One of the first dyi maintenance things I ever did to a car was to change the oil in my 1965 Ford Galaxie 500 w/352 v8. It was easy and I have done oil changes on about 20 other cars. I now have physical problems that make it hard for me to do it anymore, but like to buy my own oil/filter and pay someone to get oily. I took my xj6 to Walmart since I had to go there anyway and figured that even Walmart could not screw it up. I asked them to see if they could see where the small oil leak that I knew it had was coming from while they were under there. The tech told me that he had never seen an oil drain plug like the Xj6 has and I needed to get a mechanic to do the oil change. They said there were two large plugs. One 33mm and the other. >36mm and the leak was coming from there. What goes with the drain plug(s)? Is it really that different? I have trouble believing that. The oil leak is getting worse and I never had any leaks before. Please no comments about how stupid I was (I know it)to take it to Wal-Mart. Just advise please. Thanks!

 

Hi dskul1,

I can't recall the year of your car - it's a good idea to add the year, model and engine information to your signature line so others can give you the most accurate replies.

On the 3.6L engines, the oil drain plug is Part 8 in the diagram below. I don't know what wrench size is required, but the drain plug on our '93 with 4.0L engine requires a 30 mm wrench.

Part 4 in the diagram is the oil relief valve plug. It's been years since I've seen a discussion about this, but if I recall correctly about 1/2 quart of oil will come out if you remove this plug, but what I can't recall is whether the relief valve will come out or fall apart, requiring reassembly. By the way, the diagram is from jaguarclassicparts.com, an extremely helpful site from the folks at Jaguar that allows you to look up exploded diagrams and part numbers - I highly recommend becoming familiar with it:



Here's a photo from the Haynes manual, which you can download free from this forum. The oil drain plug is Item 9, and the oil relieve valve plug is just to the left of the number 4 flag that is pointing to the alternator:



To seal up a leak at the oil relief valve plug, you could check to see if Jaguar can still sell you a washer, Part 5 in the diagram. But it might be easiest just to remove the plug, let the 1/2 quart of oil drain out, clean the plug and sump threads with solvent, then apply a little Permatex Ultra Grey RTV Silicone to the drain plug before reinstalling it. This assumes the sump threads or relief valve plug threads have not been stripped or damaged. The torque spec for the plug should be in the workshop manual, possibly even in Haynes.

As far as other oil leak points go, there are only a handful of places on an XJ40 / AJ6 engine where oil leaks can occur under ordinary conditions:

Cam cover gasket & cam journal half-moon seals (very common)
Cylinder head rear cover seal
Oil filter housing
Oil cooler and pipes
Oil fill tube gasket
Dipstick tube seal
Oil pressure sender
Oil pan/sump gasket (somewhat uncommon)
Front and rear main crankshaft seals (also somewhat uncommon)

At the link below are some photos of common leak points on the left side of the engine block:

Welcome to Jag-lovers - Members Photo Viewing Page

Cheers,

Don

 

Thanks for the info. I thought when I posted the car information was included at the bottom of my post. I have been traveling in the Jag (just got back)and it used/leaked about 2.5 qt.s (over 2K miles), of oil, but seems to have slowed. I will be draining all the oil and getting new plugs/washers.

 

Hi dskul1,

That does seem to be excessive oil consumption. Is all that oil leaking from the relief valve plug?

Can you tell from the appearance of the exhaust if the engine is burning excessive oil? One issue that leads to oil burning is that the valve stem seals harden and fail, and the 3.6L engines were only equipped with seals on the exhaust valves, none on the intake valves.

There is no PCV valve on an AJ6 engine to become plugged, but oily fumes are constantly inhaled into the air intake via the crankcase breather system. If the piston rings are worn or stuck, combustion gasses can increase the crankcase pressure which could potentially lead to excessive oil being inhaled through the breather system.

I feel like I'm missing something. Hopefully someone else will chime in.

Please keep us informed.

Cheers,

Don

 

The oil is not being consumed. There is no smoke and there is oil on the bottom of the engine; quite a bit of oil. I hope it is an easy fix and it is coming from the oil drain plug having a bad washer. I have owned the car for 6 months and this leak just seemed to come out of nowhere. I have not had time to slide under the car to look since I've returned. Thanks for the advice and I will let you know what I find.

 

Hi Don, thank you for your information on this matter...
I was wondering if you can tell me what is the purpose of the Oil Relief valve on the process of draining the Oil, can you help me with that? Is it just to let some air in and make the draining process faster?
I'm Still learning a few thing on my fathers Jaguar and I'm going to change the oil on it and I'm looking for some answers and while looking, I found your post and got a little confused. Shaw I just drain the oil from the main valve on nº 9 on Haynes Manual or do I have also to relief the Oil Relief valve on nº 4 of the first image from Jaguar Classic Parts?
Thanks for your help!
Best regards,
Alexandre

 

Hi Alexandre,

Yes, just drain the oil from the main oil sump drain plug, No. 9 in the Haynes manual photo and No. 8 in the parts diagram from jaguarclassicparts.com (thank you, Larry, for catching my error!!! I was looking at the quote from Alexandre's post and typed 4 when I should have typed 8).

Regarding the plug over the oil relief valve, part 4 in the jaguarclassicparts.com diagram, most owners don't bother with the removing the plug over the oil relief valve - only about 1/2 quart of oil will drain from that plug, so leaving it alone won't hurt anything.

Cheers,

Don

 

Thanks a lot for your feedback Don.
Just changed both alternator and AC belts and planning on changing the oil next, after a flush cleaning with Wurth Flush.
I let you know how it goes.
Tks again!

 

The drain plus has always been 30mm HEX with M20 X 2.5mm hole.

bob

 

This is interesting. I have stripped down three AJ6 engines and never seen/noticed that there is a plug in that position on either the 2.9 or the 4.0 , and in 13 years of ownership of the 4.0 have ever removed that plug (because I never saw it?)
I would remove it and drain the remaining oil from that mini sump so that the new oil isn’t contaminated, I also removed the oil cooler for the same reason, tired of changing the oil and having it go black almost immediately. One word of advice is to be very careful when tightening the sump plug, they only have a finite life with regards to the thread in the sump. Its not a case of IF the threads will come out with the plug more a case of WHEN. BTDT.
I modified a brass plug that now stays in the sump with a smaller brass plug that I can be taken out. I had to do this on my S11 XJ6 as well when those threads gave up the ghost.

out

 

The reason the threads in the sump have a finite life is because the STEEL plug will tear the threads from the ALUMINUM pan when overtightened.

STEEL WINS!!!!!!!!!

Jaguar 'screwed-up' by using such a large drain plug. The 30mm wrench used to remove/install the fastener is so long that people think it needs to be REALLY TIGHT.

After all, why would a giant wrench only need to 'snug' a giant bolt????? Tighter must be BETTER!!!!

Then Jaguar used a steel pan on the V8 engines with a steel M14 drain plug (13mm or 16mm hex head). I don't ever see the pan stripped on the V8.

bob

 

Agree with you Robman25. I have only service my father's XJ6 X300 4.0 Liters Sovereign and apart form the main drain plug size 30mm I have found no other drain valve. I'm sure they have different types of oil carters regarding each different model and each different year of manufacturing.
The best way to not over tight the main plug is to used the correct torque with an especial torque wrench and of course have Jaguar service manual along to know what torque to aptly. In my case the plug seems to be in pretty good shape and I don't think I'll have any problem with it.
I have already used 2 units (800 ml) of WURTH engine cleaning flush for 15 min and the old oild came out in pretty bad shape since the car have been out of use for the past 5 years standing parked in our garage.
Decided to open the engine's top cover to clean it better and after the process brand new 100% sintetic oil inside along with a new oil filter and it's done!
Thanks for the help guys!
Best regards to all.
Alexandre