Slight rust on camshafts

[wwatu]

So I started finally to put engine back together, but forgot to oil everything up and had to leave it open for a week, and since this year it's been raining nonstop for the past two months, it developed some surface rust on cams.

So far I have used scotchbrite with wd-40 on gears that connect two camshafts and rag with wd-40 on lobes and journals. I have added pictures of the cams from worst to best. This is a daily with an OM642 engine. Hard to find any specific information on the issue so any input would be appreciated. Are all of those cams scrap or could I save some/all of them?

1. Camshaft


Went about 40 light passes over this with 2000grit sandpaper and WD-40, got a lot better but unsure how long would be okay to go over this until too much material would be removed, since I think all of them would clear up with some further polishing.


These are the worst teeth on gears after scotchbrite and wd-40, total about 12 teeth, some pitting on one side only. Should I touch them also with 2000 grit or rather not, how much stress would be on those and how deep is the hardening?


2. Camshaft
Not sure if this is pitting or just some wear that was there before. Around 10 teeth with same/less pitting than on 1. camshaft.


3. Camshaft
Same/less wear on journals/lobes as 2. Around 8 teeth that have same/less pitting than on 1. camshaft.


4.. Camshaft
No pitting on gear teeth. Just some minor wear marks.

 

[wwillson]

Frankly, the cams all look like they are junk. Lots of pitting and scoring. I guess it depends on what life you expect out of the engine. If it's a short term engine that is going to the boneyard, then run it. If you expect a long life then junk the cams. However, I'd want to completely go through the engine to make sure you aren't adding new cams to a worn out lower end.

 

[dbias]

What? Is that delamination or something else?

 

[Pablo]

What? Is that delamination or something else?

Looks like wear and galling

 

[Kestas]

I'll be the optimist here. The corrosion pitting is somewhat even on the surface, and may act as reservoirs for lubrication.

My biggest concern was for the scuffing I see near the lobe tip in the very last picture. That is not good and would likely progress in service.

I'm curious, do the lobes run on roller followers, or does it slide on rocker arms?

 

[Mechanician]

I's apart, fix it right the first time.
There used to be a commercial that stated "Pay me now, or pay me later", you'll need to pay up either way.

 

[OVERKILL]

Frankly, the cams all look like they are junk. Lots of pitting and scoring. I guess it depends on what life you expect out of the engine. If it's a short term engine that is going to the boneyard, then run it. If you expect a long life then junk the cams. However, I'd want to completely go through the engine to make sure you aren't adding new cams to a worn out lower end.

Yeah, I'd not be confident in their longevity, given what we see in the pictures.

 

[SammyChevelleTypeS3]

I's apart, fix it right the first time.
There used to be a commercial that stated "Pay me now, or pay me later", you'll need to pay up either way.

That is very sound advice. Nothing worse than having to open up a machine after you worked hard, and you put it all back together.
Then, because you were not sure and decided to let something slide , now you must do over.

What service / time length was the engine in? How was it maintained? Proper / timely oil change cycles?

What did it look like when you pulled it open? (hard to believe that all happened since tear down).

Lots of times when that condition is found in an engine without lots of service hours , the manufacturing process (heat/chem) treatment is suspected if there is no other obvious things the user can point to.

Like someone said. Short term/light use, nail it shut and run it. Long term, don't chance it unless you like to tear down and rebuild for fun.

 

[We're Metals]

Those look terrible...

 

[Cujet]

If that were a Lycoming aircraft engine, the camshaft would have a lifespan measured in the double digits. If it were a Continental aircraft engine, with the camshaft below the crankshaft and bathed in oil, the camshaft would be expected to live a long life.

Here's my guess, the parts will hold up for quite some time with high viscosity oil. I believe the cams are on top, so replacement is not so difficult.

I'm not saying they are in good shape. Only that I'd expect them to last for quite some time with the use of (for example) 15W-50 oil.

 

[wwatu]

Thank you everybody for your fast input, much appreciated.

Frankly, the cams all look like they are junk. Lots of pitting and scoring. I guess it depends on what life you expect out of the engine. If it's a short term engine that is going to the boneyard, then run it. If you expect a long life then junk the cams. However, I'd want to completely go through the engine to make sure you aren't adding new cams to a worn out lower end.

Bear in mind that these are super closeup macro shots. But I'd rather like to get some longetivity out of this engine, hence why I am asking about the thoughts on those. Leak down test and compression test checked out, so I expect the lower part to be in okay condition. So none of those cams seem usable with a little touch up?

I'll be the optimist here. The corrosion pitting is somewhat even on the surface, and may act as reservoirs for lubrication.

My biggest concern was for the scuffing I see near the lobe tip in the very last picture. That is not good and would likely progress in service.

I'm curious, do the lobes run on roller followers, or does it slide on rocker arms?

As I said the scuffing probably seems worse on the images than they are due to the macro shots. But none of the scuffings on the lobes are felt by the not so scientific method of finger nail, they feel smooth as silk. They run on rocker arms with rollers that are on hydraulic lifters.

That is very sound advice. Nothing worse than having to open up a machine after you worked hard, and you put it all back together.
Then, because you were not sure and decided to let something slide , now you must do over.

What service / time length was the engine in? How was it maintained? Proper / timely oil change cycles?

What did it look like when you pulled it open? (hard to believe that all happened since tear down).

Lots of times when that condition is found in an engine without lots of service hours , the manufacturing process (heat/chem) treatment is suspected if there is no other obvious things the user can point to.

Like someone said. Short term/light use, nail it shut and run it. Long term, don't chance it unless you like to tear down and rebuild for fun.

Yeah, I agree. Engine has around 360k kms, so around 223k miles? Not sure how was it maintained before me, but by the looks of the air filters that had bugs in them I'd guess not that well.

Here are some images I found that were taken before the rusting happened, as seen on one of the images the micro dimples seem to be already there as seen on previous images.

I have replaced valve stem seals, rollers, lifters, have a new chain with guide rails, refurbished the turbo, alternator, water pump and pulleys and a lot of while you are in there stuff, so the cost is going up there, that's why I am wondering if any of these could be saved. The scuffing really isn't that bad, but my main concern would be the pitting and rust damage and if I could go over them, or over some of them with some sandpaper and oil, meaning would I lose too much material to matter on gears/lobes/journals. If all of them are beyond ****ed, meaning that I'd have to sooner than later come back at this then I'd rather get new ones. And by new ones I mean junkyard, because 4 new cams for dealer is just not viable. I think I'm going to look at some options tomorrow to see if they look worse or better than these ones.

If that were a Lycoming aircraft engine, the camshaft would have a lifespan measured in the double digits. If it were a Continental aircraft engine, with the camshaft below the crankshaft and bathed in oil, the camshaft would be expected to live a long life.

Here's my guess, the parts will hold up for quite some time with high viscosity oil. I believe the cams are on top, so replacement is not so difficult.

I'm not saying they are in good shape. Only that I'd expect them to last for quite some time with the use of (for example) 15W-50 oil.

Cams are on top yes, but the difficulty is subjective, since it's a diesel a lot of parts have to come out before you could even get to the head covers. I guess longevity is also subjective but I would just not like to do the job again in few upcoming years nor to spend again on chain or other new parts that I have currently invested on. High viscosity oil is also not an option, due to low temps on winter and manufacturer specs being 0w-30 - 10w-30, most common is 5w-30.

 

[wwillson]

As I said the scuffing probably seems worse on the images than they are due to the macro shots. But none of the scuffings on the lobes are felt by the not so scientific method of finger nail, they feel smooth as silk. They run on rocker arms with rollers that are on hydraulic lifters.

Listen closely to what @Kestas says. He is a career metallurgist that decades of experience doing failure analysis.

 

[eljefino]

As an aside, ScotchBrite inside an engine is no bueno-- it slips through the oil filter and attacks the main bearings.

I had flash cam rusting on my Dakota 2.5 which sat with a loose valve cover during the humid season for a week while I did the head gasket. I figured it would work itself out so put it back together and ran it for years.

 

[Hohn]

Frankly, the cams all look like they are junk. Lots of pitting and scoring. I guess it depends on what life you expect out of the engine. If it's a short term engine that is going to the boneyard, then run it. If you expect a long life then junk the cams. However, I'd want to completely go through the engine to make sure you aren't adding new cams to a worn out lower end.

The cam and all gears are toast, 100%.

These are parts where the surface is critical. Corrosion compromises not only the surface finish (and thus oil film formation), but you've also compromised the surface hardness that is so important.


If these parts don't fail immediately due to oil film insufficiency, they will fail in fatigue very soon. That cam has no fatigue life in it with normal hertz stress levels. The gear teeth will have a fatigue failure initiated if they have any kind of real loading.

Parts are toast. Expensive lesson learned perhaps.

Likely outcomes: if roller follower, cam shaft will spall, toss chunks of hard cam surface and take out rollers. If flat tappet, galling first and then wiping the lobes and tappet.

Gear teeth flex in usage and with the surface compromised you will likely initiate a fatigue failure that starts at the surface and migrates through the teeth.

 

[Hohn]

Lots of people who don't look at parts regularly don't have much of a reference point for what good parts look like.

Here is the camshaft from a Bosch CP9.1 pump after the pump had a top end failure at 31,000+ hours of service in a coal mine. New parts look very similar, you can barely see the path of the rollers on the tappets.

This is a good surface finish for a camshaft.

 

[crashz]

This is a good education for the rest of us. Much appreciation to the original poster and those that responded.

 

[Hohn]

Another datapoint. Here is a BNIB camshaft for a 95L V16. That's a single camshaft in its two halves. The surfaces are not super mirrored because there's protective shipment preservative (like a modern Cosmoline) on them to protect from corrosion. Corrosion is catastrophic to cams because of what they do to the surface grain structure. Since these cams are from a specialized supplier in Germany, great care in preservation, handling, and shipment is required.

 

[Chris142]

Cams are hardened and the hardening is very thin. I don't think you did yourself any favors by sanding the hardness like that .

But I'm no metallurgist.

 

[Nessism1]

My opinion, get a low grit 3M deburring wheel for your grinder, and use that to very lightly kiss the surfaces with the pitting sitting proud. After dressing the worst bits, slam the engine back together. Should be good for another 100k, at which point, the rest of the engine will be done.

 

[Hohn]

Cams are hardened and the hardning is very thin. I don't think you did yourself any favors by sanding the hardness like that .

But I'm no metallurgist.

I'm not either, but I've picked up a bit from working alongside them over the years.

The white layer on a typical gas-nitride cam is going to be below 0.001" thick. If you've removed enough material to clean up more than 0.001", you've probably trashed the surface hardness.

Those pits are quite clearly deeper than than in many places.