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Push rod separated from rocker arm

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midwestbird
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Push rod separated from rocker arm

Post #1 by midwestbird » Tue Jul 02, 2019 6:50 pm

My engine recently began starting/idling terribly (1990 4.9L). I performed a compression test: cylinders 1, 3-6 measured 160 - 170 p.s.i. Cylinder #2 was about 10 p.s.i. My engine vibrates excessively at idle and a piece of paper in front of the exhaust tail pipe pulses in and out. According to what I've read, these symptoms indicate a burnt valve. So, over the weekend, I started the process of removing the cylinder head. As soon as I removed the valve cover, I was surprised to see this:

IMG_20190701_205122543.jpg

It seems the push rod is jammed up against the side of the rocker arm, keeping the exhaust valve partially open. I'm not experienced with the cylinder head, but I've asked a few folks and they seem to think I should just replace the push rod (and maybe spring, arm, etc.), put it all back together and hope for the best. I should be able to manage that, but I am concerned as to how/why this happened. Any ideas? Might this have been caused by the lifter, and dare I try to replace the lifter too?
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1990 Ford F-150, 4.9L 5 spd

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bubba22349
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Re: Push rod separated from rocker arm

Post #2 by bubba22349 » Tue Jul 02, 2019 9:21 pm

All you may need is just the push Rod, but check to see if the rocker shows any damage and that the exhaust valve is moving freely. Good luck :thumbup: :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Re: Push rod separated from rocker arm

Post #3 by jason832 » Tue Jul 02, 2019 10:07 pm

You can pull the lifter easily to check it, if its got damage it may be a bigger problem.

Take the side cover off, put a very small flathead screwdriver inside the lip around the rim of the lifter and ram it up and down until it comes out. If all looks good just drop it back on and put a new side cover gasket on. Don't tighten the side cover too tight or it will leak.

Seems weird to me that it popped out of a non adjustable rocker arm.

Edit: I just noticed its an EFI motor. I don't know how hard it is to get to the side cover.

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Re: Push rod separated from rocker arm

Post #4 by midwestbird » Tue Jul 02, 2019 10:27 pm

Thanks for the suggestions. I may just replace the pushrod and see what happens. And I should at least inspect the other components for obvious damage as well.

jason832 wrote:Edit: I just noticed its an EFI motor. I don't know how hard it is to get to the side cover.


I just recently took off the pushrod cover to replace the gasket because it was leaking oil. The symptoms started just before I changed the pushrod cover gasket, so I don't think anything I did while removing the cover caused the pushrod to separate.
1990 Ford F-150, 4.9L 5 spd

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Re: Push rod separated from rocker arm

Post #5 by pmuller9 » Tue Jul 02, 2019 10:39 pm

Looking at the picture, the valve stem end of the rocker arm is high and it is not holding the exhaust valve open.
The problem may be that the valve is stuck open and is what caused the pushrod to push out from the rocker.

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Re: Push rod separated from rocker arm

Post #6 by jgregg13 » Wed Jul 03, 2019 12:35 am

pmuller9 wrote:Looking at the picture, the valve stem end of the rocker arm is high and it is not holding the exhaust valve open.
The problem may be that the valve is stuck open and is what caused the pushrod to push out from the rocker.


I agree that the valve is likely stuck open. But it's the intake valve. It could be that it tried to ingest a big lump of something and the lump is holding the valve open. You might have to pull the lower intake manifold and have a look into the port. If there's metallic debris there you might be able to get it out with a magnet while pushing the valve down a bit more. A compression or leak down check after should tell if the valve is bent and not sealing. Otherwise I think you will have to pull the head.

Good luck.

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Re: Push rod separated from rocker arm

Post #7 by midwestbird » Wed Jul 03, 2019 4:44 pm

Thanks for all the input. I looked at the service manual, and sure enough, it shows that valve as the intake valve. I suppose I will first investigate what might be lodged in the intake valve...
1990 Ford F-150, 4.9L 5 spd

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midwestbird
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Re: Push rod separated from rocker arm

Post #8 by midwestbird » Thu Jul 04, 2019 11:54 am

A view from the passenger side.
IMG_20190704_104515893.jpg
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Re: Push rod separated from rocker arm

Post #9 by bubba22349 » Thu Jul 04, 2019 1:12 pm

Yes that’s an intake does that intake valve stem tip look like it’s setting up as high as the other intakes? Does the valve move and return if you push or pry on it with a small bar? Rocker arm looks bent in that picture. Good luck. :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Re: Push rod separated from rocker arm

Post #10 by midwestbird » Thu Jul 04, 2019 2:48 pm

bubba22349 wrote:Yes that’s an intake does that intake valve stem tip look like it’s setting up as high as the other intakes ? Does the valve move and return if you push or pry on it with a small bar? Rocker arm looks bent in that picture. Good luck. :nod:

I measured the heights of the flat surfaces on top of the springs. The measurements weren't precise, but it seemed the #1 intake valve was the only one higher (about .060"). As far as trying to compress the valve, I was hesitant because I was concerned that if debris is lodged under the valve, and I open the valve, the debris may fall into the cylinder.

I'm starting to disassemble. I took the fuel rail off and had a thought. If the valve is open, gas should flow from the spark plug hole to the fuel injector hole, I imagine. I have one of those smoke machines used for finding leaks, so I pumped some smoke through the spark plug hole expecting to see some traces of smoke come through the fuel injector hole, but nothing did.
IMG_20190704_131743073.jpg
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Re: Push rod separated from rocker arm

Post #11 by bubba22349 » Thu Jul 04, 2019 4:48 pm

Yes if there is an object stuck between the valve and seat it could drop into the cylinder and then there might be a repeat this kind of damage later on. So as far now as you already have it torn down, maybe at this point it's best to pull the head off to check everything inside the cyclinder. Good luck :thumbup: :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Re: Push rod separated from rocker arm

Post #12 by jgregg13 » Thu Jul 04, 2019 4:55 pm

Before pulling the head off, I'd be looking more to the lifter being collapsed or damage to the rocker arm or the rocker saddle being worn badly as it sounds like your valves are sealing. With the intake not opening, the exhaust won't let much air in to give much of a compression test reading. I assume that you had the exhaust valve closed when you did the smoke test.

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Re: Push rod separated from rocker arm

Post #13 by drag-200stang » Fri Jul 05, 2019 9:24 am

jgregg13 wrote:Before pulling the head off, I'd be looking more to the lifter being collapsed or damage to the rocker arm or the rocker saddle being worn badly as it sounds like your valves are sealing. With the intake not opening, the exhaust won't let much air in to give much of a compression test reading. I assume that you had the exhaust valve closed when you did the smoke test.

I agree with this^...Take that rocker off fist and inspect every thing before taking the intake or head off.
Maybe take off the exhaust rocker off and put the piston at the bottom , get a spark plug air fitting and pressurize the cylinder that should tell you if the valves all sealing ok.
After that without air on cylinder push down on valve and see if it moves ok.
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Re: Push rod separated from rocker arm

Post #14 by midwestbird » Fri Jul 05, 2019 10:48 am

Thanks for the input/suggestions. I plan to do some combination of what has been suggested here. My co-worker has a leak-down tester I plan to borrow - which I am hoping will confirm that my valves are sealing, and whether this issue has caused any problem with my piston ring. With the intake valve stuck closed, I imagine the cylinder was repeatedly under a vacuum it normally isn't subjected to. I am not experienced enough to make an educated guess, but I wonder if a consequence of this abnormally high vacuum was a disruption to the piston ring, or anything else.
1990 Ford F-150, 4.9L 5 spd

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Re: Push rod separated from rocker arm

Post #15 by THE FRENCHTOWN FLYER » Fri Jul 05, 2019 11:06 am

If the intake valve was closed for a period of time it should not have damaged the piston ring. It may have sucked a little oil up into the cylinder which should be evident on restart by blue smoke, after everything has been put back in its proper place.
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Re: Push rod separated from rocker arm

Post #16 by midwestbird » Fri Jul 05, 2019 11:28 am

THE FRENCHTOWN FLYER wrote:If the intake valve was closed for a period of time it should not have damaged the piston ring. It may have sucked a little oil up into the cylinder which should be evident on restart by blue smoke, after everything has been put back in its proper place.

That makes me feel better. Thanks. I doubt I can get a picture of it, but it does appear there is oil on top of the # 2 piston (looking through the spark plug hole). I was concerned when I noticed the oil, but your comment explains it. I'll try to report back what I discover along the way... I appreciate all the input. I'm enjoying the discussion and hoping it'll be a good learning experience for me (and maybe get my truck running again!).
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Re: Push rod separated from rocker arm

Post #17 by midwestbird » Sat Nov 02, 2019 1:36 pm

I wanted to provide an update to this issue, in case anyone discovers this thread in the future. The resolution wasn't clear or immediate because this pushrod issue occurred while attempting to resolve other issues. The short of it: I ended up just reinstalling the pushrod, lubing the valve stem, and repeating compression test. I measured psi in the range of the other cylinders before and after restarting the engine. If this pushrod issue recurs, I'll try to update this thread, but for now, the push rod has stayed in place.

The other engine issue caused me to eventually just have the truck towed to a nearby mechanic (I spent a good deal of time trying to resolve it myself). I had it towed there 6 weeks ago! And it's still there. He discovered a faulty fuel pump module; replacing it made a huge improvement, but he's still trying to chase down one remaining problem. I had foolishly ignored the fuel pump, in part, because the previous owner had supposedly just replaced it, so I marked it off my list of potential causes.
1990 Ford F-150, 4.9L 5 spd

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