAPA, 2 O'Reilys gauges and nothing changes. Engine is not boiling even when the guage says 250. Coolant in resevoir feels only warm. This is getting ridiculous

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  • Mercury Master
  • 6,826 Answers

OK, that is getting kind of hot. I would check that the fan is turning on when it reaches normal operating temperature.

Recently, I had to replace both fans, the relays, and the relay contacts on the harness to fix a similar problem on a 1997 Cadillac Deville Limousine.
The heat got tot he relays and messed things up.

Hope you can fix your overheating problem like I did.

Posted on Oct 12, 2010

  • 6 more comments 
  • Duane Wong
    Duane Wong Oct 12, 2010

    Sometimes on hot days my vehicle runs up to 220 to 230 something and that's considered still below the 250 to 260 deg. F specification for turning on the engine saving feature (on Cadillac Northstar engines) where air is pumped into 1/2 of the cylinders to drive up to 40 mi. without damaging the engine.

    Your engine may be able to run that hot and still not blow a head gasket.

    Now that it's fall in Pennsylvania, my vehicle runs noticeably cooler with the new relay/fan/harness connections (on a 13 year old car).

    I might also try a flush and fill of the cooling system to get rid of deposits in the engine, although, one would think that with changing the water pump and the radiator and the thermostat that most of the sediment would have been flushed out.

    I did read that you said that there wasn't any visible fluid contamination.

    Gee, this is a tough one.

  • Duane Wong
    Duane Wong Oct 13, 2010

    So, it did have sediment at one time. Maybe try a powerflusher where they add chemicals that dissolve any sediment that has caked up and may not come out with just tap water through a hose.



    At Sears in the early 1990s when I worked as a technician there, I remember we used to add a chemical that would dissolve deposits in the cooling system.



    Kind of like how Draino dissolves hair, sometimes there's still residue left that doesn't get flushed out of the plumbing system in your house with just tap water flowing through the pipes.



    Maybe go to a parts store and look for flushing chemicals to add to the radiator that are designed for this purpose.



    Good luck, again.

  • Duane Wong
    Duane Wong Oct 13, 2010

    I will chat as long as it takes to find a valid solution, I guess.

  • Duane Wong
    Duane Wong Oct 13, 2010

    That's interesting... the thermostat could be put in the wrong way, if the tech didn't note the way it came out.

    ---
    2.5L Engine

    Fig. 7: Thermostat mounting — 2.5L engine



    Drain and recycle the engine coolant.
    Remove the battery from the vehicle.
    Remove the radiator hoses from the thermostat housing and remove the housing from the vehicle.
    Remove the two thermostat housing bolts and separate the housing.
    Remove the thermostat and O-ring from the housing.
    To install:

    Thoroughly clean the housing and install the thermostat and O-ring into the housing.
    Place the two thermostat housing halves together and alternatingly tighten the retaining bolts to 15–22 ft. lbs. (20–30 Nm).
    Place the housing into position and attach the radiator hoses.
    Install the battery into the vehicle.
    Fill the cooling system with the proper 50?50 mixture and start the vehicle.
    Bleed the cooling system and check for leaks.

  • Duane Wong
    Duane Wong Oct 13, 2010

    I looked at the thermostat diagram and it looks like the spring end goes in only one way. I would be surprised if it could be turned around and reassembled and sealed in the opposite orientation. Maybe you can tell by looking at the tube length on your actual vehicle.

  • Duane Wong
    Duane Wong Oct 13, 2010

    According to autozone.com:

    2.5L Engine

    See Figure 7






    Fig. Fig. 7: Thermostat mounting-2.5L engine

    Drain and recycle the engine coolant.
    Remove the battery from the vehicle.
    Remove the radiator hoses from the thermostat housing and remove the housing from the vehicle.
    Remove the two thermostat housing bolts and separate the housing.
    Remove the thermostat and O-ring from the housing.


    To install:

    Thoroughly clean the housing and install the thermostat and O-ring into the housing.
    Place the two thermostat housing halves together and alternatingly tighten the retaining bolts to 15-22 ft. lbs. (20-30 Nm).
    Place the housing into position and attach the radiator hoses.
    Install the battery into the vehicle.
    Fill the cooling system with the proper 50 / 50 mixture and start the vehicle.
    Bleed the cooling system and check for leaks.

  • Duane Wong
    Duane Wong Oct 14, 2010

    I took a closer look at it, yes, after you mentioned the 'strange' nature of this cooling system.



    I'm used to working on foreign cars where things aren't like your typical GM setup.



    I know this is a Mercury/Ford product.



    I guess it should work if all of the orifices are clear. But on a vehicle from the year 1999

    still working in 2010, I would say that it should be flushed out with chemical flushing solution from

    your local auto parts store and go from there.


  • Duane Wong
    Duane Wong Oct 30, 2010

    Thanks for letting me know what happened to your Cougar running hot.

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