30 lb compression
Thread Starter
|
Junior User
Joined: Nov 2007
Posts: 77
Likes: 0
30 lb compression
Looking for some advice/direction to ensure that i am on the right track.
<O
</O
I have a 98 expedition, 4.6L , 2wd.
<O</O
A Little Background:
the top timing chain guide broke on the passenger side which cracked the bottom guide causing it to jump timiing and damage the crankshaft position wheel gear. this in turn caused the number one intake to snap off and damage the head where it meets up with the block. This also caused number 3 intake to snap off and bend all 4 exhaust valves. I had the head shaved and took care of the problem with the mating surface. installed all new valves and seals, and lapped them in.
<O</Othis also caused damage to the drivers side because the chain jumped on it as well since there was nothing keeping them against the block. The only damage was all exhaust valves were bent and the exhaust valves rocker arms were all bent. I replaced the bad rocker arms and valves, lapped all valves in on the drivers side and installed the head with no issues.
<O</O
Back to the passengers side. Since then I have had all kinds of noises coming out of the passenger side valve train. I replaced all the lifters and most of the noise went away. I am planning to replace the exhaust rocker arms on the passenger side as well and probably the intakes as well.
<O</O
Now back to the question/concern. When I do a compression test on all cylinders, they all run about 150-160lbs with the exception of number 1. number one will only get up to 30-40lbs max. I removed the rocker arms to make sure the valves were closed and still got the same reading. Then I added a little oil to the cylinder and the reading jumped up to 180lbs. From what I can remember the oil trick is an indication of bad rings. I then did a leak down test on number one at TDC and got a reading of 20% loss, number 2 was about 25%. Then I connected the air hose straight to the spark plug hole and checked for air leaks at the intake, exhaust, dip stick and fill tube. There was some air coming out of the exhaust but I expect that there would be some since it was 100lbs going in. when I moved the crank around a little to ensure that I was sealing it then I still got some out of the exhaust but also out of the valve cover fill tube which to me still indicates rings. Even with the rockers off and the valve cover off the air was coming up from the timing chain cover which still points to the rings for me.
<O</O
Can anyone confirm or suggest any other checks that I can make before I pull the head and piston out? I bought another piston, ring set, and plan on having the head pressure tested if I have to pull the piston just in case.
Does anyone else have a better idea, suggestion, smack in the head, friendly guidance to assist me with this? This is now going into 2 weeks and I need to get my truck back up so I have 2 cars again.
<O</O
ANY AND ALL TIMELY SUGGESTIONS WILL BE GREATLY APPRECIATED.<O</O
<O</O
Thanks in advance,<O</O
rog
<O
</OI have a 98 expedition, 4.6L , 2wd.
<O
</OA Little Background:
the top timing chain guide broke on the passenger side which cracked the bottom guide causing it to jump timiing and damage the crankshaft position wheel gear. this in turn caused the number one intake to snap off and damage the head where it meets up with the block. This also caused number 3 intake to snap off and bend all 4 exhaust valves. I had the head shaved and took care of the problem with the mating surface. installed all new valves and seals, and lapped them in.
<O
</Othis also caused damage to the drivers side because the chain jumped on it as well since there was nothing keeping them against the block. The only damage was all exhaust valves were bent and the exhaust valves rocker arms were all bent. I replaced the bad rocker arms and valves, lapped all valves in on the drivers side and installed the head with no issues.<O
</OBack to the passengers side. Since then I have had all kinds of noises coming out of the passenger side valve train. I replaced all the lifters and most of the noise went away. I am planning to replace the exhaust rocker arms on the passenger side as well and probably the intakes as well.
<O
</ONow back to the question/concern. When I do a compression test on all cylinders, they all run about 150-160lbs with the exception of number 1. number one will only get up to 30-40lbs max. I removed the rocker arms to make sure the valves were closed and still got the same reading. Then I added a little oil to the cylinder and the reading jumped up to 180lbs. From what I can remember the oil trick is an indication of bad rings. I then did a leak down test on number one at TDC and got a reading of 20% loss, number 2 was about 25%. Then I connected the air hose straight to the spark plug hole and checked for air leaks at the intake, exhaust, dip stick and fill tube. There was some air coming out of the exhaust but I expect that there would be some since it was 100lbs going in. when I moved the crank around a little to ensure that I was sealing it then I still got some out of the exhaust but also out of the valve cover fill tube which to me still indicates rings. Even with the rockers off and the valve cover off the air was coming up from the timing chain cover which still points to the rings for me.
<O
</OCan anyone confirm or suggest any other checks that I can make before I pull the head and piston out? I bought another piston, ring set, and plan on having the head pressure tested if I have to pull the piston just in case.
Does anyone else have a better idea, suggestion, smack in the head, friendly guidance to assist me with this? This is now going into 2 weeks and I need to get my truck back up so I have 2 cars again.
<O
</OANY AND ALL TIMELY SUGGESTIONS WILL BE GREATLY APPRECIATED.<O
</O<O
</OThanks in advance,<O
</Orog
Laughing Gas
Joined: Feb 2006
Posts: 843
Likes: 0
The common though was that the wet test you did will raise the compression if you have bad rings. Yes I would get the head checked for cracks etc. You might have lost a piece of valve and damaged the rings or scratched the cylinder wall. That should only leak if you are in the damaged area. I would be concerned about a bent rod as well or a problem with the piston itself. It sounds like you are on the right track.
Thread Starter
|
Junior User
Joined: Nov 2007
Posts: 77
Likes: 0
Thanks for the quick reply. I plan on checking the rod once i get the piston out, but when i did have the head off and ran it to TDC there did not seem to be an issues with the height of it or the movement.
Will know more today if it warms up some more.
Will know more today if it warms up some more.
Fleet Owner
Joined: Apr 2008
Posts: 24,316
Likes: 5,127
From: 0,0,1
The head sounds fine. The problem is either the piston cracked when the valve piece got wedged between it and the head, or the cylinder wall has a good sized scratch in it. Putting oil in the cylinder will never raise compression if the problem is with the head. The fact that oil did raise the compression make it a problem down in the cylinder.
Thread Starter
|
Junior User
Joined: Nov 2007
Posts: 77
Likes: 0
Update:
So found out that when #1 took that hit, it was hard enough that it damaged the piston and pushed the top of the piston with enough downward pressure to dent it and pinch all 3 rings so that they were closed around the piston allowing the pressure to escape.
Put in a new piston and rings, and pressure is back up on #1.
But NOW, a new issue. It seems to have a lack of power and almost acts like it is misfiring. all plugs are getting spark, checked to make sure i did not cross up any plug wires, which are new as well as the plugs.
Not sure if this is timing related, which it seems to be to me, or if it is something else. Setting up the timing on this engine seems like it should be fairly simple but now it's got me wondering. I lined up the black marks on the chains to the timing marks on the camshats and on the cranck shaft sprockets with the mark pointing to the 6 oclock position making sure that all the slack was on the side that had the tensioners on them so that it would take up the slack as it should.
Can anyone help out here with other suggestions, possibilities or a .357 to put a hole in it???
So found out that when #1 took that hit, it was hard enough that it damaged the piston and pushed the top of the piston with enough downward pressure to dent it and pinch all 3 rings so that they were closed around the piston allowing the pressure to escape.
Put in a new piston and rings, and pressure is back up on #1.
But NOW, a new issue. It seems to have a lack of power and almost acts like it is misfiring. all plugs are getting spark, checked to make sure i did not cross up any plug wires, which are new as well as the plugs.
Not sure if this is timing related, which it seems to be to me, or if it is something else. Setting up the timing on this engine seems like it should be fairly simple but now it's got me wondering. I lined up the black marks on the chains to the timing marks on the camshats and on the cranck shaft sprockets with the mark pointing to the 6 oclock position making sure that all the slack was on the side that had the tensioners on them so that it would take up the slack as it should.
Can anyone help out here with other suggestions, possibilities or a .357 to put a hole in it???
Thread Starter
|
Junior User
Joined: Nov 2007
Posts: 77
Likes: 0
what would the symptoms of a bent rod be? jsut curious?
Anyone else with thoughts about the timing, or other problem that might cause it to run rough like it was misfiring, although it is not.
Please assist with any suggestion as i am running out of ideas on what to do.
Anyone else with thoughts about the timing, or other problem that might cause it to run rough like it was misfiring, although it is not.
Please assist with any suggestion as i am running out of ideas on what to do.
Logistics Pro
Joined: Jan 2001
Posts: 3,740
Likes: 37
From: Central NYS
It must have taken a pretty good rap if it bent a rocker arm. That being the case, perhaps the rocker arm bent the camshaft or a lobe shifted. (I t-h-i-n-k the camshafts are hollow and the lobes are pressed on the hollow shafts.)
Trending Topics
Laughing Gas
Joined: Feb 2006
Posts: 843
Likes: 0
I have 3 sets of modular cams setting around and you may be correct about the lobes pressed on but they sure do not look or feel hollow.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Fleet Owner
Joined: Apr 2008
Posts: 24,316
Likes: 5,127
From: 0,0,1
If a rod was bent the compression would be low in that cylinder. Since you now have good compression in all cylinders you can rule out cylinder, piston, or rod issues. Hopefully your confidence in aligning the timing marks to the chain correctly is beyond question. It only takes being off one tooth to give you the lack of power problem. Other than that, double check your vacuum lines to make sure they're all in the right place.
Have you checked for any trouble codes?
Have you checked for any trouble codes?
Thread
Thread Starter
Forum
Replies
Last Post
jstephens2
1961 - 1966 F-100 & Larger F-Series Trucks
9
Aug 12, 2011 06:56 PM
NAMDROF
1999 - 2003 7.3L Power Stroke Diesel
13
Apr 5, 2011 11:02 PM
