V6 Engine mounts - V6 engine mounts are an oil filled vulcanised rubber design, with an added support bar. Age, heat and use results in either spliting, leaking or saging. Splitting and leaking are usually obvious enough to be detected, but saging is often overlooked. The support bar is located at the base of the engine mount, and as the mount sags, the support bar ends up resting on the crossmember. That is basically like having a solid mounted engine. The vulcanised rubber is no longer supporting the engine. When this happens, the engine sits lower (up to approx 15mm lower than new), the engine is more harsh, and engine resonance can be felt in the car. It also reults in the engine sump siting lower than the engine crossmember, leaving it more vulnerable to underbody damage.

Engine mount - Part number 17989020

Oil sender unit - The oil sender unit used in V6's and V8's are a commone source of oil leaks. The sender unit is a combination of steel crimped over bakelite, and leak between the crimp joint.

Oil sender unit - Part number 25037204

V6 Harmonic balancer - Standard harmonic balancers consist of inner and outer hemispheres which are located together by vulcanized rubber. Over time the rubber perishes or loosens and the outer hemisphere can move freely of the inner hemisphere. V6 balancers also contain a counter weight on the inner hemisphere to help absorb harmonic vibrations, but when the rubber splits or fractures, the counter weight can rattle against the outer hemisphere, which can be very loud. Harmonic balancer bolts are torqued and thread locked when installed, and can be difficult to remove. Early VN V6 balancers slide off of the crank once the retaining bolt is removed (usually), but update VN V6 balancers need a puller tool for removal after the bolt is removed. Balancers are readily available from most spare parts outlets.

Harmonic Balancer - Part number M40983 (up to build date of 11/90)

V6 Serpentine belt tensioner - The engine serpentine belt uses a spring loaded self adjusting bracket and pulley. The pulley's are often responsible for bearing noises and are a common replacement item. A word of warning; the 18mm pulley retaining bolt is left hand thread. The spring loaded bracket can be responsible for loud rattles, usually at low engine revs, when the tensioning spring fatigues. The tensioning spring can not be replaced separately, and therefore the entire tensioner bracket will need to be changed.

Tensioner pulley - Part number M41023

Tensioner assembly complete - Part number92034888

V6 Thermostat and housing - VN V6's have a common problem with the thermostat, and also the thermostat housing. These early V6's have the thermostat assembly located at the rear of the inlet manifold, underneath the throttle body. Besides being in an awquard position to access, the thermostat housings have a tendancy to corode, and bond themselves to the inlet manifold, making removal difficult. The thermostat housings are held in with one locating bolt only, and use a single O-ring to seal them. The thermostat's themselves usually behave in 1 of 3 ways : 1- They stay closed, causing high operating temperatures. 2 - They work normally, and allow the coolant to flow once operating temperature is achieved. 3 - They stay open, causing cold running temperatures, increased fuel consumption, and inneffective heaters! There are many other possibilities regarding overheating, specifically in VN's, which are - Welsch plug corrosion/leaking ; Engine cooling fan innoperative ; Split radiator side tank (plastic) ; Coroded or blocked radiator core ; leaking water pump ; leaking head gasket or cracked head etc.

Thermostat housing - Part number 92032569

Thermostat housing seal - Part number 12337860

Thermostat - Part number 10207377

Thermostat housing retaining bolt - Part number 11041092

V6 Radiator - V6 radiators have plastic tanks and an alloy core, and are crimped together instead of soldered. The plastic tanks can perish and split (usually the right hand tank, where the fan housing mounts) which results in coolant and pressure loss, and the alloy core can suffer from electrolysis, caused by electrical currents from the thermo fan motor.

V6 Balance shaft bearing - Buick V6 engines have been around since the late 50's, and have been used in GM vehicles as well as Jeep vehicles. Initially, these engines were very harsh, and suffered from bad vibrations, which resulted in broken brackets. The engine was eventually altered, and a balance shaft was installed above the camshaft. This eccentric shaft helped equalize harmonic vibrations, but its rear bearing is now becoming a common source of engine noise. The rear bearing is a needle roller design, which can loose its hardening and damage the balance shaft surface. This results in an unusual rattle/noise from the rear of the engine below the inlet manifold. Repair can be costly and time consuming.

V6 Timing chain - The original timing chain is a pressed link steel design, which is quite strong, but does suffer from excessive stretching. When these chains become over stretched, they usually break the timing chain tensioner, which is mounted on the right side of the engine block. This results in engine rattles from the front of the engine, as well as engine performance loss. Engine detonation (pinging) under load can also be a sign of timing chain stretch. New chain and gear sets are available, along with revised timing chain tensioners.

Timing chain and sprocket assembly - Part number M40755

Timing chain tensioner - Part number 25535668

V6 Engine rattle but changes with A/C - The air conditioning compressors used on the V6, have a large front support bearing which can become noisy. Most times the noise will present itself under all conditions, except for when the air conditioning is on. The front bearing is replaceable and available.

Bearing assembly - Part number VS18161

V6 Coolant Loss - There are a few areas that the V6 engines leak coolant. Firstly is the water pump. There is a drain hole on the water pump housing that is specifically there to leak, if the internal seal of the water pump perishes. Secondly, if coolant has not been used or maintained, the front timing cover of the engine can corrode, and leak. Thirdly, the welsh plugs used in V6's are steel and not brass. The idea of this is that some corrosion is imminent, and it is cheaper for a $1 welsh plug to be corroded, than other more expensive aluminium engine parts. Problem is, V6 welsch plugs are in a prick of a place, and can be awquard to change.

Oil pressure V8 - Some VN V8 engine suffer from oil circulation problems and low oil pressure at cold idle. The oil pick-up strainer in VN's is smaller than earlier models, and is easily clogged by carbon deposits in the oil system. Insufficient servicing of the oiling system can increase carbon and soot deposits in the oil system, which can cause general oil circulation problems. Scheduled servicing and oil system cleaners can reduce carbon build up, but in extreme cases the sump and pick-up need to be removed and thoroughly cleaned to rectify oil pickup/pressure problems.

Rear Main seal - Commodore rear main seals are rope, and these rope seals squeeze against the crankshaft at the rear of the engine. Hot engine oil and age reduces the seals ability to work effectively, and this can result in an oil leak from the back of the crankshaft. To replace the rear main seals the crank needs to be removed from the engine, which usually means that the engine needs to be out of the vehicle. Some tools (Sneaky Pete by Lisle) are available from auto parts stores, which are used for removing and replacing the rear seal with the crank still in place, but are not always successful.

Sump gasket - The sealing edge of VN sumps have raised ridges to prevent over tightening, but the rubber gaskets can split and deteriorate with age, which allows oil to leak.

Throttle body - The throttle body is responsible for idle and acceleration control. The Idle Air Control (IAC) valve is bolted to the throttle body and controls idle speed and stability. The IAC works by allowing air to bypass the throttle body butterfly, and the amount of air supplied controls engine idle speed. The throttle butterfly and the IAC bypass ports can clog with carbon which can directly affect idle control and idle speed. To rectify carbon and idle problems, the throttle body assembly should be removed, cleaned and reset to factory settings.

V8 Cam and lifters - Major problems can arise when cam lobes wear down, as insufficient lobe lift will restrict valve opening and therefore cylinder operation. After many kilometers, V8 cams and lifters wear naturally, but can equate in reduced engine power and noisy valve train operation.

V8 Rocker gear - Rocker gear wear is inevitable. Alloy rocker bridges and steel rockers arms wear with age, and wear increases noise and reduces valve lift. New rocker arms and bridges are available.

V8 Harmonic balancer - Harmonic balancers usually consist of inner and outer hemispheres which are located together by vulcanized rubber. Over time the rubber perishes or loosens and the outer hemisphere can move freely of the inner hemisphere. A few problems arise here, one being the danger of damage from loose parts, and the other being the loss of timing position which is located on the outer hemisphere.

V8 Exhaust manifold - VN V8's have steel headers factory and suffer from cracking. The RH header is most likely to crack around #8 primary tube to collector, mainly due to uneven expansion and contraction. External welding will not repair all of the cracks, as the manifold also cracks internally around the collector. New manifolds are worth almost $300, and second hand manifolds are often already showing signs of cracking, if not already cracked.

Catalytic converter - Catalytic converters are responsible for filtering oxides from exhaust gas to reduce emission. The inners of a catalytic converter are similar to honeycomb, and can become clogged with carbon and unburnt fuel. In this scenario, exhaust flow is dramatically reduced and engine power is taxed. A typical scenario of a blocked catalytic converter is when a vehicle struggles to rev over 2500 rpm. Competent exhaust mechanics can diagnose and/or check catalytic converters if needed.

Fuel tank - The majority of fuel injection fuel tanks contain a swirl pot. The internal primer fuel pump is situated in this swirl pot, which is designed to keep the fuel pump submerged in fuel, irrespective of fuel and vehicle movement. There is also a fuel return line (from the engine) above the swirl pot, which constantly keeps fuel flowing over the fuel pump. If this fuel return line becomes dislodged from the top of the fuel tank, it can fall into the swirl pot and aerate the fuel. This results in noisy pump operation and a gurgling fuel tank. Rectification of this problem usually requires another fuel tank.

Fuel pump - VN Commodores mainly run 2 fuel pumps, 1st an internal primer pump and 2nd an external high pressure pump. Some VN's run an internal high pressure pump only, but there is no set reason as to why. All 3 types of pumps can suffer from the same problem; overheating due to lack of fuel. The internal primer fuel pump and the external high pressure pump both require adequate fuel for lubrication. Continuously running with very little fuel or running out of fuel can damage the pumps, as there is no fuel for lubrication. The EFI (Electronic Fuel Injection) system requires approximately 30-40 PSI to operate effectively, and as fuel pumps wear out pressure can drop.

Electric fuel pumps are also a cause of engine starting problems. Sometimes the car will start, run for a while, and then stall. As the fuel pumps get older, and lose efficiency, they get hot. Eventually they seize. Sometimes, if the car is let to cool (and the pump), the car can be restarted. (A little cheat note hear in case you ever get stuck, if you can't hear the internal pump working on first ignition, tap the bottom of the fuel tank, which jars the pump, and sometimes unseizes it. You will still need to get it checked/replaced, but it may not leave you stranded.)

VN Internal Fuel Pump V6 - Part Number 6441303

VN Internal Fuel Pump V8 - Part Number 6441303

VN External Fuel Pump V6 - Part Number 92032529

VN External Fuel Pump V8 - Part Number 92017845