The Top 5 Common Dodge 5.9 Magnum Engine Issues. Chrysler developed the 5.9 Magnum, a naturally aspirated 5.9L V8 engine, from 1992 until 2003. With a displacement of 360 cubic inches, the engine is also known as the 360 Magnum. The 5.9 Magnum was replaced in 2003 by the 5.7L Hemi V8. The 5.9 Magnum has a younger brother, the 5.2 Magnum, which is likewise a naturally-aspirated V8 and was utilised as the base engine choice for Dodge Grand Cherokees and Jeep Grand Cherokees at the same time.
The Magnum is based on the Chrysler LA engine family, which consists of a series of pushrod overhead valve, 90-degree short block gasoline engines. The LA 360 V8 was built from 1971 to 1993, when it was completely replaced by the 5.9 Magnum. While the Magnum is an enhanced LA-series engine, the title “Magnum” was only used as a marketing slogan for the engines.
Despite its greater engine capacity, the 5.9 Magnum has been criticised for its lack of power compared to its Ford 5.4 Triton and Chevy 5.3 Vortec counterparts, delivering 245-250hp and 335-350lb-ft of torque. The large engine size has a drawback in terms of gas mileage. The engine’s reputation as a gas guzzler has led to additional criticism.
Despite earning a bad name when compared to Ford and Chevy engines of the time, the 5.9 Magnum holds its own in terms of dependability. While the 5.3 Vortec was regarded for its dependability, Ford’s Triton engines were notorious for their issues.
Vehicle Applications for 5.9 Magnum
- 1998-2003 Dodge Dakota
- Dodge Ram (model years 1992-2002)
- Dodge Ram Van & Waggon, 1992-2003
- 1998-2003 Dodge Durango
- Dodge Ramcharger 1992-2001
- Jeep Grand Cherokee 5.9 Limited 1998
Common Dodge 5.9 Magnum Issues
- Plenum Gasket Failure
- Cylinder Head Cracks
- Failure of the Timing Chain
- Front End Flaws
The 5.9 Magnum has two major issues: plenum gasket leakage and weak cylinder heads. Aside from these two faults, the 5.9 is a strong and dependable engine. People either have no problems with their 5.9 or they have a lot of problems with it. People who have no problems appear to outnumber those who have many problems.
1. Leak in the 5.9 Magnum Plenum Gasket
On the 5.9 Magnum, the intake manifold, also known as an intake plenum, is made up of two different sections. The plenum’s top section is a cast aluminium manifold, while its bottom section is a stamped steel plate. To seal the top and bottom portions together, a plenum gasket is employed.
Gaskets are infamous for degrading and wearing out over time in any engine. The plenum gasket on the Dodge 5.9 Magnum is prone to failure. When the gasket fails, an air leak develops and the engine loses vacuum pressure, resulting in a variety of performance difficulties.
While there are a few strategies for recognising a faulty plenum gasket, most people are unaware of the problem until the catalytic converter becomes clogged. When the cat becomes clogged, you will notice a significant loss of power. With clogged cats, engine pressure rises because air cannot easily exit the engine, increasing the probability of cylinder heads splitting because they are already weak.
Symptoms of 5.9 Magnum Plenum Gasket Leak
- While accelerating, the engine makes a pinging noise.
- Excessive use of oil
- Spark plugs that are faulty
- Idling in a rough manner
- Misfiring cylinders (usually cyl #8)
- Inadequate overall performance and a lack of power
- Poor gas mileage
- O2 sensor failure
How to Diagnose a Leaking Plenum Gasket
Unfortunately, there is no infallible way to identify if your plenum gasket is faulty. Having some of the aforementioned symptoms is a good indicator. There are a few diagnostic techniques that can give you a good indication whether or not the gasket is faulty, but none are guaranteed.
Option 1: Open the throttle body and shine a torch into the manifold. The inside of the manifold should be relatively clean, with no standing oil or sludge. If there is any oil or other buildup, the gasket is most likely faulty.
Option 2: Take the PCV valve off of the valve cover and check the air pressure. There should be air coming out of the valve cover; if there is a vacuum coming from the cover, the gasket is leaking.
Alternatives for Plenum Gasket Replacement
Because this is a widespread problem, there are various aftermarket repair kits available. Replacing the gasket with an OEM replacement is a terrible idea because it will most certainly leak again. Dodge attempted to replace the gasket with a metal gasket rather than a rubber gasket, which is also known to be a temporary repair. According to some, the original gasket can be completely removed and replaced with metal washers under the bolt heads to allow the intake manifold plenum lid to be snugly fastened down.
Instead, aftermarket repair kits like the Hughes Engine Plenum Repair Kit employ a larger metal plate with heavy-duty fasteners and brand-new intake bolts. The replacement should take roughly 4-6 hours of labour from a professional shop, but most DIY’ers, regardless of skill, can complete it in less than a day.
The final alternative is to replace the intake manifold with an aftermarket one that eliminates the two-piece arrangement. The plenum gasket is no longer an issue because to the removal of the two-piece design. Additionally, changing the manifold and intake system might result in significant power improvements.
2. Cylinder Head Cracks – Dodge 5.9
The 5.9 Magnum’s main disadvantage is its cylinder head fragility. While the heads were redesigned for the LA 360 engine, with higher air flow, larger valve sizes, and an improved combustion chamber structure, they are still known to be quite weak.
Excessive heat is the most prevalent cause of cracked cylinder heads. Coolant loss, faulty water pumps, serpentine belt problems, and other factors can all contribute to elevated engine temperatures. Cast iron heads expand and break as engine temperatures rise. Because the valve seats are induction hardened into the heads rather than forced in, cracks are most likely between them.
While some shops estimate that over 50% of 5.9 heads are fractured, the good news is that the bulk of the flaws are quite tiny. While we don’t encourage it, we’ve seen folks drive around with cracked skulls for years without incident.
Symptoms of a Cracked Cylinder Head – 360 Magnum
- Overheating of the engine
- Water in oil (thick white substance)
- Leaking coolant or oil from the cylinder head
- Gas is applied to spark plugs.
- Misfires in the engine
- The best approach to detect a damaged head is to do a cylinder leak-down or compression test.
Options for Cylinder Head Replacement
While it is possible to continue driving on small cylinder head cracks, it is a dangerous game to play. Cracked heads can cause substantial internal engine damage, necessitating the purchase of a new engine. As a result, we advise replacing damaged heads with stronger aftermarket replacement heads.
Because of the frequency of this issue, there are dozens of reasonably priced aftermarket heads for the Dodge 5.9 Magnum. Because aftermarket heads have thicker metal in the combustion chambers and decks, the cracking problem is eliminated.
3. Failure of the Timing Chain
Timing chains link the camshaft and crankshaft, which are in charge of opening and closing valves. While the exhaust valve remains closed, the intake valves open and allow air and gas into the engine. When the intake valve shuts, the exhaust valve opens, allowing exhaust gases to escape. The timing chain is in charge of controlling this procedure for each cylinder and valve.
The chain on the 5.9 Magnum, like most timing chain engines, stretches over time. While a lack of frequent oil changes can hasten this issue, the timing chain on the 5.9 Magnum often begins to stretch around 100,000 miles. While it is not required to be replaced at this exact time, I would recommend changing the chain after 150,000 miles if it has not showed signs of wear or stretching previous to that.
When the chain is overstretched, it can jump a few teeth and produce substantial performance problems. When the timing chain strains, the timing of each valve’s opening and closing becomes out of whack, and the engine begins to function very poorly. If the chain strains to the point where it breaks off its guides, it can cause the engine internals to slam against each other, necessitating a full engine rebuild.
5.9 Magnum Symptoms of Timing Chain Failure
- Frequently occurring cylinder misfires (the most common)
- Inadequate power
- Idling rough/rattling while idling
- Poor overall performance
- The engine will not start.
- Optional Replacements
If your timing chain is stretched, the only real solution is to replace it. When replacing the chain, we recommend using a double roller chain. The twin roller timing chain gives added strength and reliability for only a few dollars more than a stock/OEM timing chain.
4. 5.9 Magnum Inadequate Front End
The Magnum 360 is a fairly large engine at 5.9L, therefore it carries substantial weight. Unfortunately, the front ends of the Dodge Rams in which the 5.9 is installed are a weakness of the truck.
While these issues aren’t necessarily engine-related, I thought it was worth emphasising that certain trucks may require additional maintenance. Parts must obviously be replaced, as with anything old.
That being said, the front-end components on the Dodge Ram are notorious for being weak and in need of replacement as the truck accumulates more miles. These fixes aren’t unusual for high-mileage trucks; just be aware that problems with these parts may manifest themselves slightly earlier than expected.
- Bearings and axle seals
- Bearings and joints for wheels
- tying rods
- Hubs for wheels
5.9. Magnum Gearbox Issues
Although not an engine issue, gearbox dependability is a typical issue worth discussing. Overall, the 46RH and 46RE transmissions utilised with the 5.9 are, at best, erratic.
Torque converters and gearbox cooling lines are known to fail in addition to improper gearing ratios. The reverse and overdrive assembly on 44 transmissions frequently malfunctions as well. People who tow frequently, especially in overdrive, will encounter problems far sooner than those who do not tow and drive conservatively.
These engines are rock solid when properly rebuilt with updated internal components. Keep in mind that these trucks are now 20+ years old, and tiny internal components such as seals have degraded and worn down dramatically since they were new. Overall, without a rebuild, the gearbox is likely to be unreliable, especially if the mileage exceeds 150,000 km.
Some Dodge 5.9 Magnum owners may shift into neutral before a cold start to allow gearbox fluid to circulate throughout the system from the start. Because the pump does not circulate fluid in park, shifting into neutral provides a bit of extra lubrication before taking off. This can help with interior wear and potentially extend the life of any problems.
5.9 Magnum Dodge Reliability
Overall, with proper maintenance and care, the 5.9 Magnum can be a dependable engine. The reliability reviews are uneven, with many people experiencing no troubles at all. Those that do report difficulties, on the other hand, tend to report a lot of them. One of the most significant concerns is that these trucks are now more than 20 years old.
While a plenum gasket failure is almost always a given, cracked cylinder heads are less common, though still a danger, and the cracks tend to be less serious. There are no other faults with the 5.9 Magnum save these two. Fortunately, the plenum gasket can be replaced with an aftermarket kit for less than $200, and cylinder head repairs are affordable in comparison to other engines. Front-end components will almost certainly need to be replaced at some point, and the gearbox is another unknown, depending on how the truck has been operated over its lifetime.
These engines can last up to 350,000 miles if properly maintained. However, it is worth mentioning that the 5.9 will require a number of standard maintenance items to be serviced in order for it to last this long. Water pumps, oil pumps, gaskets, seals, belts and chains, and so on will most likely fail once or twice on the trip to that kind of miles.