You know how when someone tells you not to do something - its like
throwing gasoline on fire and telling it not to burn? That's the way I
feel about my 86 300SDL. I bought it wanting to jump on the homebrewed
biodiesel bandwagon. It ran strong and had a superior ride to it. And
it had a decent interior and good body. So I started to restore the
thing. My eventual plan was to install a Frybrid grease burner system.
I had about $6,000 into it at this point including new ball joints,
tie rods and brakes. It always started fine when warm but roughly or
just barely when cold. So I tested the glow plugs and found no.5 to be
bad, all others tested good. But I couldn't figure out how to reach
no.5 to change it without tearing it half apart. So I let it go by
keeping it plugged in most always last winter. Then I took it in for
an antifreeze leak this summer. It held good
pressure on testing and wouldn't leak.
So the mechanic wanted to overnight pressure test it. The next
morning, he said No.5 filled with antifreeze. So now they had to pull
the head to see if the gasket is blown. But first, they wanted to
compression test it to see if its even worth opening up. And it
passed. So I had them pull off the head and hoped it was only a blown
gasket. But the gasket is perfect. On closer inspection, there's
hairline cracks between the valves on numbers 3,4 and 5. So now it's
head replacement time. The mechanic told me not to fix it and just
walk away, but how could I do that? Just to test the compression, he
had to put a new starter in it (I'm sure I fried it with that bad glow
plug). Now we're up to a $1200 for the starter, the compression test
and the head tear down and I'm being told to pay my bill and just walk
away. Why didn't he just hand me a bottle of Scotch and a .44? He did
warn me, but I had to roll the dice. I paid him and was going to just
walk away. Then I got pissed off when someone offered me $200 for it.
I think I could have kept walking if it wasn't for that. For some
crazy reason, that insulting offer made me want to fix it more than
ever. Can you feel me? From reading the threads, the likely cause of
the cracked head was overheating once climbing Teton Pass overloaded
with gear and one other time when I forgot to put the radiator cap
back on. But it didn't start using antifreeze until two months after
the overheating. So how do the experts weigh in? Am I crazy for
putting a new head on it? Or even crazier putting a used head on it?
(I've read all the cracked head threads) The car passed a compression
test prior to tear down... the only reason I had the mechanic go any
further. And it still hauled ass up the pass.
But I think it's D.I.Y. or die from
here on out. The rest of the drive train appears quite solid. I'm
considering buying a new long block from Metric and after that a
Frybrid system. Then making a video out of my alternative energy
project car. That's why I bought the thing in the first place... So I
could tell OPEC to take a flying leap. I already have my used grease
suppliers lined up. And in a few years when gasoline shoots up to $5 a
gallon, I''ll be sitting pretty. So what do you think guys, can I get
a few more gallops out of the horse before I give it a heart
transplant? Or should I just rip it's heart out now? It's on it's
second engine with unknown mileage.

1984 300d Turbo
R&r The Engine Metric Motors. Do The Trans Same Time Save $400.00
New Engine Mounts, Water Pump, Water Hoses, Fan Clutch Labor
Same New Parts, 4 Years 50,000 Miles

Ouch, sorry about the bad luck.

One thing I try to remember when I am pouring money into my old cars
is that even if I had a new car that did not need any work,
I would still be pouring money into the bank loan for it.

Working on older cars has been a gamble for me.
Sometimes I win, sometimes I lose.
But at least I have learned in the process.
And had a little fun in the garage.

Thank You
RichC

__________________

When the power of love overcomes the love of power the world will know peace.
Jimi Hendrix

Cracked heads are typical for an '86 SDL. You must have an original #14 head.

Buy a replacement head, #17 or higher. I have a #22 on mine.

I'm surprised that the mechanic told you to walk away. Doesn't he want the work, or doesn't he trust his work. Maybe you should find someone else.

If you have decent DIY skills. It's something you can also do yourself.

You'll find plenty of help and advise from us here.

Fix it. You'll love the car and be glad that you did.

__________________
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

If it didn't use any oil then FIX IT. Compare the price of fixing it and getting another car that may have it's own problems. I personally wouldn't put a new engine in it unless it had other issues. The bottom end of MB engines are usually bullet proof.
Just my $.00 cents worth.

__________________
84 500 SEL (307,xxx miles)

It's not uncommon to find cracked cylinder heads on these vehicles. They start to consume coolant and most folks think they might get away with a head gasket. It's rarely that simple. The heads crack between the valve and the injector port and it's usually the result of overheating.

The crack starts out quite small and gradually opens up after many heating and cooling cycles. That's why you don't realize the event when it occurs.

Most mechanics don't want this type of work because of the difficulty and the risk..........so they charge accordingly.

The fact that the bottom end is in good condition definitely warrants the repair of the vehicle.

As mentioned, you can do this work yourself if the vehicle is not a daily driver.

This forum is the only reason I'm going to DIY. I can't tell you how much confidence you guys give me. And how good a feeling it is. Thankyou

Some mechanic will tell people to "walk away" hoping to get a "good deal". Then they will fix it and sell for top dollar.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

So what fix it and keep driving it.

Metric Motors can hook you up with a head.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I am just finishing a rebuild of my 87 300 SDL. It had the same problem. Mine had cracks in all six cylinders. There are many online parts locating services that usually cost maybe $4.00 and you can have the parts people contact you with what you need and offer their best price. I found many good #14 heads that way. I opted to hold out for a later casting number. When you use the online search services, don't tell them you have a 300 SDL. Tell them you have a 1990 350 SD or SDL and you will find the later casting numbers and have a better quality part. Also if they ask for your engine type number, which is 603.961 on the 300 SDL, tell them it is a 603.971. This is the engine number for the 350's. The "971" or "97" as it is called is a later version of the 603 series motor and has a vastly improved cylinder head. The lowest number I would recommend to get is a 17. Do not accept a head from a non turbo charged motor! Also read my string titled "300SDL timing chain". Read this and the other strings mentioned in it, there is a wealth of information. And lastly, look for other machine shops. Metric usualy charges two or three times as much for the same work.

I'll be watching your string from now on. Do the job yourself it's not that hard and the special tools needed can be rented in the tools forum on this site.

Keep us all posted

Eddie E.

I found the opposite to be true. Metric charged the same as the locals........but knew exactly what to do and how to do it.

Others have found out the hard way that rebuilding a M/B diesel head is much more difficult than a Chevy...........and you have absolutely no way to confirm the workmanship until it's way too late.

thankyou, quite helpful Eddie!

If I go new, it will be Metric. They do some things to improve the new heads that come straight from Germany... they tweak a few things that I doubt any average place would know or care to do. Talked to them today.

If you manage to snag a used head.........it should go to Metric before you install it. The benefits of new seats, guides and/or valves are worth the trip.