Camshaft lobe pitting!

jason07-1zzfe · Apr 21, 2003

To see a larger version please copy this URL into new window or drag it to the address bar:
http://www.imagestation.com/picture/sraid60/pce7f21a63b6c21689f4af7800c38d616/fc4bfbaa.jpg.orig.jpg

All of my cam lobes are pretty similar to this. The car is an 89 BMW 325is with 174k miles. I noticed the pitting last time I adjusted the valves. Didn't notice the time before that so not 100%sure when it occured. Probably before I bought car...
What is the cause of this? Is it bad? I read at some website that it can be cause by moisture. Basically moisture is not compressible, so when under high pressure it finally explodes, like a microcopic bomb going off on the lobes. But then I found a website of some engine builder saying its caused by not changing oil often enough. I guess moisture could be a function of that...don't change the oil for a long time moisture will build up.

Then yet another builder said, I think, it was due to lack of lube. The first site was an an oil analysis info site, probably from one of WearCheck's tech docs. So I tend to trust that one first.
I never went over 5k on my oil changes since I bought the car 50k miles ago, so I don't think I caused this

M1 since I bought it, now Red Line.
My last analysis had fairly low iron, so I don't think the lobes are pitting any more or that it is causing any accelerated wear.

dickwells · Apr 21, 2003

I wonder if there was a period when the car sat idle for a long period of time with diry oil in it? On another note I seem to remember this type of pitting being due to "spalling" from heat build up and lack of lubrication. Did you examine the shelf areas under the cam for residual particles that could be felt? RW

TheLoneRanger · Apr 21, 2003

Jason, cast iron is not uniform in consistency when it's poured. I think what you're seeing is imperfections in the iron. Over time, acids and water in the oil have eroded the imperfections and left the craters in the surface. I don't think it's anything to worry about, and I doubt if it'll get any worse.

That lobe actually looks pretty good to have 174K miles on it.....

7TFord · Apr 21, 2003

...I agree. You are doing pretty good for that many miles. That cam has gone around once or twice in 174K and is bound to show some signs of wear. You wouldn't think that there was much down time involved with that many miles logged, but I've also read that lack of use will accelerate this pitting.

sprintman · Apr 22, 2003

Looks like an Auto-Rx clean would be useful too IMO?

jason07-1zzfe · Apr 22, 2003

Thanks. That's good to know, makes sense.

cryptokid · Apr 22, 2003

Looks like an Auto-Rx clean would be useful too IMO?

how would autorx help restore a pitted cam?

sprintman · Apr 22, 2003

Rreread my answer. I'm looking at the pictures and see it sure could do with a cleanup. Not suggesting it will replace metal.

Shannow · Apr 22, 2003

Jason, looks just like the lobes on my Camira (Aussie version of the "J-car").

Bought the thing with 120,000km, change the oil with Mobil 1. Changed the oil again, and saw pitting on the lobes, in exactly the same place. Cannot tell (didn't look) whether it was there before, but it certainly is now.

Hasn't seemed to stop the thing working to date.

The water exploding story is cavitation, however to cavitate, the pressure has to be brough to quite high vacuum, pulling the droplet apart. It then collapses, and forms an extreme pressure pulse which can severely damage metal items (pump impellers etc).

jason07-1zzfe · Apr 22, 2003

sprintman, it just had two AutoRX treatments. 1000 miles on first and 800 on second.

Thanks for the info shannow

MolaKule · Apr 25, 2003

Check the nitration levels on your used oil analysis.

Nitric acid, formed by nitrous oxides and moisture in the combustion process and blowby, is the main cause of camshaft wear problems.

You may need to switch to a "fleet" oil to get more acid fighting additive.

jason07-1zzfe · Apr 25, 2003

My last UOA with Red Line 10w40 had a nitration of 13% after 5k miles. The one before that was Mobil 1 15w50 at 5k miles, nitration not reported, but TBN was 6.5. I have yet to go over a 5k interval. So I don't think I caused this. I do know have have some blowby because I have some consumption and the oil gets black pretty quick.
But you got me to look through the reciepts from the 1st owner again. (I bought from 2nd owner) There are some crazy intervals unless he got it changed somewhere else and didn't save reciept. He did a lot of driving for a while. I got 2 in a row, 4mo/11,000 intervals. Then 7mo/10k, 4mo/3k, 7mo/3k. Next owner, 8mo/4k. That took me from 67k to 116k. Then I bought it at 121k and changed the oil shortly after.
So I think I found the culprit. Bonehead prev owner. The reciepts have the first owners name, add, and phone if it's same...I should call and ask him what the heck.

Funny thing is, the shop he took it to for service and oil changes is one of the most reputable BMW tuner and shop in the area. EXPENSIVE. So why he skimped on oil changes, is beyond me

JohnBrowning · May 11, 2003

Hellow All, I haope I rad the origanal post right. I wanted to take this time to site these photo's as similar to what I find with all cars ran on M1(Not the pitting the varnish!). If you look at the portion of cam lob that the follower does not ride on you will see the brown varnish. According to the owner this car has been run in M1 for a total of 124,000 miles. He has run M1 since he bought it with 50,000 miles on it. He has had Redline in the car for more then one oil change now so alot of the varnish has probably been removed by the esters in the Redline. This is exactly what i was refering to in a different thread about varnish issue with M1.

jason07-1zzfe · May 11, 2003

John,
Sorry I probably made it a little confusing. It has used Mobil 1 the last
~45k miles(since I bought it) with one 5k change of Red Line and then 2 Auto-RX treatments before that photo. I am running Red Line still.
The first ~124k mi I did not own the car, but I have a lot of the reciepts. In the winter it was mainly Pennzoil 15w40 and in the summer, unknown brand 20w50. And as you can see in my post above this, some of those intervals were quite long for a plain jane conventional oil.

So that is probably the cause of the varnish (and pitting).
Now I didn't notice much difference in the cleanliness under tha valve cover from when I bought it and after running M1 for ~45k miles. If anything it was a little cleaner. It was definitely cleaner after running Red Line for 5k. And the two treatments of Auto-RX made about the same difference Red Line did, maybe a little more(for example: the clean tip of the lifter). End result in photo.

[ May 12, 2003, 10:04 AM: Message edited by: Jason Troxell ]

jason07-1zzfe · May 11, 2003

By the way, here's a shot from further away:

And drag this to address bar or copy to a new window to see full-size:
http://www.imagestation.com/picture/sraid60/p400194d82721088640208df1c6cd577f/fc4bfba5.jpg.orig.jpg

Camshaft lobe pitting!

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