Cut yourself a break: install cylinder liners the right way

What’s the worst thing that can happen after you’ve just repaired an engine? Seeing it break down again straightaway, perhaps. We’ll explain how you can avoid this nightmare scenario and what to pay particular attention to when replacing the cylinder liners.

It’s crunch time: identify the cause

Right after replacing the cylinder liners, the engine suffers fatal damage—how is this possible? In these situations, the damage scenario is always pretty much the same.

In this case, the damage was detected quickly and the engine was not started

You’ve repaired the engine, installed new pistons and cylinder liners, and then, just when you’ve put it all back together, you find one or more cylinder liners has torn off, just below the flange.

You quickly identify what you believe is the perpetrator, but actually the new cylinder liner is just a victim. The damage was caused during the installation itself. The following mistakes are often made when replacing the cylinder liners or machining the engine block:

  • 1. Foreign objects (e.g., dirt, sealing residue, chips) between the cylinder liner and the flange seat in the engine block are not completely removed.
  • 2. After machining the seat surface in the engine block, the sharp edge of the flange seat is not chamfered.
  • 3. The flange seat in the engine block is machined at an angle and is no longer parallel to the cylinder liner.
  • 4. The wrong cylinder head gasket is used. Its diameter is too small, and it protrudes too far toward the combustion chamber.
  • 5. The cylinder head is planed but the seat of the fire protection rim has not been reworked or cleaned.

All these factors can result in an incorrect application of force when tightening the cylinder head bolt. This produces a bending moment on the flange seat, causing a forced rupture. The cylinder liner ruptures below the flange at an angle of approximately 30°.

If you hear a crack, don’t start it

Broken cylinder liner flange with coarse fracture structure
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If you hear the cylinder liner breaking (cracking) while you’re still tightening the cylinder head bolt, you can prevent a large part of the damage. However, if you don’t hear it and you start the engine, you’ll find the new cylinder liner in little pieces in the crankcase. This will cause significant damage to the pistons—and possibly also to the engine block.

Brute force causes the cylinder liner to crack

A bent conrod, deformed steel piston, and what used to be a cylinder liner
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The lift motion of the piston causes the cylinder liner to work its way downward in the direction of the crankshaft. That’s all well and good until the first piston ring pops into the resulting gap and gets jammed. The piston then pulls the cylinder liner down toward the crankshaft. If this takes place under full load and at a high enough speed, only fragments of the cylinder liner will remain. Even highly resilient steel pistons and solid conrods are unable to withstand these forces and fall victim to the brute force of the crankshaft.

Cleanliness is half the battle

You’ll save yourself a lot of trouble by making sure that everything is clean and free from chips or other residues. If you have machined any surfaces—e.g., on the cylinder head, flange seat, or face of the engine block—you must ensure that all radii, chamfers, and the fire protection rim are strictly in line with the specifications.

Once you have followed these steps, there is no reason why you cannot repair the engine successfully. You’ll find additional information on this and other topics in our
>> engine parts and filters damage brochure .

 

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