Hello all, I just purchased a cream puff 1991 xj6 sovereign. Currently has 39010 miles on it! I put about 250 miles of it myself. I use to have a 2000 xj8 and 1989 xjs v12, I am excited to learn about the different quirks of this xj40. It has only been driven 10k miles in the last 20 years. Has had the SLS shocks replaced with conventional shocks in 2014 and water pump in 2014 or 17 have to check records again.

Here are some issues I noticed if anyone can help me out and recommend how to fix.

-coolant expansion tank cap leaks. Cap looks good, tried tightening it some more, I believed I overfilled it first but after searching the forums I filled it to the bottom of the white piece in there. Very minimal leak now I say but I can still hear a slight hissing from the cap after running Is that hiss normal? Or is air trapped? I “burped” the top radiator hose.

-every time I press the brake pedal the brake warning light illuminates. I have the “pad” warning with vcm check. Brakes work fine. When parked and pressing the brake the brake light illuminates. also the anti-lock light illuminates for a moment if I time the vcm press right I can get “fail” message to pop up.
-when pressing the brake pedal the brake accumulator shakes/jiggles like it’s about to explode. Is this normal? Or is it going bad?
-my brake fluid level is about a inch below the max fill line. The manual says to fill it to the max line, could this be causing my issues?

-car shut off on me randomly while driving, lost power steering can’t remember if I lost braking or not but the battery light and also the transmission light was illuminated. Coasted to the side of the road and car started immediately afterwards and drove home no problem. Scary???

-weird gargling noise coming from the backseat area? Not from outside or underneath car so ruling out the exhaust. But I can hear it from inside the cabin. Is fuel tank behind backseat? Pump going bad? Normal?

-annoying rattle coming from steering column, the trim covering the under side of steering column. Is this common? Any “real fixes” or do I just tape it? Haha


Thanks you for the help in advance! Is there any books comparable to Kirby palms book for xjs for the xj40?

 

Hi stran0020,

Congratulations on your great find! That is amazingly low mileage for an XJ40!

Regarding the coolant header tank cap, it may be that the gasket in the cap is no longer sealing properly, or the threaded filler neck of the tank may have distorted from thermal cycling over time. As far as I know, the tanks are no longer available (NLA) from Jaguar, but the caps may still be. You can look up part numbers at jaguarlandroverclassicparts.com.

The PAD warning on the instrument cluster when you press the brake pedal typically means that one of the brake pad wear sensors has worn through, so its wire is touching the brake rotor when you press the brakes. There are two pad wear sensors, one at the Left Front, and one at the Right Rear.

Regarding the accumulator, it shouldn't vibrate simply due to the brake pedal being depressed, but if the electric pump is running every time you press the brake pedal, you will feel vibration in the accumulator. This could indicate the accumulator is not holding sufficient pressure. If I recall correctly, the valve block/pump/accumulator assembly is secured via rubber vibration isolating mounts. Check to be sure yours are not torn. Also, you do want the brake fluid full and the system bled of air. You can troubleshoot the hydraulic brake system with the help of the Power Hydraulic System manual at the link below:

Jaguar XJ40 Power Hydraulic System Manual

There are a lot of reasons the car may die unexpectedly. Low transmission fluid has been associated with stalling while slowing to stop or make a turn. The crankshaft position sensor (CPS) can fail intermittently, as can the fuel pump, which is inside the fuel tank behind the rear seat as you guessed. The fuel pump is normally very quiet and you have to listen to hear it run a priming burst when turning the key to position II. Once the engine is running, it is usually not easy or possible to hear the pump.

There are lots of possible causes of a rattle in the steering column, but a likely cause is that the lower steering column cowl is missing its screws. If I recall correctly, there are two or three machine screws that secure the cowl to the underside of the steering column. If you get under it or use a mirror or your phone, you'll see the holes where the screws are supposed to be. I want to say the screws are about an M4 thread but I may be wrong.

The closest thing we have to a Kirby Palm book is the XJ40 eBook at the Jag-Lovers forum:

Jag-Lovers XJ40 eBook

Here are a few other documents to get you started:

Jaguar AJ6 Engine Management System / OBDI Diagnostic Guide

Jaguar XJ40 Electrical Guide 1990

Jaguar XJ40 Model Year Update 1990

Haynes Jaguar XJ40 Repair Manual

Cheers,

Don

 

Thanks so much for all the info Don! I appreciate it. Regrading the noise I hear coming from fuel tank it is like gargling. Not the usual high pitch whine I hear from fuel pumps of different cars. It is hard to hear but i can definitely hear sitting in drivers seat and especially when I put my ear on the rear parcel tray. I will see if my iPhone can register the noise tomorrow

 

Should have time to work on the xj40 this weekend. Here are links to YouTube containing he symptoms I’m having. Hopefully it is helpful in figuring out what’s wrong

 

I too have a relatively low mileage '90 XJ40 (36 K miles when purchased last October). My coolant tank cap also leaked unless I literally cranked it down with channel locks. Purchased a new cap and found that it still takes more tightening than I would have thought necessary to keep it from leaking. I now snug it by hand as tight as my arthritic hands can handle to keep it from weeping but then cannot open it without the aid of the aforementioned channel locks. It leaks no more but requires that I keep the channel locks in my tool kit when travelling any great distance.

 

Tony,

A rubber-strap wrench will be kinder to your coolant reservoir cap. I kept one in the trunk of our '93. Harbor Freight carries cheap sets that work reasonably well:

Cheers,

Don

 

stran0020,

Can you tell if the electric hydraulic pump is running every time you press the brake pedal? That may be the cause of your accumulator vibrating and would suggest that your accumulator is not holding sufficient pressure. Do your BRAKE or ANTI-LOCK lamps illuminate often?

Regarding the noise from the fuel tank area, I can't hear it well on my computer, but it almost has to be associated with the fuel pump. It could be that the pump has become noisy, or a fuel line may be touching sheet metal which is amplifying the normal sounds of fuel flowing through the system. If you want to get serious about diagnosing the sound, one less-involved method would be to run your fuel level down to 1/4 tank or less, then remove the fuel level sender, which is mounted on the rear vertical side of the fuel tank, accessible behind the spare tire and carpeted trim panel. You could then run the pump and listen via the fuel sender hole.

Cheers,

Don

 

Pardon the dumb question but how do I tell if the electric hydraulic pump is running? When park with the engine idling, every time I press the brake pedal the BRAKE and the ANTI-LOCK lights up. While driving every time I press the brake pedal the BRAKE light comes on and sometimes the ANTI-LOCK light comes on.

Today I took the trim off in the boot and tried wiggling the various wires around while the car was idling to see If I can get the car to shut off. It is really bugging me how it randomly shuts off. Behind the trim I found a loose blue jumper cable, any ideas what this might be? And also the number 94 written on the tank?

blue jumper

tank replaced before??

blue jumpere

 

The BRAKE and ANTI-LOCK lights illuminating almost certainly means your accumulator is not holding sufficient pressure. You can tell if the electric pump motor is running by holding the tip of a long screwdriver or socket extension against the pump body (part of the accumulator valve block) and holding the other end against your ear, and having an assistant press the brake pedal. You should be able to easily detect the sound of the electric pump motor running. Search this XJ40 forum for a recent thread on sourcing a new accumulator.

I can't think of an explanation for that little blue jumper wire except that perhaps a previous mechanic has worked in that area to try to diagnose the same sounds you are trying to track down.

Regarding your intermittent stalling, it would not be a bad idea to replace the crankshaft position sensor (CPS) as a matter of course. These are known to fail intermittently and cause stalling and other difficult-to-diagnose gremlins, so many XJ40 owners just replace it preemptively to rule it out, and if the old one was working at least most of the time, put it in the trunk/boot as an emergency spare.

Have you checked your transmission fluid? To do so, drive the car a good 15-20 minutes to get the fluid up to operating temperature. Park on a level surface, and while holding the brake pedal, shift the gear selector through all the gear positions, holding each for at least 3 seconds. This fills the valve body and other passages to ensure a good fluid level reading. Put the gear selector in Park and set the hand brake, then, with the engine running, check the transmission fluid level. You may have to check several times before you get a clear reading on the dipstick. The fluid level should be exactly at the HOT MAX mark. Even a little low or high can cause problems, including stalling.

The blue Hella relays are known for developing malfunctions, so if you still have some in critical positions, it's a good idea to replace them with new sealed units (Hella, Bosch and Siemens still make these "ice-cube" size relays in 4- and 5-pin versions). Note that some relays have built in resistors and/or diodes to protect the contacts, so check the schematics and be prepared to add external resistors or diodes if required.

That 94 on your fuel tank may just be a match number used during assembly in the factory. You'll find those kinds of hand-written marks in lots of hidden places in your car.

Cheers,

Don

 

I also just purchased a 1991 low miles Sovereign and I’m very interested in your “Brake Light” issue. On my car, the light typically comes on and remains on until the car starts moving, then it goes off. This is not 100%, but certainly about 70% of the time. I’ve also noticed it stay on the entire time the car was running, approximately 20 minutes. Any thoughts on this?

 

I would start by checking your brake pads, and then brake pad sensors. On your 1991 there are only two brake pad sensors rear passenger wheel and front driver wheel. My light use to go on every time I pressed the brake pedal.

I changed the front brake pads and sensor because they were low. Now the anti-lock and brake light only illuminate while in park and pressing the brake pedal. I ordered a brake accumulator and hopefully that will resolve the issue.

also try hitting “VCM” to see if you get any messages. I was getting “pad”

 

Thanks, I’ll check into the pads and sensors.