So last Thursday I managed to over rev my truck by leaving the OD off when I got on it. The truck immediately died mid drive and would not start. After getting it back home and running a compression test, cylinders 1-3 were dead. I then followed by running a leakdown, where the loss of compression was obviously coming from the valves. After pulling the timing cover to confirm timing wasn't lost, I found both crank and cam gears in perfect condition... keyways still in place..
So, valves did float... my question to anyone here is, how likely is it the pistons were damaged from this? Has anyone else had this happen? I'm pulling the head this weekend, and am a little scared that I might be in this further than just a valve job....:confused013:
Anything is possible.. but there shouldn't be anything much more than a ding on the top of the piston.. might be able to just cut any nicks off with a wood chisel.. Only way to tell for sure is to take it off, which you need to anyhow.. I'd probably want to replace the pushrods or inspect them all very closely.. they take a beating when that happens.
Yeah, I know... lol I'm just looking for any possibility of good news at this point. But yes, I truly wont know if any damage was done to this pistons till this weekend, but I'm trying to stay optimistic
But I have already pulled cylinder 1-4's pushrods considering the rest are under the cowl, and so far all are excellent.. As for rpm, I want to say 3800-4k... with the tune I have the boost is around 40... so I know that didn't help matters.
Couldn't drive home, the truck died on the side of the road with a dead (no compression) crank.. All the damage was done instantly. whether or not that was hard enough or long enough (2-3 seconds)to cause damage, I don't know... Just curious if anyone has had a similar situation, if not actually busted a piston from valves on these motors...
Oh, the pistons have eyebrows in them for sure. Whether it hurt them will take removal and examination. Hit it hard enough to bend the valves, definitely would worry about pistons.
Over rev at 4000rpm? I would guess someting else went wrong. Pull the rockers and look at the tops of the valve springs and see if there all level....my guess dropped a valve seat....just a gut feeling
All the rockers are pulled... I just went out now and double checked; no look of any valves bent or not level... looking from up top that is. As I said, I am 100% positive they are bent considering when I performed the leakdown, all the air came out the intake and the exhaust with all rockers off. And considering cylinders 1-3 are all leaking... as soon as I got to cyl 3, it seemed pretty clear the rest of the cylinders are the same. The truck has a no compression crank.. feels like a gasser that has all the plugs removed for a compression test
i didnt have any issues gettng my head bolts out. i wish i could remember what i did to get them out, but just play around with them and you should get them out.
Lifting the cab isn't a HUGE deal, though I avoid it whenever I can... Undo all the cab mounts except for the rearmost ones, and jack up the front from both sides, should be able to get a couple inches of extra clearance on the cowl before your cab touches the box.. Put pieces of 2x4 between the framerail and cab to hold it.
sweet, that's definitely a relief. Im working on that pain in the heater hose bracket that mounts to the exhaust manifold stud, and im ready to pull the head off. Thank you guys for the info... much appreciated.
40psi and 4000rpm thats not really a over rev but stranger things have happened. Plenty of stock trucks turn 4000rpms. High boost with stock springs is what causes ptv. I would pull the oil filter or drain some oil first before pulling the head. Look for debris Either way keep digging and look the pistons over good. Good luck and yes it sucks man!
You've got everything unbolted, and are going to pull the head off anyhow, so once that's off we'll know a lot more... Perhaps the valves burnt? you'd think that would show up on the exhaust side far before the intake side though.
Over 50 psi or over 3500 rpms with stock springs equals valves touching the pistons. High boost and high rpms on stock springs equal bent valves and possible piston damage. Will have some noice mark sin the piston that will be hot spots.
Be very careful pulling that head. It weighs something like 4,000 pounds or at least it sure felt like that! Use a cherry picker. I didn't and I left a portion of my manhood on the ground below the bumper. When you go back be careful that when set down it goes straight down.
I will say this, pulling the front cab mounting bolts under the head lights, front of the cab, middle of cab and loosening the rears then jacking the cab up just two inches will make a world of difference in the ease of the job. Just my 2 centavos!
5.9 Cummins head being heavy? Try a dt466 head by hand by yourself without removing the head studs. But anyhow, I don't see how he floated the valves at 4k rpm and 40psi and firepunk did their 5200rpm HPTUNERS dyno testing on a bone stock 3rd gen, but I guess stranger things have happened.
So, some info towards this ordeal.... Got the head off this morning. Found the turbo was the culprit behind this whole mess. So the other day when I pulled the intake I found the turbo was grenaded. I honestly didn't think much of it, figured the valves floated and fluttered the turbo causing opposing pressures from the exhaust and charge sides to conflict one another. Anyway, pulled the head this morning... found NO indication that any contact was made in all 6 cylinders between valves and pistons... I did see that there is metallic bits in between the valves. So long story short, turbo grenaded, debris got into intake leaving valves open. And luckily, no scoring or damage has been found on any of the cylinder walls. So tomorrow I get to pull valves and see if I can clean the seats.... hopefully the bits of turbo (aluminum) didn't damage the seats or valves. Crossing fingers.. otherwise looks like a complete valve job.
Just wanted to thank everyone for the info... especially when it came to the head bolt clearance. bolts came out flawlessly, no clearance issues
Grunt has a point.. you should at least get the valves lapped... yeah, it's just aluminum that went through them, but it would be peace of mind, and while they're at it, check it for level, may need to take a couple thou off it... Damn, might as well port it while you're in it!.. and put a cam in.. yeah, it just doesn't end!
Time for a new CAC, you'll never get all that finely ground aluminum chunks and powder out of it.
Just cause more headaches in the future. Remember, much of it will end up in the crankcase and then the bearings after it has SEX with your rings. Less than 30 micron passes right through the oil filter. Truck will have some weird oil analysis numbers, not something I would run or buy.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Cummins Diesel Forum
8.8M posts
379.2K members
Since 2005
A forum community dedicated to all things Cummins Diesel! Originally founded for owners and enthusiasts of Cummins powered Dodge pickups, the Cummins Forum has expanded to include ALL Cummins Engine applications! Come join the discussion about reviews, drivetrain swaps, turbos, modifications, classifieds, builds, troubleshooting, maintenance, and more!