Below are the common issues of a Ford 4.0 SOHC Engine.
Hydraulic camshaft tensioners and cassettes failure.
The Ford 4.0 SOHC engine’s design is far different from other Over-Head-Cam V6 and V8 engines; it optimizes the use of crankshaft to directly drive both overhead camshafts using timing belts or chains.
In the 4.0 design, Ford has optimized the use of an intermediate jackshaft. This shaft serves as a countershaft which allows the left camshaft to drive the front crankshaft and the right camshaft to be driven from the rear timing chain.
The Teflon camshaft chain tensioners, which are called cassettes or guide rail, along with the hydraulic chain tensioner, keep proper pressure on the chains, thus keeping this complicated network of chains and countershafts in sync.
Due to the weak design of the Teflon chain guides (cassettes), these guides have tendencies to stretch, resulting in the chain rattle. The same noise problem can further develop into guide breakage, which may scatter debris on the engine and throw the valves and pistons timing off.
Another cause of chain rattle is the oil sludge build-up on the hydraulic tensioner, which prevents the chain from getting the proper tension.
Although this engine is a non-interference engine (meaning that the valves will never hit the pistons), it still creates expensive repairs for the owner.
Can you fix the Timing chain rattle on your own?
We do not recommend fixing the cassette problem on your own; the access points to these components are unreachable without removing the engine from the car; also, you need to purchase special tools to remove these components.
Symptoms camshaft tensioners and cassettes failure
The common symptom of cassette or hydraulic camshaft failures is chain rattles which can be heard in front of the engine or at the back.
Service Bulletin: TSB 02-7-6 4.0L SOHC Timing Chain Rattle
Replace the Primary Timing Chain Tensioner, Chain Guide, Jackshaft, and Crankshaft Sprockets with a Primary Timing Chain Tensioner Kit. The kit includes an improved Primary Chain Tensioner, as well as an updated Primary Chain Guide, Jackshaft, and Crankshaft Sprockets. Required fasteners, primary timing chain, and front cover gaskets are also included. Refer to the following Service Procedure for details.
Verify the condition. Obtain the correct kit and follow the sheet supplied with the kit.
Use kit 2U3Z-6D256-AA (balance shaft engines) for:
- 99-01 4x4 Explorer/Mountaineer
- 01-02 4x4 Sport/Sport Trac
- All 02 Explorer/Mountaineer, except engine codes 2G-960-AA and 2G-964-AA
Use kit 2U3Z-6D256-BA (non-balance shaft engines) for:
- 99-01 4x2 Explorer/Mountaineer
- 01-02 4x2 Sport/Sport Trac
- 02 Explorer/Mountaineer with engine codes 2G-960-AA and 2G-964-AA
- All 2001-02 Ranger
Crankshaft and Harmonic balancer slack and separation problem
The Harmonic balancer for this model consists of the center hub, which seals the timing cover and attaches to the next part, which is the reluctor ring.
The reluctor’s teeth are used by the crank sensor to determine the crankshaft position. There is also a third outer part which is commonly known as crankshaft pulley. These components are joined by a dense rubber, which is designed to absorb engine vibrations.
Over time, the opposing forces from different loads on the serpentine belt, along with engine heat and exposure to engine oil, take a toll on the rubber, weakening its structure.
The assembly continues to loosen up until it separates; when this happens, the debris from the harmonic balancer could hit the radiator or the fan blades causing expensive repairs.
Can you fix a Ford 4.0 SOHC with a separated harmonic balancer?
Before you take this route, you need to understand that the crankshaft bolt was installed by a special tool that is designed by Ford, and this device was phased out a long time ago; also, the bolt is not reusable.
Symptoms of harmonic balancer failure
The early symptoms include an engine vibration and serpentine belt noise that changes with increasing RPMs.
This engine is notorious for developing oil leaks from a variety of sources such as valve cover gaskets, rear main crankshaft seals, front main crankshaft seals.
Valve cover on these models is known to crack at extreme temperatures. It may develop a crack in extremely cold or extremely hot weather. A crack from this side of the engine would cause a significant oil leak and may deprive the engine of its lubrication requirements.
Can you fix an oil leak on this engine yourself?
You can replace the valve cover gasket quite easily, but replacing a cracked valve cover gasket would be expensive. Fixing the oil seals on the bottom parts of the engine requires expensive tools and huge effort.
Oil can be seen on the floor where your car is usually parked, oil leaks visible on any side of the engine, and high engine oil consumption.
Valve spring breakage
There are several occurrences of engine valve spring breakage on this model, which shows up at only 60,000 miles.
These breakages cause engine damage from valves falling into the combustion chamber and being compressed by the piston, resulting in engine failure requiring a complete engine rebuild or replacement.
Symptoms of valve spring breakage include engine misfire and unusual loud knocking noise from the top of the engine.
Can you fix a broken valve spring by yourself?
This job requires taking off the engine from the car and rebuilding the engine. Engine rebuild should be done by a professional mechanic and a reputable machine shop.
This Ford engine is also prone to overheating due to coolant leakage from old coolant hoses and water pump seals.
Water pumps’ impellers may disintegrate due to rust. As a result, coolant can no longer circulate.
Another possible cause of overheating is the Thermostat. Its housing may crack due to corrosion, or it may be stuck in a closed position.
If the overheating progresses, it may cause the cylinder head gasket to leak or crack.
Symptoms of overheating
Common symptoms of an overheating engine are coolant loss, coolant over-flowing from the coolant reserve, and a very high-temperature gauge reading.
Can you fix a Ford 4.0 overheating problem by yourself?
If the overheating problem is caused by coolant leakage from the hoses, then fixing the problem is as easy as learning to shift on an automatic transmission. However, if the cause of overheating is a faulty water pump or cracked water pump housing, you may experience great difficulty in removing the clutch fan, which may stop you from moving forward with the repair.
If the cause of overheating is a damaged cylinder head gasket or a damaged cylinder head, We highly recommend you let the professionals handle this issue.
Ford 4.0 are well known for engine misfires, which are caused by faulty spark plug wires and coil pack.
Fuel injectors may also fail or clog, throwing the same fault codes.
Symptoms of an engine misfire
Check engine light may illuminate, and OBD2 may throw fault codes p0300-p0306.
Can you fix a Ford 4.0 engine misfire by yourself?
Spark plugs, ignition coils, and injectors are easy to replace. However, pinpointing the actual culprit is not an easy task even for an intermediate DIYer. You may end up replacing everything, but the problem may persist.
Failure of DPFE sensors
p1401 and p0408 are infamous Ford 4.0 codes for DPFE sensors.
DPFE sensor is a part of the EGR system used to monitor pressure difference of exhaust gasses versus intake manifold pressure. DPFE sends a signal to ECU, then ECU sends a command to EGR to regulate the amount of exhaust gasses feedback to the intake manifold. In conjunction with EGR, it helps with fuel efficiency because some air and unburned fuel from the exhaust is sent back to the combustion chamber for combustion, thus adding more power to the engine.
If DPFE fails to send the proper signal to the ECU, it will cause the EGR to let more exhaust gasses feedback to the intake manifold causing a lean condition that greatly affects engine performance.
Symptoms of faulty DPFE sensors
A common symptom of defective DPFE is an illumination of check engine light with fault codes p1408 and p0401. There would also be hesitation issues and erratic idle due to lean fuel conditions.
Can you replace DPFE sensors by yourself?
DPFE sensors are easily accessible and are easy to replace on your own; all you need to do is find the sensors, disconnect the electrical connectors and pull the sensors. Reinstallation is just a reverse of disassembly.
EGR component failure
EGR system or Exhaust Recirculation System takes some unburned fuel and air from the exhaust back to the intake manifold for combustion.
Below are some common failures from EGR components on this model.
EGR tube failure
Another common problem with Ford is the ERG tube failure. The EGR tube that feeds into the plastic upper intake of the O-ring could fail. When this happens, the engine could stall, have a rough idle, and may fail emission tests; this is due to unregulated outside air coming into the intake manifold.
Symptoms EGR tube failure
Due to possible lean conditions, there could be erratic idle and loss of engine performance. There is also a possibility of Check engine light illumination throwing p1408 and p0401 codes.
Can you fix a broken EGR tube by yourself?
We do not recommend replacing this tube yourself; this part is exposed to exhaust heat and corrosion, which may give you a hard time loosening the bolts. Also, it is difficult to access the retaining bolts and connectors for this part and may require you to do acrobatic stunts.
Catalytic converter failure
The catalytic converter transforms hazardous byproducts of the combustion process exiting the tail pile into nonharmful substances.
Since catalytic converters are connected to the exhaust pipe, should the catalytic converter get clogged or fail, it could send hot gasses back to the exhaust manifold, resulting in poor engine performance and excessive heat under the vehicle, which may also melt the exhaust pipes.
Symptoms of Catalytic converter failure
Poor engine performance, possible stalling, and excessive heat under the vehicle.
Can you replace a damaged catalytic converter yourself?
Removing exhaust bolts to take out the catalytic converters requires lifting the car and heating the bolts with an acetylene torch. If you have no access to the acetylene torch, we do not recommend doing it yourself. Although you can buy an acetylene torch, you need to buy acetylene and oxygen tanks and their contents, which are very expensive.
Intake gasket leaks
Air and fuel mixture should go into the engine thru intake runners. These runners are connected to the engine and isolated from the outside air by an intake gasket. If the intake gasket fails, outside air would displace the metered air and fuel, causing a lean condition.
Symptoms of Intake gasket leaks
Due to lean condition, the engine may stall at idle, run rough, and check engine would illuminate with codes po171 p0172 engine is lean.
This issue is often blamed on faulty oxygen sensors, and as a result, a lot of oxygen sensors are replaced without any positive results.
Can you fix a broken intake gasket by yourself?
You can easily replace your Ford 4.0 intake gasket; you just need to have a torque wrench and information regarding the proper torque specifications for the bolts.
If you are planning to buy a Ford with this engine, you have to think twice because of too many issues that are plaguing this engine; you could end up wasting too much money on repairs.
If you need a replaced Ford 4.0 SOHC V6 engine, we recommend buying one newer than 2002 as many of these issues were resolved for those models.
- 2001 - 2011 Ford Ranger
- 2001 - 2010 Mazda B Series
- 1997 - 2010 Ford Explorer, Mercury Mountaineer
- 2005 - 2010 Ford Mustang