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were all 4.0s created equal?

X

xjtroudt

NAXJA Forum User
Location
Denver
What is diffrent between lets say a 95 4.0 and a 99 4.0?
shrug.gif
I have a quote for a master rebuild kit for a 95 at $450 and a 99 at $610. I know that the intake/exhaust manifold gaskets are diffrent, but what else is diffrent? If anything? Would love to save $140
 
Blaine B. said:
In 96 there was a slight redesign of the motor. Not sure of anything after that besides the aluminum head in 2000.
Click to expand...


Just a minute there professor, no aluminum head is made for the Jeep 4.0 other than the one made by HESCO.....or some other after market company. Never came stock with Al Heads.
 
2000-2001 aluminum heads. Had a casting defect. Still used aluminum heads after tha for the 4.0 but they were changed....

I'm no professor but thanks for the title.
 
Blaine B. said:
2000-2001 aluminum heads. Had a casting defect. Still used aluminum heads after tha for the 4.0 but they were changed....

I'm no professor but thanks for the title.
Click to expand...

they had bad castings but they arnt aluminum. where did you get the idea that they are aluminum?
 
Yeah, not aluminum, but 2000-2003 0331 heads are prone to cracking. Supposedly they fixed it in either 03 or 04. Also, the 00-01 XJ has some engine mount and accessory mount differences.
 
The 4.0L never came stock with an aluminum head. The 00-06 (or is 07?) head wasn't significantly lighter than its predecessors either. The only aluminum head currently available for the 4.0L is Hesco's.
 
Blaine B. said:
Since when are the 2000-2001 heads not aluminum? This is what I've been hearing for years! More lightweight than the pre 00 iron heads too.....so what gives?
Click to expand...

do you believe everything you hear?

i think you just confused the head cracking issue as a problem becuase they were aluminum.
 
- Around 96ish I believe the internal ribbing on the engine was improved to make it more rigid
- 99 got an improved intake manifold to improve performance, but also more emissions which took back some of that performance
- 99 or 2000 got the coil packs
- some bad castings for the heads, as mentioned before
- 91+ had the good (NOT Renix) fuel injection systems
- Somewhere around 99 I think there was a problem with heat soaking the injectors, causing hard starts. There was a fix for this


I'm sure there's a ton of other stuff people will chime in about ;)

Overall, any 91+ 4.0 is a darn good motor and good for a few hundred thousand miles. Just make sure the last owner took at least slightly good care of it. I bought a 97 4.0 that a previous owner installed a 160 degree thermostat in and then drove lots of short trips with, so the motor never heated up and carbon built up inside to the point an intake valve is sticking... so now I have to pull the head. I have two other Jeeps with 4.0's, one with 200K miles that run perfect.
 
mikeprince said:
- Around 96ish I believe the internal ribbing on the engine was improved to make it more rigid
- 99 got an improved intake manifold to improve performance, but also more emissions which took back some of that performance
- 99 or 2000 got the coil packs
- some bad castings for the heads, as mentioned before
- 91+ had the good (NOT Renix) fuel injection systems
- Somewhere around 99 I think there was a problem with heat soaking the injectors, causing hard starts. There was a fix for this


I'm sure there's a ton of other stuff people will chime in about ;)

Overall, any 91+ 4.0 is a darn good motor and good for a few hundred thousand miles. Just make sure the last owner took at least slightly good care of it. I bought a 97 4.0 that a previous owner installed a 160 degree thermostat in and then drove lots of short trips with, so the motor never heated up and carbon built up inside to the point an intake valve is sticking... so now I have to pull the head. I have two other Jeeps with 4.0's, one with 200K miles that run perfect.
Click to expand...

The Renix motors aren't that bad either. It was still a 4.0! I'm sure there are plenty of those with well over 200k. BTW I don't own one with a renix.
 
mikeprince said:
- Around 96ish I believe the internal ribbing on the engine was improved to make it more rigid
- 99 got an improved intake manifold to improve performance, but also more emissions which took back some of that performance
- 99 or 2000 got the coil packs
- some bad castings for the heads, as mentioned before
- 91+ had the good (NOT Renix) fuel injection systems
- Somewhere around 99 I think there was a problem with heat soaking the injectors, causing hard starts. There was a fix for this


I'm sure there's a ton of other stuff people will chime in about ;)

Overall, any 91+ 4.0 is a darn good motor and good for a few hundred thousand miles. Just make sure the last owner took at least slightly good care of it. I bought a 97 4.0 that a previous owner installed a 160 degree thermostat in and then drove lots of short trips with, so the motor never heated up and carbon built up inside to the point an intake valve is sticking... so now I have to pull the head. I have two other Jeeps with 4.0's, one with 200K miles that run perfect.
Click to expand...

Can't chime in regarding the heads but but the heat saoking problem is mainly with 00 and 01. I have the problem which only seems to happen in colder temperatures (weird). A buddy of mine has tried the "fix" and it doesn't work.
 
SharkXJ said:
Can't chime in regarding the heads but but the heat saoking problem is mainly with 00 and 01. I have the problem which only seems to happen in colder temperatures (weird). A buddy of mine has tried the "fix" and it doesn't work.
Click to expand...

Hook up a timer to your efan so that it runs for 1 or 2 minutes after shutdown, that is "the fix" IMHO.
 
SharkXJ said:
Can't chime in regarding the heads but but the heat saoking problem is mainly with 00 and 01. I have the problem which only seems to happen in colder temperatures (weird).
Click to expand...

There is another TSB for the cold start issues on the 00-01.. requires a reflash of the PCM.
 
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