OM606 Head - Bent Valve - what else?
 

Forum Members,
In the process of installing a new injection pump, and injectors, we have somehow bent one of my valves. I am still trying to get my head around how the valve bent in the first place, but the head is being pulled and sent in to replace/repair the valve in question.
Here are some major items being done while the engine is apart:
-New injection pump
-All 6 injectors rebuilt by bosch shop
-Checking charge cooler and replacing hoses
-Turbo is fine

Is there anything else I should have tested/replaced while the head is off and at the machine shop?

I had the same thing happen to me when I was rebuilding a 1980 Julia Spider with a double overhead cam. I was tuning the engine over by hand very slowly, with the timing chain disconnected, and one of the pistons just tapped one of the valves, and ended up bending it. Good luck with your vehicle.

Thanks for the feedback. We did turn the engine a bit, but I never disconnected the timing chain.

How do you know the valve is bent? Being a 24V engine, I'd have expected you to bend two valves, not one if you actually had piston/valve contact. The valves are pretty tough, turning the engine over manually isn't enough to bend one unless you were hanging off a 4' breaker bar or something.

Is it possible you rotated the engine in the opposite direction that it rotates when it is running?

Define "a bit".

Was the injection pump out when this was being done?

How do you know that a valve is bent?

How do you know you've bent a valve?

Updates:
First I'll answer the big question... how do we know the valves are bent? It's very difficult to see the valves without the head removed. We could see parts of the valves after removing the injectors. We were able to fit a small piece of wire into the valve area and turned the engine. We were able to slide the wire in and out of the valve when it was supposed to be fully seated. That's how we know there's a bent valve.
Now to what happened... There are two timing marks on the OM606. These timing points are spaced 180 degrees from one another. He lined up the new injection pump with the opposite, small timing point not realizing there were two.
We ran the engine and took it for a test drive. The mechanic insisted the engine was running bad because there was still air in the lines. I told him there's no way air is still in the lines, but he had me drive it anyway. The engine ran progressively worse and then wouldn't start again after I shut it down.
It was at this time the second timing point was identified and he realized his mistake. We decided to remove the head and inspect what is going on in there.
-Two precombustion chambers are damaged
-Two valves are bent
-Top of the pistons are fine and still smooth
-Cylinder walls are fine and you can still see the machining marks from the factory.

The mechanics at my shop are very solid guys. They said they are paying to have a machine shop inspect the head in order to provide a solution. They will be paying to have the head and valves fixed/replaced/etc and put back together.

Why were the injection pump and injectors being changed in the first place?

Were there any marks on the tops of pistons where the valves hit?

An injector pump out of time won't cause a bent valve.

The cam to crank timing would have to be affected in order for valves to bend. If cam to crank timing is out, all intake or exhaust valves will bent because they are open as a piston is coming up. If the timing chain comes off and cam stops turning , only a couple of valves are open and only those bend.

With the cams out, are the bent valves still not seating?

Did you stick anything in the injector hole to find TDC at any point?

With a bent valve caused by an outside source, they generally get better not worse as the valve hammers straight again.

Does the machine shop know the history of this head and to look for actual causes of damage?

97 SL320, I might be wrong, but I think only one of the cams were timed correctly, not just with the IP but crank also.

EdBenz, whilst you have access, check TDC for number one piston against crank marker as these can move during water pump maintenance/repair.

I'm still not buying that only 1 cylinder's valves are affected. If the cam timing were messed up due to slack chain or whatever, I'd expect ALL SIX cylinders to be affected since the timing is common to ALL SIX cylinders. Something in the story isn't adding up! As said above, improper timing cannot cause bent valves. Only an impact will cause the valves to bend, and that should be obvious by witness marks made on the piston crown where it struck the valves in question.

Uh, this doesn't sound right. The injectors are screwed into a pre-chamber, and there are tiny openings from the pre-chamber into the cylinder, but no access at all to valves from the inside of the pre-chamber.

Do you mean that either the intake or exhaust manifold was off?

Was the timing chain ever removed?

Were the camshafts ever removed?

When I replaced the head on my OM603 engine, I had one valve that would hang open because the hydraulic lifter was over-filled and not bleeding down. If your shop did anything with the camshafts or hydraulic lifters, they could have ended up in the same situation. In my case I had to remove the camshaft and the lifter, and manually bleed it all the way down, and then put it all back together and the problem was fixed.

Yes, it is unsettling that the shop is being blamed for the bent valves and apparently doesn't have enough knowledge to defend themselves.

If they have only noticed one 'dimple' timing mark, on one cam, it's entirely possible the other was assembled at any point.

This is only my interpretation reading through.

Agree with above comments on accessing the valves via injector when removed, not possible - it may be doable via the inlet/exhaust ports as though?

It seems to me that someone (your mechanic?) must have moved either a camshaft or the timing chain or both in order to cause this damage. Why was that necessary? Installing and setting the timing of an injection pump does not require any work on the camshafts or timing chain.

If pistons and valves made contact, then the piston heights must be measured to determine if a rod has bent or the bearings damaged. It would be grossly negligent to only repair the damage to the head and not check the rod and bearings. If there is any damage to the rod and bearings, then I would also replace that piston out of an abundance of caution.

These "mistakes" would cause me to find another shop, have a good used engine installed, and have the original shop pay the bill.