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Broken/Dropped Valves in the VM
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=84171		 Page 1 of 2
Author:  dhenderz [ Sun Mar 06, 2016 8:11 am ]
Post subject:  Broken/Dropped Valves in the VM
Seems it might be time to get a thread started to discuss why the VM seems to randomly (and most distressingly - more often now as the miles are piling up) drop/break valves off. Many of you know that I experienced a broken #3 fwd intake valve. Sotry and pics here: viewtopic.php?f=5&t=83692

Dieselguy (now Jay) has a broken #4 fwd exh. Both appear to have broken at about the same spot. That is - at the end of the stem near the valve head.


So let’s try to go at this logically. Certainly one would logically conclude something had to impact the valve to cause it. But that could only be caused by the piston, with just a few root causes -

1) possible if the timing belt broke or slipped

2) if a glow plug broke and a piece got stuck behind a valve

In my case (and dieselguy's) we know it wasn't #2. So that would mean it has to be #1.

Or ----- are there some other root causes? I haven't posted any numbers, but I did take some measurements of the valve stems out of my old head. The stem diameter is definitely smaller in the area between the end of the guide and the head. Looking closely at the valve it appears as though that taper is intentional and by design. OK, got it - maybe that's not the problem. But I also noticed that same area of the stem has some pretty heavy corrosion, surface pitting and wear marks (will post pics in the next reply). Not sure if this is leading to any clues or root causes, but it is interesting. What is causing this?


I have done some research on generic causes of broken valves. Certainly you find overheating being a logical root cause. Engine overheats, valve stem gets too hot, expands, gets stuck in the guide and gets impacted by the piston. Is this what we are seeing? I found the analysis/discussion on this site rather good: http://www.aa1car.com/library/ar1192.htm

Another interesting root cause was leaking valves (at the seat) due to excessive build up of soot. With the valve leaking you can overheat the stem due to combustion gasses slipping by the valve and increasing the temp of the stem to the point of sticking or embrittlement and ultimately failure.

And the last one I found interesting was again related to excessive soot build up. But in this case the near(er) term cause of failure was the valve being held slightly open and ever so slightly contact by the piston upon each crank rotation. In this case the valve gets impacted very slightly, but takes the impact thousands of time and eventually breaks at the weakest point.

Not sure, lots of data. Little to conclude.

Thoughts?
Author:  dhenderz [ Sun Mar 06, 2016 8:13 am ]
Post subject:  Re: Broken/Dropped Valves in the VM
Pics from my broken valve project.

ImageImageImageImage

Sent from my SM-N920V using Tapatalk
Author:  dirtmover [ Sun Mar 06, 2016 9:09 am ]
Post subject:  Re: Broken/Dropped Valves in the VM
Maybe a chunk of soot breaking away from a caked up intake?
Author:  Hexus [ Sun Mar 06, 2016 9:42 am ]
Post subject:  Re: Broken/Dropped Valves in the VM
Soot, PH Levels due to EGR Re-Introducing NOx, and it's a well-known fact that improperly or poorly engineered EGR valves increase engine wear and contribute to engine durability issues.

The sooner you can disable/remove your EGR, the better off you're going to be. But don't tell the government.
Author:  flash7210 [ Sun Mar 06, 2016 11:21 am ]
Post subject:  Re: Broken/Dropped Valves in the VM
Quote:
1) possible if the timing belt broke or slipped


If this were the case, I would think there would be two broken valves.
Both intake valves open/close at same time.
Both exhaust valves open/close at same time.

Chunk of carbon is possible but hard to prove (where did the chunk go?).

If it were always an intake valve or an exhaust valve, that would be a clear indication of a manufacturing or design flaw. Especially if it were always an exhaust valve (exhaust valves always run hotter than intake)

But, is it always the valves of the rear most cylinders?
That would be a good indicator. If its always the valves of cylinders 3 & 4 and not cylinders 1 & 2 then that would help narrow down the possibilities.
Author:  olypopper [ Sun Mar 06, 2016 12:52 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
In the late 90's we saw quite a few valves on a certain brand of marine engine we service fail. They snapped off just like our VM's are doing. The ultimate root cause for that particular failure was due to faulty valve metallurgy. Most valves are two piece units that are friction welded together. If the friction weld was of poor quality, failure would result. Also, different types of metals don't play well together and can also make for an interesting mix of failures, non of which are pleasing for the end user.
Author:  Mountainman [ Sun Mar 06, 2016 1:06 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
This is interesting, especially since the higher mileage engines tend to get a new head on them, so who's to say how long these valves really do last? I have an almost new head on standby for my daily driver which has a very slow HG leak. I've been waffling between just doing the one for one ARP's, or slapping the newish head on there. With almost 190k miles, maybe I should just throw the newer head on there for insurance. After several, I am really tired of head R&R's on these though :banghead:
I will say, of all of the CRD's out there, it still appears to be pretty rare.

Oh, I have noticed on about half of the engines I open, that there are impact marks from glow plug pieces on the pistons. Since this is so common, maybe the majority of valve failures are from glow plug tips getting smashed in-between piston and valve, and causing slight bends, that eventually manifest into a break :?:
I guess a piece of carbon or glob of EGR goo could do the same thing, even if it got caught at the seat like someone already mentioned :banghead:
Author:  Jay ne Ohio [ Sun Mar 06, 2016 1:17 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
In my case, I don't think it was a timing issue. No broken rockers and only one valve was involved. And it wasn't a glow plug in this case either. The glow plug in #4 was perfect and survived the carnage. The glow plug in #2 is missing it's tip, but no damage can be seen in #2.

Previous owner mentioned in one of his posts that he had to spray lube on the valves and tap them with a hammer to get them unstuck when he was replacing the rockers about 20k miles ago:

dieselguy wrote:
Oh, btw, I haven't updated my profile, I now have 220,000 miles on it, and to bring u up to speed, I bought this jeep with 200,000 on it and the owner had never touched it. It had factory everything, and to make things worse the guy had run conventional 15-40 shell Rotella in it all the time he owned it. He said it was running rough so he took it apart but couldn't figure out anything. First thing I found was the intake ports were so clogged you couldn't even stick a pencil in the silver dollar sized ports. Also about half the rockers were wore slap out, they wouldn't even touch the valve stem. About half the valves I had to drive open with a shop hammer because they had so much gunk and tar junk, but when I drove them open they stayed open. I got a spray bottle and sprayed kerosene around each valve stem every day. Btw, I did not pull head, just intake with cam assembly had been removed when I bought it. After a cpl weeks I walked in my shop and the valves stuck open had closed, but when I hit them with a hammer they stayed.so every day I walked through my shop I sprayed valves with kerosene.


When I first opened this engine up and saw the valve head embedded into the piston, my guess was that the valve got stuck open in the guide and then impacted the piston. Might not have broke the first time. Might have stuck on several occasions and eventually snapped.

But it could also be a metallurgy issue as olypopper mentioned.
Author:  dhenderz [ Sun Mar 06, 2016 3:28 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
I am starting to lean towards sticking valves (in the guide). We know the history of these engines with getting so dirty they destroy rockers, clog up intakes and soot up oil like crazy. With just slow to close valve you are going to start to have contact with the piston, even if just a tiny bit - over and over again. Eventually you are going to fatigue the stem and it is going to fracture. Plus that line of reasoning makes more sense than a sudden large impact because the rockers are supposed to be designed to fail first if a timing belt slips/breaks. But that is not what we are seeing here. Instead whatever/however the piston is contacting the valve must be slight enough that you don't break the rocker.
Author:  rankom [ Sun Mar 06, 2016 6:35 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
thank you D.H for starting this thread , when valve drops the engine is basically done and so expensive to repair again . you are right about sticking valve (not closing fast enough, i did mention it somewhere before , but Olypoper saw this problem long before I'm glad that he jump in , reason for me to support he's ideas is because i worked on fiat cars and lada cars in the 80s made in eastern europe , they had bad quality parts , cams rockers didn't last . I'm not sure if quality control is the problem ., but definitely VM reminds me of them and is very similar to polski fiat and lada cars .
Author:  Mountainman [ Sun Mar 06, 2016 6:38 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
hmm, you might be right (for the rare one that drops a valve), but of the 8 or so (averaging about 140k miles each) that I've had the machine shop work over, only one needed a valve job, and there were no signs of sticky guides. How are the rest of the guides in your trashed head?

The insides of these heads are actually incredibly clean, so any sticking would probably have to be head warpage, or bent stem? I can definitely see the head being warped with the eneveness of the torque. Do you have a machinists strait line/plane, or whatever it is called to see how flat your busted on is?
Author:  rankom [ Sun Mar 06, 2016 7:32 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
olypopper wrote:
In the late 90's we saw quite a few valves on a certain brand of marine engine we service fail. They snapped off just like our VM's are doing. The ultimate root cause for that particular failure was due to faulty valve metallurgy. Most valves are two piece units that are friction welded together. If the friction weld was of poor quality, failure would result. Also, different types of metals don't play well together and can also make for an interesting mix of failures, non of which are pleasing for the end user.



I think this is a very good explanation.
Author:  dhenderz [ Sun Mar 06, 2016 8:39 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
Mountainman wrote:
hmm, you might be right (for the rare one that drops a valve), but of the 8 or so (averaging about 140k miles each) that I've had the machine shop work over, only one needed a valve job, and there were no signs of sticky guides. How are the rest of the guides in your trashed head?

The insides of these heads are actually incredibly clean, so any sticking would probably have to be head warpage, or bent stem? I can definitely see the head being warped with the eneveness of the torque. Do you have a machinists strait line/plane, or whatever it is called to see how flat your busted on is?


Hmm. I did have the shop check the original head because I was planning on reusing it (v. $1800 for a new one from ID). It checked out good (no leaks, cracks or warpage). I ended up not using it because I found that used head for $100. I still have the original head.
Author:  PANHEAD [ Sun Mar 06, 2016 8:56 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
My 139000mi 06 CRD dropped #4 valve after HG repair with rebuilt head from Motori (via Imparts). Head replacement job had 5000 mi.

I found a nice 2006 (driven by little old lady) CRD and swapping all goodies and I'll just sell old one as drivetrain & body
Author:  racertracer [ Sun Mar 06, 2016 9:21 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
Panhead, do you have any pics of the broken valve stem?
Author:  diesel_guy86 [ Mon Mar 07, 2016 4:24 am ]
Post subject:  Re: Broken/Dropped Valves in the VM
We should start a build date list, if its a faulty part, it would have been a batch, and that batch could be isolated down to a couple month timeframe. I have an 05 (unsure of build date right now) with 200,000 miles, 52k of those being at almost 2x stock power with no issues, and 148k of those miles with egr and crankcase vapors. Seems to me to be a bad batch...
Author:  flash7210 [ Mon Mar 07, 2016 10:04 am ]
Post subject:  Re: Broken/Dropped Valves in the VM
diesel_guy86 wrote:
We should start a build date list, if its a faulty part, it would have been a batch, and that batch could be isolated down to a couple month timeframe. I have an 05 (unsure of build date right now) with 200,000 miles, 52k of those being at almost 2x stock power with no issues, and 148k of those miles with egr and crankcase vapors. Seems to me to be a bad batch...


A good idea, but which build date do you want to go by?
The build date of the vehicle?
The build date of the engine?
The date that is stamped on the cylinder head?

My original cylinder head that cracked at 160,000 miles had a 2004 date stamped on it.
The used replacement I got from VMspecialist has a 2007 date stamped on it.
Author:  Dent [ Fri Mar 18, 2016 4:07 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
Shouldn't this be an extensive problem in Europe? These engines has must more use there. Is it common in Europe?
Author:  jws84_02 [ Fri Mar 18, 2016 7:11 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
Dent wrote:
Shouldn't this be an extensive problem in Europe? These engines has must more use there. Is it common in Europe?



Good idea. If it's not a problem over seas then we can almost lean to blaming the egr system and causing excessive wear.
Author:  rankom [ Fri Mar 18, 2016 7:48 pm ]
Post subject:  Re: Broken/Dropped Valves in the VM
well we all know EGR is a bad guy ,,, but Oly did explained his theory about faulty part and quality control , (vw tdi has egr too) did not see valve dropping like this on there engines. one day will find out.
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