Lets play name that sound! Motor or Transmission?? - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > Lets play name that sound! Motor or Transmission??

ZONE 4.25" combo lift for TJ available at Rockridge4wWarn, Smitybilt, Engo, Rugged Ridge Winches at CCORRough Country Lift Kits and Parts!

Reply
Unread 05-29-2013, 10:32 PM   #1
skyj
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
Posts: 2,980
Lets play name that sound! Motor or Transmission??

Ok my jeep started this rattle after a run over a mountain pass this weekend.
It only happens when the jeep is warmed up and around range 1500-2000 rpm, in all gears. oil pressure is 40psi on start up then after warm 10 to 15 psi at idle, sometimes drops to 0 but never knocks, when im cruising it stays at 20 psi.
Specs on Jeep: 1990 4.2 118,000 miles with 4.0 head , HEI, motorcraft 2100 carb, AX-15, NP231 SYE.
Back in '08 I installed the 4.0 head and checked the compression and all cylinders where in 130-140 range, and rod bearing clearance all were within spec. In '10 I replaced the transmission with a recent rebuilt AX-15 with external slave and new clutch with resurfaced flywheel, at the same time installed the SYE in the np231.I run an el cheapo Mr Gasket fuel pressure regulator set at 4psi, for the 2100 carb. Recently in january '13 I replaced the timing chain and gears, along with oil pump and fuel pump. I did not replace the dampner at the time although the TDC notch was way off on the dampner I set motor to TDC and put a paint mark on dampner to give it a new TDC mark timed it at 8*TDC. it has ran great with no problems since then.
I cant quit pinpoint the location of the sound but it seems to be back of motor bell housing area. in the recording I have it in 4th gear and am just cruising at 45 mph, I let off the gas and the rattle comes in at 2000 rpm, then I accelerate and sound goes away, let off gas again and rattle again, then acelerate, goes away and... well you get the picture.
click on black spot to hear recording \/\/\/


At first I think its a detonation problem should I retard my spark?? am I running lean?? havent checked plugs yet, they are new bosch platinums, I know, I know Or is it a pressure plate on the clutch chattering?? I cant tell Im confused Rod bearings bad??

__________________
build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
skyj is online now   Reply With Quote Quick reply to this message
Unread 05-30-2013, 09:35 AM   #2
zeus87gn
Automotive Neurosurgeon
 
zeus87gn's Avatar
1987 YJ Wrangler 
 
Join Date: Sep 2006
Location: Houston, Texas
Posts: 2,413
That's a vavletrain rattle
Bent rocker, broken tip on the valve, bent valve, broken valve spring, collapsing lifter, etc
Your crank dampener being separated is BAD
You need to replace it before it comes apart on you
__________________
Handicapped license plates are not for mentally handicapped people -

"Man has not yet evolved an inch from the primordial slime that spawned him." Mark Blankfield, Jekyll & Hyde... Together again

Holley Carb thread
zeus87gn is offline   Reply With Quote Quick reply to this message
Unread 05-30-2013, 12:16 PM   #3
skyj
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
Posts: 2,980
Quote:
Originally Posted by zeus87gn View Post
That's a vavletrain rattle
Bent rocker, broken tip on the valve, bent valve, broken valve spring, collapsing lifter, etc
Your crank dampener being separated is BAD
You need to replace it before it comes apart on you
Thanks zeus I was going to pull the valve cover and see if it was a bent push rod. And I will replace the dampner soon, real soon. Thanks!
__________________
build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
skyj is online now   Reply With Quote Quick reply to this message
Unread 06-06-2013, 07:22 AM   #4
skyj
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
Posts: 2,980
Ok bringing this one back to the top.
I've been driving it around a little and the sound is definately coming from the front of the motor. I had the club listen to it last night at our meeting while it idled in the parking lot. Some guys think its a rod knock.
My buddy who is really good with sbc thinks its crank and rod bearings. I know I said earlier that it comes when load is applied in fact its the exact opposite The sound completely goes away when load is applied, until a certain rpm range making him think that when there is no pressure on the rod its allowing it to "slop".
I trust Zeus guess on Valve train but wanted to hear what others thought. Lower end of motor or top, or both?

I guess the next move is to pull the valve cover and see what I find there.
__________________
build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
skyj is online now   Reply With Quote Quick reply to this message
Unread 06-06-2013, 07:13 PM   #5
caoboy
Registered User
1991 YJ Wrangler 
 
Join Date: Jul 2012
Location: Modesto, CA
Posts: 325
I had a sound similar to that and it turned out to be a broken bracket on the windshield washer bottle. Probably not as loud though, and the only way I figured it out was by feeling on bolts by where the sound was coming from.

Is it all over the engine bay or can you pinpoint it?

http://www.harborfreight.com/mechani...ope-41966.html

That might help you out as well.
caoboy is offline   Reply With Quote Quick reply to this message
Unread 06-06-2013, 08:09 PM   #6
pasinbuy
Registered User
1994 YJ Wrangler 
 
Join Date: Feb 2007
Location: florida
Posts: 3,842
Try taking a long screw driver and feel around the motor with the screw driver handle pressed to your ear. Try to find the sound that way until you can buy or borrow a stethoscope.

I used a long screwdriver to the ear for years.
pasinbuy is offline   Reply With Quote Quick reply to this message
Unread 06-06-2013, 09:11 PM   #7
Odie4az
Registered User
 
Join Date: May 2013
Location: Prescott, AZ
Posts: 13
I had the same noise on my 4 banger, all at the same rpms as you described.... Pulled valve cover, checked: rocker, springs, then changed out the lifters, checked rods, noise never went away.... I will check washer bottle but I'm now thinking maybe a chain noise... Just ordered the stethoscope and hope I can narrow it down, I did the screwdriver check but could not pin point it.... If I can figure it out I will let you know.. I just hope it's nothing that I have to pull the motor, I bought this a year ago and supposedly the engine was rebuilt with only 2,000 miles on it....
Odie4az is offline   Reply With Quote Quick reply to this message
Unread 06-06-2013, 09:25 PM   #8
skyj
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
Posts: 2,980
Quote:
Originally Posted by caoboy View Post
I had a sound similar to that and it turned out to be a broken bracket on the windshield washer bottle. Probably not as loud though, and the only way I figured it out was by feeling on bolts by where the sound was coming from.

Is it all over the engine bay or can you pinpoint it?

http://www.harborfreight.com/mechani...ope-41966.html

That might help you out as well.
Yeah I have that exact stethoscope I can hear it in the top end but when I hold it to block next to the #4 cylinder it definately gets louder. If I hold it to the exhaust manifold I hear it loud to. I just don't know when I will get around to tearing into it, or just run it and build a stroker from the 4.0 and spare 4.2 I have. If its just crank/ rod bearings I can just get new bearings and lengthen its life or see if its valve train issues and hope its an easy fix without removing the head.
__________________
build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
skyj is online now   Reply With Quote Quick reply to this message
Unread 06-07-2013, 12:21 AM   #9
greyarea
Registered User
1990 YJ Wrangler 
 
Join Date: Aug 2009
Location: gwinett, GA
Posts: 293
That is what my 4.2 sounded like just before it wore through the aluminum cam sprocket teeth after the nylon went away.
__________________
90 YJ Magnum 5.2 v8 , 1'' BL, 1'' booms, 4" Procomp, 35/12.50-15 MTR/kevlar Ford 8.8 4.10 lsd Aussie and TJ shafts up front.
KI4UTU
greyarea is offline   Reply With Quote Quick reply to this message
Unread 06-07-2013, 06:02 AM   #10
skyj
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
Posts: 2,980
Quote:
Originally Posted by greyarea View Post
That is what my 4.2 sounded like just before it wore through the aluminum cam sprocket teeth after the nylon went away.
I just replaced my timing set two months ago.
__________________
build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
skyj is online now   Reply With Quote Quick reply to this message
Unread 06-07-2013, 10:50 AM   #11
skyj
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
Posts: 2,980
Sound almost completly goes away when I disconnect the vacuum advance. What's the cure to this problem?
__________________
build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
skyj is online now   Reply With Quote Quick reply to this message
Unread 06-07-2013, 11:04 AM   #12
rykemc
Senior Member
1988 YJ Wrangler 
 
Join Date: Jun 2011
Location: lubbock, tx
Posts: 536
Could it be detonation?
__________________
My Jeep build. :)

http://www.jeepforum.com/forum/f12/m...build-1502848/

APRIL 2013 YJOTM

JUNE 2014 YJOTM
rykemc is online now   Reply With Quote Quick reply to this message
Unread 06-07-2013, 11:06 AM   #13
rykemc
Senior Member
1988 YJ Wrangler 
 
Join Date: Jun 2011
Location: lubbock, tx
Posts: 536
Quote:
Originally Posted by skyj View Post
Yeah I have that exact stethoscope I can hear it in the top end but when I hold it to block next to the #4 cylinder it definately gets louder. If I hold it to the exhaust manifold I hear it loud to. I just don't know when I will get around to tearing into it, or just run it and build a stroker from the 4.0 and spare 4.2 I have. If its just crank/ rod bearings I can just get new bearings and lengthen its life or see if its valve train issues and hope its an easy fix without removing the head.
Have you pulled that plug and compare it to the others? Maybe even do a compression test on that cylinder
__________________
My Jeep build. :)

http://www.jeepforum.com/forum/f12/m...build-1502848/

APRIL 2013 YJOTM

JUNE 2014 YJOTM
rykemc is online now   Reply With Quote Quick reply to this message
Unread 06-07-2013, 11:29 AM   #14
skyj
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
Posts: 2,980
Quote:
Originally Posted by rykemc View Post

Have you pulled that plug and compare it to the others? Maybe even do a compression test on that cylinder
The sound didn't change when I pulled the plug in that cylinder infact I got a little lifter noise when I pull the plugs on the cylinders. I still need to do a compression test. I did one years ago when I swapped on the 4.0 head and they were all around 130-140 psi so I figured good to go.
I'm thinking I will retard the spark and turn up the idle on the carb and take her for a ride.
__________________
build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
skyj is online now   Reply With Quote Quick reply to this message
Unread 06-07-2013, 03:24 PM   #15
skyj
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: Helena, MT
Posts: 2,980
Ok its definitely the vacuum advance causing this..... Dunno why but it is,I assume its a bit of predetonation...ok maybe a lot of predetonation. How do I fix this?? when I installed this HEI years ago I followed a thread I found on wrangler forum and simply just followed what he did. It's worked for years so don't know why it had reared its head now.
My only thought is maybe I got a bad batch of gas with a lot of Ethanol in it?? No matter how much I retard the spark I can't get it to stop with the vacuum advance hooked up. If I advance it without it hooked up it won't do it... So where do I go from here?? It runs best at 8* btdc, but knocks like crazy with the vacuum advance...
__________________
build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
skyj is online now   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.