OM604 OM605 OM606 Camshaft Pinning & Crank Hub Fix – Complete Guide

OM604 OM605 OM606 camshaft pinning is one of the most important upgrades you can do on these engines. Today we cover that and the crank hub problem – and why most solutions you see online are not actually fixing anything.

The Intake Camshaft – Most Important Upgrade

The intake camshaft sprocket on OM604, OM605 and OM606 engines is notorious for coming loose. I've experienced it myself in the shop – on a fully running engine I lifted the intake cam out and the sprocket came off in my hand. No force. Nothing holding it. That's how serious this problem is.

This is not a random problem. It happens regularly and needs to be addressed on every serious build.

How to Pin the Intake Camshaft Correctly

First you need to find true TDC. The needle on the block that indicates TDC is movable and cannot be trusted. The dots on the cam sprockets will roughly line up but again – we're talking about the camshaft position, not the sprocket position. Since the camshaft isn't sitting tight on the sprocket you can't trust the sprocket either.

The correct method:

1. Look at the camshaft caps – on OM604, OM605 and OM606 engines the third cap from the front has markings
2. There are also dots on the camshafts themselves
3. Use the exhaust camshaft as your reference – it's bolted down and cannot move
4. When the exhaust cam dots line up correctly, adjust the intake cam until its dots also line up
5. When both are aligned – drill, tap and fit your grub screw or TIG weld

Grub Screw vs TIG Weld

Both methods work. Here's what to know about each:

For the grub screw method use an M6 grub screw. Drill carefully – you want to stop just before breaking through into the camshaft base circle. Tap the hole, apply the strongest Loctite you can find and fit the grub screw. Don't drill all the way through because you need the screw to tighten against something.

For TIG welding – clean, simple and we've seen no issues with it on any build. If you're comfortable with TIG welding this is an excellent solution.

The engine position doesn't matter when doing this job. What matters is that the cams are correct relative to each other.

The Crank Hub Problem

At the front of the crank you have two components – the chain sprocket hub and the crank damper. Both are held in place by friction only. There's a fake key – a small bent piece of metal – used as a guide, and then a large bolt torqued to 200Nm plus 90 degrees. That's it. No physical retention. Friction only.

This is a known problem and there are many solutions on the market. Most of them are wrong.

What the Chain Sprocket Hub Actually Drives

This is critical to understand. The chain sprocket hub drives:

• Both camshafts via dual chain
• The oil pump
• The vacuum pump

The crank damper drives:

• The alternator belt
• Air conditioning
• Water pump

If the crank damper fails your alternator warning light comes on. You notice immediately and it's not catastrophic.

If the chain sprocket hub fails your camshafts stop. Your oil pump stops. Your engine is destroyed.

Why Most Solutions Are Wrong

Most products on the market focus on the damper – not the chain sprocket hub. And many of them make things worse.

Drilling a hole in the damper and fitting a grub screw or pin actually reduces the clamping friction on the assembly. When you drill and tap that hole the damper is no longer under the same pressure. The big bolt that creates the friction clamping force now has less effect on the chain sprocket hub. You've made the real problem worse while thinking you fixed it.

Short pins that don't interfere with the bolt and washer are less harmful but still not fixing the chain sprocket hub problem.

The Correct Solutions

For DIY builders – cylindrical locking compound. Disassemble, clean everything thoroughly, apply cylindrical locking compound, reassemble and torque correctly. Cheap, quick and very effective.

For professional builds – machine the crank and fit a proper key. Then apply cylindrical locking compound as well. This is what we do on engines that need to last and cannot have any comebacks.

Summary

• Intake camshaft pinning is the most important modification on OM604 OM605 OM606 engines
• Use the exhaust cam as reference – it's fixed and can be trusted
• Both grub screw and TIG weld solutions work when done correctly
• The chain sprocket hub is far more critical than the crank damper
• Most crank hub kits on the market focus on the wrong component
• Cylindrical locking compound is the quickest and cheapest correct fix
• Professional solution is machining a real key into the crank

Bye!