Theory on causes of broken valves and rockers

MRausch82 · **Posted:** Mon Aug 26, 2013 7:23 am

Here it is: worn rockers, caused by egr in the US, cause excessive carbon buildup due to incomplete combistion (if you see excessive black smoke, an everything else checks out OK, that is a sign of trouble...) which causes valves to stick open or closed, or possibly even overheat. If carbon drops and jams a alive closed between pispn and valve, rockers break. If carbon jams a valve open, the piston hits the valve, perhaps momentarily, perhaps several times which weakens the valve, which then causes the valve to fracture and eventually break. Glow plugs can cause the same issue. I have seen a few VW Diesel engines with broken timing belts that has "good" valves from some cylinders reused only to later have the valve fail from one of those cylinders. I suspected the impact was enough to weaken the valve and later break it. Thoughts? Nobody has mentioned this so far that I know of... I think this is a feasible cause and effect.

flash7210 · **Posted:** Mon Aug 26, 2013 8:05 am

So you are saying that carbon buildup on the valves may cause sticky valves which lead to
rocker arms pounding the valve stem or piston pounding the valve face?

Sounds plausible.

Of course there is still the issue with excessive soot in the oil causing premature rocker
bearing failure.

Either way, the solution seems to be disabling and blocking the EGR valve.

And of course, performing the occasional Italian tune-up.

MRausch82 · **Posted:** Mon Aug 26, 2013 8:16 am

flash7210 wrote:

So you are saying that carbon buildup on the valves may cause sticky valves which lead to
rocker arms pounding the valve stem or piston pounding the valve face?

Sounds plausible.

Of course there is still the issue with excessive soot in the oil causing premature rocker
bearing failure.

Either way, the solution seems to be disabling and blocking the EGR valve.

And of course, performing the occasional Italian tune-up.

Kinda. I think chunks can break off, as someone else mentioned in a previous thread, and that jams a valve open momentarily, or, it can cause the chunk to get "stuck" between the piston face and the valve which does not allow the valve to open, which then breaks rocker arms. When the valve hits the piston one or more times, it can weaken it allowing it to break later on.

As for the oil contamination, I agree. The EGR causes a lot of contamination of the oil, which causes the rocker bearings to wear.

Disabling the EGR with either the ORM, losing the EGR, blocking it, or adding a tune to limit it is the best method. I have been running since 47K with the ORM, and my oil stays pretty clean. I am eventually going to get a tune, but the money has not been there, so I live with a CEL.

bentrod · **Posted:** Fri Aug 30, 2013 1:35 pm

MRausch82 wrote:

flash7210 wrote:

So you are saying that carbon buildup on the valves may cause sticky valves which lead to
rocker arms pounding the valve stem or piston pounding the valve face?

Sounds plausible.

Of course there is still the issue with excessive soot in the oil causing premature rocker
bearing failure.

Either way, the solution seems to be disabling and blocking the EGR valve.

And of course, performing the occasional Italian tune-up.

Kinda. I think chunks can break off, as someone else mentioned in a previous thread, and that jams a valve open momentarily, or, it can cause the chunk to get "stuck" between the piston face and the valve which does not allow the valve to open, which then breaks rocker arms. When the valve hits the piston one or more times, it can weaken it allowing it to break later on.

As for the oil contamination, I agree. The EGR causes a lot of contamination of the oil, which causes the rocker bearings to wear.

Disabling the EGR with either the ORM, losing the EGR, blocking it, or adding a tune to limit it is the best method. I have been running since 47K with the ORM, and my oil stays pretty clean. I am eventually going to get a tune, but the money has not been there, so I live with a CEL.

That's an understatement ... The EGR causes a lot of contamination to the oil.
I have the GDE eco tuner installed, and then had my mechanic custom remove the whole EGR system off the engine, cooler and hoses too. Now the engine oil is crazy clean since the 2ed oil change with it removed. It's unreal! It's cleaner looking now then a gas engine at 3K on it. It's amazing.

DOC4444 · **Posted:** Sat Aug 31, 2013 4:19 am

The "clean oil" phenomenon has been well documented here since 2009, with GDE tunes, However, it is due to a COMBINATION of eliminating ingestion of exhaust gasses AND better mixture control, which results in less unburned fuel going into the oil. (People using other tunes, including stock, and SEGR do NOT observe the same results. I used IM SII and SEGR before GDE came along. My oil never "cleaned up" until switching to GDE tunes.)

When using a GDE tune, there is NO advantage gained by physically removing the EGR valve from the vehicle. However, there is a HUGE disadvantage by doing so because you eliminate the turbo overspeed protection which is critical to turbo longevity.

GDE tunes maintain the OEM feature of using the EGR valve like a wastegate to bleed off boost when it exceeds the design limits of the OEM turbo.

DOC

MRausch82 · **Posted:** Sat Aug 31, 2013 8:00 am

I only have the ORM, and have since 47k. I am now at 93k and the oil stays clean. It never gets really black... As most may or may not know, diesel oil gets black. That's the way it is. Period. My oil in the CRD is an exception. It stays cleaner than any diesel I have ever owned, serviced, rebuilt, repaired, sold, etc.

DOC4444 · **Posted:** Sat Aug 31, 2013 3:26 pm

I have a 2001 7.3 4WD Excursion with 43K miles on it and a tune for economy. It was built by Ford with no EGR or CAT. I change the oil once a year (4 gallons of Mobil 1 5-40 plus ZDDP) and it looks like it just came out of the bottle when I drain it. No EGR, close to complete combustion and good ring seal=oil that stays pretty clean.

DOC

MRausch82 · **Posted:** Sat Aug 31, 2013 3:38 pm

DOC4444 wrote:

I have a 2001 7.3 4WD Excursion with 43K miles on it and a tune for economy. It was built by Ford with no EGR or CAT. I change the oil once a year (4 gallons of Mobil 1 5-40 plus ZDDP) and it looks like it just came out of the bottle when I drain it. No EGR, close to complete combustion and good ring seal=oil that stays pretty clean.

DOC

That I'd like to see. Not saying its not possible, just saying I have owned, worked on and rebuilt many Diesel engines both in cars, equipment, etc. and it always is either dark or black. It's the nature of a diesel. With the combination of blow by and high compression, some gasses are bound to get past the rings and darken or blacken the oil. Even my gas sets don't have perfectly clean oil when drained, even with fairly short intervals.

papaindigo · **Posted:** Sat Aug 31, 2013 4:08 pm

I'm inclined to agree that at least the rocker problem is soot and oil quality and change interval related; I'm also willing to agree that chunks of carbon can under certain circumstances cause sticky valves and related valve/piston problems; and it's pretty obvious that taking steps to reduce the soot load is a good idea. Those steps can include a variety of approaches to reducing EGR use, improving combustion efficiency, use of quality oil and oil filters, and (some disagree) relatively frequent oil change intervals especially for those of us who don't drive a lot.

As to Doc's Excursion at a average annual miles driven of 3,600 and 4 gallons/16 qts of oil for a full fill, as opposed to 1.75 gallons/7qts for the CRD, I would not be at all surprised to see his oil stay pretty clean. That's a lot of oil and not a lot of miles.

dkenny · **Posted:** Sat Aug 31, 2013 10:45 pm

MRausch82,
the problem I have with this theory is all the other diesels that roll coal.
yes enough to make fog the car following..
if you check other forums like a Cummins forum where lots of owners 'roll coal'
bad rockers and dropping valves don't happen..

for clean oil as being good..
well..um..my wife jeep is my 4th diesel.
1st. 8hp yanmar..1.9l oil..yep its black after a few hours of running
2nd..8.2L Detroit..3 gallons of oil at change time..took less than 1000miles before it was black. I know ran the engine to some 100k mark..might have been 300k/400k?
3rd my truck now at 233k miles..the oils is black as well( no EGR.) 11 quarts at change time
4th wife's jeep..coming up on 100k..40k with segr..yep oil is black at 10k miles for the change

so my thinking on the clean oil is a newer(less mileage engine) and not EGR..or EGR feed back into the air intake before the filter. so this might shorten the air filter life..its easy to change

turbo over speed? huh? you mean the grenade? that would be the result of over speed..why does this happen on the jeep? lets see the HX turbo or Hy used on Cummins( yes its fixed vane) with the normal PSI limit is 20..but it pushed to 35-40psi before head studs are needed? think about how much faster the turbo must run to double the psi boost?
but they live? hum?

just some thoughts
-dkenny

MRausch82 · **Posted:** Sat Aug 31, 2013 11:41 pm

My only thought on the other engines that can roll coal with no issues is: our crd's don't really smoke normally. When they do, and it is a rocker issue, it is because it is not breathing properly, not because of too much fuel. Hence, more carbon is built up and not burned off. Just a theory. Our engines can't take the abuse as a cummins. I don't hear of people rolling coal on a tdi or other common rail engines. When they do, the engines don't live a long productive life...

Auberon · **Posted:** Sun Sep 01, 2013 12:36 am

Indeed, I do wonder how many of these failed engines are operated merrily without EGT being monitored.
Also ponder, now you've raised these thoughts that aside from the outstanding job the GDE tune does re EGR, (so that does not apply to this post) if the oil isn't dirty it is not keeping the solids in suspension so they can be filtered out by a quality full-flow filter before sludging, etc......which should be changed on a regular basis as Papa indicated....which keeps them from coalescing and becoming an issue. Is it the snowball effect here?

I read posts of guys running these cars often at 75 mph - how many know where EGT sits relying on the slow to react sensors that CJD provided us with. Run hard like this when it's like a toilet inside and what will happen?

Best indicator I've ever had on many diesels (operated under numerous bosses who carried big sticks and weren't afraid to use them if you didn't treat their machines responsibly) - it was OK to work it hard by all means but idle down whilst you do the lunch-time shutdown check was carried out.

thermorex · **Posted:** Sun Sep 01, 2013 12:50 am

I can add that the old 3.0 td Mercedes (om617) that was very popular in 80s, also has egr on its latest versions and I've never heard of rocker failure. Granted, egr on that time hasn't been that bad, but that engine runs at over 3k rpm on 75. I think main issue with crd is a bad design for current epa norms and wasn't tested properly for the US market, with the draconian epa regulations. Europeans don't have similar issues with their crds either. VW also doesn't have those issues in us.

Regarding oil getting black, every diesel I had, blackened the oil in less than 1000 miles, which I think is related more to diesel combustion rather than egr.

MRausch82 · **Posted:** Sun Sep 01, 2013 9:01 am

thermorex wrote:

Regarding oil getting black, every diesel I had, blackened the oil in less than 1000 miles, which I think is related more to diesel combustion rather than egr.

It is. I have dealt with lots of non EGR motors and this is the case with them as well. What other diesels have rockers with roller bearings? The oil/soot suspension issue is probably not oil related unless you are using a realy crappy oil. I've opened TDI's and other VW/Audi Diesel engines that have run Mobil 1 0w40 (gasp!) and have not seen ANY issues with ANY wear, sludge, etc. The engines were pristine. No measurable wear, and no sludge or other deposits. Even on ones with EGR. I am inclined to think it is fine in our engines. I think as long as a known good oil is used, that should not be an issue. The egr, design, and EPA mandates which have a different computer map most likely all contribute to the engine troubles we have seen. Out of curiosity: what were these things rated, as in from the factory on the window sticker, in terms of MPG in Europe?

lostFinn · **Posted:** Mon Sep 02, 2013 6:11 pm

MRausch82 wrote:

Out of curiosity: what were these things rated, as in from the factory on the window sticker, in terms of MPG in Europe?

These are the numbers in 2005 finnish Jeep Cherokee brochure for a 2.8 CRD:
8.2 L/100km highway
12.7 L/100km city
9.9 L/100km combined

And if my conversions are right, in MPG:
28.7
18.5
23.8

DOC4444 · **Posted:** Mon Sep 02, 2013 6:31 pm

Sounds right on the mark for a stock KJ CRD with less EGR than is standard for NA.

DOC

MRausch82 · **Posted:** Mon Sep 02, 2013 7:48 pm

Yeah that's about the same here. I think ours were rated at 28mpg highway? Perhaps I am off a little though...

SVY · **Joined:** Thu Aug 22, 2013 9:51 pm **Posts:** 5

MRausch82 wrote:

thermorex wrote:

Regarding oil getting black, every diesel I had, blackened the oil in less than 1000 miles, which I think is related more to diesel combustion rather than egr.

It is. I have dealt with lots of non EGR motors and this is the case with them as well. What other diesels have rockers with roller bearings? The oil/soot suspension issue is probably not oil related unless you are using a realy crappy oil. I've opened TDI's and other VW/Audi Diesel engines that have run Mobil 1 0w40 (gasp!) and have not seen ANY issues with ANY wear, sludge, etc. The engines were pristine. No measurable wear, and no sludge or other deposits. Even on ones with EGR. I am inclined to think it is fine in our engines. I think as long as a known good oil is used, that should not be an issue. The egr, design, and EPA mandates which have a different computer map most likely all contribute to the engine troubles we have seen. Out of curiosity: what were these things rated, as in from the factory on the window sticker, in terms of MPG in Europe?

Mike, I have to admit I'm a bit puzzled here, or maybe I'm just missing something. In a post on facebook where I was commenting about the high level of soot that several analyses showed, you recommended that I do the ORM modification until I can get the GDE EcoTund done (I did a day or two later). You also recommended that I change oil ASAP (I'll be doing that tomorrow, even though the Pennzoil Ultra 0W-40 only has about 2500 miles on it). But reading your comments here, I gather that you don't think that the soot is an issue. (I do have high iron readings, too.) Am I misunderstanding something? Sam

P.S I'll be going in for a hip replacement in a couple of weeks. While I'm out of commission, I'll be having a local shop pull the brain box and sending it to GDE for the tune.

MRausch82 · **Posted:** Tue Sep 03, 2013 7:59 am

No... Soot is certainly a problem with WORN rockers. As for people dropping valves, etc... That is the purpose of my OP. The egr also causes oil contamination due to the soot getting past the rings, thus wearing the bearings in the rockers. The ORM or tunes limit or eliminate the EGR and thus the oil contamination issue. When the rockers wear, driving long term with worn rockers leads to excessive carbon buildup and possible sticky valves, combustion chamber temperatures, an possibly broken valves, etc. That is my theory anyhow...

kjjet · **Posted:** Tue Sep 03, 2013 11:53 am

Mike...My take is rockers get worn due to EGR soot. DONE

As far as broken valves? A few reasons.

1. RPM's! These engines will not handle prolonged high RPM's.
2. Glow plugs break off and cause valve breakage.
3. Ultra Low Sulfur Diesel (ULSD) has very low lubrication and is hard on the valves.

Limit RPM's, Change your glow plugs and run a fuel lubricant is what i do.

That's my :2cents:

KJJET

Theory on causes of broken valves and rockers

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