Just put the car on axle stands, start it up, get underneath with a good light, lie down with you head just under the oil filter and wait until it starts dripping, you'll see where it comes from, its not rocket science. I just had the same issue as you and as it turned out the oil pressure sensor leaked oil, took maybe 3 minutes to figure it out while under the car as oil was everywhere and I could swear it was coming from under the oil filter mount but no, it was sensor, just the oil was then spreading everywhere on that part of the engine. Was easy to swap though, took no longer than a minute.

 

Hi Phil,

In addition to the common leak points already mentioned, the oil filter housing gasket, oil dipstick tube seal, and oil filler tube gasket are common leak points.

Cheers,

Don

 

Thank you, Don. How likely would any of these issues have occurred due to work done in the course of the oil change? I would attempt the oil change myself but as Jerry mentioned, the location of the filter is not very convenient, and I don't trust my minimal skills to do the work myself.

I'm going to talk to a gentleman tomorrow about some of the maintenance work that I want done on the car, so knowing all these things is very helpful regarding the leak issue. I am most grateful to everyone here for the kind assistance.

 

I think the most likely possibility is that the old oil filter gasket was not removed before the new oil filter was installed, so the filter is double-gasketed and leaking as a result, as Bob suggested.

Unfortunately it's not easy to see the gasket from below or above. If your local shop has an inspection scope (borescope or endoscope), you can get a good look at it without much difficulty.

Cheers,

Don

 

The XJ40 has been at a specialist shop while I awaited a diagnosis, and I have been told it is the "oil bleeder" (?), and thermostat. In addition, they said the valve cover gasket may need replacement at some point, so I am wondering if it just makes sense to do this as well. Any input on this work would be appreciated.

Incidentally, and this is what I was told the other day before I had the current rundown of work, the mechanic thought that possibly the oil level had been low (I do check it though, and have not noticed that), and that when the oil change was done, the increased amount of oil caused a valve to leak.

Apologies that I am unable to be more precise in expressing all this as auto mechanics is not my first language.

Edit: without verifying with the shop, it sounds like the scenario of the oil bypass / thermostat. Any advice on whether to do a valve cover gasket replacement now, or wait?

 

Does the car have oil cooler lines or has that system been replaced with the AJ16 style 'bypass' pipe?

There are some 'O'rings that get hard and need to be replaced. It is a very simple job.

Maybe the cooler lines themselves are seeping?

bob

 

Because these are overhead camshaft engines, Jaguar calls the cover the "camshaft cover." Replacing the gaskets is relatively easy. There's a large perimeter gasket, two "half moon" seals that sit in semi-circular recesses at the rear of the head that were created when the camshaft journals were machined, and six spark plug tube seals.

The screws that secure the cover to the head have plastic sealing washers that do not work particularly well, so I replaced mine with stainless steel/neoprene rubber sealing washers like the ones at the link below. I can't remember the specific size but if the screws on your cover are M6, 1/4 inch washers should work. If they're smaller than M6, 3/16 may be the size.

Stainless Steel - Neoprene Sealing Washers - McMaster Carr



Cheers,

Don

 

Thanks again, Bob and Don. I need to talk to the service manager tomorrow. The thing I hate about shops with service managers is that you don't get to communicate directly with the mechanic. I'll have to read up on this before I talk to him tomorrow.

So Bob, if the "valve cover gasket" needs replacing for $800 including labor, is that a fair cost? I plan to take an auto mechanics course at some point so I can actually get my hands dirty and do some of the work myself because I actually enjoy it. Right now, I just don't have time to do the work and ensure it is done properly. I don't doubt it is a straightforward and relatively simple job, but I want to devote the focus and time to the car that it deserves.

 

I'll be very curious to see what Bob has to say, but that seems to be an exorbitant price. The last time I purchased a cam cover gasket set for a late XJ40, my recollection is that the entire set was less than $60.00 including shipping. This would have been one of the common brands like Fel-Pro, Mahle or Victor Reinz. If the shop marks up the cost, or if they purchase the gaskets from Jaguar, they might charge you $120.00 or more.

I think any experienced mechanic should be able to do this job in 60-90 minutes tops, including cleaning up the cam cover and the cylinder head gasket mating surfaces and applying RTV silicone sealant on the rear half-moon seals or "bungs." Ideally, the RTV should be allowed to set up for awhile before the engine is started. I like to do the job near the end of the day and let the car sit overnight.

Are you sure the $800.00 is only for the camshaft cover gasket replacement?

BTW, you don't need to take an auto repair course to be able to perform many common maintenance procedures on your Jaguar. Just search the forums and YouTube for DIY instructions, and download all the service documentation available on the forum. Besides the sealant that has to be applied to the half-moon seals, the only other issue is that the cover screws have heads for a Phillips or crosshead screwdriver, and most folks don't have Phillips sockets and an inch-pound torque wrench. But that's not usually a problem. Most of us just tighten those screws by feel in several steps, taking care not to overtighten them, and following the typical pattern of starting with the middle screws and working outward toward the ends of the cover in a spiral fashion to spread the stress from the center outward.

Cheers,

Don

 

Thanks Don....yes, the way you describe it, I am not getting a great feeling this is anywhere near a fair price. I may get a written estimate, and if I don't like what I see, plead poverty and take it elsewhere. I am running out of reputable shops, but I haven't exhausted my resources.

I definitely will begin trying my hand with these things when I can devote some attention to some video tutorials. I am very grateful for the encouragement!

 

I am a dinosaur mechanic that is mostly retired but I can replace a cam cover gasket set in an hour or less. (probably way less time)

As Don B says, it is an easy job with fairly inexpensive parts.
Even with dealer parts and $150/hr shop rate it should not be more than $250 to $300. (I still charge $70/hr here in my rural area shop)

 

$800 sounds standard in NY. My brother lives in NY and it seems to be normal to charge $100 per single bolt/nut removal, he paid $1000 or $1200 to replace two VVT sensors on his BMW recently and that's 4 small bolts under bonnet and two plugs and that's probably not even the top 10 jobs he had to do.
Valve cover gasket is one of the easiest jobs on a Jag, don't think it would take more than an hour or two even to a novice. I've changed it on mine three weeks ago and it took me maybe half hour. I highly recommend getting a Haynes manual for your car, they have some excellent howtos on everything on your Jag including how to change that gasket.
Other than that probably best to look for an old school car garage outside of the city that might still not charge an arm and a leg for doing simple work.

 

I was not liking how the shop kept delaying work on the car, vague explanations of required work, and most concerning, lack of a straightforward price, so I took the car back. Whilst doing some other work today, I found my Haynes manual and plan to look at it closely when I have some time.

Their diagnosis is needed replacement of the oil breather, thermostat, and themostast housing gasket. I've already acquired OE parts for the thermostat and gasket, and can obtain the oil breather parts once I determine which ones I need to order. Before I take it to another garage, are all of these things something a novice can take on? If not, can most qualified mechanics complete this, or does this require the work of a specialist?

Thanks all.

 

This car doesn't really have an "oil breather" as such, the cam cover "breathes" back into the intake via a system of hoses ......so unless they were going to replace a hose, I'm not so sure this shop was familiar with the 1993 XJ40.

Sounds to me like yours may be the first car of this type they have run across.

Find someone else!

Larry

 

I think two things resulted in my amateur and misleading diagnosis of an oil leak. 1) I noticed the puddle after the oil change, and 2) the color.....but I had been going on the old fluid color coding system of coolant being green. To me, the orange coolant on the garage floor was fresh oil. I have a gasket and thermostat that I am going to get a garage to replace, but are the symptoms of a coolant leak that only occurs after the car has been driven consistent with need for gasket and thermostat?

Since I have the parts, are these easy jobs? I saw a youtube video that shows the gasket seems like a pretty simple switch out.

 

Hi Phil,

Your XJ40 should not have orange coolant in it, unless the entire system was thoroughly flushed with distilled water before the orange coolant was installed. The anti-corrosion inhibitors in orange Organic Acid Technology (OAT) coolant are not compatible with those in conventional green Inorganic Acid Technology (IAT) coolant and when mixed can form a sludge or gel that can clog your heater core and other small passages in your cooling system. The first models in which Jaguar specified OAT coolant were certain X100s and X308s in 1999. All XJ40s used conventional green IAT coolant.

A coolant leak that only occurs after the car has been driven could be almost anywhere, but logic would tell us that it would be less likely to be lower in the engine bay where gravity would cause coolant to leak even while the car is sitting. More likely the leak would be up higher where coolant is forced out only when it is hot and under pressure. Another very likely suspect is the water pump: when its seal begins to leak, coolant drips out of the weep hole only when the engine is running or shortly after it is shut off.

You may be able to see the leak while the engine is running, just take care not to touch the radiator fan, belts or pulleys.

Cheers,

Don

 

Replacing thermostat is really simple, just two bolts off, pop the cover off, coolant will come out of it(so you might wanna drain it first by removing bottom radiator hose and pointing it into a container), swap thermostat and fit the cover back in. Only thing to remember is that the you cannot force cover into place with bolts, it needs to fit over thermostat fully and flat with the housing(well, almost), if it doesn't and you'll try to force with tightening bolts, it will snap.
Good instructions in Haynes on how to do it, including some pics I think.
If you have a coolant leak, it should be obvious where if you start the car, wait until it gets up to temp, open bonnet and turn throttle, where throttle cable attaches(to mimic pressing gas pedal), that way, water pump spins quicker so extra pressure in the system should show any leaks, just have a good look at all hoses that you can see under bonnet. That said, oil vs coolant should be pretty obvious on your fingers.
As Larry explained no 'oil breather' as such here so not really sure what they were talking about.

 

Thanks Don B and Katar83 for the input.

I did have the coolant system flushed last year, and I can contact the garage and ask them what they used / whether they flushed the system with distilled water.

 

Other leaky coolant spots, water rail and heater valve - mine leaked both places ....

Larry