Rocker Arm Popped off. Causes?

[jefo]

Hey Guys,

I parked my van recently and when I started it a rocker popped out of its spot, leading to the Intake valve not being actuated/staying closed. Blue smoke poured out of the tailpipe as it was sucking air past the rings for combustion instead. I put a new lifter under that rocker and the van ran great and had full compression.

It drove perfect for a few days with full power, and many stops and starts. Then today I parked the van for maybe 20 mins, came out and started it and the same thing happened. This time both the intake and exhaust valve followers came off on cylinder 3, which made a bunch of noise as they bounced around inside. (I'm thinking the same rocker that fell off the first time knocked the exhaust valve out.)

These are PT lifters with the 2 (Pope) washers under them (had them in for 6 months). Would adding another washer under each help? (3 per lifter)

What can cause this??

[GLHS60]

The problem is "usually" a valve seat that has fallen out of place in the cylinder head.
They often pop back in place a couple of times before finally ending up crooked..
As the valve is now stuck partly open, the engine runs rough and a rocker pops out as there is no valve spring pressure holding it in place.
It can be fixed or find another head.

Good Luck !!

Thanks
Randy

[Force Fed Mopar]

Or sticky valves/valve guides. I've seen it happen on cars that sit long enough for the oil to get a little gummy. I have one here now that you can push the valve down, and watch it come back up slow. I can replace the rocker and fire it up and it'll run fine, let it sit a day or so and it'll spit one off again on start-up.

It could possibly be due to whatever oil you are using if you are driving it regular. And what temp the engine runs at. Lots of short trips without fully warming the engine can cause oil gunk issues also.

[Vigo]

Yup, valve guide or seat problem is the most likely thing. Be careful of a loose rocker taking out a cam lobe with damage.

[thedon809]

I'm working on a 3.7 right now that dropped a seat and spit the rocker.

[jefo]

Yea I was sure to take the rockers out when it happened. Made it home on 3 cylinders with both rockers taken out and the fuel injector unplugged on #3.

I have a spare head I will throw on if it turns out to be a dropped seat. Is there any way to confirm without pulling the head? When I pulled the valve cover to put the lifter back on the valve spring never looked compressed or stuck down and was at the same level as the other springs.

I swapped lifters from cyl 3 to cyl 2 just in case its a lifter issue.

[Vigo]

Well, if one of the valves is sitting 'shorter' than the other with both rocker arms off, good chance it's being held open by a dropped seat or stuck guide. Hopefully you will be so lucky as to have the smoking gun right in front of your eyes, but i kind of doubt it. Its possible a leakdown test would show a poor number on a cylinder with a loose seat even if it was sitting mostly in its correct place, but i'm not sure of that either.

[GLHS60]

A guy on Allpar posted a picture of his dropped seat using a bore scope/inspection camera.
It was plain as day.
His popped off several times then would work fine for a while then it finally jammed.
Its happened to some a few times over the years, twice for me!!

Thanks
Randy

[jefo]

I tried to replicate the problem by taking the van for a 30 min drive, parking it in the garage and making sure the cam lobe was pushing down on the valve the rocker fell off last time (marked the cam gear with its location), then starting it 20 mins later. It started up and ran perfect and no rockers popped off.

For now I have all the tools i need to pop the lifter back in the van.

[mopar-tech]

I'd plan on replacing the head in the very near future.

[jefo]

You guys were right! Turned out the head was cracked behind the seat allowing it to drop. New head is on. Thanks!

[player1up]

Sweet, Thanks for posting the cause. Lots of posts go unanswered and are frustrating for folks with the same issue to search and read only to find that the fix was never confirmed.