My 4.6 l marquis gets hotter as I drive and on the temperature gauge goes to the "L" in normal. I have changed the water pump, upper hose, flushed the radiator and changed the coolant pressure cap. There is no white smoke out of the tail pipe and the fan does turn. A little fluid does come out of the overflow bottle. Any suggestions would be helpful. Thanks.

 

A good place to start is the thermostat more than likely it has failed slightly open.
A small hole in the cooling system will cause this as well, When the mtr cools down instead of drawing water from the over flow bottle it will suck air from the hole instead, giving you an air bubble in the system.
This can be checked with a cooling system pressure test. If DIY do not put more pressure in the system than the cap states.
good luck.

KIWI

 

I failed to mention that I did replace the thermostat. Thanks

 

Just a suggestion, Chevy, but could you have another go at describing the symptom/problem. I confess I'm not real clear on what you're saying. The engine is overheating, but the temp gauge reads "L"?

 

The engine is hotter than normal but does not get hot enough to boil over. The engine temp gauge is working OK. If you shut the engine off when it gets very hot and then start it up again , the engine runs rough. Thanks.

 

Ford/Merc thing T_G

The gauge reads:


N-O-R-M-A-L
^.............^
cold_____hot(red)


L = Bad

 

Have you run a pressure check on the system ? You can buy a coolant system pressure tester at a parts store (pretty expensive comparitively speaking - $100 or so) or have it done at a local repair shop. If your coolant system does not HOLD the required pressure, it will run hot and / or overheat because higher system pressure = lower boiling point, thus allowing your engine to run cooler. Also, the 4.6 has a plastic upper intake manifold ( also called the plenum) and they are very prone to failure. I am not sure if your particular year has this problem or not. Good luck !!

 

My outlaws had a similar problem with their Crown Vic, the radiator was clogged.
Replaced the radiator and no more running hot.
Not saying that is your problem but being 13 years old it could be likely.
Simple test, if you can pull the radiator you can do a simple volume test.
Stand the rad on your garage floor, while blocking the bottom outlet, fill the rad with fresh water to the top and let go of the bottom outlet, the water should shoot across the floor about 6 feet or so if good.
And since it's out blow out the bugs and stones from the fins with a garden hose and flush out the core.
This might do the trick.

 

If you're able to eliminate the cooling system as the cause, try doing a compression test on all cylinders. A blown head gasket can also cause overheating.

 

When it shoots out 6 feet, is that counting water running away from the radiator on the floor for the 6 feet? (minor pressure could even allow this to happen and if the floor had a pitch you wouldn't have a clue)...or do you mean the water flies out the botom hole 6 feet in the air before hitting the concrete floor? Obviously the latter woud be more indicative of some really fine pressure.

 

OH! DUH! Guess you figured out that I was thinking:

L------------H
^ ............ ^
Cold_____ Hot