4 cyl. has water in oil has been running good, wouldn't heat thought thermostat, pulled dipstick,milky, pulled plugs normal, do not smell antifreeze in exhaust ??

This is common issue early sign head gaskets failure for EJ251 SOHC engine for external coolant leak. Second gen 96-99 with EJ25D is worst because when head gaskets failed, it's an internal leak that allows coolant and oil mix together in the combustion chamber to destroy engine.
You can drive it for at least 6 months or more as long as you keep top up coolant since the leak should be small at a slower rate leak. I drove mine for a while before change head gaskets. You're looking at `$1000-1200 job a dealership since you might as well change the timing belt, water pump, idlers while engine is pulled to replace head gaskets.

Is your antifreeze leaking on the ground in the front of the motor ? There are many different things to do to find the right answer to this question. 1 : pull the motor dipstick. If oil mixes with the water - antifreeze the dipstick will look milky. If it does not. And looks good. Then 2: with water in the radiator don't put antifreeze in it keeps wasting $$ til leak is found. 3 : start motor look from under the front of the water pump with a flashlight if you have a dripping from a weep hole in the water pump bottom behind the fan. If you can't find a leak shut off the motor. Feel the bottom of the water pump if there is a presence of water you'll need a new one. If not .4:if the motor is over heating or has been blowing antifreeze out of the overflow hose along the side of the radiator. If so the thermostat may be stuck. Much cheaper repair.

Do you have heat coming out of the heater after the thermostat opens? If you do and the truck is still over heating the head gasket could be blown and burning the antifreeze through the cylinders and thus would cause a rough idle. You may want to run a compression test on the truck. Just to be sure your assumption is correct that the head gasket is good. Have you felt the heater hose to make sure it is circulating through the heater and it is not plugged. Hope this helps.

Make sure your transmission fluid is not milky. Your trans fluid cooler is located inside of the radiator. If it splits or leaks you will get trans fluid in the coolant and coolant in the trans. This is not good for your transmission and it will not last long at all.

Generally that means water in the oil. Is the oil on the dipstick the same color? If so, it could potentially be something very bad, such as a leaking head gasket or coolant passage that is allowing antifreeze to leak into the engine when under pressure. If the milky appearance is just on the refill cap and the oil on the dipstick looks normal, then you could just have a small amount of water from condensation. That can happen if the vehicle sits a long time without being used.

REPLACE THERMOSTAT.ITS STICKING CLOSE TO KEEP COOLANT FROM CIRCULATING THROUGH ENGINE AND RADIATOR. THE FANS SHOULD COME ON WHEN VECHICLE SETTING AT A LONG IDLE.THE COOLANT TEMPERATURE SENSOR GET TO CERTAIN TEMPERATURE WHICH WILL COMPLETE CIRCUIT PCM SEND POWER TO COOLANT SENSOR THEN TO COOLANT FANS RELAYS AND FANS.IF VECHICLE OVER HEATING WHILE MOVING THERMOSTAT FAULTY.IF YOU TURN AC AND COOLANT FANS DONT RUN CHECK COOLANT FANS FUSE AND RELAY.IF COOLING FANS DONT TURN ON WITH AIR CONDITIONER ON EITHER COOLANT TEMPERATURE SENSOR FAULTY OR PCM FAULTY.IF ALL LOOKS GOOD.IF ENGINE OIL LOOKS LIKE MILK SHAKE.YOU HAVE BLOWN HEAD GASKET.

bad head gasket or cracked cyl head coolant getting in cyl

A car this new should have a warranty right? the only other place for anti-freeze to go is through a blown headgasket into your oil. Pull out your oil dipstick and make sure it is not milky in color. If not check behind the engine and see if any coolant lines going into the firewall are leaking. When inside the car do you smell steaming coolant(anti-freeze) or hear gurgling? The temp gauge that stays on is the overheat indicator?

Need details

[email protected]

Often (but not always), a blown head gasket will also cause deposit of water on a piece of cardboard held an inch from the tailpipe output while the engine is running (when this is happening, it is likely that the catalytic converter has been ruined and the muffler will corrode in short order as well).

Sometimes drops of water will be seen dropping from the end of the tailpipe. Another clue: turn on the heater; often when the head gasket is blown an odor of antifreeze and synthetic rubber will emanate from the heater vents.
Many of the symptoms of blown head gasket can be caused by some other problem in the cooling system, without the head gasket being damaged. Conversely, other problems with the cooling system can cause a blown head gasket and/or warped head.

When checking for a blown head gasket, one of the most common tell-tale signs is a milky-gray ring around your oil cap. When coolant enters the engine oil through a crack in the head or through a blown gasket, it evaporates and leaves a milky ring around the oil cap. Another easy way to tell is to check your oil dipstick. Change your oil and pull out the dipstick. Make sure that you take note of how far up the dipstick the oil is. Top off your cooling system and fill your cooling reservoir to the top. Screw radiator cap back on and start engine. Run engine for about 20-30 mins. or until it reaches normal operating temperature. Allow engine to cool (engine must cool completely to get accurate oil reading!!). Check oil dipstick again. If the oil has a watery appearance and has risen noticeably up the dipstick, the you probably have a blown head gasket or a warped head. Also look for a dripping, sweet-smelling liquid coming out of your tailpipe. Any of the above symptoms could be the result of a blown head gasket. The easiest way to tell is with a compression meter. This replaces the spark plug and lets you know what compression each cylinder is running at. If your compression is abnormally low, then you have a blown head gasket or a warped head. (note: consult repair manual for appropriate compression of each cylinder.)

The thermostat is found by following the top large radiator hose and following it to where it connect to the engine. Pull your oil dipstick and see if the oil on the stick looks milky. If so, that is an indication of water/antifreeze which points to a blown headgasket.

Good luck!