Slight rust on camshafts

[Hohn]

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.

I'd discourage this approach in strongest possible terms.

 

[KrisZ]

I was gonna say that there is now way these cams pitted so deeply after only one week of sitting inside, just being exposed to some humid air.

Since you bought it used, you don't really know if these are originals or perhaps someone just slapped these on before they sold the vehicle. If you knew 100% these were originals, I would be inclined to re-use them, but since that's unknown, I would get new camshafts.

 

[50yr Street Mech]

223k ???? The lower end can't be all what it's cracked up to be. Slap them in, use a heavier oil, hope for the best, call it a day. When it craps the bed, then worry about it.

 

[Nessism1]

I'd discourage this approach in strongest possible terms.

And I'll disagree with you.

 

[Nessism1]

I was gonna say that there is now way these cams pitted so deeply after only one week of sitting inside, just being exposed to some humid air.

Exactly. Some minor surface rust. Knock it off and put the engine back on the road. It's a high mileage engine, anyway. Just looking to get some extra years out of it.

 

[50yr Street Mech]

I agree to disagree... YAY

 

[SammyChevelleTypeS3]

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.
View attachment 289919

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.

View attachment 289923

TRUE statement if ever there was: RUST NEVER SLEEPS

When I worked in a Power House mechanical shop, (Back in the days, many facilities kept their own in house maintenance crews. Unlike today, they yank machines out of units and ship them to factories to rebuild) Every machine we opened , cleaned , inspected or even put aside for later rebuilds or plain storage , we encased to the best of our abilities in heavy COSMOLINE military grade spray , film paper. We then wrapped it up in plastic sheeting before boxing up. We did that even if we were going to leave something for after weekends or over night. It only took a couple times for someone NOT to prep coat some parts (gears, shafts, valves, turbine rotors etc...) to learn the hard expensive lesson often heard over and over. RUST NEVER SLEEPS!
STILL , there were several guys who worked in the same shop who always ragged on us "you guys are wasting time just trying to get out of other work," etc... Those guys could care less about the quality of work they did. Matter of fact they ended up reworking several machines they had repaired.

 

[Hohn]

And I'll disagree with you.

That's ok. I admit I work in some rarefied air with stringent requirements, and I might be unreasonably applying a high standard to a situation where "rinse it in the creek and slap it together" is what someone is leaning towards.

And if that's the situation and the engine is completely expendable, then fine.


BY all means, OP please most a follow up when it's still going in 20k miles and point out how they naysayers like me were all wrong.

 

[02SE]

Well, I've seen cams in worse condition...

But those posted by the OP are ones I wouldn't choose to use.

 

[Hohn]

Did a bit of research since I know very little of Mercedes engines.

Apparently these cams are made of cheap cast iron (as the photos suggest), perhaps not even ductile. LIkewise, the gears look like pretty cheap parts to me. I don't see any induction hardening witness marks, so they are were probably flame hardened.

SO you can interpret that two ways. One way is that the engine has really low stresses, so it's unlikely to initiate any cracking on the gear teeth or spalling of the cam lobes.

The other is that they're cheap cast parts that are as strong as needed and not a bit more.


So it could go either way-- it's not conclusively bad as I was thinking it might be. Best of luck.

 

[50yr Street Mech]

I'm not knocking you're expertise on this matter, this is just my opinion. If the lower end has 223k on it, how much life can there left in it, even though it passed compression test and what not. How are the bearings down below ? Nobody knows. That's the ONLY reason I said to put it all back together, run a heavier oil as a cushion, and see how much more life he can get out of the engine. If the lower end was rebuilt, that's a whole new ball of wax we're talking about. I meant no harm in my statements.. Just my opinion given the 223k on the lower end. I would never put those shafts into a " new" lower end.

 

[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.
View attachment 289919

As additional context for these photos:
1) this cam is lubed by crankcase oil and the oil level is about in the center of the cam (it sits in an oil bath)
2) The film load is the highest load on any part of the engine into which it is installed. Those lobes are about 35mm wide (I don’t recall actual width just now) but support a roller of about 20mm diameter with over two tons of force per lobe.
3) oil is a plain nonsynthetic 15w-40 CK4 rated oil ( think Shell Rimula in this case), and it is filtered by an Alfa Laval eliminator which is less efficient than a 30 micron spin on.

Basically, this cam spent over 30k hours loaded with peak force of two tons per lobe using boring cheap oil (think Rotella T3) and filtered by something about as efficient as a. Purolator BOSS and yet it has almost no perceptible wear. There’s something to be said for having the cam bathing in oil…

 

[wwatu]

Wow, thanks everybody for so much replies, lots of interesting information to take in.

Anyways today I ordered 4 used camshafts since I'm not too comfortable putting these in with all the replies, more so with all the new parts I've invested in, seems like pointless if there is a chance it would destroy the new parts also.

I'll post pictures once I receive those, hopefully they are in better condition, at least it'd be easy to compare between mine.

Some different opinions, but what about polishing/grinding in any way the journals on camshaft, since the cams will see some dirt during the lifetime of the vehicle, more so on high mileage vehicles, which will leave some minor marks on it, so better to leave them be? Someone with real world experience on this?

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

Awesome, great to see someone with real expertise on this.

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.

Yeah, cams are removed from the engine. That's interesting, I read similar stories from other places when googling the issue, that's what got my interest, some polished the journals/lobes with 2000grit and said that the difference would be barely noticeable, but then again nobody comes back to tell how great/bad the results were I guess. And I gues that it comes down to the how these parts were hardened and made, since it varies by make and model. So the results vary and better be on the safe side.

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.

For sure, is there some kind of product in a spray can that you could use for such purposes, I guess it wouldn't be available in europe, but still interesting to see.

Since rollers and lifters are new, I wouldn't want to risk messing those up.

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.
View attachment 289919

That's the thing, hard to know what too look for if you don't do this with daily and just for yourself. I have the dealer documentation and that helps a ton, but all the specifics are missing and surprisingly not too much information on the internet either.

Did you forget to add the image for the shot camshaft?

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.

How thick is the hardening layer per different hardening methods, and any way to tell which way was it hardened?

Since you bought it used, you don't really know if these are originals or perhaps someone just slapped these on before they sold the vehicle. If you knew 100% these were originals, I would be inclined to re-use them, but since that's unknown, I would get new camshafts.

The dates on the cams match around the production date of the car so I guess they are originals.

223k ???? The lower end can't be all what it's cracked up to be. Slap them in, use a heavier oil, hope for the best, call it a day. When it craps the bed, then worry about it.

I'm not knocking you're expertise on this matter, this is just my opinion. If the lower end has 223k on it, how much life can there left in it, even though it passed compression test and what not. How are the bearings down below ? Nobody knows. That's the ONLY reason I said to put it all back together, run a heavier oil as a cushion, and see how much more life he can get out of the engine. If the lower end was rebuilt, that's a whole new ball of wax we're talking about. I meant no harm in my statements.. Just my opinion given the 223k on the lower end. I would never put those shafts into a " new" lower end.

It's a diesel, so I don't think 223k is that much, with maintenance 350-400k if not more should be reasonable.

That's ok. I admit I work in some rarefied air with stringent requirements, and I might be unreasonably applying a high standard to a situation where "rinse it in the creek and slap it together" is what someone is leaning towards.

And if that's the situation and the engine is completely expendable, then fine.


BY all means, OP please most a follow up when it's still going in 20k miles and point out how they naysayers like me were all wrong.

I'm not looking to just slap them together, just looking for the reasonable outcome without spending more than the car is worth in parts, hence why I bought used cams, which hopefully look better.

Did a bit of research since I know very little of Mercedes engines.

Apparently these cams are made of cheap cast iron (as the photos suggest), perhaps not even ductile. LIkewise, the gears look like pretty cheap parts to me. I don't see any induction hardening witness marks, so they are were probably flame hardened.

SO you can interpret that two ways. One way is that the engine has really low stresses, so it's unlikely to initiate any cracking on the gear teeth or spalling of the cam lobes.

The other is that they're cheap cast parts that are as strong as needed and not a bit more.


So it could go either way-- it's not conclusively bad as I was thinking it might be. Best of luck.

I think since it is a diesel there also isn't that much stress, since the revs would be lower.

 

[Kestas]

Cams are hardened and the hardening is very thin.

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.

The hardened surface of cam lobes typically has substantial thickness. I can't imagine the lobe metallurgy being designed with a thin nitride layer. Thin nitride layers are usually designed for sliding applications where there is little load and no Hertzian loading.

Did a bit of research since I know very little of Mercedes engines.

Apparently these cams are made of cheap cast iron (as the photos suggest), perhaps not even ductile. LIkewise, the gears look like pretty cheap parts to me. I don't see any induction hardening witness marks, so they are were probably flame hardened.

I've seen many camshaft designs, from hardenable cast iron (which has just enough carbide in the matrix to give a decent wear surface, yet allow for machining of the bearing journals), chill cast lobes, electron beam hardening, powder metal induction hardened lobes, and induction hardening. I was involved with camshaft design when Chrysler was pushing for diesel engines back in the mid-80s. Diesel engines were tougher on camshafts because the oil is compromised more quickly than with gasoline engines.

 

[Kurtatron]

Back on 2015, I bought a 2.4 Toyota JDM engine. It sat in a warehouse for at 15 years. When I opened it up, I was aghast at the amount of rust. The rods and crank had surface rust. The camshafts had rust spots, albeit not on the lobe peaks.

I had no choice but to install this engine, since the company would not pay for a return shipping, which was hundreds of $.

Installed it, and it still runs fine today. First oil report showed high iron wear levels, but it settled down and now wears like a normal engine.

I’d run those cams and not worry about it. If. The engine is a reliable design, I think it’ll run for a while longer.

 

[SwampSurvivor]

I was gonna say that there is now way these cams pitted so deeply after only one week of sitting inside, just being exposed to some humid air.

Since you bought it used, you don't really know if these are originals or perhaps someone just slapped these on before they sold the vehicle. If you knew 100% these were originals, I would be inclined to re-use them, but since that's unknown, I would get new camshafts.

I've had the heads off the original engine from my Grand Marquis in my shed in super humid central NY for 3 years and there's no pitting on the cams.

 

[Hohn]

The hardened surface of cam lobes typically has substantial thickness. I can't imagine the lobe metallurgy being designed with a thin nitride layer. Thin nitride layers are usually designed for sliding applications where there is little load and no Hertzian loading.

I've seen many camshaft designs, from hardenable cast iron (which has just enough carbide in the matrix to give a decent wear surface, yet allow for machining of the bearing journals), chill cast lobes, electron beam hardening, powder metal induction hardened lobes, and induction hardening. I was involved with camshaft design when Chrysler was pushing for diesel engines back in the mid-80s. Diesel engines were tougher on camshafts because the oil is compromised more quickly than with gasoline engines.

Thank you for the expertise, I appreciate your posting.

 

[sdowney717]

I would have not even started the thread and just used those cams, as long as they still had the correct lift profile.

I needed to drill and grind an oil passage in a rare bird old 1970 IH392 flat tappet non hydraulic camshaft, and it was tough to drill. Grinding was no problem. Those cams can be very hard, and the hardness is more then surface

My cam project has worked perfectly to this day.
I have 2 of these engines in a boat, the cam I worked on was reverse rotation.
One had a flat tapped get run in so that could no longer lifter bore spin, developed a groove, cam measured ok.
I resurfaced that lifter. Modded cam to match the oil gallery of the standard rotation engine.

I think they screwed up on the reverse rotation engine! Because without the groove and hole, the lifter galleries got less oil flow.
A groove is needed as it then passes oil PSI continually to the lifter gallery versus only when the oil hole aligns with the oil gallery block passage. They likely decided not to bother as the tappets are manual adjustment not hydraulic.
The lifter galleries get oil from the cam bearings and now the cam's oiling design are matched.

Before

After

Oil flow on these blocks is on the end! For the tappet gallery.
The drilled hole passes oil to the hole in cam center at the back, and that oil flows to the tappet gallery.
Blocks have a removable plate bolted on at the end of cam bearing. and a groove to the oil gallery for tappets.

To this day, makes me wonder why they did that. Or how the tappets were even properly lubed.
Maybe the cam was never even finished by the machine shop who ground it.
I suppose the tappet and cam lobes got some splash lube from the crank.

Intermittent due to no groove in cam, but if no hole, no oil to tappets.
Pushrods do not carry oil in IH 392, tappets can not get oil from them.

Diagram is for engine with hydraulic tappets