2004 4.0l V6 broken intake spring

[logan222]

Ok....neighbors kid truck. 2004 2wd Explorer 4.0l OHC V6 with maybe 95k. Need some advice.

Sudden hard misfire with code PO305. No compression at all on cylinder 5. Suspected broken intake rocker or valve spring.

Got intake and rocker cover off yesterday. Could see the rocker over to side. Spring obviously broken. No retainer or keepers on top of valve. I was amazed the valve had not dropped into the engine.

Looked some more today with the owner. Valve spring broken in half. Rocker appears ok. Found the valve retainer and the 2 keepers.

At first glance yesterday, it seemed valve was locked in guide (did not really try too hard...ran out of time) Today...maybe not. I can move the valve down using my thumb...I can pull valve back up with pliers.

Is it possible for the valve seal to be tight enough to make the valve 'hard' to move?

Looking down the cylinder head intake plenum..valve tulip looks ok.

Should I just swap a new valve spring in...run compression test and hope for the best?

 

[Flag Gibby]

If one spring is broken then most likely more are on the way. With that many miles on the engine I don't like the idea of one new spring with a bunch of worn ones. If all that can be afforded is the one replacement spring then go for it and like you said hope for the best. IMHO:
It sounds like the kid has been aggressively running the engine at high RPM's.
Also, if there is some resistance to the valve dropping down that is good since it indicates the seal is still good.

 

[Flag Gibby]

Also, make sure that the shaft of the valve did not get scratched/notched. If it got damaged at all it will need to be replaced.

 

[logan222]

Thanks for the replies. I do not see any scuffing on the valve stem.

It's a girl kid truck...so I don't think she has been drag racing. That said, she has been in 3 wrecks with it already within a month of getting her permit.

I do not have a good way to measure the resistance of the valve. Last night I tried my thumb...and my thumb is hurting by the time the valve starts to move.

I'm leaning toward installing the 1 new spring, do a compression test, and hope for the best.

Chances are the truck will be wrecked within 6 months.

Being a newbie. I'm unable to post a picture of whats going on.

 

[Flag Gibby]

Don't think that it really matters that it is a teenage girl and not a boy... I have known several teenage girls that have absolutely no restraint of which one of them managed to completely separate an upper ball joint on a vehicle. Constant agressive accelerating the engine RPM's to 5000+ off of stoplights will do it. None the less, difficulty moving the valve up and down can be good because it implies the cylinder has good compression, unless of course the valve is bent and that is why there is excessive drag.
The best way to check the play is to pull the spark plug and see if the resistance goes away. Then check for full straight movement with no catching, but be careful to not drop the valve inside the cylinder (put some sort of retaining clip on the end to keep it from falling all the way down) because then you will have to take the head off to get it back out.
If it ends up being bent, you can just disconnect that cylinder and let it run on the other 5. It will be underpowered but will at least run so it can be used.

It really does send a good message to the kids when you spend your weekend giving them a helping hand and hopefully they remember it and pass it on.

 

[logan222]

The plug is out. So it's not compression holding it.

When I first pulled the valve cover, I was amazed to see the valve..with a broken spring....just sitting there with no retainer at all. I did put a plastic cable tie on the valve stem so it would not drop into the cylinder. I was very surprised that the valve had not fallen into the cylinder already.

Further investigation shows that the valve can be moved. But requires a very steady force. No obvious damage to the valve.

So...kind of 2 schools of thought....

One. Put a new spring on. Do a compression test. If that works...button it up and hope for the best.

Two. Thank our lucky stars the valve did not drop into the engine...pull the head and get new guide and valve installed.


My money is on the truck will be totalled within 6 months with this girl driving it. That said, it is a nice truck. Too nice IMO for a new driver. They just got it back from the body shop from the previous wrecks.

 

[Flag Gibby]

The valve or guide is bent then so don't connect it back up. Devise a way to keep it up out of the way and let it run on 5 cylinders or go with option 2. At any rate it sounds like you have it all covered at this point.

 

[logan222]

Well...that's kind of the verdict today. Pull the head....and thank our lucky stars the valve did not drop in.

The theory is.....something got bent.

Even with a new spring...it will be a sticky valve and create new problems.


I've heard of these engines breaking valve springs hence the post here. I guess I was hung up on the wishful thinking part.

 

[Flag Gibby]

Yeah, you can always hope for a miracle, but I have never seen a spring break and not have the valve kiss the piston at least a couple of times. Very lucky that very little damage was done.

 

[logan222]

Update to all. Truck is fixed.

Owner purchased timing tool. Pulled the intake and drivers side head. Lap in new intake valve and install new valve spring. Put it all back together and has been running fine for a week.

Notes: Goofy Ford timing setup. Thankfully we only had to play with the drivers side this trip.

New valve was also sticking in guide. We had to gently file the lower valve guide ID edge. Just the inner edge...Valve loosened right up.

3 very minor valve witness marks on top of piston. Old valve actually looked ok but we would be crazy to reuse it. Maybe $12 new from Ford.

One interesting note. After reinstalling head and timing. We thought it would be a good idea to check compression. Hmmm....very low compression in 2 of the 3 cylinders. Maybe 30 psi max. Half a day of thinking and double checking cam timing etc. It appears the lifters will bleed down during head work. By design this engine looses so much oil thru the cam lube system that the cranking rpm speed is not enough to pump the lifters back up. The engine actually has to start and run to bleed the lifters. After starting the engine normal compression numbers returned.

 

[balston]

This happens on my explorer at 50kmiles

i just remove the camshaft (make sure to place a mark before remove the sproket) repace the spring ($5 dollar cost) and everything ok