The engine coolant in my 03 7.3 Ex will not stay at the max mark. It will always end up about 1 1/2 inches below the min mark. I have refilled it several times. I drive it for a week or so and it ends up about 1 1/2 inches below min and stops. It doesn't continue to drop. Any ideas?

 

I would say you have a small leak in the system or it is using it. I would have it pressure tested.
gseeders

 

i would also send my oil to blackstone and have them check to make sure you dont have an internal leak into the oil system.

 

Got my results from Blackstone. Everything looks good. No coolant in the oil. Any other ideas why my coolant level will not stay at the max mark?

 

Look in the area around the waterpump - t-Stat housing. Bet your WP is on it's way out. That's the way mine started. Wasn't enough of a leak to leave anything on the ground but, I would gradually loose coolant. Just a little bit from week to week. Another area to look @ is the hose clamps on the U&L rad hoses. The OEM ones are known to break from time to time.

Hope this helps,
DG

 

My 99 did the exact same thing after I changed the WP. It turned out that I had a small leak around the t-stat housing. A leak in that area lets coolant leak from the top hose and then no more. That is why it stops a little below the mim mark. Hopfully it is the t-stat or a hose connection. If it is the WP its not too bad of a job.

 

Either that or it's a small crack in the degas bottle. (The nylon resevoir that you pour coolant into.) The coolant runs out until it gets to the level of the crack and then no more.