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General Maintenance Tips

  Experience in a Book
General Maintenance Tips


PARTS REPLACEMENT STRATEGIES: For those obsessed with keeping their cars in original condition, obviously only original parts will do. The suggestions below and throughout this book are for those who simply want their cars to run, and to minimize cost and grief in the process.

Experienced British car enthusiasts will agree that most of their reliability problems come from two sources: Non-metallic parts and Lucas electrics. This is especially true for Jaguars, where the rest of the car is generally excellent.

Rumors abound as to why the rubber and plastic parts on British cars tend to crap out so soon. One rumor says there is a law in Britain requiring the use of natural rubber rather than the far superior synthetic elastomers. Whatever the cause, the Jaguar owner is well advised to replace the original Jaguar seals, hoses, belts, etc., with non-British substitutes whenever feasible. The same replacement strategy applies for other non-metallic parts.

It has been suggested that the various vinyl and rubber protectants on the market, such as STP Son Of A Gun, can be used to help many rubber components last longer. Sandy Gibbs: "When I owned a TR8 I had many of the same problems regarding engine heat and rubber components. I found Armor All and Son of a Gun were useless unless applied every three or four days (if you drive the car much). What did work was brake fluid, of all things. You have to soak the part in question pretty well then rub the fluid in. Let the part dry before running the car. This procedure may have to be repeated two or three days in a row but then the rubber is revitalized, after that one need only repeat the procedure every two or three months. The key here is keeping the brake fluid off anything but the rubber part. This process works on nearly any rubber part except, for some reason, tires."

Lucas has been called the "Father of Darkness". Contrary to popular opinion, Lucas did not invent darkness -- they merely perfected it to a fine art! The owner is well advised to replace Lucas electrical components with alternative products when feasible. It should be noted that many of the electrical parts on a Jag are not really Lucas; the "Jaguar" stereo is probably made in Japan, and the EFI components are Bosch.

Other than electrical and non-metallic parts, Jaguar components are typically excellent, and most are reasonably priced. Whether it is better to replace a broken item with the Jaguar original or a substitute must be decided on an individual basis. A good general rule is: if the original failed of its own accord, it might be better to try another source. But if the failure was secondary (due to something else failing first), the Jaguar parts may very well be the best there are; substitutions are in order only where the prices of the originals are excessive.

Regarding rebuilt parts, Randy Wilson says, "There are many companies out there that rebuild to a price, replacing only the "common" failure part. Their attitude is it's cheaper to only replace the one part and let the consumer figure out which units need more work than it is to full rebuild and test every unit. This is true with electrical, a/c, steering gear, and other things. The real sad part is these unscrupulous clowns often drive the reputable rebuilders out of the market by the price difference.

"I bring this up because I've seen several instances of this... alternators and steering racks. Rebuilds are a pain. The cheap ones are no bargain. And just buying an expensive one is no guarantee. It may be a thorough rebuild, or it may be a cheap one that your vendor is making a killing on. The only recommendations I can make that are available to the general public (US)...For electrical, units rebuilt by Bosch are good. The ones by Lucas used to be the best going... but Lucas gave up competing with the cheapies... and joined them by selling off their name."


REPAIR MANUALS: For a listing of sources for manuals, see "PUBLICATIONS AND PERIODICALS."

As mentioned elsewhere, this book is not intended to substitute for a proper repair manual; you will need to buy one. In general, there appear to be three to choose from: a "Repair Operation Manual" from Jaguar intended for owners, a set of shop manuals from Jaguar intended for dealers and authorized mechanics, and a Haynes manual. The Jaguar publications come in several varieties for different model years, while the Haynes appears to have been published in only one version.

The Repair Operation Manual, part no. AKM 3455 (along with a Supplement, part no. AKM 3455/S1) is expensive and mediocre; not only is it somewhat difficult to follow, it is also fraught with errors. However, the electrical section of the Supplement has descriptions and diagrams for individual systems, and this alone may be worth the price.

The manual you actually end up with may vary according to what year you ask for. Steve Draper reports on his: "What I got was the "Repair Operation Manual" for the XJ-S, which incorporates "HE & 5.3 Supplements" and is printed by Jaguar Cars Ltd. The book includes supplement A (1979-1984) and supplement B (1984-1988). It is a single softbound volume and seems fairly comprehensive. The book includes repair procedures and illustrations, wiring diagrams, and maintenance schedules."

An aside: If you get the softbound Repair Operation Manual and later want to tear it apart, holepunch it, and put it in a 3-ring binder, you will find that it is a metric sized book -- and won't fit in a standard 8" x 11" binder. If you're in Europe or somewhere, that's no problem, but here in the US you may find it a bit of a challenge. Better office supply stores sell "A" size binders, but you'll also need to get the proper 4-hole punch. Another option is to drop into a Wal-Mart and buy a photo album intended for the Kodak Advanced Photo System; these albums are quite a bit larger than standard notebooks yet retain the standard 3-hole pattern. Having a 3-hole punch with an adjustable paper stop is a plus, so you can adjust the stop to center the holes on the longer pages. Just throw the photo sleeves out, although the section dividers are nice, you'll wanna keep them to separate the manual from the supplement and the like. These photo albums have the added benefit that they are really nice quality; I even found one with a dark green, gold, and black cover that looks like it could have come from Jaguar.

Owners with the Repair Operation Manual wishing to work on the GM400 automatic transmission will need to get a separate manual for this tranny, as the Jaguar manual (mine, anyway) covers only the early Borg-Warner automatic and the supplement doesn't address the transmission at all. Andrew Kalman suggests "How To Work With And Modify The Turbo Hydra-matic 400 Transmission" by Ron Sessions, Motorbooks International, 1987, 224 pages, 300 illustrations. Kalman says: "It seems quite complete, with a historical overview, basic maintenance, operation, overhaul, modifications and speed tuning."

Alternatively, you can purchase the actual shop manuals for the XJ-S, which come as several volumes. If you thought the Repair Operation Manual was expensive, the series of shop manuals ought to be good for a major coronary. Not only that, but you may end up having to buy more books than you anticipated; regarding the Jaguar repair manuals for later cars, Richard Mansell shares his experience: "Now that I have the manuals in my hot little hands it appears to be more complicated than I thought. The pre-H.E. to 87-88 manuals (JJM 10 04 06) appear to be based around the pre-H.E. with extra sections to cover the differences between these and the H.E. (pretty logical so far). The new manuals, up to 91, (JJM 10 04 06-20) come in 5 volumes rather than the earlier 4 but only appear to cover the additions since the earlier manuals for the 5.3 plus a random selection of the original information. Oh, and it covers the 4.0 engine too.

"In other words, if you have an '89 to '91 5.3 and you want to know about the new ignition, etc., you will need both sets as the later volume set refers to many sections that only exist in the earlier set; e.g. under the heading "Cylinder heads overhaul" it says:

 Remove left and right hand cylinder heads, see 12.29.01.

 Where is 12.29.01? Only in the earlier set!

"Since the five-volume set costs more than the earlier one, I assumed it would be a complete guide to the later cars. Wrong!

"I understand that there are add-ons, JJM 10 04 06-201 and 202 that cover models '92 to '96. 6.0L engine plus other changes."

The Haynes manual #478, "Jaguar XJ12 & XJS" is a lot cheaper, to the point where you might as well pick one up even if you plan on buying the Jaguar books anyway. It's based on portions of the factory manual with some photos of a teardown of a Daimler Double Six added. It benefits from some recall and technical bulletin info that does not appear in the Jaguar books. It also includes some basic procedures for the GM400 automatic. It only covers up to 1985, though, so owners of later cars will not get any info on the ABS brakes, Marelli ignition, etc. Classic Motorbooks catalogs lists a Haynes manual titled "Jaguar 12-Cylinder 1972-85", but this is actually the same book -- they merely misdescribed the title.


PRIMERS: If you are new to automotive tinkering, you should buy one of the many books on the market explaining general procedures for car repair. While this book is written to be as clear as possible, it is not intended as a primer and no efforts are made to explain standard auto repair procedures. For example, this book may describe in great detail how a particular electrical component has a history of shorting out at a particular spot, but it will not provide any instructions on how to use a VOM to track down a short. Quite the contrary, the reader is expected to know how to track down a simple short, so failures that are easily isolated and corrected may not even be mentioned.


OTHER MANUALS, ETC.: Jaguar also makes parts manuals; for example, according to Stephen Wood, "Jaguar Parts Manual, RTC-9109-B, for the XJ-S, 1976 to 1982, pre-H.E. cars." Many owners suggest these books are more helpful to the mechanic than the repair manual; they contain exploded views of about everything, which are often easier to understand than the step-by-step text in the repair manual. And it helps to know the part number of what you need when placing a parts order by phone; many mail-order catalogs have lousy illustrations, and many parts shops carry more parts than they list in their catalogs.

Richard Mansell bought a parts manual -- "...the Jan '87 to late-'89 parts book (RTC9900CA). IMHO this is laid out a lot better than the earlier parts manuals as it has a description for each item on the same page as the pretty picture. If you have an '87 to '89 3.6 or 5.3 XJ-S this guide is well worth getting, especially to aid reassembly."

Owners who don't have an owner's manual might want to get one; it's more complete than most, with wiring diagrams and all.

According to Loren Lingren, "...Jaguar supplies wiring diagrams called "Electrical Guides". They are supplied individually by year, and IMHO are better than the diagrams that are supplied with the shop manuals. Here is a partial list by Jag publication number:








"I believe these are much more reasonably priced than a complete shop manual."

Alldata once offered a CD-ROM on the XJ-S. According to Michael Minglin, "It is my understanding that Alldata Corp. provides technical support to automotive repair shops through a rather expensive computer system. They also offer individual car support on a CD-ROM. The information on this CD is more and less than the factory service manual.

"In some areas it is rather sketchy and is missing many of the things listed in the service manual. On the other hand it has excellent wiring and vacuum diagrams. It has clear drawings showing where parts are located and what they look like. It has some excellent drawings of components. It has a section listing the hours and estimated parts costs for many repair jobs. It also has technical service bulletins that often do not find their way into the Jaguar manual. Most sections offer a description of how that system works as well as repair and service procedures. There is a section offering specialized tools, mostly from Snap-On or Blue Point.

"On balance I consider the Alldata CD a valuable addition to my factory service manual, but not a replacement for it.

"My CD is labeled: "ALLDATA FOR WINDOWS", part No. PN-099-220-R3, 2/96, Imports A-Z 1982-87, All makes Acura through Yugo, Customer support 800-859-3282. It includes a plug-in that allows me to access my '84 XJ-S. It seems the CD contains data on many cars, but you must buy the plug-in for each car you want to access. I can access data on the 1984 Vanden Plas, XJ6 and XJ-S."

Unfortunately, it may be difficult to get Alldata to sell you this CD-ROM. Minglin tried to obtain more copies for others, and reports: "I talked to Gary at Alldata who claimed they had never offered a CD for the Jaguar. When I insisted they did, and gave him the part number, he then stated that they had discontinued that CD. I could not get to anyone above Gary who could make a decision. My guess is that if enough Jag-Lovers contact them it should not be a big deal for them to run some duplicates of the CD. After all they already have all the data on a disk."


MAIL ORDER CATALOGS: To those just getting started with the XJ-S, take this bit of advice: order at least two mail-order catalogs immediately; a good selection would be Special Interest Car Parts and XK's Unlimited. You will want to have such catalogs on hand even if you never order any parts just so you can tell when some unscrupulous repair shop is trying to rape you on parts costs.

It is also suggested that the owner order a catalog from Gran Turismo Jaguar. All it costs is the phone call. Even if you never intend to do any high-performance work, you may decide to replace broken items with performance stuff instead of the stock parts. And, besides, it's a lot of fun to flip though this catalog and dream! And you can show the spouse how much money you could be spending!


OTHER BOOKS: Richard Mansell suggests: "For XJ-S fans there is a book by Paul Skilleter called Jaguar XJS: A Collectors Guide (ISBN 0-947981-99-3). It is full of pretty pictures (nearly 200) of XJ-S's and variants. There is a fair bit of history detailing specification changes, etc., covering a total of 144 pages.

"Appendix A lists the technical specifications model by model.

"Appendix B lists the location of the chassis/VIN numbers and explains what each bit of the VIN means.

"Appendix C lists launch dates and prices.

"Appendix D is a fairly detailed list of production changes by date chassis and/or engine number.

"Appendix E lists annual production numbers.

"Appendix F lists performance figures.

"If you are into XJ-S's it is well worth a look." Skilleter's book is published by Motor Racing Publications Ltd., Unit 6, The Pilton Estate, 46 Pitlake, Croydon CRO 3YR, UK, ©1996.

Victor Naumann recommends Publication #S-58, XJ-S Engine Performance. "It has photos and diagrams of ignition and fuel systems, all the controls and switches and a good section on maintenance procedures, setting throttle plates and linkage and checking the potentiometer etc."

"Jaguar XJS Gold Portfolio 1975-1988", compiled by R. M. Clarke, is a collection of road tests, specifications, comparisons, and reports on racing and other modifications. It is published by Brooklands Book Distribution Ltd., "Holmerise", Seven Hills Road, Cobham, Surrey, UK.

John T. Horner suggests "There is a brochure type booklet written by Jaguar when the V12 was introduced and which is sometimes still available: "Genesis of the Jaguar V12". It has a good official summary of the history and specifications as well as beautiful color overlay drawings of an engine cutaway. I think Bookspeed in the UK may still offer it." This author has acquired a copy of this book; it isn't much from a maintenance standpoint, but it cannot be beat for instilling an appreciation of one of the finest automotive engines ever designed, providing a concise history and background of the engine's development. From an XJ-S owner's standpoint, the worst thing about the book is that it truly applies to the original Jaguar V12 introduced in the Series III E-type; many of the details changed by the time most XJ-S's were built. The engine shown in the book has carburetors, a canister-type oil filter mounted under the front end of the sump, an oil-to-coolant oil cooler, an oil pan that is no wider than the bottom of the block, an alternator mounted backwards so it sticks out the front of the engine, etc.

"Genesis of the Jaguar V12" is also available from Classic Motorbooks.


TECHNICAL PAPERS: The Society of Automotive Engineers (SAE) maintains a collection of papers. Paper #720163, by Walter T. F. Hassan of Jaguar Cars Ltd., Div., British Leyland Motor Corp., is a quite detailed engineering study of the development of the Jaguar V12. Of course, the paper predates such later developments as the H.E. Bob Weisickle points out that SAE papers can be ordered online on the WWW from: or you can call SAE at +1 (412) 776-4970 Monday through Friday, 8:00 a.m. to 5:00 p.m. Eastern time.

There is a similar paper titled "Jaguar V12 Engine -- Its Design and Background", also by Hassan, from the Technical, Administrative and Supervisory Section of the Amalgamated Union of Engineering Workers (AUEW-TASS), Onslow Hall, Little Green, Richmond, Surrey.

Roger Bywater says "there is also a similar Institute of Mechanical Engineers paper by Harry Mundy from about the same time (1972)."


SERVICE RECORDS: Chad Bolles: "...just go to any dealer's service dept., give them the serial no. of your car; they can pull it up on the computer and give you the available history."


FUEL ECONOMY: Keeping an eye on fuel consumption is an excellent way to monitor your car's condition. Since EPA ratings are generally unreliable in the real world, it is helpful to know what kind of fuel consumption the XJ-S should have:

miles/US gal

miles/Imp. gal.
















For those who like to do their own converting, there are 0.83267 Imperial gallons in a US gallon, 3.7854 litres in a US gallon, and 1.609344 kilometers in a mile.

The values for the pre-H.E. are based on fewer reports, but those reports were fairly consistent; apparently the H.E. was a huge improvement in efficiency over the previous design! Note that reportedly the difference only occurs under light (street) use, and with harder running or racing the economy difference diminishes.

Of course, the standard disclaimer: "Your mileage may vary." But you know if you are driving harder or under worse conditions than the average driver, and if you think your fuel mileage is worse than it should be you should immediately investigate the causes. Many of the common causes also result in major engine damage if left uncorrected.

Note also that some areas require the use of "oxygenated fuels," sometimes just during particular seasons. Oxygenated fuels result in far worse fuel consumption.


THREADS: The British invented the inch/foot system of measurement, so most of the fasteners on the pre-1984 XJ-S are English fine thread (UNF or National Fine), available in any hardware store. Jaguar and other British cars extensively used fine threads, as opposed to the coarse threads (SAE or National Coarse) normally used on American cars. Coarse threads are sometimes used in aluminum parts, because aluminum is too soft for effective use of fine threads.

In 1984, many of the fasteners within the engine itself changed to metric sizes. Notably, just about every 5/16" stud appears to have changed to M8, according to David Johnson.

Thanks to a continuing effort towards metric standards, there are metric fasteners in other parts of the car as well -- even in the pre-1984. Many of the subcomponents, such as the alternator, air conditioner compressor, and stereo are made with metric threads. Later cars seem to have more and more metric threads. Mike Morrin says, "The nuts holding the wiper blades are the only metric fasteners I have found on my 1975 car."

There are no reported cases of obsolete British threads such as Whitworth being found on the XJ-S.


STUDS: Jaguar studs sometimes have fine threads on both ends, and are therefore difficult to find locally. Most studs in the US have coarse threads on one end and fine on the other. You can, of course, order studs from a Jag mail order outfit -- they're even reasonably priced. If you want to get on with the job and not wait on the mail, however, you can find a very long stud or bolt at your local auto parts store on which the fine threaded end by itself is longer than the entire Jaguar stud (many Jaguar studs are rather short). Simply cut the end off and dress up the threads. Thread the sawn end into the part, leaving the factory-made threads for assembly.


SPIRAL GROOVE WASHERS: The V12 engine is covered with an unusual type of 5/16" washer, C30075/2, that has a spiral serration pattern on it and is slightly dished. This washer serves the purposes of both a flat washer and a lock washer. While the serrations may help prevent nuts and bolts from unscrewing, the real locking feature is the dishing; it makes the washer springy, keeping tension on the fastener.

David Johnson found an acceptable substitute for the spiral groove washers: "I found at Pep Boys an 8MM spring washer. It's part number is 153-0800. They are in the racks of boxed hardware." Note these washers don't look much like the spiral groove washers; they have no serrations and are sprung the other way -- they're not dished, they're wavy. They are dirt cheap, though. If you find an auto parts store with a Dorman hardware case, Dorman sells essentially the same type wavy 8mm washer as part number 436-008. Nobody seems to sell wavy spring washers in SAE sizes, but 8mm is essentially the same as 5/16".

The V12 also uses a few 1/4" spriral groove washers. A 6mm wavy spring washer (153-0600 at Pep Boys, 436-006 in a Dorman case) will fit a 1/4" bolt perfectly and serve well.

Note that it is always recommended to use some sort of flat washer whenever a bolt head or nut tightens down onto aluminum. If you find any places on your engine where a fastener is tightened onto aluminum without a washer, it is recommended that you provide a washer.

Conversely, lock washers are only required in certain places. For example, the head studs require no locking feature because the tension on the stud is carefully applied with a torque wrench and the designers have ensured that the assembly will never allow the stud to become untensioned in operation. As a general rule, lock washers are required on very short bolts or studs but not required on longer ones because the longer fasteners provide enough spring to absorb transients without unloading.


ANTI-SEIZE COMPOUND: Since the XJ-S has many bolts and studs threaded into aluminum, be sure to keep a supply of anti-seize compound on hand. The stuff is a lubricant with tiny particles of soft metal in it -- usually copper, nickel, or silver. Use it anytime steel is threaded into aluminum, to prevent galvanic corrosion from seizing it up. It also works great on exhaust manifold studs. The fact is, many experienced mechanics (including the author of this book) swear by the stuff, buy it in one-pound cans at better hardware stores (auto parts shops usually carry it only in small tubes) and use it on everything.


SO YOU FORGOT TO USE ANTI-SEIZE COMPOUND LAST TIME: Steve Hammatt describes a product to get stuck bolts loose: "The division is called National Chemsearch and the product is called "YIELD" and is quite unbelievable in loosening rusted nuts, bolts, etc. Their number is 1-800-527-9919. Their salesmen are everywhere including (believe) even in Russia!

"The key is to use a true penetrating product that has a lubricant, plus time. Leave it on for at least an hour, then return and proceed."

Other folks swear by Liquid Wrench, and even WD-40 has its admirers. Whatever is used, allowing adequate time to soak in is always required.

Heating a bolt with a torch is also suggested as a method for loosening, but obviously it's a good idea to wipe the penetrating oil away first. It also is a good idea to replace the bolt/nut, since the heating may destroy the temper.


SILICONE SEALANTS: Apparently, some silicone sealants can corrode metal parts. Jan Wikström says: "To quote the famous Castrol ad, silicones ain't silicones. Some leave a residue of acetic acid as they cure, which is a very weak acid but could conceivable harm bare metal. The trick is to buy "neutral-cure" silicon."

Ed Mellinger says: "Silicone sealant isn't permitted in most aircraft applications for this reason (among others). Two neutral-cure silicones I know of are Dow Corning 3140 and 3145; one's an adhesive and one's a thinner "coating", but I'm not sure either is designed to be an engine gasket so buyer beware. Warning... they are priced like aircraft parts too!

"In the "among others" category is the tendency of silicone to squeeze out in a bead and then peel off in strings... possibly into your engine oil on its way to a bearing! This definite no-no is the most cited reason I've heard against use of silicone in, er, sensitive areas."


DRIVE-ON RAMPS: The need to get under a car is inevitable, and for those of us who don't have access to a garage with a lift, drive-on ramps appear to be a good solution -- cheap, easy to use, and sturdy enough to hold a 4000-lb Jaguar without dropping it on its owner. However, most ramps appear to have been designed for cars from another era, and the spoiler pushes them away long before the front tires get near them. Patrick Krejcik provides a solution: "I got the $17.95 specials, and all I had to do was to put a 2x6, about 18-24 inches long on each ramp to lengthen the slope. I used a nail in the end of the 2x6, bent it and stuck it in a hole about half way down the original slope, and made the slope longer and more shallow."

If you wanna get fancier, Mike Wilson says that Griot's Garage offers a "ramp extension kit".


CHECKING FOR CRACKS: Jan Wikström provided this "backyard Magnaflux test" for checking for cracks in steel parts: First, the area needs to be clean and smooth, so polishing may be required first. Allow a large, powerful horseshoe magnet to latch on to the part across the area to be checked. Now dribble kerosene with iron powder (collected from grinder) over the area; any crack will show up clearly.


On to Engine Maintenance


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