How To Make Your YD25 D22 D40 Navara/R51 Pathfinder Reliable

D40/R51 

Nissan Navara ST X r51

The D40/R51 YD25 is a very reliable and strong engine I've got customers with over 600 000km on the original engine.  To get the most out of your D40/R51 preventative maintenance must be done on the timing chains and cooling system. 

Common Issues

Timing Chains
 D22 Navara D40 Navara R51 Pathfinder YD25 Original single row timing chain showing wear to pin and broken link2 YD25 duplex timming chain conversion iwis kit
 Snapped Single Row Chain  Upgraded Double Row Timing Chain Kit 

The average life for timing chains is 150 000km. YD25s are an interference engine so when the chain snaps pistons hit the valves. Our double row timing chain kit fixes this issue.

 Radiator top tank
 snapped bard

 

The radiator top tank is where the hot coolant goes, the bottom tank is cool. Around 150 000km the plastic rots then the barb under the radiator cap snaps and you lose coolant and overheat the engine.  Radiator shops can replace the top tank on Spain-built cars this way you keep the genuine radiator core which is better than cheap aftermarket radiators. You cant get the top tank for Thailand built cars you need a whole radiator. On automatic models, it's best to replace the whole radiator because  the transmission cooler is in the bottom tank and can break and get coolant into the transmission. 

Heater Hose Plastic Fittings
D40 R51 heater hose plastic fitting failure closeup YD25 D40 R51 upgrade heater oil cooler hose kit
 OEM Heater Hose Plastic Fittings That Break  Upgraded Heater Hose Kit

 

Heater hose plastic fittings. The heater hose plastic fittings are made out of the same plastic as the radiator top tank, they rot and snap at around 150 000km.  Our upgraded heater hose kit fixes this issue. Nissan later changed the plastic fittings to metal on the 140kw model. 

Oil Cooler hoses
oil cooler hose location

 

The oil cooler hoses are located under the oil filter. When changing the filter, they always get oil on them. Being a coolant hose, they are not designed for oil and this perished the hoses leading to them leaking coolant. Make sure you degrease these hoses after every service or replace them if soft.

 

EGR Pipe
flange br EGR delete pipe kit
 Cracked EGR Pipe  EGR Delete Pipe Kit


The EGR pipe is prone to cracks on the exhaust manifold flange or internally in the heat exchanger resulting in coolant loss.  Our EGR Delete Pipe Kit fixes this issue.

Suction Control Valve
YD25Suction control Valve 1


Suction control valves last around 150 000km. When the SCV starts to go bad the car will surge at idle, eventually, it will cause the engine to stall. Genuine SCVs are the best there are a lot of copies on eBay.

Alternator pulley
alternator pulley  alternator pulley missing
Alternator Pulley   Alternator After The Pulley Has Fallen Off

 

The alternator pulley bearings wear out at around 200 000km when the pulley falls off it can overheat the engine because it runs on the same belt as the water pump.  It's better to rebuild your genuine alternator with new bearings than to replace it with an aftermarket alternator or replace it with a genuine alternator.

D22

d22 navara

The YD25 D22  is a very reliable and easy car to maintain.  D22s are more reliable than D40s because they don't have as many overheating issues caused by broken plastic fittings and EGR Pipes. When maintained I've seen YD25 D22s with over 700 000km.

 

Fan belts
aftermarket fan belts

 

The fan belts last around 120 000km they will make a clacking sound similar to worn chains. To test if it’s the belts making noise you can pour water on the belts and if the noise goes away it’s the belts. Genuine belts are best the aftermarket belts don’t sit in the grooves properly.

 

Timing Chains
 D22 Navara D40 Navara R51 Pathfinder YD25 Original single row timing chain showing wear to pin and broken link2 YD25 duplex timming chain conversion iwis kit
 Snapped Single Row Chain  Upgraded Double Row Timing Chain Kit 

The average life for timing chains is 150 000km. YD25s are an interference engine so when the chain snaps pistons hit the valves. Our double row timing chain kit fixes this issue.

Oil Cooler hoses
oil cooler hose location

The oil cooler hoses are located under the oil filter. When changing the filter, they always get oil on them. Being a coolant hose, they are not designed for oil and this perished the hoses leading to them leaking coolant. Make sure you degrease these hoses after every service or replace them if soft.

Suction Control Valve
YD25Suction control Valve 1


Suction control valves last around 150 000km. When the SCV starts to go bad the car will surge at idle, eventually, it will cause the engine to stall. Genuine SCVs are the best there are a lot of copies on eBay.