[Shiny]

Son's 2010 Grand Cherokee V6 died on him - 3.7l? with ~120K miles, maintained well.

Garage initially diagnosed as cam position sensor, replaced for $250. This failed to fix it completely (still misfired) and they then told him no compression in one cylinder.

He agreed to another $300 to pull valve cover and find out why.

Today is told there is a broken rocker arm, causing intake valve to stick open.

They recommended pulling heads and sending off for inspection/repair.

What would cause a broken rocker arm? Why would the valve stick open?

Why would it be necessary to pull the heads? Wouldn't the diagnosis and repair be possible with heads in place?

I know nothing about this and am a long ways away but I think it is an overhead cam engine.

Thoughts, experience, suggestions are welcomed.

[Shiny]

The plot thickens...seems that cylinder is carboned up to the point of messing up the valve motion, which in turn overstressed the rocker arm?

Per mechanic:

"Remove Valve Cover for Continued Diagnostic 297.18
After removing valve cover and inspecting valve train found
that the rocker arm on cylinder 2 intake valve has fallen off.
This is caused by intake valve being stuck open and not
keeping adequate pressure on rocker arm. Used a scope
to look inside cylinder and saw that carbon build up around
valve opening is the cause of valve not seating properly.
Recommend remove both heads and have them sent out
to be rebuilt. Even left bank cylinder head doesn't seem to
be displaying same symptoms it is advised to rebuild both
at same time so that problem doesn't happen to left bank
valve train and parts wear evenly."

Would this be caused by oil leaking down the valve guide?

Ugh.

[Sirrotica]

https://www.youtube.com/watch?v=aZU0OzhsgyQ

YouTube video pretty well describes your problem. It's fairly common on all the 3.7, 4.7, 5.7 Chrysler products.

Look on YouTube for other videos.

[mgarblik]

This is a pretty common problem on this engine family as already mentioned. Not one of Chrysler shining star engines for sure. Generally, when one comes to me with the rocker arm off, the engine is so sludged-up or has so much other damage, it isn't worth repairing. However, I have had a few that were well taken care of and I simply popped the rocker arm back on with a little pry bar and cleaned and de-carbonized the engine with engine flush and fuel injector cleaner concentrate. This is the super strong cleaner that the engine runs off of the can until it dies. The pour in the tank type may work but would need to be added to each of 4-6 tanks of fuel. Of course, the heads could be removed, cleaned and a valve job performed. At my shop, this is about a 3K repair on an OHC engine like that. It's a big miserable job. I would be inclined to replace the engine with a low mileage used one vs doing a valve job. My daughter had a Jeep liberty with that engine. About every 6 months, for no reason, a rocker would fall off or it would break a valve spring. After a couple years of that non-sense, I got rid of it. I like Jeeps, just not that engine series, 3.7-4.7. BTW, if the rocker arm is physically broken, that could be from a valve seat failure and the seat dropping out of the head. They should be able to verify that with a bore scope. That was a big issue up to 2008. By that model year, they had the seat issue more or less taken care of. Any type of overheating of any kind will kill these engines. Then all bets are off. They will drop seats and have all kinds of cam/valvetrain issues if the gauge has ever ventured past the 3/4 line. Pretty flimsy top end.

[Shiny]

Thanks, Brad! Greatly appreciate the quick reply and knowledge.

Good to know his mechanic is interpreting well but unfortunate to know it is somewhat common.

Will see how it plays out but seems he will need his heads rebuilt and/or exchanged.

I looked online and see one company gets $300 per head exchange, which sounds pretty reasonable to me:

https://www.shop.headsonly.com/JEEP-...JEEP-37-V6.htm

[Shiny]

Thank you too mgarblik. You must have posted as I was replying to Scirrotica.

Has been a good vehicle, is in good shape, and I know he still owes money on it so this will be painful for him.

This must have hit a lot of V8s too then?

I shared your experience with him. He can discuss the merits of trying to run Seafoam or something like it to get rid of the carbon and cross his fingers but I don't think the shop would feel good about sending him off that way. They have been good for him and he trusts them.

Mike

[Sirrotica]

Yes the engine families that end in .7 all have the same type of problems with valve train.

I like Jeeps and have driven them for years, as did my father, but I don't want to buy anything later than 02 because that's when they started using the engines with the OHC that is prone to failure. I've transplanted 4 Pontiac V8s in my Jeeps previously, but because the BCM/ECM (body control module, electronic control module) interact with the engine in the newer Jeeps, doing a Pontiac transplant would be a pretty major undertaking to keep the electronics working for the body functions (radio, lights, power windows, cruise, etc.)

Anyway the .7 engines are problematic when neglected, or get some mileage on them. The latest thing I've seen is an aftermarket solid lash adjuster to eliminate the hydraulic lash adjusters. It's a fairly new aftermarket solution for at least part of the problem.

[Shiny]

We had an earlier V8 Grand Cherokee (1999?) my son drove, was a total PITA with un-curable suspension issues, transfer case failure, CV joints, etc...

My son liked driving it though and when he needed a new vehicle, he had Jeep brain. I get it and don't dislike them, just personally have never had good luck with Chrysler products.

This one my son bought is nice and has been fairly reliable until now.

We recently moved to an off-road playground and are totally surrounded by Jeeps. Would be fun to have one but is not on my priority list right now.

[Shiny]

Quote for the repair was inline with mgarblik's estimate.

It included $700 for a timing chain set. Why so expensive and is this within expectation?

Yikes.

[Lightfoot]

Shiny,
After watching this video and reading down through some of the comments, I wondered if your son's engine could have been affected mostly by the 'lifters' (lash adjusters) being sluggish or sticky.

https://www.youtube.com/watch?v=ksrDE2zjC34

Here's a couple of comments that gave me food for thought;

I've "fixed" 2 of the Chrysler ".7" engines with the rocker arm issue thanks to a mechanic who posted on this quite a few years ago. The mechanic stated he had repaired the same 3.7 three different times with new rocker arms and lash adjusters on the same cylinder(s). Upon the 3rd failure of the new parts, he decided to do some precise measuring. He made the determination that if he "shimmed" the lash adjuster with an 86 thousands shim, there should no longer be enough gap to allow the rocker to fall out and still be enough clearance for everything to play nice. I had a neighbor who's mechanic said she needed a new engine in her Liberty with a 3.7 and quoted her $3500. I took a look at it and found it spit 2 rockers. I purchased 2 stainless steel washers and placed them under the new lash adjusters on the offending cylinders. That was in 2012(?). It hasn't spit a rocker since. I recently purchased a Jeep GC with a 4.7 with 126,000 miles on it that was running on 6 cyl. I bought 2 new lash adjusters and a box of 3/16 flat washers. I put 2 flat washers under each of the 2 new VLA's (aprrox. 75 thousands) and, knock on wood 350 miles and 2 weeks later, all is well. To put everything back together I just put a wire tie on the timing chain and cam sprocket loosened the cam retainer bolts, lifted the cam slightly, put the rockers on and torqued the cam back down to spec following the proper sequence. The job took about 3-4 hrs for the passenger side on a hot engine including a trip to the parts store. I would buy or repair these things all day long. It's not a bad job. I also own another 4.7 with 260,000 miles on it. I've used quality synthetic oil in it since the 2nd or 3rd oil change. Once again, knock on wood, never had a problem with it.

The problem is not the lifter . The small oil port that goes where the lifter rest in is plugged and not giving the lifter enough oil . I had the same problem changed all the lifters and the same rocker arms would fall off in a matter of days . I got tired of putting them back on just to have them fall off again . What I did was pull the lifter out , start the motor for just a second enough to blow oil out where the lifter goes doing one at a time . Put the lifters and rocker arm back on and never had a problem again . Just make sure you do one at a time so you have plenty of oil pressure.
Whatever reason they plug they do plug and my way is a quick cheap fix that works.

Concerning the mechanic's evaluation in Post #2:
Maybe the carbon around the valve seat was caused by poor valve operation from the lash adjusters being gummed up. Not the other way around.
Just a thought.

In any case, it seems these valve trains are extra sensitive to improper oil viscosity and/or prolonged oil change intervals.

[Shiny]

Thanks for the link, Lightfoot

Will be interesting to see how crudded up my son's valvetrain looks. The video is consistent with mgarblik's comment about gunked up valvetrains when this happens.

My son paid to have some kind of de-gunk flush in the last year but I suspect it was fuel system and not something like Seafoam.

I know he gets the oil changed but not sure how often and he bought the Jeep used so the history is an unknown.

The comment about oil not getting to the lifters sounds like a reasonable root cause and I agree the "carbon build-up holding the valve open" sounds less likely.

I also thought it strange how easily the rocker was dislodged in the video. That design "feature" is odd to me. I don't see how there could be so little pressure from the valve spring to let the rocker pop off so easily. The quoted fix by adding a spacer sounds good but begs questioning the original design.

The replacement of hydraulic lifters by solids would be consistent with the spacer thing.

The valve job quote my son got was reasonable. He called the shop doing the heads and they speculated a valve seat came loose... same as mgarblik said was an issue on earlier versions.

It's the $700 for timing chains that caught my attention. That seems high.

[Shiny]

Just fyi

Son's issue was caused by a valve seat coming loose from the head. Not sure why the mechanic did not see this with a borescope as he blamed it on excess carbon. The chambers don't look bad to me for 120K+ miles.

mgarblik mentioned this as an issue pre-2008.. apparently not totally corrected in 2010 or maybe aggravated by a cooling issue.

Machine shop that is rebuilding the heads mentioned this as likely cause so they have seen this before.