I have a 2000 S40, 1.9L Turbo.

While under the hood recently, I noticed coolant leaking from the upper radiator hose near that elbow where the hoses connect as well as near the thermostat housing. My initial thought was to replace the hose, which I haven't done yet. The car is driving fine and not overheating or having any temperature issues.

A few days later, I took at look at the coolant expansion tank first thing in the morning (so the engine would be cold) and it was well above the max line by about 0.5" to 0.75". This kind of threw me for a loop because I thought, "Why would my coolant be ABOVE the MAX line if it's leaking?" Could it be that there a clog backing up the cooling system somewhere?

Does anyone know why this would be? My car has about 166k miles on it and had a coolant flush about 25k miles ago. My initial thought is now to drain the whole coolant system, replace the upper radiator hose, then do a system flush to clean out any nastiness that might be in there, and then refill with new coolant.

Also, the leaking upper radiator hose is only about a year and half old and is an OEM hose. I'm thinking of just going with a cheaper hose this time if it's just going to fail on me anyway.

 

I bet it was simply overfilled when the hose was replaced last time. Just my guess. Where is the level when hot?

 

+1 on overfill and the leakage is probably from corrosion on the thermostat housing, not the hose.
Ed

 

Thanks to you both re: the overfill. So I should just suck some out of the expansion tank with a turkey baster of something of the link?

Re: corrosion on the thermostat housing...If this were the only place where I noticed leaking I'd think I should just replace the thermostat housing? But there is also leaking coming from the plastic elbow where the three pieces of hose connect. The S40 has that weird upper radiator hose that has one tube coming from the radiator, one going to the engine, and a third going directly to the expansion tank.

So are we thinking I need to replace the upper hose AND the thermostat housing? Thanks for your help. Much appreciated.

 

I would not worry about the overfill unless it's pouring out of the reservoir. The high and low marks are just for reference. If you are OCD then I know you must make it perfect.

Same for the hoses and t-stat housing. Mine too has that wierd gunk that builds on the hose and housing. It's not hurting anything but it does look bad. I even added hose clamps to stop the ooze to no avail. I wouldn't worry about it unless I saw a puddle of coolant on the garage floor.