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wj 4.7 rod knock ?

13K views 19 replies 8 participants last post by  BrokeWJ  
#1 ·
Hello all. I just bought a 2001 jeep grand cherokee limited with the 4.7. The motor has a knock but i didnt think it sounded like a rod knock. idk.
Here's what i done so far..
compression test. all cylinder are 135 psi.
took off flex plate access cover to inspect the flex plate and bolts.. all looked good.
I did notice 2 bolts are loose on the driver exhaust manifold but didnt think that would cause the engine knock..

What do you all think is causing the knocking ?

 
#2 ·
Might be an loose cam loobe, see my threads for more info
 
#7 ·
Link is down again.

However, it reads to me as broken bolts on the driver's side exh manifold. At least that is one problem you have. Common issue, moderately difficult to fix yourself.
Get new bolts & gasket from dealer.
Sound should be from the driver's side only. Might get a little more quiet once it is warmed up.

If it is rod knock, it's going to get worse/louder soon.

Exh manifold bolts broken won't get worse but your mileage may go bad as incorrect readings of burned gasses continue to leak and the O2 sensors do not see what they expect to and subsequently richen the mixture.


Search through my posts on this topic for more info on the repair procedure.
 
#9 ·
Ok....got it. Thanks.
I can tell you for certain that it's not the exhaust manifold making the loudest knock noise.

As suggested earlier, by T-Hawk, it sounds like a cam lobe got knocked loose or at the very least a rocker arm fell off.
Not a disaster in either case but it will be some labor $ to fix. Stop driving it right away until resolved.
 
#10 ·
I'm not driving it at all. Only started it when I bought it to listen to the knock and to take the video. I did a compression test and all was good but It occurred to me last night that if the rocker arm fell off, the valve will close. So tonight, I'm taking the valve cover off to see
 
#13 ·
srwells37 said:
I pulled the valve covers. Rocker arms are still there where they should be. I checked the cam lobes and the cams are good. I'm just gonna pull the engine and do a total rebuild.
Did you pull each rocker arm egen you did inspect the camlobes for play?
 
#15 ·
srwells37 said:
How do you check the cam lobes for play ? The rocker arms were tight so i was assuming the cam lobes was good
Yes thats correct, with the rocker arm in place there is no lash, or tension between the rocker and lobe, so no Way to try wiggle it with rocker arm in place.

I made a thread about it, which shows everything, pls take a look at it, you will find it by my old threads.

Also here you Go,,,

 
#16 ·
You may also have an issue with the timing chains. Chains were an excellent idea on the part of Chryco but they stretch. I'm with Tomahawk, A cam lobe may be the issue, rod is possible. If you are going to rebuild it look into having the heads taken care of, some rebuilders mod the oil passages so it flows better.