Jaguar XK8 Oil Leak
On the AJ-V8 the usual source is the cam covers: tired gaskets, bolts that have lost their torque, or the plastic cover itself cracked by a bolt. I'd wipe the shield below each cover, check the bolts with a torque wrench, and only then buy gaskets; drips at the very back of the engine are a different job.
How bad is it · Safe to drive
Safe to drive — watch the oil level and fix it soon
A cam cover seep is slow, but the oil lands on the hot exhaust and smokes. Oil in the plug wells will short a coil and start a misfire, so don't leave it for long.
Which one applies to yours depends on your symptoms, your model year and what has already been done to it.
Likely causes, most common first
Read the check cost before the odds: a free check that rules a cause out beats a likely guess that costs money.
Cam cover gaskets weeping, or cover bolts gone slack
The cam covers are plastic and clamped through rubber isolators. As the isolators crush and the bolts lose their torque, the gasket stops sealing and oil creeps out along the edge, then runs back onto the exhaust manifold heat shield.
A smell of hot oil at a standstill or after a hard run, often on the driver's-side bank near the bulkhead; a few drops on the floor. After the car has stood for weeks the first drive can bring proper smoke, though nothing shows until the engine is warm.
Wipe the edge of the aluminium shield below each cover with a tissue — an oily trail there is the cover. Then check every cover bolt with a torque wrench before ordering anything.
Often just tightening the bolts to spec stops it. Otherwise fit new gaskets, AJ8 8285 left and AJ8 8400 right, with new isolators, NCA2575CA, 14 per head, and sealant only at the joints between head and front cover. Torque 9-11 Nm, middle two bolts first, then outwards alternating top and bottom. For example under $100 in parts and two or three hours at home, against a dealer quote of about $700.
A cracked plastic cam cover
Over-tightened bolts split the plastic, and the cracks start right beside the mounting holes. A new gasket won't seal against a cracked cover.
A burning smell that comes and goes and a few drops on the floor, with the gasket edge looking fine.
With the covers off, look closely at the plastic around every bolt hole for hairline cracks.
Renew the cracked cover, and on refitting keep to the torque figure — for example about $225 a cover fitted at an independent.
Spark plug seals letting oil into the plug wells
Each plug well is sealed inside the cam cover. When a seal goes, oil fills the well, fouls the plug and shorts the coil — the leak shows up as a misfire, not as drips.
A misfire on one cylinder with the check engine light, for example on cylinder 7, and an oily plug or coil boot when it comes out.
Pull the coils and look down each plug well: there should be no oil in it.
Worth doing together: new plug seals and cam cover gaskets, clean the wells, and fresh plugs while it's apart.
The rear main seal
The crankshaft seal sits between engine and gearbox, so its oil appears at the back of the engine, under the bell housing, and gets blown back over the gearbox.
Drips from the small rubber plug at the bottom of the bell housing, or oil spread over the gearbox while the cam covers are dry.
Clean the area and look again after a drive: oil coming from behind that plug, with nothing on the covers, points at the seal.
Worth trying first: a high-mileage oil with a seal-swelling additive, and check the level often. The proper fix means taking the gearbox off.
The order to check them in
The point of the order is money: each step either rules a cause out or makes the next one worth doing. Green is free, amber costs a little, red is the one to arrive at last.
Find where the oil really is
Drive it warm, then wipe the shield edge below each cam cover and the bell housing with a tissue. Oil from a cam cover hides until the engine is hot, then runs rearwards.
freeCheck the cam cover bolt torque
Set the wrench to 9-11 Nm and go round in order, middle out. Loose bolts are the cheapest fix there is; too much torque cracks the cover.
a torque wrenchLook down the plug wells
Lift the coils and look for oil in the wells, especially if there's a misfire. Oil there means the plug seals go in with the gaskets.
freeRenew gaskets, plug seals and isolators
Remove the air box and intake, the coils and the breather tube, which pulls straight up on two O-rings. Use sealant only at the head-to-front-cover joints, clean the cover breathers, check the plastic for cracks by the bolt holes, and on early engines look at the upper chain tensioners while the cover is off.
under $100 in partsIf only the back of the engine is wet
That's the rear main seal. Try a seal-conditioning high-mileage oil and watch the level; the real repair needs the gearbox out.
gearbox offWhat it usually isn't
Don't spend money here first:
If none of this finds it:
On jagaux.com
- Jaguar XK8 Timing Chain Tensioner ProblemsWith the cam covers off for gaskets, it costs nothing to look at the upper tensioners.
- Jaguar XK8 Restricted Performance, Limp ModeIf oil in a plug well has already brought on a misfire or Restricted Performance.
- Jaguar XK8 Nikasil Engine ProblemsIf the engine uses oil without leaking it, or you're unsure which bores yours has.
- Jaguar XK8 Misfire, Coil Packs and Spark PlugsIf a cylinder misfires, oil in its plug well will have shorted the coil.
- Jaguar XK8 Power Steering Leak, Steering RackIf the fluid on the floor is power steering fluid — a hose at the rack is often blamed on the rack.
- Jaguar VIN decoderConfirm your exact model year, engine and factory options before ordering parts — free.
Ratings, fuse numbers and torque figures vary by model year and market. Read the legend on your own car before pulling anything, and use the figures in the manual for your car, not the ones in a video.
Check your VIN: exactly which car you have and which bulletins apply to it.