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Jeep inline six 4.0 #4112058 06/01/16 06:19 AM
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NavyVet88 Offline OP
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I remember having this engine in my very first vehicle. 93 jeep Cherokee 4.0L and it was a great engine...for me.

I've heard these were the best engines jeep had at the time and I was wondering what your opinions were? My dad sold mine to a family friend when I left for bootcamp in 07 and it had 272k miles on it with Havoline Dino and the transmission had started slipping. Family friend was an accomplished mechanic and offered more than what was paid for it to begin with and to my knowledge it is still on the road as we speak.


2013 Honda Civic LX 1.8L 178k M1 HM 0w20 with Fram XG7317
2002 Ford Ranger Edge 3.0L 67k Castrol Edge 5w30 with Fram XG3600
Maintenance Technician by trade, working class for life.
Re: Jeep inline six 4.0 [Re: NavyVet88] #4112064 06/01/16 06:27 AM
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yvon_la Offline
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Yep , you only had to put a gear timing instead of of a timing chain and they lasted forever .the main issue with inline 6 is the aren't small but they last so long who care lol. Vw vr6 is better .yep as surprising as it mY seem a vr6 has all the quality of an inline 6 and then do it in a v6 . Probably the best engine on the planet yet

Last edited by yvon_la; 06/01/16 06:28 AM.

Truck driver
Nissan versa note s 2014 total classic 5w30(qc.ca) drivework oil filter
Hope to see many responses [Re: NavyVet88] #4112068 06/01/16 06:30 AM
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Kira Online Content
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Hello, This engine is in the Pantheon of Gasoline Engines.

I'd love to see a list of major/minor (or frequently/ rarely occurring) faults/problems generated here.
Include good things too.

I'll go first:
I've heard they lose head gaskets around 150K (major problem?) causing coolant loss.
VC gaskets get leaky and need replacement.
PCV's hardware needs replacement (thin tube to manifold clogs, grommets dry and leak, PCV orifice clogs) No biggie!

They have a timing chain (major plus)

Re: Hope to see many responses [Re: NavyVet88] #4112069 06/01/16 06:37 AM
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Donald Offline
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The basic engine was bullet-proof. But over the years you had the #331 head that cracked, and around 2001 you had pistons (at around 100K miles) that would wobble and crack the piston skirt. If you were lucky you had a scoured cylinder and a chunk of the piston skirt in the oil pan. If you were unlucky, when the chunk of piston skirt broke off it would cause catastrophic engine failure. I had the catastrophic engine failure. The mechanic who installed my reman engine said he had done a few engine swaps for that reason.


2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: Hope to see many responses [Re: NavyVet88] #4112073 06/01/16 06:40 AM
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NavyVet88 Offline OP
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In the almost 5 years I drove it, my only issues were having to replace the radiator and a broken motor mount.

Aside from the usual routine oil, brake pads, spark plugs....it was excellent. It had 127k on it when I got it the week I turned 16 and I handed my dad the keys to it the day before I left for bootcamp with 272k( dad used it frequently on long drives for his work).

I've honestly never heard any complaints from anyone on this engine that has had one. I'm in college with a guy who claims he drove his 94 Cherokee from the west coast to here in bama and back to California multiple times over the course of his ownership and he said it never gave the least bit of trouble.

I consider my self to have been very lucky to have paid $1200 for a vehicle that held up so well. A lot of kids at that age aren't so lucky and others that are usually don't treat them very nicely. I was also leaned on very hard about taking care of my jeep from my dad as well.

Last edited by NavyVet88; 06/01/16 06:43 AM.

2013 Honda Civic LX 1.8L 178k M1 HM 0w20 with Fram XG7317
2002 Ford Ranger Edge 3.0L 67k Castrol Edge 5w30 with Fram XG3600
Maintenance Technician by trade, working class for life.
Re: Jeep inline six 4.0 [Re: NavyVet88] #4112076 06/01/16 06:43 AM
Joined: Oct 2005
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Kruse Offline
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I currently have three of them. They are a good engine, but they do have some quirks.
The engine has a tendency to break pistons or piston skirts. Late 90s-early 2000 models had a problem of cracking heads.
If you want a somewhat tough, off-road vehicle, a Jeep might be for you. If you want a super reliable vehicle, I would avoid.

Re: Jeep inline six 4.0 [Re: NavyVet88] #4112099 06/01/16 07:14 AM
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Miller88 Offline
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I like the "Renix" 4.0L as far as performance goes - as long as you can make it work right and ditch the closed cooling system with exploding coolant bottle. They didn't have issues with pistons shattering or heads cracking. But also had more torque down low.

The 91+ starts to make good power at 2500 but will pull up to 5000 without issue! Mine has spent a few days running around at 4500 most of the day. Mainly snow wheeling ... which I don't do any more.

They are easier to work on than a lot of engines.

There were some flaws. The 258 and 2.5 4 cylinder which were around since before the 4.0L was a thing also suffered from top end lubrication problems. The oil pumps weren't enough. Mine seemed to do okay when the oil pump bolts backed out ...engine is quiet again with the oil pump bolted back on!

These things really take a beating, especially in Cherokees. I have seen people show up to various off road events with a $500 Cherokee and just beat the living daylights out of it ... having it hit the rev limiter all day.

Cherokees really were a good vehicle when they were newer. Great engine, very reliable toyota automatic and relatively simple electronics.


18 Forester 2.5I 6M
00 Jeep XJ
01 F-350 4x4 5M
Re: Jeep inline six 4.0 [Re: NavyVet88] #4112263 06/01/16 10:15 AM
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SeaJay Offline
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It never occurred to me that drivers would purchase a jeep because of their legendary (chuckle) reliability.

Re: Jeep inline six 4.0 [Re: NavyVet88] #4112266 06/01/16 10:16 AM
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MNgopher Offline
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It was a good motor and lasted for a very long time and a lot of miles - very tough to kill.

That being said, compared to today's reliability standards, they certainly had their level of quirks that were offset by the general ease of being able to work on them.

I had a Renix (88 Cherokee). Things I had along the way included:

-Awful closed cooling system - that was mostly fixed by converting to the open system found in the 91+ models - all drop in parts except the fan control.
-In general, a cooling system that was always close to the edge of not being big enough (mostly in the Cherokee's - space under the hood / airflow was not not great!)
-Oil filter adapter gaskets leaking
-Fuel injectors that started leaking. Replacement was easy with Ford injectors for a 5.0 mustang engine. Only trick was the goofy quick connects for the fuel rails.
-CCV system that would either get brittle and fail or just not work well.
-Weird metric thread oil filter that often was not off the shelf
-Renix system that didn't throw codes - everything was troubleshooting with a multimeter based on symptoms. Towards the end, finding a mechanic who could deal with that was interesting.

Mine never had the Rear Main seal leak that was normal on these too.

All in all, they were powerful for their age, relatively fun to drive and well matched to their applications. Tough to kill outright and relatively easy to maintain.

I miss the driving experience with mine, but I don't miss the close personal relationship I developed with it at the end since I was constantly tinkering or fixing some little thing...

Re: Jeep inline six 4.0 [Re: MNgopher] #4112284 06/01/16 10:35 AM
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Miller88 Offline
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Originally Posted By: MNgopher

-Weird metric thread oil filter that often was not off the shelf
-Renix system that didn't throw codes - everything was troubleshooting with a multimeter based on symptoms. Towards the end, finding a mechanic who could deal with that was interesting.

I miss the driving experience with mine, but I don't miss the close personal relationship I developed with it at the end since I was constantly tinkering or fixing some little thing...


The oil filter is tough to find locally. A friend of mine has a 1990 - the only locally available filter is a Fram orange can. Which seems to work, no funny noises from it. It leaked like a sieve when he got it. Previous owner overheated it and warped the head, but replaced the gasket only , then replaced the head reusing the gasket. One of the oil passages on the right side had no gasket so it would leak. Oil filter housing, oil pressure sensor, rear main seal ... all leaked a lot of oil. It's first trip used 7 quarts of oil to go 140 miles.

They are very frustrating to troubleshoot. There is now quite a bit of information on various sites on how to troubleshoot and what - but if it doesn't start, you gotta break out the mutlimeter. Bad ground will cause a lot of issues. And they always seem to have to crank for 10 seconds or more before they will run.


18 Forester 2.5I 6M
00 Jeep XJ
01 F-350 4x4 5M
Re: Jeep inline six 4.0 [Re: NavyVet88] #4112381 06/01/16 12:14 PM
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Nick1994 Offline
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Great engine, but they need a lot of tinkering. Well the car itself. My grandfather has a 96' Jeep Cherokee 4.0L 4x4, 140k miles. Has owned it for the last 9 years/40k miles. It has had EVERY single cooling system piece replaced, which isn't too bad since its 20 years old. Also got a new distributor. (Worn and chewing up the cam position sensor) and at the same time a new timing chain, since it would set a code for a misfire. Drove it 110 miles on the highway afterwards with 5 people in it and the trunk completely full and at 65 mph, it got just shy of 22 mpg. I replaced the oil pan gasket and the rear main seal, still leaks a tiny bit.

My brother has a 91 Jeep Cherokee 4.0L 4x4 213k miles, just got it back on the road after it was sideswiped 2 years ago. Has had it for 5 years/22k miles. It's been very reliable, just cooling system parts replaced, engine runs fantastic.


2015 Hyundai Sonata 2.4L 101k STP Synthetic HM 10w30 & OEM
2000 Toyota Camry 2.2L 234k Mobil Super HM 10w40 & Fram Ultra
1996 Jeep Cherokee 4.0L 149k Mobil 1 HM 10w40 & Fram Ultra
Re: Jeep inline six 4.0 [Re: NavyVet88] #4112511 06/01/16 02:41 PM
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jeepman3071 Offline
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4.0 engines are great. With that said, they MUST be maintained. Don't maintain it, and the problems begin, mostly with the cooling system. Maintaining them is pretty cheap and easy, and doing so will make them last a long time. Mine has been my daily driver for 7 years now. A friend's dad has an '89 with over 300k. The body is pretty rough, so it's just a plow jeep now, but still runs great.

The XJ Cherokee has the best combination. 4.0 with the AW4 Toyota automatic, and available AX-15 5 speed. The Wranglers also had the 5 speed but many came with a weak Chrysler auto. Build the 4.0L into a 4.6L stroker engine and you can turn a Jeep into a rocket. There are a few guys who have added NOS and boost to them and they held up. I remember talking to guys who had to do the cash for clunkers program at their dealerships, and the 4.0 was one of the toughest engines to kill. It would blow rods out the bottom and keep running on 2 cylinders. There is a video of one that ran for 12 minutes or so with the liquid glass in it.


2013 Jeep Grand Cherokee TrailHawk 5.7L (144k) - PPHM 5w30, Wix 57899
2009 BMW 328i (46k) - Castrol Edge Euro 0w40, MANN HU816X
Re: Jeep inline six 4.0 [Re: NavyVet88] #4113096 06/02/16 08:19 AM
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meep Offline
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I sold my 4.0 with over 240k on it. As a DD it was still reliable if you checked fluids weekly. I wish I'd never sold it, but had I kept it, the 7k I spent on its replacement would have all had to go back into engine, axle, and transmission overhaul. In my case I would have preferred that.

Mine leaked oil everywhere- mostly though between the block and head- very odd. Yet no mixing with coolant and vice versa. It lost coolant but not much. I bought it used and the PO warped the head. I retorqued the head and went over a bit- 15-20 ft-lbs, and consumption dropped from 1qt per week to maybe 1/3-1/2 of that. Started every morning, drove me to work. Despite its age, I have never enjoyed a vehicle as much as I did this one. 93 grand chero with the aisin trans.

M


2018 F150
2015 crv (wifey!)
Re: Jeep inline six 4.0 [Re: meep] #4113254 06/02/16 11:24 AM
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Miller88 Offline
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Originally Posted By: meep
I sold my 4.0 with over 240k on it. As a DD it was still reliable if you checked fluids weekly. I wish I'd never sold it, but had I kept it, the 7k I spent on its replacement would have all had to go back into engine, axle, and transmission overhaul. In my case I would have preferred that.

Mine leaked oil everywhere- mostly though between the block and head- very odd. Yet no mixing with coolant and vice versa. It lost coolant but not much. I bought it used and the PO warped the head. I retorqued the head and went over a bit- 15-20 ft-lbs, and consumption dropped from 1qt per week to maybe 1/3-1/2 of that. Started every morning, drove me to work. Despite its age, I have never enjoyed a vehicle as much as I did this one. 93 grand chero with the aisin trans.

M


93 was an odd ball for the Grand cherokee. Only year I'd buy since it came with the Aisin transmission instead of the Chrysler transmission.

I was going to say - if the head wasn't warped, it isn't entirely uncommon for the head gasket to start to leak around the lifter galley.


18 Forester 2.5I 6M
00 Jeep XJ
01 F-350 4x4 5M
Re: Jeep inline six 4.0 [Re: NavyVet88] #4113782 06/02/16 10:59 PM
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DoubleWasp Offline
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Mine JGC 4.0 has 262k miles. Never an unusual problem. Take the oil cap off and put your hand over the opening, and you feel nothing. She has practically no blowby at all.

RMS is a little leaky, but hey, it's been a quarter million miles.


07 Lincoln Navigator M1 0w-40/FU
68 Charger R/T / Supercharged 440 VR1/DBL7349
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