Another 4.7 Knock, but with video - Dodge Durango Forum and Dodge Dakota Forums
4.7L/4.7L HO/4.7L Gen II Engines Questions regarding the 4.7L V8 engine

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post #1 of Old 12-19-2010, 01:13 AM Thread Starter
lurch1980
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Smile Another 4.7 Knock, but with video

Hi All,

I just found this site a few days ago and I've been reading all the useful info on her and it's great! Thanks for having such a great community. I'm hoping to get a little help on diagnosing this issue.

So I started off with buying a 2000 Durango (my first Durango ) with a bad motor. I took the heads off the motor and found that a chunk of the piston in cylinder #7 was missing. So I bought another used motor out of a 2001 Jeep Grand Cherokee that had been over heated. The heads came off, the bottom end looked good so the heads went off to the machine shop.

I reassembled the motor with the rebuilt heads and with the help of some good friends swapped it out. The motor fired up on the first attempt but had a knock. The odd thing is it didn't sound like any knock I've heard before (I'm use to push rod engines) So I started to investigate. Here's what I have done so far.

1. Try to isolate the sound with a stethoscope. It sounds like its coming from the back of the passengers side head around cylinder 6 or 8.
2. Unplugged one coil pack at a time, the knocking did not change.
3. Check the cylinder compression. Every cylinder is between 131 and 136 lbs.
4. Put my extra fuel injectors on to make sure an injector wasn't acting funny. Knock was still there

So based off of the coil pack experiment and compression test I think the bottom end is still good. I'm wondering if this could be the lash adjusters not pumping up? (there was a good amount of sludge in the oil pan when I first took it apart) Maybe they have some sludge or crap in them?

Here's a link to the video on YouTube.

What do you guys think?
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post #2 of Old 12-19-2010, 01:27 AM
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I'd pull the passenger side valve cover and see what the valve train looks like. It sounds to me a rocker arm has slipped out of position. I had a friend with a 99 Jeep GC that had a similar sound and the rocker was the issue. We replaced all the lash adjusters and put the rocker back in position and it's been fine for over a year now. Pulling the valve cover is where I would start.

Mike

91 CC Carbed 414 R3
01 Quad Cab 4x4 4.7L
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post #3 of Old 12-19-2010, 01:41 AM Thread Starter
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Thanks, but I forgot to mention that we did pull both valve covers after hearing the knock and the rockers were all still in their correct place (not laying in the bottom of the head). Can the rocker slip out of place and cause that sound without completely falling out?

I also forgot to mention that when assembling the timing chain setup the cam (on the passenger side head) got a away from me when turning it to line up the sprocket and it rolled over pushing a valve into a piston (I'm not sure which one hit). I was told since it wasn't running and it stopped once the valve hit the piston it wasn't going to be an issue.
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post #4 of Old 12-19-2010, 04:40 PM
DakotaMike
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When you took the valve covers off were the rockers loose? As in the lash adjusters not pumped up?

I doubt that the assembly problem you mentioned hurt the valves.

I'm sure some others will chime in with other ideas. I was hoping it would be something easy for you.

Mike

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01 Quad Cab 4x4 4.7L
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post #5 of Old 12-19-2010, 06:05 PM Thread Starter
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Quote:
Originally Posted by DakotaMike View Post
When you took the valve covers off were the rockers loose? As in the lash adjusters not pumped up?

I doubt that the assembly problem you mentioned hurt the valves.

I'm sure some others will chime in with other ideas. I was hoping it would be something easy for you.

Mike
I didn't actually check to see if the rockers were loose. I'll pull the cover again and take a look at it.

So basically to make sure I understand this.. since the engine has been running the lash adjusters should be pumped up thus keeping the rockers tight. If any rockers are loose then there is a good chance that the lash adjuster on that rocker is bad?

Thanks for the response, and thanks in advance for this one!
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post #6 of Old 12-19-2010, 10:32 PM
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If the bottom end is rebuilt with new bearings... then we will assume its still in good shape and not the cause of the knock. Also since you say you feel the sound is in the head then we should look closely in that area....

With that said, the knock is most likely caused by slack in the valvetrain.

Slack can be caused by, (all some or none of the following) poor spring pressure, poor oil pressure, bad lash adjusters, or a follower not installed correctly.

I would cross my fingers and lean towards a follower first not installed correctly since that would be the easiest and cheapest to verify.

If you find that all the followers are installed correctly (Actually look real close as each one and verify its seated on the lash adjuster & the valve stem) I would then lean towards lash adjusters as being bad... If you have over 100,000 miles on the lash adjusters it would not hurt to change them anyway...

Next if you change the lash adjusters and it still ticks... I would then look into the oil pressure. Have a REAL oil pressure guage hooked up so you can get an actual PSI reading.

If oil pressure is good then it may be time to change the valve springs... Or you can just remove the ones you have and bring them to an engine shop to have them check the seat pressure... if they pass you can reinstall them... If one or two fail you can keep the good ones and replace the defective ones... I personally would just replace them with a good aftermarket spring if I ended up at this point.

Good luck and keep us posted...

SPEED SAFE, NICK
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post #7 of Old 12-19-2010, 10:56 PM Thread Starter
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Quote:
Originally Posted by AIR_RAM View Post
If the bottom end is rebuilt with new bearings... then we will assume its still in good shape and not the cause of the knock. Also since you say you feel the sound is in the head then we should look closely in that area....
Hi,

The bottom end was not rebuilt. The way it was deemed ok, was the following...

1. Checked the old oil for the "rainbow" effect in the sun (looking for a bad bearing) nothing was seen.
2. When running the coils were unplugged one at a time and the knock never decreased or stopped.
3. The knock is very faint through the stethoscope when placed on the oil pan, but really loud on the head (more so at the bottom of the head, than the top).
4. Compression tested each cylinder. they were 131-136. (in my mind this was saying the rings were good and the possibility of skit slap was at a minimum)

To make sure I'm not throwing good money after bad and chasing the wrong issues is there anything else I should check to make sure the bottom end is good?
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post #8 of Old 12-23-2010, 03:42 AM Thread Starter
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Well I finally got some time to remove the valve cover. All the rockers (followers) seem to be installed correctly, and I don't seem to have any slack in the lash adjusters. I'm starting to fear the worst that the bottom end is bad.
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post #9 of Old 12-23-2010, 05:01 PM
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The noise is moving at 1/2 the engine speed - top end related noise.

My best guess is that an intake valve is hanging open and slapping the top of the piston lightly. Pull the intake manifold and look at the gunk buildup on the valve - if there is a lot, that could be it.

Did you have the valves and valve guides cleaned or looked at at the machine shop? Or just resurface and go? These heads also like to drop the valve seat out of the head when overheated. Probably not your problem, but could be.

Did you clean the oil passages with a brush while you had it apart? Could be a blocked oil passage reducing oil pressure to the head - new lifter won't fix.

I just put an engine in my truck - had only 49k miles and was filled with sludge from short trips (3miles a day) and 8000 mile/2year or more oil change intervals. Cut the oil filter apart and it was filled with sludge and metal. Engine was knocking - but much faster than yours because the bottom end spins at 2x the top end on a 4 stroke engine.

Have you seen these?

http://stores.homestead.com/powertra...dge/Detail.bok

That's what I just finished intalling in my truck Tuesday. Happy so far. Much more power than the engine it replaced or the one in the last truck that this truck replaced. I have an occasional random ~5k rpm intake backfire to figure out that I don't think is related to cam timing, but rather engine management.

I would NOT suggest using an engine flush as my low end knocking started immediately after I tried that and the crap in the oil filter was immense. I used 1/2 can of sea foam in the crank case and 1/2 in the fuel tank - I found no positive results from either.

You can poke a hole in the oil filter and cut it open with tin snips. Easiest method I've found yet if you don't have a dedicated oil filter cutter. If you don't find metal, your bottom end is probably not hurt.

Another likely noise causer - exhaust manifold leak on #8 port from warpage. Common problem on these engines. Have someone put their shoe sole over the exhaust tip and listen for noise increase at the front or under the vehicle.

Last edited by spoolboy; 12-23-2010 at 05:09 PM.
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post #10 of Old 12-23-2010, 06:12 PM Thread Starter
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Quote:
Originally Posted by spoolboy View Post

My best guess is that an intake valve is hanging open and slapping the top of the piston lightly. Pull the intake manifold and look at the gunk buildup on the valve - if there is a lot, that could be it.

Did you have the valves and valve guides cleaned or looked at at the machine shop? Or just resurface and go? These heads also like to drop the valve seat out of the head when overheated. Probably not your problem, but could be.
I had a machine shop go through the heads, they cleaned the heads, inspected the valves, guides for sure. I know that they had to replace almost all the guides. I'm not sure if they looked at the lash adjusters or rockers though.

Quote:

Did you clean the oil passages with a brush while you had it apart? Could be a blocked oil passage reducing oil pressure to the head - new lifter won't fix.
The machine shop cleaned the heads, I didn't do anything to the block except clean up the deck.

Quote:
The noise is moving at 1/2 the engine speed - top end related noise.
--
Engine was knocking - but much faster than yours because the bottom end spins at 2x the top end on a 4 stroke engine.
We thought the knock was engine speed. (I spliced your quote together)

This link takes me to a web design page... but I think I saw this on another thread. Is this the engine for about 2200 that they say fixed some of the factory mistakes?

Quote:
That's what I just finished intalling in my truck Tuesday. Happy so far. Much more power than the engine it replaced or the one in the last truck that this truck replaced. I have an occasional random ~5k rpm intake backfire to figure out that I don't think is related to cam timing, but rather engine management.

I would NOT suggest using an engine flush as my low end knocking started immediately after I tried that and the crap in the oil filter was immense. I used 1/2 can of sea foam in the crank case and 1/2 in the fuel tank - I found no positive results from either.
Yeah, I've never bought into the "this can of magic sauce will fix your mechanical issue". The only thing I think that might do that is break down build up and clean oil passage ways a little, but even then how much damage are you doing to the other parts while waiting for the cleaner to open up the oil passage ways???

Quote:
You can poke a hole in the oil filter and cut it open with tin snips. Easiest method I've found yet if you don't have a dedicated oil filter cutter. If you don't find metal, your bottom end is probably not hurt.
I haven't cut the oil filter apart, but I can pull off the one I have on there now to look at it.

Quote:
Another likely noise causer - exhaust manifold leak on #8 port from warpage. Common problem on these engines. Have someone put their shoe sole over the exhaust tip and listen for noise increase at the front or under the vehicle.
Last night I was listening to it run with the stethoscope some more and the noise is really loud when I put it on the exhaust, but I've heard exhaust leaks on the 4.7 before and it's different than this. This really sounds like metal on metal. Maybe it's the valves, but I already took one head off and the seats we're all still good. We're going to pull this passenger side head before calling it a bottom end knock for sure.
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post #11 of Old 12-23-2010, 10:19 PM
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http://remanufactured-engines.com/page4.htm

Try that link for some ideas. I found the metal before I got around to trying the timing light thing. Don't know what you'll have to do to get it to pick up on the individual coil ignition. Your knock definitely sounds slower than mine did at idle.

The previous link that doesn't work right is for powertrain products. According to the guy I talked to there (Eddie) they drill the oil returns oversize in the blocks and heads, install locked in valve seats in the heads, overbore all cylinders the same size and install sealed power hypereutectic pistons with a thicker piston top and lower top ring location (helps most of the heat related upper cylinder problems) along with the latest update on timing tensioners and new multi-layer shim style head gaskets with red gasket spray. Take that for what it's worth as I don't know if those things actually cure the problems, or what the problems are for sure. I can verify the head gasket thing and all new timing components (It would cost at least $300 - $400 just for those).

My engine from them was clean, well sealed to keep out debris, doesn't leak or smoke and is very quiet with good oil pressure that comes up fast on start-up and has great power. So far so good. Just need to figure out my weird intake backfire around 5000rpm. It did this with the other engine too....
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post #12 of Old 12-23-2010, 11:02 PM
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One other thing... check to make sure one of your torque converter bolts aren't backing out and hitting something - hard to get them torqued properly. Also look for a cracked flexplate since the noise is near the back of the engine. The only other thing back there is the crank sensor and it's wheel on the crank.

See if the noise gets louder with the dipstick out or oil fill cap open?

Last edited by spoolboy; 12-23-2010 at 11:09 PM.
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post #13 of Old 12-24-2010, 12:25 AM Thread Starter
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I'll check the torque converter bolts tonight. I'm also reading through the link you sent. Maybe I can train my ear to diagnose the issue correctly Thanks!
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post #14 of Old 12-24-2010, 12:27 AM Thread Starter
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oh and I did find that you can hold a timing light pick up open and get it close enough to the #1 coil pack to pick up the signal. It took two people but we got it that way and from what we saw this knock looked to be engine speed.
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post #15 of Old 12-27-2010, 11:27 AM
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Did you figure it out?
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