4.0 oil consumption - less than 7,000 miles on rebuild, good compression - JeepForum.com
Reply
 
LinkBack Thread Tools
post #1 of 21 Old 07-15-2020, 12:09 PM Thread Starter
1984Laredo
Registered User
1984 CJ7 
 
Join Date: Oct 2009
Location: Shreveport, LA
Posts: 302
4.0 oil consumption - less than 7,000 miles on rebuild, good compression

I have less than 7,000 miles on the rebuild of my 4.0 (swapped it into the CJ7 from a '94 ZJ). During the rebuild, the internals of the stamped steel valve cover were thoroughly cleaned, new CCV elbows/grommets installed front and rear, new vacuum line from rear elbow to intake, and new hose from front elbow to intake piping (I used the intake pipe and air box from a Wrangler).

This engine uses quite a bit of oil. After driving ~200 miles, it's already down halfway on the dipstick range (from being at full after oil change - and after running immediately after to compensate for new oil filter). Another 100-200 miles later, it's at the ADD mark on the dipstick.

There is no smoke from the exhaust.

There is no oil in the intake piping, air filter, or the vacuum line that goes to the manifold. All are dry.

The bottom of the intake has a very slight oil sheen, but again, the lines are dry when I checked.

There is no oil in the coolant.

There are no leaks on the ground.

I just performed a compression test, and all cylinders passed. Results are below:

Cyl 1 test 1=135 test 2=137 test 3=137 test 4=138
Cyl 2 test 1=136 test 2=135 test 3=140 test 4=138
Cyl 3 test 1=141 test 2=143
Cyl 4 test 1=145 test 2=146
Cyl 5 test 1=147 test 2=147
Cyl 6 test 1=140 test 2=141

I only performed a third and fourth test on cylinders 1 and 2 since they were both a little lower than the rest. However, they still fell within the acceptable 10% variance between cylinders.

The oil is obviously going SOMEWHERE, but it beats me where! Do you guys have any ideas?? I've read a few places where the piston oil rings can be bad even though the compression ring is good and builds good compression. I'm skeptical about that, however, with this being a low mileage rebuild. Unfortunately, because of other modifications done to the Jeep after the rebuild, I wasn't able to catch this within the warranty period of the rebuild.

I'm at a loss at this point!


1984 CJ7 Laredo
4.0 I-6 / T5 / D300 / D30 / D44
Black Diamond 3" lift, 33" tires, 4.11 gears
1984Laredo is online now  
Sponsored Links
Advertisement
 
post #2 of 21 Old 07-15-2020, 12:24 PM
mukluk
Web Wheeler
 
mukluk's Avatar
2000 TJ Wrangler 
 
Join Date: Oct 2010
Location: Clyde
Posts: 6,097
If there aren't any leaks, then it has to be burning the oil. How do the plugs look?

2000 TJ SE
2005 LJ Rubicon
mukluk is offline  
post #3 of 21 Old 07-15-2020, 04:21 PM
Goatboy4570
Registered User
 
Goatboy4570's Avatar
1983 CJ7 
 
Join Date: Jul 2014
Location: nanaimo
Posts: 52
4.0 oil consumption

If you have a bad PCV it will literally drive oil consumption, the PCV has to be working as a one way check valve , pull it out while the engine is running, is it making a purring sound ?

If your passing oil on the rings a good test is with trans in neutral bring engine revs to 3000 and wait, if after 10 seconds it starts pushing blue you know you don't have proper ring control.

Best time to check for smoke when idling is at night with a flashlight, the blue really shows up in the beam with a dark background.
Goatboy4570 is offline  
 
post #4 of 21 Old 07-15-2020, 04:21 PM Thread Starter
1984Laredo
Registered User
1984 CJ7 
 
Join Date: Oct 2009
Location: Shreveport, LA
Posts: 302
I took pics of each one as I removed them:

Cylinder 1:



Cylinder 2:



Cylinder 3:



Cylinder 4:



Cylinder 5:



Cylinder 6:


1984 CJ7 Laredo
4.0 I-6 / T5 / D300 / D30 / D44
Black Diamond 3" lift, 33" tires, 4.11 gears
1984Laredo is online now  
post #5 of 21 Old 07-15-2020, 04:31 PM Thread Starter
1984Laredo
Registered User
1984 CJ7 
 
Join Date: Oct 2009
Location: Shreveport, LA
Posts: 302
Quote:
Originally Posted by Goatboy4570 View Post
If you have a bad PCV it will literally drive oil consumption, the PCV has to be working as a one way check valve , pull it out while the engine is running, is it making a purring sound ?

If your passing oil on the rings a good test is with trans in neutral bring engine revs to 3000 and wait, if after 10 seconds it starts pushing blue you know you don't have proper ring control.

Best time to check for smoke when idling is at night with a flashlight, the blue really shows up in the beam with a dark background.
The 4.0 doesn't have a PCV valve. It has a CCV system (constant crankcase ventilation), which has an open/unrestricted elbow at the front of the valve cover that is attached to a fresh air source (intake piping) and a metered orifice elbow at the rear of the valve cover that attached to manifold vacuum. This is simply a plastic elbow with a small hole in it for, basically, a calibrated vacuum "leak" - just enough to draw out the oil vapors from the engine but not enough to cause running issues. There's no valve to get gummed up. Both elbows along with all the connecting hoses were replaced during the rebuild.

I'll have to check the exhaust at night. I've never seen any smoke during the daytime either at startup or while driving, nor have those who have followed me. The exhaust does stink and smell a little rich (need to put a cat on it), but I've never smell any burning oil smell.

1984 CJ7 Laredo
4.0 I-6 / T5 / D300 / D30 / D44
Black Diamond 3" lift, 33" tires, 4.11 gears
1984Laredo is online now  
post #6 of 21 Old 07-15-2020, 04:32 PM
Goatboy4570
Registered User
 
Goatboy4570's Avatar
1983 CJ7 
 
Join Date: Jul 2014
Location: nanaimo
Posts: 52
one, six and maybe a bit five appear to have additional deposits but doesn't look overly bad when ive seen plugs that are black as coal, you have minor indication but nothing to set off alarm bells but who knows maybe the 4.0 is really efficient at burning oil in the combustion chamber ?
Goatboy4570 is offline  
post #7 of 21 Old 07-22-2020, 04:21 PM Thread Starter
1984Laredo
Registered User
1984 CJ7 
 
Join Date: Oct 2009
Location: Shreveport, LA
Posts: 302
I did the flashlight into the exhaust test at night, and I didn't see any smoke in the exhaust. I topped the oil off to the full mark with 3/4 of a quart this morning and also documented the mileage so I can start keeping a log of exactly how much oil this thing is using. I also cleaned the bottom of the bellhousing, which had some transmission gear oil on it (apparently my T5 has decided it wants to leak now ) to see if anything appears there. I'm not expecting it to, seeing how the concrete underneath it stays dry. The oil pan is dry as well.

I also looked at the top of the bellhousing/back corners of the engine to see if either were wet from a valve cover leak, but they were dry. I just don't know why this oil is disappearing. If it was a really small amount in between oil changes, I'd be fine with that. But I don't want to have to check my oil level every 150-200 miles. That's a little excessive.

(As a side note, I did change out my plugs today from regular Autolite 985 copper to the Autolite XP985 iridium plugs. While I couldn't tell much difference at idle, I could tell a difference in how responsive the engine was - especially pulling power in 1-3 gears. It definitely revved up quicker/higher than before. Usually, it seemed to get a little winded at 3000 rpms, which is where - and why - I typically shift there. But I found it revving to 3500 with ease - and before I even realized it. I'm definitely sold on them.)

1984 CJ7 Laredo
4.0 I-6 / T5 / D300 / D30 / D44
Black Diamond 3" lift, 33" tires, 4.11 gears
1984Laredo is online now  
post #8 of 21 Old 07-22-2020, 05:08 PM
jtec
Web Wheeler
 
jtec's Avatar
2014 JK Wrangler 
 
Join Date: Oct 2017
Posts: 8,446
keep an eye on the oil level, get some miles on those new plugs hopefully they will develop a 'tell', always the rear and front crank seals... can you park same place to check for puddles or drips?

Heads were done, valve seals?

My thinking is it will seal as those rings 'seat' . yeah I am a hopeless optimist.
positive thinking

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
jtec is offline  
post #9 of 21 Old 07-22-2020, 06:10 PM Thread Starter
1984Laredo
Registered User
1984 CJ7 
 
Join Date: Oct 2009
Location: Shreveport, LA
Posts: 302
Quote:
Originally Posted by jtec View Post
keep an eye on the oil level, get some miles on those new plugs hopefully they will develop a 'tell', always the rear and front crank seals... can you park same place to check for puddles or drips?

Heads were done, valve seals?

My thinking is it will seal as those rings 'seat' . yeah I am a hopeless optimist.
positive thinking
It has its own garage, so I'm always able to keep an eye on the concrete for any leaks.

It was supposed to be a complete rebuild, but what they actually did, I cannot say.

I've been having that same hope for several years now! Maybe it'll come true one day!

1984 CJ7 Laredo
4.0 I-6 / T5 / D300 / D30 / D44
Black Diamond 3" lift, 33" tires, 4.11 gears
1984Laredo is online now  
post #10 of 21 Old 07-22-2020, 06:29 PM
mukluk
Web Wheeler
 
mukluk's Avatar
2000 TJ Wrangler 
 
Join Date: Oct 2010
Location: Clyde
Posts: 6,097
If the rings haven't seated by 7000 miles, they never will. With the compression numbers as good as they appear I wouldn't suspect a ring sealing issue, maybe sloppy valve guides or bad/missing valve stem seals.

2000 TJ SE
2005 LJ Rubicon
mukluk is offline  
post #11 of 21 Old 07-22-2020, 07:05 PM Thread Starter
1984Laredo
Registered User
1984 CJ7 
 
Join Date: Oct 2009
Location: Shreveport, LA
Posts: 302
Quote:
Originally Posted by mukluk View Post
If the rings haven't seated by 7000 miles, they never will. With the compression numbers as good as they appear I wouldn't suspect a ring sealing issue, maybe sloppy valve guides or bad/missing valve stem seals.
I recently bought a cylinder leakdown test kit. That should reveal any such valve issues if they are present, correct?

1984 CJ7 Laredo
4.0 I-6 / T5 / D300 / D30 / D44
Black Diamond 3" lift, 33" tires, 4.11 gears
1984Laredo is online now  
post #12 of 21 Old 07-22-2020, 07:37 PM
mukluk
Web Wheeler
 
mukluk's Avatar
2000 TJ Wrangler 
 
Join Date: Oct 2010
Location: Clyde
Posts: 6,097
A leakdown test will reveal if there are compression sealing issues with the rings or the valve to seat surfaces. It will not tell you if the valve guides are out of spec or anything about the stem seals, only an inspection with the valve cover off can do that.

2000 TJ SE
2005 LJ Rubicon
mukluk is offline  
post #13 of 21 Old 07-22-2020, 08:26 PM Thread Starter
1984Laredo
Registered User
1984 CJ7 
 
Join Date: Oct 2009
Location: Shreveport, LA
Posts: 302
What is the inspection procedure for that?

1984 CJ7 Laredo
4.0 I-6 / T5 / D300 / D30 / D44
Black Diamond 3" lift, 33" tires, 4.11 gears
1984Laredo is online now  
post #14 of 21 Old 07-23-2020, 12:01 AM
mukluk
Web Wheeler
 
mukluk's Avatar
2000 TJ Wrangler 
 
Join Date: Oct 2010
Location: Clyde
Posts: 6,097
Pull the valve cover off and look to see if the stem seals are present or not. If they are present, see what condition they're in. To check the valve guides you'll have to remove the rocker arms and the valve springs, then see if each valve stem has excessive radial play in its guide. This is best done with the cylinder head removed and the valve held open about half an inch.

2000 TJ SE
2005 LJ Rubicon
mukluk is offline  
post #15 of 21 Old 07-23-2020, 04:46 AM
jtec
Web Wheeler
 
jtec's Avatar
2014 JK Wrangler 
 
Join Date: Oct 2017
Posts: 8,446
my bad . . . thinking newly rebuilt I overlooked the 7000 mile mention

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
jtec is offline  
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.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome