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Cracked Cylinder Head Repair/Replace

37K views 63 replies 10 participants last post by  winmutt 
#1 ·
Today I found out I have two cracks in my 602 aluminum cylinder head, from my '91 300D 2.5TD. The car is in good shape, ran great until the cracks, and I want to continue with the repair.

I'm looking for experience and suggestions on either repairing the cracks or replacing the head. I would prefer to weld the cracks, at a recommended shop. I am in central Illinois.

Thanks! Wade.
 
#54 · (Edited)
You can accomplish this by cutting the heads off the old head bolts and using the main portion as locating studs by screwing them into the block a few (2-3) turns.

Once the head is in place, remove each stud (a.k.a. old cylinder head bolt) and replace with new bolts.

That should keep the head & gasket in place without the slightest chance of it shifting on you or disturbing the new headgasket prior to torqueing the head down.
 
#55 ·
You can accomplish this by cutting the heads off the old headgasket bolts and using the main portion as locating studs by screwing them into the block a few turns.

Once the head is in place, removing each stud (a.k.a. old cylinder head bolt) and replace with new bolts.

That should keep the head in place without the slightest chance of it shifting on you.
Like this:



:)
 
#57 ·
Nice technique; I'm learning. I do recall struggling with alignment, keeping the gasket and head in place, and, I had to remove the head a couple of times before final installation. I may have damaged the head gasket while struggling.

Good photo Ps2cho, what model is that?

If I pull the head, I will use this technique for certain, with a slot to unscrew.

Thanks!!
 
#58 · (Edited)
, what model is that?
....

Thanks!!
Photo shown is from a M103 SOHC motor as used in the 260E & 300E US spec W124s. Technique is the same for diesel. I suggest using at least 4, preferably 6 locating studs spaced evenly from the center out.

Regardless, the head will have to go back to the machine shop for checking flatness/straightness as you did run the engine after install. No way around it.

Once you get it back, use the locating stud technique along with a engine hoist holding the head for precise control lowering the head onto the block.
 
#59 ·
"Torque to Yield" Head Bolts

Because of the Process used:
1.Torque to one set of Ft Lbs
2.Then Re-Torque to a Higher Value.
3.Then Two Separate "Angle Torque" Procedures.

There is no Sane Way to sufficiently Re-Torque the already Installed,Torqued Bolts.
("Averaging","Throwing Chicken Bones for Reference Values",Etc.,Etc.,Do Not Work)

Head Bolts must be removed, in the proper sequence, AND (If T'were Mine) NEW HEAD
BOLTS installed and Torqued in the Proper Sequence.

I LOOK VERY,VERY favorably on VHT Copper Gasket Cement.
 

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#62 ·
HI, guys. I am researching the #14 alloy heads subject, as I am considering buying a car with leaky head.
I bought 1987 300DT for my son couple years ago and it runs perfect, so being in need for work wagon, I found the same MY wagon, but with head problem. If I can get it cheap enough and DIY, what are potential expenses to have the head replaced, or repaired? The engine has 220k on it.
Diesels MB are at premium in CA, but than I can buy 1990 Volvo wagon for around $2000, so I am split between love for MB and good prices on Volvos.
 
#63 ·
Reporting back on cracked head repair: I should not have done it. The head cracked and leaked again about 20,000 miles later.

I stripped a junked perfect match a couple of years ago in coastal NC (what a find), and had that salvaged head rebuilt by a local machinist. I reinstalled it over the winter, she's running beautifully. No coolant or oil leaks.

So, I prove once again, do it right the first time.
 
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