Well, the title says it all. My Jaguar has been burning oil after it hasn't been run in a while. Once I start driving it often, the smoke level diminishes. This problem in my opinion just ruins the look of the car. I know it isn't vapor because it has that burning smell. Do you have to remove the timing chain (and does it have to go back perfectly)? Also, my oil pressure gauge says it's low? Any help would be much appreciated.

 

Hi jaguarguy13,

The head gasket on our '88 failed about about 100K miles, and the one on our '93 failed at about 90K miles and again at around 170K miles. All three times, the symptom was white steam from the exhaust and very rough running and a severe loss of power due to coolant leaking into a cylinder.

A puff of smoke at startup is a very common issue on the XJ40 because the rubber exhaust valve stem seals fail and due to the cant of the engine, oil that pools below the cams drips down the exhaust valve stems into the cylinders and burns for a short time after startup.

In my experience, more constant oil burning tends to indicate worn or sticking piston rings, a problem with the engine crankcase breathing system, or using oil with viscosity that is too low.

A constant issue in the XJ40 design is oil in the crankcase vapors drawn through the breather hoses into the plastic elbow in the air intake plumbing, where it condenses and collects just ahead of the throttle body and is then inhaled into the combustion chambers.

The engine breathing system is designed to maintain a specific degree of vacuum in the crankcase. If a problem develops with the breathing system, excessive crankcase pressure can presumably cause even more oil than usual to make its way into the air intake. Worn or sticking piston rings could presumably allow crankcase oil into the combustion chambers and combustion gasses to pressurize the crankcase forcing more oily vapors through the breathing system into the air intake. But worn or sticking piston rings seem to be very, very rare on XJ40s.

The first thing I might recommend is that you remove your air intake plumbing, throttle body and breather hoses and clean everything really well, including the EGR/carbon canister purge valve fitting on the underside of the intake manifold. Then use the highest viscosity oil recommended by Jaguar for your climate (in places where summer temps are warm, 20W-50 is Jaguar's recommendation for our '93). You might also try adding two bottles of CD2 engine oil detergent in the crankcase to help clean piston rings, valve lifters, etc., and add two quarts of Lucas Oil Stabilizer in place of two quarts of regular engine oil.

Based on burning oil, I wouldn't suspect the head gasket unless you have oil in your coolant, coolant in your oil, or coolant steam in your exhaust and a noticeable loss of power.

The links to photos below show the disassembly and cleaning of the air intake plumbing on our '93, which should be very similar to your '94 (you may have two small coolant hoses that attach to your throttle body).

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page


And to answer your question, no, it's not difficult to replace the head gasket, it's just a process. The instructions in Haynes are pretty good.

If you don't have the Haynes XJ40 manual and the Jaguar Workshop Manual for the 4.0L XJ40s, I highly recommend them.

Cheers,

Don

 

Hey Don B, nice to see you still are helping people like always.

Regarding the burning, the smoke is white and frankly I am not sure if it is oil or coolant. I posted this a bit late at night and wasn't quite thinking clearly.

Typically what happens is I start the car, and a cloud of smoke comes out and stops after some time. There also is a loud squeaking noise that I have come to suspect is simply the timing belt. I likely will disassemble the intake and clean it out thoroughly. And where are those exhaust seals?

The reason I asked the question is because I have fully restored a 1969 Mustang 302 engine, and a 1970's ford 351, and I haven't had much experience on newer engines. Thanks again.

 

If the white (or sometimes "blue") smoke goes away after less than a minute, then it's probably just the normal valve stem seal leaks that are common to the XJ40 and nothting to worry about - just a little embarassing when you have an audience! The exhaust valve stem seals are on the stems of the exhaust valves under the camshafts & lifters, so they can't be replaced without removing the head, which is why most owners just live with the puff of smoke).

Regarding the loud noise you are hearing at startup, these cars have timing chains rather than a belt, and the upper timing chain tensioner is known for allowing some slack in the chains to "clatter" at startup until the oil pressure in the tensioner builds up. Jaguar introduced a revised tensioner to help address this problem, and I would assume your '94 has the revised tensioner but I'm not certain. Our '93 clatters briefly at startup and I haven't found time to take a look at the tensioner to see if anything can be done to improve its operation (I think I recall one or more rubber O-rings in the tensioner - maybe replacing them would help).

If the noise you're hearing is really more of a squeak than a clatter, could it be one of the drive belts? It might be worth checking your belts to confirm they are all tight and in good condition, and that, for example, coolant isn't dripping out of the water pump weep hole onto one or more of the belts and causing them to slip.

Cheers,

Don

 

Not that it may be much help, but I had a persistent squeak/clatter on my 94 which I'd assumed to be a belt issue - however it was caused by an inoperative air pump due to a failing relay on the bulkhead! Swapped out relay, noise gone!

As far as your "low" oil pressure goes, I wouldn't get too concerned about it as the oil pressure senders on these cars are notorious for incorrect readings that tend to be scaringly low when the oil pressure is just fine. Jaguar replaced the original senders with the equivalent of an idiot light, a sender which just registers halfway on the gauge or zero.

Larry

 

Well, the low oil pressure was the sender I started the car and the oil pressure was back to normal. I did however clean away the whole intake, it had a large amount of oil in it? The smoke lasted quite some time, in fact it didn't stop. It was still smoking but very faintly after I turned the car off. Thanks again for helping out guys.

 

Very normal, plan to clean it out fairly regularly. Sludge builds up a lot in the colder months with short runs. Not a bad idea to clean out the breather hoses too once in a while.

Larry