Question about 1996 Mercury Grand Marquis

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1986 mercury grand marquis LS overheating

My 1986 grand marquis seems to overheat after you run it down the highway for a while. The radiator was overflowing into the plastic tank which was squirting water out too. It doesn't seem to have a whoal lot of pick up and the engine started cutting out. I'm trying to sell it, and don't know where to start on fixing it. also, it's been sitting for 8 years.

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  • aubrey12 Aug 13, 2008

    This car was given to me, and the lady said she replaced the radiator before it was parked for eight years. I just replaced the fuel tank, fuel pump, fuel filter, engine oil and filter, and the transmission fluid looks clean. I had the head off and replaced some of the coolant hoses because they were squirting out coolant. I also replaced the throttle body gasket. The engine is a 302 v8 5.0L and is fuel injected. sorry I didn't include all this info before.

  • aubrey12 Aug 13, 2008

    I just replaced the thermostat today and drained the radiator - the water looked pretty brown. I put new water in the radiator and started it with the radiator cap off and after the engine warmed up, it sucked the water into the engine so i added more water to it. does that mean it's pumping correctly? I'm also thinking that the reason it doesn't seem to have a lot of pick up is because the fuel injectors are dirty. do I have to replace them or is their a way I can clean them? I don't really want to take the car in to have the system flushed because the car is only worth about $700 and I have $500 in it. is their a way I can flush it myself?

  • aubrey12 Aug 23, 2008

    thanks for all the help. I replaced the thermostat and flushed the radiater and it quit overheating. It still doesn't have a lot of power but I think its just because its old and has 186,000 miles.

    Thanks Again


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Sounds like the thermostat is stuck closed.
If the car is overheating, they will also hurt perfomance.

But after sitting 8 yrs, it's hard to say what else might be wrong.
Was it just sitting, and you threw some gas in it to get it running? Or did you go through the car first to do some maintenance? Like an oil change, flush the gast tank and carb and put in all fresh. Change the fuel filter? and the list goes on. A car sitting that long can develope some problems just from sitting. If you could list what you have and haven't done to the car before this would help.

Posted on Aug 11, 2008

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  • Coss Aug 13, 2008

    Wow, you did do a lot of really good prep work.

    So back to the original problem.

    The lack of power probably directly related to the overheating.

    Even though she said she replace the radiator, doesn't mean it didn't have time to gather junk in it.

    I would replace the thermostat, take it in, and have the radiator flushed (actually, if you can find a place that will do it, do a complete cooling system flush, not all places do). You might also talk to them about replacing the thermostat for you, so that it can be taken out, flushed, and then put the new one in, and filled and purged (just like brakes, you don't want air in the system.

    And I would look more towards a full service shop to do this, not the local quick lube.

    From there, I would look at a bad water pump. If the pump isn't moving enough volume, it will cause it to overheat.

    Let us know what you find.

  • Coss Aug 13, 2008

    Yes, there is a do it yourself flush kit (at least there used to be, haven't looked for one for a while).

    It was a T fitting you would splice into your heater hose. You hook your garden hose up to it, and let it flush the system. I think it was Prestone that made them.

    You can clean the injectors. They had a couple of different kits for doing it. Here again, trip to the local parts store to see what they have.

    Yes, if you see it moving water through the system, the water pump is probably good (won't give it 100%, but OK).

    Hold the fan, and if you can "rock it side to side", more then just a hair movement could mean the bearings are going out.

    Agreed, if you are just going to sell it, I would do just basic fixes. But be up front with who ever you sell it to, and list the work you have done. But don't warranty it past waving good bye.

  • Coss Aug 23, 2008

    You're very welcome.

    And thanks for the rating on the answer.

    Agreed, something that has 186K on the clock is not going to be burning the tires off at the local dragstrip.

    Your plan about selling it, is probably the best thing you can do.

    Have a great weekend.


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Any car sitting that long is going to have some issues. It could be several things. The thermostat could be stuck closed. The radiator could be stopped up. The fan clutch could be inoperative. The waterpump impellar could be deteriorated to the point that it will not circulate coolant. The worst would be that a head gasket could be bad and causing to overheat and misfire. The first thing to do is replace the thermostat and purge any air from the system. Use water and not coolant to verify the repair. If this solves your issue you can drain the water and fill with proper amount of coolant. I must recommend checking for white cloudy smoke from the tailpipe as it is a sure fire sign of a blown headgasket.

Posted on Aug 11, 2008

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