D6T C9 valve set

[simonsrplant]

I have a DJG prefix D6T, just changed an injector... Amongst other bits I replaced a bent pushrod and refitted the valve bridges as one had fallen out.
Re checking the valve clearances I need to turn the engine. According to the procedure there is a barring tool hole under a cover on the flywheel housing on the opposite side of the starter...
It's not there. The trans oil cooler is in the way of where it would be. There is also no TDC locking hole.
How can I turn the motor and be sure it's at TDC on 1?
Pull off the starter and use a screwdriver to turn it? Will checking it "on the rock" be accurate enough?
Thanks in advance.

 

[Nige]

According to what I can see for D6T DJG-prefix the Timing Pin installs in a hole on the LH side of the flywheel housing just below the ECM. See below - marked 1.



The recommended Turning Tool is either a 178-8615 or a 350-7549. It is referred to as Tooling C and according to the Service Manual - "Note: Tooling (C) uses the bolts on the front of crankshaft."

 

[kshansen]

Probably not what you want to hear but try looking at this link:
https://parts.cat.com/wcs-static/pdfs/03-Engine_Tools.pdf

Scroll down to about page 257 to 260.

The older engines had the egg shaped hole with the 1/4 inch pipe plug next to it that the timing pin went through into the flywheel. Guess that was too convenient!

If starter is not too hard to remove that would be one way or something on front of crank. To position for valve settings I would go with the "Valve Over Lap" method. On a six cylinder assuming this is the normal 1-5-3-6-2-4 firing order engine. As the exhaust valve closes on #6 and intake just starts to open you are very close to TDC on #1. Next turn till over lap on #2 and set valves on #5, next overlap on #4 and set on #3. And so on for the other three.

Not sure if the overlap positioning would be close enough to do half the valves each time but you may be able to figure out where the timing pin hole is in the flywheel once starter is off.

Any good reason why the push rod bent and the bridge fell out. Does not seem to be a normal thing!

Good luck

 

[simonsrplant]

Bent pushrods and valve bridge fallen off...
Ya. Not normal.
The job was investigate a misfire... Excessively high oil level, (fuel contamination) I figured simple injector...
My theory is the injector leaked fuel into the bore sufficiently enough over X amount of time to hydraulic the one pot when cranked, bending one pushrod. Why the bridge jumped off is a mystery.
Injector and sleeve replaced and briefly test run. Seemed to run evenly immediately, misfire gone.
Still need to set the valves accurately and run her up to temp.
Looks good just now tho.
Thanks for the advise on turning and locking.
Most appreciated.

 

[Scrub Puller]

Yair . . .

simonsrplant

I'm missing something here mate. Could you explain how "hydraulicing" would bend a pushrod?

I just can't get my head around the sequence of events that occurred within the engine . . . to my mind the volume of fluid required to bend a pushrod would have caused a catastrophic failure when it slammed the valve closed on the next revolution.

As I have mentioned on this board before . . . to this day I find it disconcerting to start a machine when I have no control of injection. Once it was mandatory to bump an engine over to check for fuel or water on top of a piston before starting.

On any large marine or stationary engine it was mandatory to bar them over and on several occasions I have had "lockups". Likewise on smaller engines I have seen several ventilated blocks caused by just turning the key.

Not trying to be a smart azz, just curious as I always imagined bent pushrods were just part of the catastrophic failure.

Cheers

 

[simonsrplant]

Scrub,
I really don't have the reason as to why I have a bent pushrod and valve bridge jumped off...
My theory is that enough fuel to prevent the valve opening was in the bore yet not enough to lock the cylinder up...
The valve gear will continue to work... No movement from the valves and something has to give.
Now I may be a way off... But it's the only way I can figure three quarters of the symptoms.
I'm all for listening to anyone else's ideas?

 

[Scrub Puller]

Yair . . .

Gotcha mate, appreciate the reply.

It's a curly one and, like you I am having trouble getting my head around it. Your theory sounds like decent logic . . . strange about the bridge though.

I am sure there are folks on here that can add to this discussion.

Main thing though it appears you have the unit back into production.

Cheers.

 

[kshansen]

Well I had to look at the cam and lifter set-up on a C9, never that deep into one. It is basically the same as a 3406C like we had in our 980Gs.

Well had one of those that bent a push rod twice. First time not real long after a dealer rebuild. They suggested put in new one and see how it runs. So that's what I did. Sounded good after installing new push rod so put back to work. Then a couple weeks latter same skip. Pulled cover and another bent push rod. This time was not able to just lift out the bent one. Just as I touched it it went clickity click down into the oil pan. Long story shorter after getting rod out found the lobe on cam damaged. Then found the reason, the spring clip (467-4243 in a C-9) had broke letting the lifter turn sideways in bore at times and messing up the cam. In our case it also messed up the lifter bore in the block, Cat bought us a new reman short block!

Not saying this is your problem but might be worth taking a good look down into the block near the lifters to see if those clips appear to be in place.

Clip is #1 in this picture:


Like Scrub, I'm not 100% convinced hydro-static lock in cylinder would cause a bent push rod

 

[Delmer]

If a valve sticks open, then the pressure is released and the pushrod will fall to the side of the rocker, and get caught on the edge of the "cup" and bend the pushrod as the piston comes to the top of the exhaust stroke. Never seen this on a running engine, but I've done it at least twice working on junk engines, not Cat though.

 

[Scrub Puller]

Yair . . .

Oh yeh! I'm thinking along the lines of kshansen.

It seems to me something may have got in where it shouldn't and gave some extra lift on that pushrod to bend it and flip the bridge . . . I do not know the engine or if that is a realistic possibility.

I can imagine the scenario suggested by Delmer but on a well maintained "in service" engine I would have thought it unlikely a valve would stick.

Cheers.

 

[GregsHD]

I've encountered bent push rods on two different 3126's, both times the cam follower on an exhaust lobe had failed allowing excess valve lash, the operators fail to hear anything wrong and just seem to turn up their music! Anyway the lash became great enough that the pushrod(s) jumped partially out of the rocker(s) and jammed, bending them. Both times the valve bridges for the offending cylinders had fallen off as well, I think once the pushrod bends and falls out from under the rocker the rocker lifts and hydraulic suction pulls the bridge off the valve stems? Both these engine's required new cams.....

 

[simonsrplant]

Thanks for all the feedback here...
So I think it's fair to say the general consensus is a cam issue in the making...
It's an odd one for sure.
It's running now. If I were to be picky with my work, I'd say it is a little rattlely, thinking the valve set, but I could be being paranoid. I'll keep everyone's points in mind and watch it.
Thanks all.
Most appreciated.

 

[kshansen]

Just had another thought. I know dangerous thing!

Did you take a real good look at the valve springs? Depending on how one broke it might be possible for tension to be good enough most of the time then at some point let the valve hang open just a bit and let the push rod jump out of the follower and get bent. Just something to cause you to loose sleep over!

If you have not been back into do a valve set it would be something to look close at while the valve cover is off.

 

[simonsrplant]

So...
Less than two hundred hours later and I'm back inside in valve cover. Dead miss on number 1, same as last time, only no oil/fuel contamination. One pushrod S shaped and the opposing bridge fallen off.
From what was discussed it seems like I have a cam issue?
Any and all options are greatly appreciated.

 

[simonsrplant]

Assuming the cam is wearing prematurely, is 150 hours sufficient for oil analysis to detect (or prove) an internal failure?

 

[GregsHD]

Assuming the cam is wearing prematurely, is 150 hours sufficient for oil analysis to detect (or prove) an internal failure?

Absolutely, But I would dehead the oil filter and take a look right off the bat.

 

[Nige]

Assuming the cam is wearing prematurely, is 150 hours sufficient for oil analysis to detect (or prove) an internal failure?

From my experience the cam wear is usually of the spalling variety i.e. initially great big lumps of the case-hardened layer falling off, followed by abrasive wear of the core of the camshaft itself which produces a finer metal particle. Incorrect hardening is actually the root cause in most cases. You ought to find traces of metal flakes in the oil filter but if they were really big then maybe they might even be in the suction screen for the oil pump.

Either way there ought to be increased iron in SOS readings, but at 150 hours after an oil & filter change whether the iron levels are high enough to trigger comments on the analysis then your guess is as good as mine.

 

[ETER]

Recently repaired a cam failure on a Mack E7 460...put a dial indicator on the failed cylinder's push tubes (with rockers removed) and barred crank over and measured lift on both int. and exh. lobes...found a lobe about 100 thou (+/-) low at full lift point. Did not detect this lobe failure when on the inner base (valves set point). Also, you might be able to pull up with a magnet on each lifter to check for "H" style retainer or other lifter retaining clip for positioning?
Regards, Bob

 

[simonsrplant]

Thanks gentlemen...
I poked my head back inside and the retaining clips are all intact and ok, since the head is still on I cannot remove the offending lifter for inspection.
Question for the knowledgeable whilst it is still in near running condition:
Can a person do a compression test on the engine or contribution test? Not relating to the fault but to give a further insight into the motor when considering routes of repair.

 

[Cmark]

Are you sure you can't get the lifters out? I replaced a timing case on a C9 a couple of years ago which involved removing the camshaft and I know for a fact that I didn't remove the head to get the lifters out.

I don't see why you couldn't do a compression test if you made up a dummy injector but with the automated cylinder cutout tests, I've never found a need to do one.

Edit:
I've just looked at SIS and it does say to remove the head first, but I stand by my earlier remark. SIS could be wrong??