Broken Rocker Arm

blown99 · March 10, 2010

UPS dropped off a package car that supposedly needed an egr cooler because it was steaming out the tailpipe. So I start to check it out and immediately notice and uneven cranking condition. I remove the egr valve and find lots of coolant in the intake, I run the engine and decide it is going to get an oil cooler too. Perform a relative compression test and find #5 to come up with 0. I am guessing I have a bent rod. I give the customer the worst case scenario of it possibly having a bent rod. Remove the valve cover and find #5 intake rocker arm broken, push rod has a slight bow, so now I figure that the cylinder was filled with coolant, someone cranked it over, the intake valves try to open but the wall of coolant pushes back and causes the rocker arm to break. I go in with a scope and inspect only to find the piston appears to come all the way up, no signs of a bent rod. The manager wants me to slap a rocker arm in and send it but we were slow and I gave the customer a worst case scenario so I pulled the head. Everything looked good. Leaked checked the valves - ok, recehcekd the piston-ok, no coolant in the cylinder. Found both heads to have been replaced six months ago by another dealer and had the updated dowl pins etc. So since we are slow I decided I would try out my new valve spring compressor and found one of the #5 intake valves to be frozen in the guide. I wacked this thing with a 2 lb hammer and can't get it to budge. If I listened to the boss this thing would have been a mess, if I was busy I would have never pulled the valve springs and probably would have stuffed the head on and been screwed. I wonder how long the engine has had a skip from the dead #5? This is the first frozen valve I have seen, but have heard about it numerous times on this site in new trucks that have sat on the lot for a while. This truck gets run hard everyday. (has 20,000hrs on it). Just thought I would share my almost missed diag.

Keith Browning · March 10, 2010

The seized valve phenomenon is something I have seen on all Power Stoke engines - four 7.3L engines, two 6.0L engines and one 6.4L engine. Out of those I only had one where I could not get the valve to move and come out which was on a 7.3L. The rest were removed and replaced with new valves and I honed the valve guides with a transmission valve body hone I bought just for this purpose. It works fantastic and I have never had any of those engines return.

Incidentally only two of those engines were brand spanking new, one a 7.3L came off the car carrier popping out of the intake and the last was a 6.4L that was on our lot a month or so. As a matter of fact that truck was sold to an overhead door company and was parked outside my shop a week or two ago as they repaired one of our shop doors.

jimmy57 · March 10, 2010

Blown99, When the stuck valve was removed from this head, what did you find? Can you tell what stuck it?

Keith, the same question to you, did you see anything you could attribute the stuck valves to?

jimmy57 · March 10, 2010

Blown99, When the stuck valve was removed from this head, what did you find? Can you tell what stuck it?

Keith, the same question to you, did you see anything you could attribute the stuck valves to?

Keith Browning · March 10, 2010

Rust. On all of them the stems were dry and had a dark rusty layer of crud in the guides. It is actually surprising to see just how little oil is on the valve stems of the good valves... and I mean they really seem dry!

cbriggs · March 10, 2010

Yeah, i had a 6.4 with 3 exhaust valves seized, one bad enough to break the rocker. Truck was a specially ordered 550, went in service 20ish days after build, so it didnt sit on the lot. Had 20000km on it when it let go. All i found was rust and corrosion builup in all guides on left head, right hand side was ok.

Aaron · March 10, 2010

Yeah, i had a 6.4 with 3 exhaust valves seized, one bad enough to break the rocker. Truck was a specially ordered 550, went in service 20ish days after build, so it didnt sit on the lot. Had 20000km on it when it let go. All i found was rust and corrosion builup in all guides on left head, right hand side was ok.

blown99 · March 11, 2010

I put a reman head on it. I was unable to get the valve out. I heated the guide and it still would not budge even with my persuader (5lber) . Customer wanted a replacement head so that is what it got. There was no visible rust or excessive carbon when looking into the ports. No overheat codes, but there were codes for low coolant level caused by the egr cooler leaking. I did find the engine to run a little warmer than normal once it was back together. These usually run 192. This one was running 198-201. Found the radiator to have a partially plugged core but of course management doesn't want to say anything to the customer because they have spent enough money already. These heads are 6mos old and the truck is run everyday except Sundays.

LARRY BRUDZYNSKI · March 11, 2010

You better story that on the R/O and CYA. This will come back and bite you in the ass if you don't. How about replacing a rad for free and looking like a idiot if you don't.

blown99 · March 11, 2010

You can bet that I write everything down. When I first started in this business I had an engine fail that I rebuilt, 3406B cat. The cam gear was no good, showed the boss, he said to reinstall it. I documented everything. About 2 weeks later it came in with all the push tubes bent. Pulled it apart, found the cam gear had spun on the cam. The fingers pointed, all the old guys laughed. In the end, I had the final laugh, called up the corporate office and had my papers faxed over to the big boss with my documentation. I also now, photo copy stuff like this. I've had stuff get "lost" and info scribbled out etc. You just have to remember that nobody looks out for you, except you.