Help Please- Possible exhaust leak/overheating 4.0/AX15 - JeepForum.com
 
LinkBack Thread Tools
post #1 of 10 Old 07-15-2015, 11:15 PM Thread Starter
asf06
Registered User
1993 YJ Wrangler 
 
Join Date: Apr 2009
Location: San Antonio
Posts: 281
Help Please- Possible exhaust leak/overheating 4.0/AX15

JF-

I hope y'all might be able to help me out or at least give me some ideas. To keep things concise, I do ask that y'all read the whole post before jumping to conclusions; based on other things I've read online while trying to troubleshoot this.

Here are the symptoms:
-Firewall very hot, 150+ degF
-Transmission hump hot, 130-40 degF
-Coolant temp hotter than normal, upwards of 210 degF w/o blower on
-Lower-than-normal oil pressure, 40 psi
-At idle, can hear what sounds like a valve rattling, can't hear anything while driving, Jeep/road noise too loud
-Loss of power: Top speed ~84 mph, Accel from 70-75 takes about 0.3 miles

Here's the story:
While driving, I noticed that my right foot was uncomfortably warm. Something was hot enough that I can be uncomfortable in leather boots, my everyday attire. I first noticed this a week ago, driving back from the Austin airport to San Antonio. The change came about quick; within 20 minutes of highway driving. As some more time passed, I noticed the temp gauge steadily climbing. To remedy this, I turned on the defroster (i.e. engage the blower to draw more heat from the coolant). I've been running like this pretty much every day for trips longer than 25 minutes. On that trip I was able to maintain 80 mph for the whole drive. During the [usually] traffic-laden commute to work I don't really drive over 70 mph, so I didn't notice the top speed issue till today, but acceleration seemed a little lacking while passing slow vehicles. For the record, the Jeep is a '93 4.0L, AX-15, 33" KM2s, 3.73 gears. Perfect setup for the highway, good speed and accel, 70-75 yields ~17 mpg. Anyways-

As time passed, I talked to some folks and poked around the internet. With the exhaust location on the YJ, and [what sounds like] valve chatter, I am led to believe this is an exhaust leak; at or near the manifold. This would make sense as the passenger side firewall isn't as hot. So I began to feel for a leak. No luck, as y'all know, it is very tight under the intake manifold so I couldn't feel around well enough without burning myself. Also, the Jeep doesn't smoke at all (invisible exhaust), so seeing a leak was out of the question. I'm going to further pursue this, using a fog machine and a Shop Vac. (Check it out here- http://forums.nasioc.com/forums/show....php?t=2524954)

Poking around under the Jeep and in the engine bay, I could not notice anything leaking. Radiator is full and holds pressure and no oily drips/splatter/coatings underneath. AX-15 shifts fine. I believe that the transfer case is too far back in the drive train to heat up the firewall; in other words, I'm not worried about it.

Just today, I for-sure noticed the power issue, as I was on open highway. It's normal top end is ~94 mph, very quick acceleration (for a box on 33s) and it had the ability to maintain 80-90. Today while I was paying attention, it would take damn-near full throttle to maintain 75 and acceleration was terrible. It was tough to get it to 80 and I had no chance of staying there (wide open). I also looked at the oil pressure and noticed it was steady at 40 psi, down from the normal 50. This would indicate that the oil is lighter (hotter) than usual.

Okay, I think I've covered all the bases, now here's the backstory:
I've owned the Jeep for 7 years, since high school with nary an engine problem. It has had it's problems in the past, but the engine has always been solid and running well. I know how it likes to run, no hotter than 190 degF coolant temp ad 50 psi on the oil. I've never had any problems with excessive heat, as you shouldn't with a MT. Now, people online say without carpet, it will get hot. Bulls--t. It hasn't had carpet for 6 years and you could drive it comfortably while barefoot, with the passenger's bare foot on the hump. Since I swapped the 8.8 with 3.73s, It has been a well-balanced machine, in terms of speed, highway acceleration and gas mileage. So this loss of power is troubling.

Backing up- When I moved to Texas, I had to leave the Jeep behind temporarily. During that time I had my mechanic tune it up and fix what needed fixing. By the time I got it to San Antonio it was tip-top. It ran like new. This pattern continued until recently.

Now, since this has been my DD since high school, I haven't wheeled much, and if I did it was usually mud and/or moderate trails. In college, I A) needed a vehicle and B) couldn't afford repairs, so hard wheeling was out of the question. I still don't wheel it, as this is once again my DD after my 7.3 got stolen. Anyways, I went to check out a truck on Craigslist and ended up doing a trail run on this dude's property. It was a pretty technical trail, no rocks, just sandy clay hills and ruts and stuff. There were some pretty hard hits. To put it into perspective, I was keeping up with a Nissan on 40s with a doubler. Also, (because it's a DD) I didn't have my front skid on, just the factory one under the TC.

Since then, the Jeep's developed some new squeaks and sounds. They're probably piddly s--ts like u-joints or whatever (yes, I'll fix them eventually). Nothing that seemed to affect performance. But, nevertheless, I'm afraid during that hard wheeling I may have knocked something out of whack and it seems like it's getting worse as time passes.

Pros:
-I can afford moderate shop bill, ~$600.
-I can fix most simple mechanical things myself or with the help of a friend. (I don't f--k with engine internals.)

Cons:
-I live alone in an apartment. It's hard to troubleshoot by myself and even tougher to work on things without pissing off the management.
-I need to arrange a place to work and help if I get into anything serious.
-This is currently my only vehicle.
-Without knowing what's wrong, I can't estimate a MTTF.

SO, what do y'all think?

Thanks for taking the time to read this. I really do need y'all's help.

Regards
Franz


1993 YJ, too broke to swap the tranny and my 60s
Quote:
Originally Posted by Rob99 View Post
It can't be a scam. There's pictures of Asian people in business suits pointing at charts and graphs.
PIKE Jeepers #1
Jeep Smokeless #4
asf06 is offline  
Sponsored Links
Advertisement
 
post #2 of 10 Old 07-15-2015, 11:58 PM
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland
Posts: 6,034
First, do you have any check engine light on? Any codes thrown if you do this:

I think if you are used to driving faster, then this accounts for your oil pressure drop. It may be 40 psi at 70 mph and 50 psi at 80 mph. Although as you said, if it used to run cooler, this can account for some pressure drop as well.

210 is a reasonable highway temperature for this engine.

As far as your drop in power goes, is your normal maintenance up to date? what did the mechanic do when you left it for a tuneup? Do you have new champion copper core spark plugs, wires, distributor cap, rotor, air filter, fuel filter?

I'd be more worried about a slight exhaust clog than an exhaust leak with the symptoms you describe. It is possible that it is leaking and throwing off the O2 sensor though.
mike134 is offline  
post #3 of 10 Old 07-16-2015, 12:11 AM
Drednot
Registered User
 
Drednot's Avatar
1991 YJ Wrangler 
 
Join Date: Aug 2005
Location: Phoenix
Posts: 3,810
I think the smoke test for the exhaust leak is a good step to take. Your symtoms could stem from a lean condition. You just gotta find out why. Also, get aholt of a fuel pressure tester and let us know the results.

91 YJ Sahara, 4.0L, AX-15/NP231, D30/[email protected]
12 Cherokee 4x4,3.7L,42RLE/MP1522, D30M/[email protected]
Emission test=YES
"Non Vi Sed, Arte"
Drednot is offline  
 
post #4 of 10 Old 07-16-2015, 12:13 AM
deathtrap
Registered User
1993 YJ Wrangler 
 
Join Date: Jun 2011
Location: Hemet
Posts: 406
Your decrease in performance and elevated temps. would lead me to think you may have a partially clogged cat converter. might be worth it to find a shop that can do a back pressure test on it. 2x on the manifold leak. get your self cheep inspection mirror from the parts store and check for cracks on the back side between manifold and engine.
deathtrap is offline  
post #5 of 10 Old 07-16-2015, 07:48 AM Thread Starter
asf06
Registered User
1993 YJ Wrangler 
 
Join Date: Apr 2009
Location: San Antonio
Posts: 281
Quote:
First, do you have any check engine light on? Any codes thrown if you do this
No lights.

Quote:
I think if you are used to driving faster, then this accounts for your oil pressure drop. It may be 40 psi at 70 mph and 50 psi at 80 mph. Although as you said, if it used to run cooler, this can account for some pressure drop as well.
I don't drive fast normally (daily). My commute is 65-75. The oil pressure was 50 even at slower speeds.

Quote:
210 is a reasonable highway temperature for this engine.
This engine has NEVER run at 210. Normal is 170 in the winter, 190 in the summer.

Quote:
As far as your drop in power goes, is your normal maintenance up to date? what did the mechanic do when you left it for a tuneup? Do you have new champion copper core spark plugs, wires, distributor cap, rotor, air filter, fuel filter?
All that was done 8 months ago. It's ran great since then. I keep up with all that on a regular basis.

Quote:
I'd be more worried about a slight exhaust clog than an exhaust leak with the symptoms you describe. It is possible that it is leaking and throwing off the O2 sensor though.
Possible. What would be the symptoms of a bad O2 sensor?

Quote:
I think the smoke test for the exhaust leak is a good step to take. Your symtoms could stem from a lean condition. You just gotta find out why. Also, get aholt of a fuel pressure tester and let us know the results.
Thank you. I will check the fuel pressure.

Quote:
Your decrease in performance and elevated temps. would lead me to think you may have a partially clogged cat converter. might be worth it to find a shop that can do a back pressure test on it. 2x on the manifold leak. get your self cheep inspection mirror from the parts store and check for cracks on the back side between manifold and engine.
Cat's empty. The smoke test will show that. I'll get a mirror.

1993 YJ, too broke to swap the tranny and my 60s
Quote:
Originally Posted by Rob99 View Post
It can't be a scam. There's pictures of Asian people in business suits pointing at charts and graphs.
PIKE Jeepers #1
Jeep Smokeless #4
asf06 is offline  
post #6 of 10 Old 07-16-2015, 08:50 AM Thread Starter
asf06
Registered User
1993 YJ Wrangler 
 
Join Date: Apr 2009
Location: San Antonio
Posts: 281
Engine cold, oil at 55 psi. Accel from 70 to 75 took 0.1 miles



Sent from my SAMSUNG-SGH-I337 using Tapatalk

1993 YJ, too broke to swap the tranny and my 60s
Quote:
Originally Posted by Rob99 View Post
It can't be a scam. There's pictures of Asian people in business suits pointing at charts and graphs.
PIKE Jeepers #1
Jeep Smokeless #4
asf06 is offline  
post #7 of 10 Old 07-16-2015, 01:59 PM
bruinjeeper
Web Wheeler
 
bruinjeeper's Avatar
1995 YJ Wrangler 
 
Join Date: Jun 2013
Location: New West
Posts: 6,534
Oil pressure readings should seldom be relied upon the stock gauge.

Forgive me if i missed it - did you try a mechanical gauge direct to the sender?

Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
~YJOTM MAY '16~
~YJOTM JULY '19~
bruinjeeper is offline  
post #8 of 10 Old 07-16-2015, 02:46 PM Thread Starter
asf06
Registered User
1993 YJ Wrangler 
 
Join Date: Apr 2009
Location: San Antonio
Posts: 281
-deleted-
asf06 is offline  
post #9 of 10 Old 07-16-2015, 02:48 PM Thread Starter
asf06
Registered User
1993 YJ Wrangler 
 
Join Date: Apr 2009
Location: San Antonio
Posts: 281
Quote:
Originally Posted by bruinjeeper View Post
Oil pressure readings should seldom be relied upon the stock gauge.

Forgive me if i missed it - did you try a mechanical gauge direct to the sender?
No I haven't tried. Whether or not the reading is numerically correct, it is still lower than normal.

1993 YJ, too broke to swap the tranny and my 60s
Quote:
Originally Posted by Rob99 View Post
It can't be a scam. There's pictures of Asian people in business suits pointing at charts and graphs.
PIKE Jeepers #1
Jeep Smokeless #4
asf06 is offline  
post #10 of 10 Old 07-16-2015, 03:02 PM
unkajeffy
Registered User
 
unkajeffy's Avatar
1991 YJ Wrangler 
 
Join Date: Jul 2010
Location: Camden, TN
Posts: 422
Check your temp at the thermo stat housing with an infra red gun They are pretty cheap. As for a place to work I used to rent a big storage locker for a month. Used to be $30 bucks. Cracked manifolds are pretty common, but run the codes and post em up. Is it getting hot in stop and go traffic or just highway speeds?
Jeff

Michigan Yankee in Redneck Land
unkajeffy is offline  
Reply

Tags
4.0 , ax-15 , exhaust , overheating , YJ

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