[99wjtx]

Any aluminum head engine that overheats is probably going to suffer some physical damage - warped heads, melted pistons, dropped valve seats, cracked heads (certain early 2000s GM LM7 LS Gen III 5.3L, for example). The WJ cooling system is not really a great design. Often, the radiators end up leaking and sometimes do so in a way that causes replenishment from the reservoir to not function correctly, ultimately resulting in a surreptitious low coolant, overheat event without ever appearing as though they ran low on coolant.

That's not the fault of the 4.7L long block but rather a failure of supporting parts and accessories around it. If anything, the WJ design team failed the 4.7, not the other way around.

 

[virginiamountainman]

Any aluminum head engine that overheats is probably going to suffer some physical damage - warped heads, melted pistons, dropped valve seats, cracked heads (certain early 2000s GM LM7 LS Gen III 5.3L, for example). The WJ cooling system is not really a great design. Often, the radiators end up leaking and sometimes do so in a way that causes replenishment from the reservoir to not function correctly, ultimately resulting in a surreptitious low coolant, overheat event without ever appearing as though they ran low on coolant.

That's not the fault of the 4.7L long block but rather a failure of supporting parts and accessories around it. If anything, the WJ design team failed the 4.7, not the other way around.

Well, I suppose there is some truth to that. However, radiators fail on just about every 20+ year old car. I've seen way more Toyotas with leaky radiators than Jeeps - for whatever its worth.
I would honestly prefer to overheat a 4.7 than a 5.3 given the GM engine's tendency to crack the head vs. the 4.7s just warping. You can fix a warped head. A cracked head is garbage - and it costs a lot more than just a machining job to replace. In either case, the head is coming off.
But I do realize that the cooling system on the 4.7 WJs aren't the best. The hydraulic fan in particular can be problematic.

 

[99wjtx]

Well, I suppose there is some truth to that. However, radiators fail on just about every 20+ year old car.

Maybe the OE radiator is marginally better, I'm not sure, but the consensus of experience here on the forum several years ago was that a WJ radiator might be good for about 5 to 8 years give or take. That's not scientific but that seems to be the experience of a lot of us. As far as I know, WJ radiators are not fundamentally different from any other hybrid aluminum plastic tank design, so I'm not exactly sure why that is, but I have a theory that I've posted before about torque-induced fatigue cracks or stress fractures in the radiator plastic under the fan shroud transmitted from the engine by the upper radiator hose - something that an accordion-type hose could probably resolve.

 

[virginiamountainman]

Maybe the OE radiator is marginally better, I'm not sure, but the consensus of experience here on the forum several years ago was that a WJ radiator might be good for about 5 to 8 years give or take. That's not scientific but that seems to be the experience of a lot of us. As far as I know, WJ radiators are not fundamentally different from any other hybrid aluminum plastic tank design, so I'm not exactly sure why that is, but I have a theory that I've posted before about torque-induced fatigue cracks or stress fractures in the radiator plastic under the fan shroud transmitted from the engine by the upper radiator hose - something that an accordion-type hose could probably resolve.

That's interesting. I can definitely see why a cracked radiator would cause 4.7 problems lol.

 

[Mr. Bitey]

I have a theory that I've posted before about torque-induced fatigue cracks

THAT is a solid theory I can wrap my pea brain around. 100% in my Heep notes....

 

[cDee63]

^^ That is a very good theory I have thought about myself. Drive around with the hood off, most would be shocked at just how much the engine does move around in it's mounts. When I was stroking lines as a designer one of the hats I wore was under hood packaging on the original Durango with the 5.9L. The envelope on movement for the engine was 60 mm, that is over 2.25 inches. And that envelope was around the entirety of the power train in all vectors. Which in our WJ's means the upper hose is getting quite a bit of flex, and due to it being a pretty short hose it transmits a lot of the movement to the radiator.

 

[99wjtx]

Thanks. That theory comes from reading through the forum and my own experience with two WJs after several long periods of unexplained overheating. I bought my '01 from a salvage auction with an overheated engine. When I started disassembling it, it wasn't long before I discovered that it had been leaking for YEARS under the upper hose connection - pictured below.

On my '99, I went through a couple of periods of mildly overheating, like in stop and start traffic. I'd check the reservoir and it would be fine or only slightly low. Trying to track it down, I replaced hoses, thermostats, water pumps and even tried the stop leak stuff. Finally, I realized the cooling system was not pulling from the reservoir as it should for replenishment. It would sometimes pull a little and other times not at all. I also had water splash marks all around the upper part of the radiator on the upper hose and around the fan shroud, but nothing really ever looked wet. It was mostly a vapor leak.

I went through the same scenario at least twice, with nearly a decade in between, and had to slowly re-remember and re-learn the suspected cause - a small crack leading to a vapor leak at the top of the radiator that would generally NOT drip anywhere but would still slowly release coolant over time. During cool down, the cooling system was replenishing with air from the atmosphere.

Also, I believe the upper radiator hose is a bit different for '99 to '00 model years. Some application guides don't even make a distinction but there ARE different part numbers. Technically, you can make the later years hose fit. I remember trimming one at some point because it seemed slightly too long. I thought I was doing a good thing by making it have less kink when in reality I was probably only contributing to the actual problem.

On top of all that, I had those tragic incidents with Dayco hoses. The lower hose ruptured on my '01 but I barely caught it in time. A couple of years later, the lower hose ruptured on my '99 while the adversary was driving it, and it suffered a fatal heat stroke. 😐

 

[Mr. Bitey]

Both the 4.7's that puked a seat on me had no cooling issues (99 & 04, both puked the #8 intake seat). BUT - both were private sales with no records. One had a newish rad and water pump, the other had aftermarket hoses and a booger glued outlet on the rad with the "vapor" leak. I smelled coolant occasionally on the latter, and assumed a heater core getting ready to say bye-bye. I only noted the vapor leak when sitting first in line at a light, directly facing the low late-afternoon sun. Despite no cooling issues under my ownership, I think it is safe to assume both had a history of it. The other 3 4.7s I have owned lived long and strong lives in term of mileage, 2 WJ's well over 200k, and a Durango that blew the trans about 1200mi shy of 300k.

The current also came with the booger glue and vapor leak. I also discovered just this summer that the water pump was replaced at some point, and the timing cover had witness marks of the previous pump coming apart. At 198k, she hasn't puked yet, BUT - it did come with HO cams and a 2008 intake installed - someone likely replaced/rebuilt the heads. Now that I think of it, I should stick a borescope into #8 for giggles and poops and see if the piston is dinged up....

 

[cDee63]

I blame my drop on bad remanned heads. Nice fresh ones, never overheated and a seat dropped after 12,000 miles. I replaced it and then took them both to a REAL shop to be rebuilt. Of course all the components were trash, my luck. After dropping a G on new valves, seats, guides, seals and the rebuild itself it runs great. Number 1 piston does have a pretty good ding in it however it doesn't seem to bother anything.

 

[oomanoptt]

Just because you had one bad experience doesn't mean you should call 4.7s junk. What about all the success stories? You pick any "good" engine (Ford I-6, Jeep I-6, GM 3.8, GM 5.3/6.0, etc), I'll find you somebody who had a horrible experience with them.
Personally, I've never had a 4.7 fail on me. I've owned two. My dad has owned two. I work at a shop and have never seen a 4.7 come in with dropped valve seats. Frankly, I've hardly seen a 4.7 come in for any problem. Mostly just maintenance like oil changes, coolant exchanges, etc. The worst problems I've seen was oil leaks and one cracked vacuum line.

Every time and I mean every time I start my 4.7. I think about what might happen the next time I turn it off. I bought my 04 Overland for 5k. I’d be crazy to drop 4k on a rebuild.

 

[99wjtx]

The guy in this vid totally riffs on the 4.7. I think he's a little too harsh and is lacking some info I've come across over the years regarding thermal issues and causes. Anyway, the 4.7 definitely has its haters and he's one.

Whatever the actual truth (they made millions of 4.7s) once anecdotal reports take root in the auto industry it can quickly become gospel and effectively tank a product, science and statistics be damned - especially when, for example, people wanted to justify to themselves and their wives a Hemi upgrade. Why should the automaker argue with that or make much effort to change the perspective?

I've had exceptional reliability out of it overall but that's obviously not been everyone's experience.

 

[oomanoptt]

Both the 4.7's that puked a seat on me had no cooling issues (99 & 04, both puked the #8 intake seat). BUT - both were private sales with no records. One had a newish rad and water pump, the other had aftermarket hoses and a booger glued outlet on the rad with the "vapor" leak. I smelled coolant occasionally on the latter, and assumed a heater core getting ready to say bye-bye. I only noted the vapor leak when sitting first in line at a light, directly facing the low late-afternoon sun. Despite no cooling issues under my ownership, I think it is safe to assume both had a history of it. The other 3 4.7s I have owned lived long and strong lives in term of mileage, 2 WJ's well over 200k, and a Durango that blew the trans about 1200mi shy of 300k.

The current also came with the booger glue and vapor leak. I also discovered just this summer that the water pump was replaced at some point, and the timing cover had witness marks of the previous pump coming apart. At 198k, she hasn't puked yet, BUT - it did come with HO cams and a 2008 intake installed - someone likely replaced/rebuilt the heads. Now that I think of it, I should stick a borescope into #8 for giggles and poops and see if the piston is dinged up....

Thats very encouraging. My 04 has 145k on it. Im 74. If I could squeeze another 55k out of it before I kick off. I'd be very happy.

 

[oomanoptt]

Thats very encouraging. My 04 has 145k on it. Im 74. If I could squeeze another 55k out of it before I kick off. I'd be very happy.

"Taping a spoon to a screwdriver". I like that. Im going to guess the Rams are much heavier than the WJ and that might be one reason for a high failed rate in those trucks.

 

[99wjtx]

Both of my WJs also ended their first lives with dropped valves BUT in both cases it was clearly due to a failure of the cooling system. A radiator leak the previous owner appeared to have finally given up on at 162,500 miles and a ruptured lower radiator hose in the other case at 233,092 miles where the driver didn't notice she was driving a vehicle with ZERO coolant until it literally died from catastrophic heat stroke right there on the road.

In my recent rebuild project I've since discovered that particular Jeep had a clogged line from the reservoir which I'm sure contributed to its unpleasant end of life experience.

 

[virginiamountainman]

All I can say is that I have had exceptionally good experiences with my 4.7s. If you just "jimmy-jam do the right things" (as Doug from D&E in the Garage on YouTube would say), you'll probably have good experiences, too.
And let's face it: all engines break down and need repairs at some point or another. I recently did a head gasket job on a project 4.7 and was just amazed at how straightforward and simple it is to work on. We have excellent service information and countless videos on these 4.7s...they're just so easy to work on. You can buy cars with them for cheap, flip them and sell them at a decent profit because of people who talk them down and think they're worthless.
The long and the short of it: I will be driving a 4.7 till I'm dead and gone. Countless 4.7s will still be going strong when these new turbocharged 4 and 3 cylinders drop like flies.

 

[cDee63]

I agree. I received a well abused and neglected 4.7 in my 04, which I bought for $500 bucks (the Jeep, not just the engine) Had no coolant and leaked like a net but ran strong though it did smoke on start up, valve seal issues. After messing around with 2 head remann companies, both of which should do the world a favor and fold, and three different heads, one of which dropped a seat after 12,000 miles of use, I had the set rebuilt completely by a reputable shop in Detroit area. I replaced the entire timing set and chains because I was already in there, updated the valve train with revised factory parts and now it runs excellent. A lot of work yes, none of it caused by the engine itself. All of it caused by incompetent retailers and junk remanned parts. The bottom end is untouched with the exception of an oil pump, again because I was in there (replaced a rusted out oil pan as well. Michigan winters will do that). Number one piston survived a valve seat banging away at it with no problems. Now at 186,400 it runs strong and I am sure it will well past 200,000. I will say the one issue IMO is the oil pump could be more robust as far as pressure and volume. My LS puts out almost twice the pressure at idle according to the mechanical gauges I have hooked up to each one at the same temp and oil weight, I believe that is the cold start rattle issue root cause. Ford's bullet proof 4.6 2V uses the same part number lash adjuster and those don't rattle on cold start at all even with very high mileage (over 300,000).

 

[virginiamountainman]

I agree. I received a well abused and neglected 4.7 in my 04, which I bought for $500 bucks (the Jeep, not just the engine) Had no coolant and leaked like a net but ran strong though it did smoke on start up, valve seal issues. After messing around with 2 head remann companies, both of which should do the world a favor and fold, and three different heads, one of which dropped a seat after 12,000 miles of use, I had the set rebuilt completely by a reputable shop in Detroit area. I replaced the entire timing set and chains because I was already in there, updated the valve train with revised factory parts and now it runs excellent. A lot of work yes, none of it caused by the engine itself. All of it caused by incompetent retailers and junk remanned parts. The bottom end is untouched with the exception of an oil pump, again because I was in there (replaced a rusted out oil pan as well. Michigan winters will do that). Number one piston survived a valve seat banging away at it with no problems. Now at 186,400 it runs strong and I am sure it will well past 200,000. I will say the one issue IMO is the oil pump could be more robust as far as pressure and volume. My LS puts out almost twice the pressure at idle according to the mechanical gauges I have hooked up to each one at the same temp and oil weight, I believe that is the cold start rattle issue root cause. Ford's bullet proof 4.6 2V uses the same part number lash adjuster and those don't rattle on cold start at all even with very high mileage (over 300,000).

That's an interesting observation about the oil pressure. What kind of LS are we talking about? If it is an LS with the AFM system, having twice as much oil pressure as an old-school 4.7 V8 wouldn't surprise me.
Although the 4.6 is a good motor, I would still give the 4.7 an edge over it in overall reliability. My co-worker bought an F150 with a 2V 5.4 last year, rebulit the transmission himself and got it running this summer. The transmission has been great. He has had nothing but problems with the engine, though, in spite of having only 150k miles on the clock. It has been misfire after misfire, rough idle, etc., etc., etc. He finally parked it last month, bought one of our customer's Subarus with a blown engine, put a used motor in it and is now commuting in it 😂. I have just seen a ton of crazy misfire and idle problems with 4.6/5.4s, as well as timing issues (even on 2Vs, much less 3Vs). Nevermind the horrible exhaust manifold leaks they have.
To be honest, most every 4.7 I've seen coming in my shop doors was running smoothly and powerfully. 99% of the work I've done to 4.7s has been maintenance, and I do mean 99%. We have only done basic repairs like oil leaks, a broken vacuum line, etc. I just haven't seen or personally experienced many 4.7 problems. Can't say that at all about Tritons, although I wouldn't say they are horrible. They are one of the last V8 motors I would choose to own, though, if for no other reason than there is so little room in those engine bays to work on them.
And I also am impressed by how much more torque the 4.7 makes compared to the 4.6...30 Lb-Ft is no small difference!

 

[99wjtx]

The 4.7 design is pretty straight-forward. They really didn't put any kind of wonky new tech in there. All metal chain guides might have been better, but I haven't heard much about the plastic ones causing trouble either. As I've mentioned many times in other threads, my personal opinion is that 4.7 failures actually had more to do with supporting infrastructure around it rather than the long block itself - things like the cooling system (primarily!), cramped engine bay encouraging excessive heat, etc.

The head gaskets always baffled me as well. I guess there are obvious economic and logistical advantages to making a single gasket that flips, but the result of that is blocked or partially blocked coolant passages. Obviously, they wouldn't have done it if they thought it was a problem but yeah - that decision seems ... weird.

 

[virginiamountainman]

The 4.7 design is pretty straight-forward. They really didn't put any kind of wonky new tech in there. All metal chain guides might have been better, but I haven't heard much about the plastic ones causing trouble either. As I've mentioned many times in other threads, my personal opinion is that 4.7 failures actually had more to do with supporting infrastructure around it rather than the long block itself - things like the cooling system (primarily!), cramped engine bay encouraging excessive heat, etc.

The head gaskets always baffled me as well. I guess there are obvious economic and logistical advantages to making a single gasket that flips, but the result of that is blocked or partially blocked coolant passages. Obviously, they wouldn't have done it if they thought it was a problem but yeah - that design seems ... weird.

The project 4.7 I replaced head gaskets on actually had a broken timing chain guide. Well, to specify, the guide itself was still attatched but the nylon part was cracked. It wasn't making a bit of noise prior to the repair. I've also seen that on the notorious 5.4 3V, where the timing chain guide may be completely broken off the engine but you couldn't hear a thing...and the engine was still in time. Ford Built ToughTM I guess, lol. (Just kidding, that 3V isn't very tough )

 

[cDee63]

That's an interesting observation about the oil pressure. What kind of LS are we talking about? If it is an LS with the AFM system, having twice as much oil pressure as an old-school 4.7 V8 wouldn't surprise me.
Although the 4.6 is a good motor, I would still give the 4.7 an edge over it in overall reliability. My co-worker bought an F150 with a 2V 5.4 last year, rebulit the transmission himself and got it running this summer. The transmission has been great. He has had nothing but problems with the engine, though, in spite of having only 150k miles on the clock. It has been misfire after misfire, rough idle, etc., etc., etc. He finally parked it last month, bought one of our customer's Subarus with a blown engine, put a used motor in it and is now commuting in it 😂. I have just seen a ton of crazy misfire and idle problems with 4.6/5.4s, as well as timing issues (even on 2Vs, much less 3Vs). Nevermind the horrible exhaust manifold leaks they have.
To be honest, most every 4.7 I've seen coming in my shop doors was running smoothly and powerfully. 99% of the work I've done to 4.7s has been maintenance, and I do mean 99%. We have only done basic repairs like oil leaks, a broken vacuum line, etc. I just haven't seen or personally experienced many 4.7 problems. Can't say that at all about Tritons, although I wouldn't say they are horrible. They are one of the last V8 motors I would choose to own, though, if for no other reason than there is so little room in those engine bays to work on them.
And I also am impressed by how much more torque the 4.7 makes compared to the 4.6...30 Lb-Ft is no small difference!

When I speak of Ford Mod motor reliability I speak ONLY of the 4.6 2V common in the Panther platform, aka Crown Vic. I have had several over the years and they are rock solid. 3V, 5.4 anything, not so much. The LS I refer to is the OG in my 2K Vette, an LS1 with 123,000 on the clock. Not that it is perfect either, has noticeable piston slap when cold for about a minute..