Launched in 1992, the 5.2 Magnum is a naturally aspirated 5.2L V8 engine produced by Chrysler. The engine was predominantly used in Dodge trucks and Jeep Grand Cherokee’s from 1992 until 2003 when it was replaced by the Hemi. The 5.2 Magnum is also commonly referred to as the 318 Magnum due to its 318 cubic inches of displacement.
However, the 318 Magnum is not to be confused with its predecessor engine, the Chrysler LA 318. The LA 318 was produced from 1967 until 1991. The 318 Magnum is an upgraded version of the LA 318 and was given the Magnum name by the marketing department.
The 5.2 Magnum produced 230hp and 295 lb-ft. of torque. It’s bigger brother, the 5.9 Magnum, produced 250hp and 350 lb-ft. of torque and was featured as an upgraded engine option to the 5.2 Magnum for many of its vehicle applications.
Known to guzzle gas, the 5.2 and the 5.9 have both received poor reviews against the competing 5.4 Triton and 5.3 Vortec engines. Producing less power and less torque while consuming more gasoline hasn’t given it the best reputation, despite being solid from a reliability perspective.
Despite being a very similar engine mechanically and design-wise, the 5.2 Magnum actually tends to be more reliable and have less common problems than the 5.9 Magnum.
5.2 Magnum Vehicle Applications
- 1992-2000 Dodge Dakota
- 1992-2001 Dodge Ram
- 1998-2000 Dodge Durango
- 1992-1993 Dodge Ramcharger
- 1992-2003 Dodge Ram Van
- 1993-1998 Jeep Grand Cherokee
Dodge 5.2 Magnum Engine Problems
- Plenum Gasket Leak (also called belly pan gasket)
- Camshaft Sensor Failure
- Exhaust Manifold Bolts & Gasket (ticking noise)
- Weak Transmission
1. 5.2 Magnum Plenum Gasket Leak
Just like its 5.9L big brother, the most common problem on the 318 Magnum is a leaking plenum gasket. The intake manifold on the Magnum engines is built in two pieces, a stamped steel plate is connected to the cast aluminum manifold. A plenum gasket, also referred to as a belly pan gasket, connects the plate and the manifold together.
The plenum/belly pan gasket deteriorates and wears down more quickly than most gaskets should. The end result is an air leak / vacuum leak that can lead to some significant performance problems and other engine problems.
When the intake manifold leaks, the engine looses vacuum, or its ability to suck air into the cylinders from the manifold. This will affect air to fuel ratios and the engines ability to generate power. Ultimately, a leaking plenum gasket can result in excess oil consumption, spark plug fouling, poor fuel economy, and can even clog the catalytic converters. While a small leak might not be noticeable for conservative drivers, it will quickly expand and can clog the cats.
Once the cats become clogged you will notice a huge loss of performance and be stuck with costly repairs. Additionally, this can lead to cylinder heads cracking as the clogged exhaust pushes hot engine gasses back into the engine and therefore causes overheating.
5.2 Magnum Plenum Leak Symptoms
- Bad spark plugs
- Poor idling and performance
- Lack of power
- Bad O2 sensors
- Excessive oil consumption
- Pinging noise from engine under acceleration
318 Magnum Plenum Gasket Repair Options
The two methods for determining whether the plenum gasket is leaking is (1) looking for oil and buildup within the intake manifold, and (2) removing the PCV valve and testing for air pressure or vacuum pressure. It’s important to catch this problem early on before you end up needing to replace the spark plugs, O2 sensors, and catalytic converters.
Since this is such a common problem on the Magnum engines, there are dozens of aftermarket repair kits available. While the OEM gasket was made of rubber, Chrysler also tested metal gaskets which didn’t solve the problem either. Aftermarket kits, such as the Hughes 5.2 Magnum Plenum Repair Kit, use a thicker aluminum plate, high strength fasteners, new bolts, and a new gasket to fix the issue.
We don’t recommend just replacing the OEM gasket as this problem is almost guaranteed to surface again if you do so. The only alternative to the aftermarket kits, which are very reasonable price wise, is replacing the whole intake manifold with a performance manifold that removes the two-piece design. A performance manifold is also a solid idea if you are looking to add some power to your 5.2, albeit it comes at a higher cost.
2. Camshaft Position Sensor Failure
As the name suggests, the camshaft position sensor measures the position and speed of the camshaft. These readings are sent to the ECU to help determine how much fuel should be sent into the combustion chamber. Additionally, it helps control ignition timing and ensures that the right amount of fuel is being ignited at the right time.
As is with all sensors, the cam position sensor is prone to becoming clogged up or failing. Dirt, dust, grime, etc. builds up on the sensor over time and can cause it to malfunction or completely fail. When a cam sensor fails it sends incorrect readings to the ECU which then sends incorrect amounts of fuel into the engine. Ultimately, timing and air-to-fuel ratios get out of whack and lead to noticeable performance issues.
5.2 Magnum Failing Camshaft Position Sensor Symptoms
- Check engine light
- P1391 and P0340 are common codes
- Engine no start or hard start
- Poor performance
- Rough idling
- Cylinder misfires
Cam Sensor Replacement Options
You can try cleaning off your sensor to see if that does the trick without having to replace the part. However, a new sensor is something like a $30 part so I generally recommend just replacing it and having the piece of mind that it isn’t going to become a problem again for awhile.
3. Broken Exhaust Manifold Bolts – 5.2 Magnum
The exhaust manifold connects the cylinders together with the exhaust pipes. It collects the used air from the engine and sends it out to the atmosphere via the exhaust. On the 5.2 Magnum, a lot of owners have reported a ticking noise coming from the engine bay area. While most peoples initial reaction is that the sound is lifter tick, it is actually from the exhaust manifold.
The bolts holding the exhaust manifold to the cylinder are prone to breaking which causes an air leak and the associated ticking noise. An exhaust leak is harmful to the environment as it allows engine gases to pass into the atmosphere without being burned in the catalytic converter. Outside of this, it can also decrease performance and lead to other engine problems.
Fortunately, the replacement options are as simple as replacing the broken bolts. However, we also highly recommend replacing the gasket at this time as well as it has likely further deteriorated from being exposed to open air.
318 Magnum Exhaust Manifold Leak Symptoms
- Ticking noise from engine bay
- Louder exhaust note or raspy exhaust sound
- Decreased fuel economy
- Poor performance and lack of acceleration
- Gas or burning smell from engine bay
4. 46RE & 46RH Transmission Weakness
Like the 5.9 Magnum, the 5.2 also uses the 46RE and 46RH transmissions. Pre-1996 vehicles have the 46RH transmission with 1996 and onwards have the 46RE. Despite which transmission your 5.2 Magnum has, the outlook for it is not great.
Torque converters and transmission cooling lines commonly go bad on these transmissions. The overdrive assembly and reverse assemblies are known to go bad on the 4×4 vehicles, and the gearing ratios overall are not great. These transmissions do not hold up well with towing or to additional horsepower.
Especially for those with a lead foot or who do a lot of towing, these transmissions usually start giving problems around the 100,000 mile mark. While these transmissions can be bulletproof, they require some internal upgrades to be considered reliable. With the age of these trucks nowadays, any transmission that hasn’t been rebuilt or upgraded yet will likely require one in the near future. We have heard stories of these tranny’s lasting more than 200,000 miles without a rebuild, but I would say that this is rare overall.
Staying on top of transmission fluid changes will help but it’s likely not enough to save the 46RE or 46RH.
Transmission Failure Symptoms
Transmissions don’t fail instantly. They tend to go bad over time. Given this, you usually have a lot of heads up when the transmission is on it’s way out. Here are some common signs of a failing transmission:
- Slipping gears
- Hard shifting
- Noises when shifting from park to drive, or difficulty in doing so
- Grinding or shaking when tranny shifts
- Leaking transmission fluids
5.2 Magnum Reliability
The 5.2 Magnum used in Dodge trucks and Jeeps is a pretty solid engine. It doesn’t suffer cylinder head cracks to the same extent that the 5.9 Magnum does. Additionally, the internals and major engine components seem to be fairly strong and adequate for good longevity at stock power levels.
With that being said, there are a few weaknesses of the 5.2. The plenum gasket is virtually a guaranteed problem and the transmissions are weak. However, outside of these two problems there really aren’t any Achilles heels of the 5.2 Magnum. Broken exhaust manifold bolts and bad sensors really aren’t material problems and there aren’t too many other issues that are common and costly.
It is worth noting that these trucks and Jeeps are pushing 20+ years old now. Age is certainly a factor in reliability and old engines will require more maintenance and overall repairs. The 5.2 Magnum can last to 300,000 miles and onwards, but expect to end up replacing a number of parts before you hit this mileage. You will certainly need a transmission rebuild. Additionally, you will probably have gone through a water pump or two, had to replace hoses, replace the timing chain, various suspension components, etc.
The 5.2 Magnum is more reliable than the 5.9 Magnum but still requires its fair share of TLC to make it into high mileage territory.
Let us know your experience with the 5.2 Magnum in the comments!