Looked at a 2001 H6 with well over 200,000 miles, it's for parts but I'd like the engine to be good.  Two questionable items:

 

1.  Thick black sludge in the overflow container - coating the insides, not just the bottom. Seemed way more than normal - I could reach down and get a good glob on my finger.

 

2.   After idling for 30 minutes the overflow container level changed...I think it rose maybe 1/4 the level of the tank.  Do they normally rise that much? 

I've never paid attention but seemed more than it should.

 

Did not see bubbles or overheating while idling.

Coolant was brand new, obviously recently filled.

 

Maybe I can get an HC tester and just take it to the lot.

I wouldn't buy it.  To me, that signals lack of regular oil changes, and you know we already had this conversation!

ah, do you mean the 100 per day that show up on online forums?!  lol

i say all this having repaired H6 headgaskets, have another on hand, have some friends with the issue, and seen them on lots for sale before.

 

never seen that much sludge before - anyone else?

I think the real question is:

How bad do you wanna do another head gasket job on one of these?

 

Crud in the expansion tank could just be rubber and nastiness fom old coolant, but poor cooling system maintenance usually leads to failed head gaskets.

One thing I've always looked for is pressurization of the cooling system after only 30 seconds to a minute of running.

Normally, No heat = No pressure. If the cooling system is cold (no heat), and there is pressure in the hoses, thats gonna be a head gasket.

from my exp on junk in the coolant its usually some kind of stop leak. did the previous owner put a stop leak in the car at some point?

I think the real question is:

How bad do you wanna do another head gasket job on one of these?.

 

HA HA!!!!!!  true.  true. okay, you're probably right.  And i wouldn't want to do one on an unknown engine either.

 

Used car lot so there's no telling if it's had stop leak in it.  It has a blown transmission and good rust so I was hoping the engine was good.