V6 3litre and V8 4litre engines

[J44EAG]

This posting is intended to give members a basic overview of ownership experience applicable to petrol V6 and V8 engines commonly found in the S-type model.

Both engines are reliable units given good regular basic servicing allied to the fitting of replacement parts as detailed below.

Regular oil changing at manufacturers defined mileages is recommended. If about to purchase a used S-type, perusal of the service record book is needed. Missing stamps and documentation could indicate missed maintenance.

Spark plugs have a recommended life of 60k miles on both V6 and V8 cars. In practice many owners have found that the reliable life of a plug set is more likely to be around 50k miles after which the engines may develop misfires at idle speed and across the rev range generaly.

The V6 requires the inlet manifold to be lifted to acces one bank of plugs. It is not unknown for that bank of plugs to be ignored by some people attempting a plug change due to panic when they see what is required!

V6 and V8 engines are both liable to coil failure due to rain water finding its way under the plug chamber plates and gasket on the top of the engine. The spark plug wells fill with water and the individual plug on coils fail due to water ingress. Good gasket sealing is essential. It is not unknown to see S-types fitted with a section of tarpalin fitted under the front of the wiper scuttle panel and behind the engine as a local modification. Any stray rain water then runs down behind the tarpaulin and alliviates any chance of water entering spark plug wells. Crude but effective if not pretty.

V8 models can also suffer from internal rocker cover gasket failure. New seals should be fitted every time a rocker cover is lifted from the engine. Failure to do so may cause engine oil to drown the plug on coils and cause mis fires.

Regular cleaning of the throttle body butterfly plate and area around it is benificial to smooth running on both V6 and V8 models. The plate can sludge with crankcase breather fumes and oil residue which becomes baked to the throttle body and butterfly plate. Carburettor cleaner, clean rag and an old toothbrush is most effective for sludge removal. A clean up every 20k miles will help with maintaning smoth running, particuarly at idle speeds. About a ten minute job and worth every second of time spent.

V6 cars require replacement of the small air pipes to the rear of the throttle body from around 60k miles. They have a tendency to split which upsets engine running and air leaks can usually clearly be heard by the human ear. Pipes are not expensive although the inlet manifold may need to be lifted to gain access and new gaskets fitted to maintain inlet vacuum integrity.

On V6 cars with high mileages the front crankshaft damper pulley should be inspected and replaced if found to be wobbling on the end of the crank.
The unit has a tendancy to disinitigrate.

Both V6 and V8 models can suffer plastic header tank failure at quite low mileages . Early evidence of tank failure can be seen behind the off side front wheel where coolant may leak from the tank onto the ground. These signs of failure must not be ignored and the tank replaced immediately. Cracks in the plastic tank occur due to pressure, heat and age. The replacement of the tank can prove difficult as the scuttle bar under the windscreen wiper panel is fitted with six bolts which can shear due to corrosion where they exit under the car structure. Before replacing the tank, remove the under wing plastic mud shields, remove corrosion from the exposed bolt threads and lubricate with copper grease before bolt removal is attempted. A sheared bolt scenario can be a nightmare to rectify.

V8 models require updated aluminium secondary timing chain tensioners to be fitted. Some cars may still have the early plastic units fitted which crack causing failure at mileages as low as 40k miles. If ignored, failure will occur and valve and piston contact will require a full engine rebuild. Often there is no audible that failure is about to occur. When it does, the noise heard is one of devestation! Do not ignore this item.

Occasionaly, a clatter on start up may be heard as evidence of impending failure. This is the timing chain fouling the tensioner slipper plate. the noise indicates that the plastic running plate has parted company from the tensioner and metal to metal contact is taking place. Do not drive the car in this condition. Switch off and call the tow truck. Failure is about to take place!!!

V8 models are fitted with a plastic thermostat tower with can fail due to the same reasons as the plastic header tank. More cracks and splits. An aluminium after market unit is available from Norman Motors in East London and is highly recommended. No more leaks.

Although the above post may lead you to think that V6 and V8 units are less than satisfactory, given a close eye on maintenance, the fitment of replacement service parts and aftermarket upgrades, the two power units are capable of reliable high mileage use. In perspective, they probably have no more issues than many other makes of engine in common use on the motoring scene today. It is simply that as Jaguar Enthusiasts, we are very aware of potential failure points on our cars and do our best to diseminate information to other members within the JEC.

Please add to this post by using the "reply" button at the foot of this page. Your experiences will be well received by us all.

If you have any queries or require further information, please e-mail me and I will do my be to assist you. My contact details may be found in the S-type Forum pages of our JEC magazine.

Mike Kennedy. S-type Co-ordinator. JEC

[Roger47]

I ran a 4.0ltr S Type for the best part of 8 years during which time I clocked up in excess of 175,000 miles in her and have to say that the engine was (with regular main dealer servicing) pretty reliable - pity about the geabox but that's another story......

67,000 miles header tank failure (and again at 70,000 but this time foc)
90,000 miles head gasket failure
105,000 miles replaced all 8 suppressors due to low speed misfire
150,000 miles replaced water valve heater

At 175,000 miles the engine was still going strong and using little if any oil between services when I was involved in my first accident in 39 years of driving and wrote her off....... As the saying goes " It's an ill wind that blows nobody good" as I managed to pick up and now run one of the last S Type R's with just a few thousand miles on the clock.