Should I keep this car?

About a year and a half ago I bought a 1987 Mercedes 300SDL for $880.00, it was in pretty rough shape but ran and drove decent so I rebuilt the front suspension, replaced the springs and shocks, brakes, replaced the windshield (although its broken again already), fixed most of the nasty interior, and a bunch of other stuff.  It has probably cost about $6k total. 

I have put about 10k miles on it since, and recently (a couple months ago) I noticed that the radiator was leaking at the top seam, and the cooling system still had a lot of pressure in it (enough to spray everywhere when you take the cap off) even several days after being driven.  These engines (OM603 diesel) are known for head and head gasket issues, so it is entirely likely that the head gasket and/or head are bad.

I have two extra heads for it that I have gotten from the junkyard (the updated #18 and #22 versions), but I am not sure what I should do next.  I have tried testing for combustion gas in the coolant and didn't get any result, and I have attempted to do a leakdown test and realized it's beyond my ability to do or learn to do just from reading about it on the internet.  I could do a compression test, but it means buying an expensive compression gauge and new seals for the injectors so I can put it back together when I am finished.

I could just hope that swapping the head will fix it, and with about $1500 and a lot of time I could probably have it running by the end of next summer with a new head, but that's a lot of time and money to just throw parts at it without knowing what the problem is.  Otherwise, I think I will just have to sell it and get something else. I would probably have to give someone one of the extra heads with it, and get about the same for the car + cylinder head as putting the cylinder head alone on Ebay. 

I'm inclined right now to just give up and get something else, because it's beyond my skill to repair and a beater Mercedes isn't worth being frustrated and angry everytime I try to do anything with it, but I am not sure whatever else I get instead would be any better.  I have had a couple of newer cars (an S55 and a TDI Jetta) that were horrible and I ended up having to sell them at a loss shortly after buying them so I would rather not do that again either.  I could spend $3500 on another car without really having any negative effect on my life, as long as it was something that was at least slightly interesting and reliable enough to get in and drive 250 miles and not have to worry about it.  I would still like driving the 300SDL if it was fixed, but it is a long way from that point right now.

I'm a bit in the same boat with my 96 Impala SS.  There is nothing (yet everything) wrong with it.  It runs and drives great, but has a million things that SHOULD be done.  The steering box has play, the evap hose to the charcoal canister is rotted, the A/C pulley bearings squeal like a pig, the exhaust manifold popped a bolt, the seats are wasted...

I can't really find anyone to give me decent money for it, so it's going to likely sit in my driveway as a backup vehicle.  I did find a neighbor who wants to pay me crazy money for it because he's passionate about SSs, but then I can just imagine buyer's remorse setting in and he's a friend so I don't really want to invite that potential feud.

I would let the market decide.  Put in on CL and FB and see what kind of response you get.  If you get a decent chunk of cash, let it go.

Mine got more lowball offers than I care to admit, so instead I may end up buying another SS roller and making one out of two.

^I still want your SS at the right price 

In reply to Curtis :

Sounds like you need to sell your SS around where I live. They go for $$!

I would guess that the car is worth less than scrap value even though it's still drivable, I don't want to scrap it and I can afford to take less for it to sell it to someone who wants to still use it though.  The only other car I have to use (96 Subaru) has a gear oil leak that's dripping onto the cat and blows gear oil smoke into the car anytime I need to use the heater so that may end up making the decision for me, I have two extra transmissions for it so it will only cost gear oil and a couple seals to fix, but it will take me 3-4 weekends to do and I need a way to get to work during that time. 

Can you try some Bars leaks or Blue Devil on the Benz?

In reply to Justjim75 :

That stuff does too much damage to be worthwhile in my opinion.  I could probably drive it as it is for a while if I had to, but I can afford to sell it and buy a better car too.  The main annoying part is that I did a lot of work to it with the intention of keeping it for a while, but I don't have the time or skill to return it to the condition where I can use it for what I would need it for.

Tk8398 said:

In reply to Justjim75 :

 I don't have the time or skill to return it to the condition where I can use it for what I would need it for.

^^^ Here's your answer, let it go for whatever you can get for it.

Where are you?