5.9l Misfire

[Bear_Gibson]

I am now reading stuff where these magnum heads crack very often. So.... that would suck. Would that cause a misfire? How common is this?

My misfire was a burned #1 exhaust valve. The reason the heads cracked is usually because the plenum leaked oil into the combustion chambers. This would clog the cat which is right below the right side head. The heat from the cat can cause the head to crack. I relocated mine further back and used a magnaflow y pipe in place of the stock converter.

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[Bear_Gibson]

I totally missed your question. Yes a cracked head can cause a misfire it's the same as a blown head gasket basically.

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[Braeden Clark]

My misfire was a burned #1 exhaust valve. The reason the heads cracked is usually because the plenum leaked oil into the combustion chambers. This would clog the cat which is right below the right side head. The heat from the cat can cause the head to crack. I relocated mine further back and used a magnaflow y pipe in place of the stock converter.

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Well all the sudden I am not so sure about purchasing a Ram. At least one with a misfire. At first I was thinking simple tune up but now it seems like it may be a bigger deal. A more expensive deal.

 

[Bear_Gibson]

Well all the sudden I am not so sure about purchasing a Ram. At least one with a misfire. At first I was thinking simple tune up but now it seems like it may be a bigger deal. A more expensive deal.

I fixed mine in 2016 and I'm just mow having the plenum issue. I would worry about transmission more than the engine. The engine is easy to work on.

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[Braeden Clark]

I fixed mine in 2016 and I'm just mow having the plenum issue. I would worry about transmission more than the engine. The engine is easy to work on.

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Would the cracked head show up in a compression test? My Jeeps issues showed up with a coolant pressure test because of where it was located

 

[Bear_Gibson]

Once you remove the fan and fan shroud you can stand in front of the engine and work on it. Piece of cake. Its an old school pushrod v8. Move your cat further back. Hughes engines makes a plenum fix kit if you wanna keep the torque monster keg intake. They also sell an Edelbrock bolt on air gap intake if you never wanna worry about it again.

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[Bear_Gibson]

Would the cracked head show up in a compression test? My Jeeps issues showed up with a coolant pressure test because of where it was located

That I'm not sure. I forget where they crack, i just know its the passenger head that does it. Mine wasn't cracked.

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[Braeden Clark]

That I'm not sure. I forget where they crack, i just know its the passenger head that does it. Mine wasn't cracked.

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Pretty sure I read between the valveseats. I honestly wasn't worried about the engine until I read about the head cracking. I don't mind working on it. I just don't want to keep having to dump money into it because a head keeps cracking. A lot to think about. Thanks for the great info.

 

[Bear_Gibson]

Pretty sure I read between the valveseats. I honestly wasn't worried about the engine until I read about the head cracking. I don't mind working on it. I just don't want to keep having to dump money into it because a head keeps cracking. A lot to think about. Thanks for the great info.

Its not something that happens all the time. It can be prevented.

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[pacofortacos]

Stock heads crack between the valves - but that very seldom causes a miss or leak.
Exhaust valve seats on the other hand tend to sink and go bad since they are just induction hardened instead of inserts.
My 01 would miss at idle and run good after 1700 or so rpms - several sunk seats and wiped out guides.

Almost all 5.9 heads will be cracked, 5.2 not quite as much but still very common.

Go aftermarket and the issue is fixed, do not get stock reman heads as they will crack eventually. Doesn't matter which side on the 5.9, both crack.

 

[Bear_Gibson]

I didn't use the hughes kit for mine. Because I didn't know about it then. That's why I'm having to do it again. The factory bolts are too long and bottom out. They used a steel cover on the aluminum intake. This causes different expansion rates. I'm gonna run a tap in mine because I don't have time to wait for the hughes kit.

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[Bear_Gibson]

Stock heads crack between the valves - but that very seldom causes a miss or leak.
Exhaust valve seats on the other hand tend to sink and go bad since they are just induction hardened instead of inserts.
My 01 would miss at idle and run good after 1700 or so rpms - several sunk seats and wiped out guides.

Almost all 5.9 heads will be cracked, 5.2 not quite as much but still very common.

Go aftermarket and the issue is fixed, do not get stock reman heads as they will crack eventually. Doesn't matter which side on the 5.9, both crack.

I'm on stock remans 5 years later.

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[pacofortacos]

Would the cracked head show up in a compression test? My Jeeps issues showed up with a coolant pressure test because of where it was located

Most will, esp. if you do it on a dry cold motor. Do not add oil, do not do it hot.

 

[Braeden Clark]

Stock heads crack between the valves - but that very seldom causes a miss or leak.
Exhaust valve seats on the other hand tend to sink and go bad since they are just induction hardened instead of inserts.
My 01 would miss at idle and run good after 1700 or so rpms - several sunk seats and wiped out guides.

Almost all 5.9 heads will be cracked, 5.2 not quite as much but still very common.

Go aftermarket and the issue is fixed, do not get stock reman heads as they will crack eventually. Doesn't matter which side on the 5.9, both crack.

What issues do the cracked heads cause? How expensive to get your valves fixed?

 

[pacofortacos]

I didn't use the hughes kit for mine. Because I didn't know about it then. That's why I'm having to do it again. The factory bolts are too long and bottom out. They used a steel cover on the aluminum intake. This causes different expansion rates. I'm gonna run a tap in mine because I don't have time to wait for the hughes kit.

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I used 2 steel covers and that worked perfectly - adds rigidity and space for the bolt.

I actually had 2 manifolds, the more modified one had the aluminum plate on it, the not as modified one ran 2 steel plates stacked w/mopar gasket. Neither ever failed.

 

[pacofortacos]

I'm on stock remans 5 years later.

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The cracks really very seldom cause any issue, it's the exhaust seat itself that fails, but happens more often if tuned and running really loaded and even then it really isn't that common on most trucks.
I was tuned and tow a boat from Pa to Fl - the 5.9 ran better than most. Even then it was over 100k miles when it failed.

 

[Braeden Clark]

The cracks really very seldom cause any issue, it's the exhaust seat itself that fails, but happens more often if tuned and running really loaded and even then it really isn't that common on most trucks.
I was tuned and tow a boat from Pa to Fl - the 5.9 ran better than most. Even then it was over 100k miles when it failed.

So i could run with a bad head and not even know it? How expensive it is to get valves fixed?

 

[pacofortacos]

What issues do the cracked heads cause? How expensive to get your valves fixed?

I personally have never seen the cracks themselves cause much of an issue - you do get some leakage past them as they go through the intake and exhaust valve seats but not usually enough to be a problem.
Mine had several sunk exhaust seats - just sunk on one side of the exhaust valve. Finally there were just too many and too severe that it caused a miss.

Just get a set of aftermarket heads and replace them if that's the problem.

An easy way to test is blow air into the cylinder at TDC for that cylinder and if there is a valve problem you will hear air come out of the intake or exhaust. Must be done cold before starting the motor. That will tell valves and/or a ring problem.

 

[pacofortacos]

So i could run with a bad head and not even know it? How expensive it is to get valves fixed?

Cracked? Yes, most often it won't do anything.
IMO the only option is new heads, other option would be to put exhaust seat inserts in but it isn't cost effective.
New heads probably $500-1000 all in if you do the work.

 

[Braeden Clark]

Cracked? Yes, most often it won't do anything.
IMO the only option is new heads, other option would be to put exhaust seat inserts in but it isn't cost effective.
New heads probably $500-1000 all in if you do the work.

I guess I will have to think if I want to deal with this. The truck seems to be rust free at a great price. Which is hella rare. But I guess I may have to dump some serious money and time into the engine. Not to mention the trans. Oh the fun...