98 Expedition spraying coolant

I have a 98 expedition a the 4.6 that randomly sprays coolant and it appears to be coming from the resivior cap(which is the fill as there is no radiator cap). I have replaced the thermostat and sending unit as the temperature was going into the red for brief periods upon warming up. Still doing it. I think I may have read somewhere posible warped head?
It seems to run normaly and a pressure test did not reveal anything.

Any ideas?

your post is close to a month old, did you already get it fixed?

I don't see how a warped head would cause problem. Blocks/Heads have multiple ports for coolant flow near the cylinder. Is it possible there is a problem with the radiator? Such as a massive build up of gunk somewhere? Or is it possible the truck has been over filled with coolant?

Hello. I have not pinpointed the problem yet. I was going with warped head because my theory is: as the truck is warming up there is a certain temperature range that it reaches and as the metal is contracting there may be a weak area in the head gasket or a warped area allowing some of the combustion to get into a cooling passage. It is not getting back into the engine(or at least not in large enough amounts) that would explain the antifreeze spraying randomly. Also the needle goes up to H for about a minute as the engine is warming up and then the gauge stabilizes at a normal temp. I am assuming when the combustion is entering the cooling passage and hitting the temp sending unit causing the 'false' reading. I have already replaced the sending unit. The coolant is not overfilled and I do not see any other leaks. I fee it has to be an overpressure problem. The antifreeze has that combustiony smell that I recall smelling before diagnosing a head gasket/cracked head.

I guess compression test would be the next step?

Yes you guess right, a Compression test will be the absolute to determine if a gasket or rings are shot. I have seen motors that have had coolant leaks.

Here are signs to check for:

If coolant is leaking into a cylinder, you should see white smoke puffing out of your exhaust (coolant burns white/blueish oil burns grayish).

That spark plug that is burning coolant will be squeaky clean and the other spark plugs will be worn as usual. Coolant burning in a spark plug will clean the cylinder chamber, top of the piston and spark plug. When you take the heads off, you will see the other cylinders are filthy from normal wear and tear (if you strip the motor). While the cylinder with the blown gasket looks brand new.

Do you have a ecu read/code scanner? They are cheap off of ebay. I got one for 30$ free shipping. They allow you to read live data of the motor. Example is coolant temp, a normal 4.6/5.4 expedition motor with a thermostat of 170 to 185 will have a digital temp around 190. Never higher than 200. If your code scanner is reading higher than 200 it will eventually over heat.

Look at your oil. Really look at it. Dirty oil will be black, thicker than brand new and murky. If coolant is leaking into the motor, your oil will be dirty like hell, with a greenish haze and watery (it will look like oil, but more watery). It will NOT be thick and dirty. If you pour a drop or 2 on a piece of paper, you should see slight separation from the coolant to the oil on the paper.

Smell your oil, then smell some coffe beans to clear your pallet, smell another cars oil. You should notice a difference in scent if you have a coolant/oil mix.

Drain 1 cup of coolant from the radiator and look at it. Oil and coolant never mixes. You will be about to see oil spots and blotches floating around the coolant (from the radiator). If that is the case, you will need to thorough flush the radiator on top of changing head gaskets.

Like I said, there are lots of chambers in a block. It is possible the gasket is not blown near a cylinder; therefore a compression test would still register a motor to be good. Use the other methods I mentioned to determine a problem. Even though at start-up your temperature rises to H then goes to normal, it may not be an over heat. It takes a long time to cool off. If the motor is properly cooling, you will notice it cooling itself while you are driving; because the air is flowing through the motor (air cooled). Once you are at a stop and idle it will over heat again. If your block is overheating and if your head gasket is shot, it will overheat and never cool itself off. You will have to turn the motor off for a few hours to cool it off.




If you do have to change the head gaskets. You could get away with leaving the block and tranny bolted into the frame. I would suggest you spent the extra $200 and buy the COMPLETE rebuild kit (all gaskets, new rings). Take the heads off, fully strip them, scrub and clean. Drop the oil pan, un-bolt the crank and pop out the pistons. fully clean the bottom. Might as well paint the block and heads while you are there. Install new gaskets everywhere from the FULL REBUILD KIT. DUDE, you will have a motor that still has spotless and clean oil after the 1st 3000 miles. Keep me posted/goodluk