Engine/Transmission (1998.5 - 2002) Comments on Cummins Overrev?

[Doc Tinker]

Since the attachment size has meet a size requirement, it is too small to really see what's there. I'll post a better picture when my ISP let's me upload to my space.



I was under the impression that all the valves were affected, but it's only the ones in hole #2.



That tells me something entirely different happened.



It looks to me like the head is original, with rust on the welch plugs, etc. I'm beginning to think that the mechanic either had the head repaired after the piston slammed it or he might have just popped in a set of new valves and pushrods, etc. I think the head should have been replaced.



Doc

 

[Bad340fish]

Oops

He could have grabbed 2nd instead of 4th in a hurrty to get on the highway???



I see what you saying about the valves being 90* to the piston. But I imagine that played a key part in the broken rocker arm you showed in the above pic.



Its also possible that a valve siezed in the guide do to overheating, lack of oil changes, or just plain lack of oil.



Whats funny is... why didn't the truck start on 5 cylinders?? Hell I drove my Barracuda home from the track with 3 bent valves one night.

 

[Doc Tinker]

Evidently both the intake and the exhaust push rods are bent, that means they were both open when/if the piston hit them.



Why only those two?



Another thing to consider, this engine uses timing gears. There is no way that a good set of gears will allow the cam lobes to be up when the piston is up. Now... if one of the gears blew, then that would explain why the truck wouldn't start and the cam lobes were up at the same time as the piston.



Does this sound logical? Did D-C check the timing gears? Did D-C check the computer and saw the over-rev signal and stop looking after that? Could a timing gear failure cause the over-rev signal?



A blown timing gear can cause a low compression situation that will allow the engine to free spin when you try to start it. If the client tried to tow start it after it quit running, isn't it possible the free spinning engine would reach over-rev speeds after the engine quit. Therefore the client wasn't responsible?



I say D-C should pull the front cover to see what's going on in there, before making conclusions.



Doc

 

[bholcomb]

Doc,



I don't know if you noticed it when you read that service bulletin, but you were supposed to run the engine at 35,000 rpm. That's right, for two minutes to warm it up. I wonder if that is an official typo, or just one on Dave's website?



I just looked in the service manual and 12v cam is keyed to the camshaft itself. The gear must be heated to install. It doesn't seem like this would slip, but I guess it is possible. I agree with Bad340fish, it seems like it would still run if this was the only mechanical problem. I've run an engine with a broken valve spring for about 100miles.



One thing about our engines is the head doesn't really have much combustion chamber, and the piston has a big dish. The valve will hit the piston on a 12v, and I assume it does on the 24v too. We use the valves as a piston stop we timing the injector pump. The service manual says to adjust the valve to zero lash plus five turns. I am almost certain the ISB has hydraulic lifters, that is why they get away with the 100k adjustments. Now this may be a stupid idea, but what if the mechanic happened to adjust that set of valves a little on the tight side. Is this the cylinder that the piston failed? That would cause lower power due to lower compression (valves open longer) and also close the gap with the piston. Then the valves should only need to float slightly to contact the piston. If you look at your old text book four stroke engine cycle, the exhaust valve should get hit first because it is down as the piston is coming up (exhaust stroke). Does this sound reasonable?



Brian

 

[MidwestMotorman]

should have started

I agree that the engine should have started with only one bad cylinder. If the timing gear had a problem or ate a gear, wouldn't it damage more than one cylinder's pushrods or valves? Especially if it started and ran again after doing damage?



Mistake one was probably the "shade tree" mechanic. I was told by a D-C mechanic that they were not allowed to internally touch a Cummins engine, and that they had to refer it to a Cummins mechanic.



Another point, does anyone see wrench or socket marks on any of the bolts of the engine or head? Something is definitely wrong here and I am afraid the poor owner is getting the shaft.



Back to the beginning, has anyone heard of a piston breaking BEFORE any valve train problem? Maybe only with a thrown rod or something entering the chamber. On engines with chain driven cams, the chain can break and cause damage like this. But a gear driven one would have to break a gear or tooth (and maybe a few) for this to happen. I think the cummins would keep running (until shut off) unless it lost all ability to turn the cam or the pump timing was greatly off because of it.



How would you bend the pushrod and break the rocker arm? I think the push rod would bend and give the valve the clearance before the arm broke.



The overrev code is the perplexing part. It may be that the ECM programming may throw this code because of the faulty programming in the first place? Is this circuit related to the circuit causing the safety recall in the faulty programming?



I guess there are multiple issues/problems here that may be interconnected.

 

[Dave Fritz]

"but you were supposed to run the engine at 35,000 rpm. I wonder if that is an official typo, or just one on Dave's website? "



bholcomb ,



Can't blame that one on Cummins. I looked at the original and it says 3500.



Dave

 

[B.G. Smith]

Overrev

I guess if DC has the truck we may never know what really happened. What if the top of the piston came off at say the third ring groove, the "shadetree" missed this and just patched the head. The top of the piston would slam into the valves on the exhaust stroke each time as the exhaust valves would be open and the intake would be starting to open. The first damage would be the pushrods, eventually breaking the crossheads that connect the two intake and two exhaust valves in each cylinder. It looks like in the picture that the rocker arms are still in place. He may also have adjusted the valve clearance wrong causing some of the valves to be partialy open causing the loss of power. Maybe the Oklahoma mechanic tried to push/pull start the truck? If he did and put it into first gear it would only have to be going 15 or so miles per hour to cause the overrev. I would think that if you tried to push/pull start a healthy truck and put it into low gear, the rear wheels would just slide but evidently this one didn't have enough compression to set off the fuel when injected. I don't think the overrev (if it actually happened) did the damage since only one cylinder appears to be involved. If the valve clearance could be checked and then the head removed, a lot of the mystery could be resolved. bg

 

[Alan Reagan]

My memory is getting old on this one, but the lawyer posted on the SETDR website



http://www.setdr.org/bm/general_diesel/messages/10500.shtml#0



about this and indicated at that time that the rod had broken causing the valve/pushrod damage. He also stated that the mechanic had removed the head, made the repair an that the truck was then driven back to Oklahoma or somewhere and wouldn't run but about 40 mph during the trip. My response was that a little more than the head should have been removed because of possible cylinder wall scoring from the rod as the engine continued rotating. But anyway, the truck was driven home and when checked with a scan tool, the owner was told the engine had been overrevved 1100 rpms. The lawyer said that when the truck wouldn't start, there was an attempt to pull start it down a dirt road and wanted to know if an overrev was possible doing that. Maybe. This is an interesting problem no doubt. Just wanted to shed some light on earlier posts from another website about this.

 

[jmeehan]

Is there any chance the monkey in Co. got into the timing gears and messed up? Why wouldn't she run over 40 (and how long does it take to get from Co. to Ok. at 40)?

I haven't been into one of these engines yet but if the cam timing was off a tooth or so (if that's possible) it could lead to all sorts of havic on a minor over rev. Not the least of which would be the cam sensor reading WAY off!

Just some thoughts off the top of my head.

 

[Ram_Kowboy]

Doc you touched on a scenerio that I am thinking thru in my head.



What if the engine jumped time? i. e. chain/gear. Easy enough to do when jump starting. Then you have a piston strike. That would also explain the broken rockers. It's been my experience (albeit minor ) that a floated engine valve strike will not break rockers .



Thoughts anyone?

 

[Alan Reagan]

Ram Kowboy, you have a good point. If you go back and read that entire link I sent from the SETDR website, I believe it's the post by anonymous (who turns out to be Justin the lawyer) that talks about the broke rod. When that happened, I image timing could have jumped along with some other bad things. If all the mechanic did was pull the head ... ... ... well, uhhhhhh, duhhhhh.

 

[Doc Tinker]

Closeup

My ISP is still screwing up, so I'll post a closeup of the second picture. Notice the "old" look of the head. Obviously the head wasn't boiled. I'd guess that the head wasn't sent out to a machine shop to be inspected or magnafuxed for damage from the head hitting it, or new valve guides installed, which would be a must, if the valves were bent. Maybe the mechanic just stuck a couple of new valves in there and said "good enough for who it's for".



I still agree that the head should have been replaced, especially if the owner requested it. I think D-C left themselves wide open on that call.

 

[rob10858]

you guys know a lot more about ctds than i do, but i will offer this bit of wisdom. the only way to over rev a series b cummins is deaccelerating, not over accelerating. [were talking about a proven powerplant, and i cannot beleive that that missing a gear and overreving hasnt happened in all applications and is not considered in the development stages] as soon as this happens, anyone with common sense shifts up and then cusses themselves out for their mistake. i was taught when i first started driving dodge ctds that engine could take everything on a pull, but couldnt govern itself [loaded] downhill. before our 2001 3500 6 speeds we had to put the heavier valve springs, throttle return springs, etc to try to keep the engine from overrev on long grades. with our new trucks the ex brakes used factory springs all around and do a great job of holding back rpms and deaccelerating [mopar jacobsen] the others would shut down at high revs, and they all said it was because the springs werent heavy enough. well, i dont care who mnfs the transmission, eng and brakes, but i will say that the "factory" set up has been flawless for our new trucks . by the way, the same guys always said use the same gear going down a grade that you would use going up. well with these new trucks, thats been a myth. i can engage my e brake on the crest of a 7 per cent in 6th, and touch the brakes 3 or 4 times, while i sure dont go up in that gear. if i get anywhere close to the 2900, i apply the brakes, engage the e brake, and then look at the scenery on the way down. beautiful.

 

[MidwestMotorman]

what if...

Is it possible to remove the piston from the lower end? Is there enough clearance to get it by the crank? What if the mechanic dropped the piston/broken rod out of the bottom and just looked up in the hole and did not catch the bent valves? He might have replaced a couple pushrods and missed the bent valves.



A pair of bent valves would let lots of pressure escape from the intake side (when the turbo is pressurizing it) and would let it flow back from the exhaust side at low rpm. Not to mention the bind than would rebend the pushrods or let the valve hit the piston.



I think if the Colorado mechanic needed a metric socket to remove the head, then he would not have torn into the front to mess with any timing. Any competant mechanic would have a set of metric sockets. How would he tear down the rest of the engine without a metric socket set?



Couldn't there be damage to the injector as well with a piston or parts hitting the head?

 

[Doc Tinker]

I was wonding the same thing, nathanbush. It might be possible to drop the piston out the bottom, but getting it back in, compressing the rings, would be a problem. I've been mulling over the idea that the mechanic had figured a short-cut and done just that.



I'd think that the injector should have been replaced, if the piston hit the head. bholcomb says the pistons have a dish. I haven't looked at a piston from the ISB, so I assume he means it is concaved. If it's concaved, then the injector probably wasn't damaged, but it should have been tested to be sure.



The trouble with D-C dealers, most of them don't hire truck mechanics to work on these Cummins. They are usually retrained auto mechanics and their experience is lacking, even if they have some of the best training. Another thing that I've noticed is that the dealers require the diesel mechanics to work on cars and I doubt they get enough hands on to thoroughly learn the diesels.



I think I would have taken the truck to Cummins for the engine work, rather than take the chance at a D-C dealer.



Doc

 

[Doc Tinker]

One thing that just occured to me: the oil pan on the ISB is very close to the crossmember and you'd have to pull the engine, or atleast lift the engine to get it out. Then, if you just lifted the engine and were able to pull the piston out from the bottom and #2 piston was the one that went bad, you'd have to work around the crossmember to get the piston out and back in.





I wonder if there is any evidence that the oil pan was removed.



Doc

 

[MidwestMotorman]

Evidence...

Doc



There should be evidence of the pan removed. If there was not, then how would the mechanic know a rod was thrown? It would have to be fixed by removing the pan. The question is, was all the work done from the bottom?



In an earlier post, I had talked about a conversation about D-C mechanics. I had my 99 in for some service work at my local no-star dealership. I asked the mechanic about some internal stuff about the Cummins, and he replied that Chrysler would not let them touch the Cummins internally. He said the work had to go to a Cummins shop, and all that the dealership could do was touch the external stuff. Do you suppose this applies to a motor under 100ooo miles or that only five-star dealers are the ones with trained Cummins mechanics?



Back to the problem. An inexperienced mechanic could easily have made lots of mistakes that would cause a loss of power. Maybe the boost hoses were left slightly loose? Who knows? I am glad that this situation is not happening to me.

 

[Doc Tinker]

I got these messages in my email today. They tend to muddy the waters on this issue, but maybe we can see something interesting in this information.



"I reviewed the repair orders from the Colorado repair job. They were somewhat cryptic, but appeared to say the 'rear piston is slapping the cylinder. replace short block, no need to remove transmission. ' Does this help or create more confusion? I've been keeping up on the thread, very informative. You were correct, this site is, by far, the best one of the several that I visited. "



"Some other documents I have received from the Okla. mechanic. They say the fuel injector pump is bad and have replaced it. They did this before the(y) 'noticed' the floated valves. They also said the turbo was bad. the ECM codes, as per the mechanic were CKP CRANK PO336 1 (since set) crank overspeed po219, 1 (since set), decreased performance engine hot, po217, 70 (since set. ) this is exactly what he wrote on a piece of paper. "

 

[Doc Tinker]

I'm going to mull over this information for a while. Go ahead, guys, and make comments if you wish.



Doc

 

[MidwestMotorman]

I bet...

I bet the CO mechanic meant "rear of piston is slapping the cylinder head". Who would change the shortblock only? This would prove the mechanic did not know the head had troubles. These head troubles would have been in his notes.



So... was the rod thrown, fixed (who knows how well, or if at all)?



If the turbo and injector pump were bad, that would be the loss of power and no start. Is it possible that the turbo threw something (or sucked in a silencer ring) into the head and cylinder, damaging everything?



Did the #2 cylinder, with no compression, have severe fuel wash on the trip to OK? Fuel wash would thin the oil, and hurt the turbo and bearings. The motor running hot would further aggravate the poor lubing of the engine. Did this trash the turbo?



I have no doubt that the whole motor is trashed. Time to get a new one at whose expense? The mechanic that botched the job and did not get to finish? The disgruntled owner who did not let the mechanic finish and who further aggravated the engine's troubles on the way to Oklahoma? The dealer who sold the truck, probably with a bad rod bearing?



Time will only tell, but the lawers will be the only ones winning this battle.