Sigh, it's losing coolant.

[Big Port Jimmy 6]

The 02 5.3 in my crew is suddenly using coolant. Replaced the coolant reservoir, the old one cracked. Coolant was down in the rad. Added almost a gallon, it's been a week and it was low again. Who want's to bet on a cracked head? 8622 castings checked 40k miles ago at the machine shop.

[BR3W CITY]

Are you burning it up, or losing it into the oil?
Check your freeze plugs!

[lutronjim]

I had this trouble. Losing coolant and couldn't find it - not in oil. Ran compression check which was OK.

Turned out to be crack or hole on one side above coolant level. When coolant expanded, it would leak out. Of course when the coolant expanded it was very hot and it would evaporate leaving no sign.

Found it by buying dye kit from Summit.

[homemade87]

If you suspect the heads , I would take the time and remove the valve covers and have a look . This takes little time to do and will answer your question if it is indeed a cracked head . There will be no question and is very evident if it is cracked ( white sludge ) . Once it gets bad enough to start to see it on the dip stick or the oil fill cap it may be to late . Possibly gotten in the bearings by that time .

A dye could be used to check for a external leak . If none most likely internal . Dont keep driving it if so . It dont get better and could need a new engine if it gets into the bearings . More money .

If this is what it is get a set of 799 or 243 heads . Better performance and does not have the crack problem .

[Big Port Jimmy 6]

Originally Posted by BR3W CITY

Are you burning it up, or losing it into the oil?
Check your freeze plugs!

None in the oil, I changed it to check, it was due any way, and no external signs. Valve covers will come off next.

[paul mora]

Be sure to check your radiator cap. Sometimes they get old and stop holding pressure and release coolant.