Theory on causes of broken valves and rockers

MRausch82 · **Posted:** Tue Sep 03, 2013 2:07 pm

kjjet wrote:

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

I agree on these items. I still think that when rockers are failing, are worn, or are otherwise working inefficiently, there is a higher build up of carbon in the combustion chambers of the said "problem" cylinders, leading to more valvetrain wear, overheating of valves, sticking of valves, etc. Hence the valve eventually fails catastrophically.

kjjet · **Posted:** Tue Sep 03, 2013 2:32 pm

Aggred

Sir Sam · **Posted:** Fri Sep 06, 2013 1:12 am

You know I was thinking about this tonight.

Again I find it all very confusing how we have these "sudden failure" cases.

I still cannot wrap my head around how it gets so bad so quick. I see the egr crapola causing wear, but that step change still confuses me.

kjjet · **Posted:** Fri Sep 06, 2013 1:42 pm

Sir Sam wrote:

You know I was thinking about this tonight.

Again I find it all very confusing how we have these "sudden failure" cases.

I still cannot wrap my head around how it gets so bad so quick. I see the egr crapola causing wear, but that step change still confuses me.

I agree, it dose come on quickly. At 94k I got a GDE tune & I thought my Jeep was running the best ever until a rocker broke @ 96k. It was worn down to the point the roller stopped moving and the cam was riding on the sides of the rocker. After replacing all the rockers/ lifters and a exhaust cam it ran even better. If I have the Jeep at the next belt change? I will pull the intake and inspect the rockers. This engine has used only M1 0W-40 since new and do not plan on changing.

racertracer · **Posted:** Sat Sep 07, 2013 11:57 am

I was reading an article on the variation of diesel fuels, as in some diesel blends are very poor in formulations even though the vehicle runs fine.

The author was saying that poor diesel formulations cause excess carbon buildup in the cylinders causing havoc when pieces break off.... and that diesel should be purchased from a trusted supply chain even though doing that is not a guarantee that you will be getting good fuel.

He said a smoky diesel is not good.

If I can find the page.... I'll link it.

hucorey · **Joined:** Tue Mar 06, 2012 4:29 am **Posts:** 378

MRausch82 wrote:

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.

I also own a powerstroke (in my SIG). Has 111k miles on it now and my oil stays very clean up until about the 10k mile mark then it starts to darken but is still somewhat incandescent. Even though a PS will stay clean (7.3L) is due to no EGR and good compression. Mine is still at OEM spec of 400-440psi in each cylinder.
Now, the problem with a 7.3 or 6.0 PS is that its a HEUI system, and they will shear the oil much quicker than anything else out there. Hence the large volume oil pan.

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hucorey · **Joined:** Tue Mar 06, 2012 4:29 am **Posts:** 378

dkenny wrote:

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..

The majority of Cummins owners are tards. They "roll coal" on purpose to look cool and help spool their slow turbo. Rolling coal is what gets extreme tree huggers to apply pressure on more EPA crap. Which makes MPGs worse and non reliable diesel engines as of old.

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

All depends on quality of oil used (synthetic vs dino oil), condition of piston ring seal, and doing a good flush once in awhile.

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

EGR is definitely the bigger culprit of soot in the oil after that, its a low compression issue.

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?

They have cast iron heads.

Turbo over speed also happens on the 6.0L powerstroke as it also has a VGT. Its caused by carbon buildup and not allowing the vanes to collapse while during defuel (over boost or less throttle under hard acceleration)

just some thoughts
-dkenny

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kjjet · **Posted:** Mon Sep 09, 2013 8:40 am

The CRD is one of five diesels i have owned. Prior to the GDE tune and EGR system removal the oil would get black in a day. Now its clean for a few thousand miles. My Mercedes Benz 300 and Volvo oil was black right after you started it. Both of those cars engines went over 200k without blinking. The Germans know how to build diesels!! That's why my newest is A VW TDI. Now with no DPF or EGR. It should go 200k with no issues.

Tinman · **Joined:** Mon Apr 10, 2006 10:45 am **Posts:** 308

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

Change the glow plugs prophetically with the newer ones????

Theory on causes of broken valves and rockers

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