• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Block flex!!!

A

arsxj1

NAXJA Forum User
Location
Tampa, FL
Does anyone else have this or has anyone else heard of it? The guy at the local jeep repair shop told me that most of the H.O.s have it. The thing is that I can start my XJ and rev it to hell and never get even a tick out of the motor... But put a load on er about 3000+rpms and it sounds like a diesel!!! If it were the bearings it would do it all the time right? He said that if you bought one new and took it in for this issue they would give you a 4yr 100K mile warranty or replace it and 9/10 times the new motor had it too... Is this correct?

BTW 93 XJ 4.0L 4x4 Auto 139K
 
It didnt do it when I got it, It just seems to have come on. I got the oil changed at midas so im sure they put 5w oil in there so that probably dont help. I did put lucas in there tonight and it seems to help. I was going to try 20w-50 with lucas next oil change and see if that helps. You think? Also has anyone done the seafoam in there oil for a couple days before an oil change to clean up the internals or would you not recommend it?
 
seafoam works, if you can handle the smoke
any tool can cause collateral damage, and the seafoam knocks lots of junk loose inside your engine... just be prepared.
 
I already did seafoam in the brake booster vac line that smoked for a while after that but it was making this noise before I did that.
 
You aren't noticing block flex. There is block flex and crank flex, etc, but you wouldn't notice it at stock RPMS, especially 3k rpm.
As others said, check your flex plate to start with.

Since you did something to your oil I would point to the wrong oil being put in though.
 
How is your exhaust header? Common problem for them to crack, and they will make a ticking noise when driving under load.
 
If it sounds like a diesel under load, I'd say check the timing and maybe get some good gas to see if it is a bad tank of fuel.
 
I put a tank of 93 in it to see if that made a difference but it didnt do anything. I do need to check the timing. How do I check the flex plate? It doesnt sound lke an exhaust leak at all.
 
Last edited:
Remove the piece of tin covering the lower part of the engine where it meets the trans. Look for 4 bolts holding the flexplate on the back of the engine. With a 15mm wrench, tighten them. If any move tighter, remove all of them one by one and reinstall with Loctite on the threads. Tighten the crap out of the bolts. The hard part is keeping the engine from turning over while tightening the bolts.
 
Don't worry about the timing. The CKP sensor fires that and it cannot be moved except by extreme measures. It could be checked with a timing light (antique store), but that is a waste of time.
 
winterbeater said:
Don't worry about the timing. The CKP sensor fires that and it cannot be moved except by extreme measures. It could be checked with a timing light (antique store), but that is a waste of time.
Click to expand...

Ok, let me re-word this then...check all timing components. A bad distributor will casue the same thing, as will a weak coil and old plug wires/plugs.


Heck the CKP sensor could even be bad.
 
Mr. mud said:
Hell, just replace it for good measure. Its' easy and theyre' really cheap.
Click to expand...

Sorry, but I just don't buy into replacing parts just because.........The part you have now is tried and (hopefully) true. Electrical parts have a high infant mortality rate. Once thru that, they last a long, long time statistically. I would rather take my chances with a 10 year old OEM part (which COULD have been made in the good ol' USA) than with a new Chinese made OEM or aftermarket (same sources, don't kid yourself). If you do throw a new part at your Heep, and the old one isn't verified bad, make sure to keep the old one in your spare parts box.
 
How do I verify its bad without replacing it? I believe the noise is oil viscosity related because since I put lucas in there its pretty much dissapeared.
 
Pretty much disappeared could be from the Lucas. You're right. Check your flexplate bolts and ALL the noise may disappear and you will have prevented a problem down the road!!!!!!!!
 
Ok... What holds the piece of thin to the engine? I want to make sure I have everything bfore I tackle this. What happens if they are loose and left untouched?
 
The loose bolts wallow out the holes in the flexplate and you get to pull the trans and all that crap to replace it. If I owned your Jeep, I would remove each flexplate bolt individually, clean the threads, add Loctite to the threads and reinstall. This whole procedure takes about 1/2 hour and can save you a ton of problems down the road, let alone possibly eliminate some of the noise you are experiencing now.
 
You must log in or register to reply here.

Similar threads

tjmotter
Old Girl
Replies
8
Views
141
asymptonic
A
L
Manual to Auto transmission swap
Replies
9
Views
205
lvcanyoneer1
L
D
Temp Gauge Reads High With New Senosr
Replies
15
Views
1K
TheDXJ
T
O
2000 XJ Failed Colorado Emissions high CO
2
Replies
27
Views
2K
Ken M
K
M
NP 231 input shaft
Replies
3
Views
2K
RCP Phx
R
Back
Top