Among the many mysteries I have yet to solve with my 1997 Jaguar XK8 project, is the proper routing of vacuum lines.

I have pored through manuals and read many threads here, but am still at a loss.

The engine runs poorly, especially at idle, though it does seem to run a bit better when thoroughly warmed up. Also, the power brakes are powerless, much of the time. I've been fighting other demons with this beast, so haven't worried too much about it until now. But now is the time to tune her up properly. (Or at least shortly as the demons are still there, albeit a bit calmer.)

To help solve my problems...and hopefully shed better light on the routing of vacuum lines, I've drawn a schematic, which is attached. I know some or the routes aren't right, but not sure how to solve the problem so I've left them be.

If someone with expertise would be so kind as to point me in the right direction, I would be immensely grateful.

If I can figure out the correct vacuum line routes, with your help, I will be pleased to put together a revised schematic to share.

Thank you.

 

Posting photos would be helpful as well.

Have you reviewed this link?:

JagRepair.com - Jaguar Repair Information Resource

 

I have tried to fix up your schematic. Not complete as some elements depend on your VIN number.

 

Thank you Oyster...Please bear with me, as I want to go at this one at a time, as there are a lot of pieces involved...

It looks like the Part Load Breather, EVAP Valve Vacuum connection splits so that one side goes to the Evaporative Emissions Purge Valve and the other side goes to the breather on the Cam cover. Then the other side of the Purge Valve goes to the plastic tube on the passenger's side of the car. The plastic tube on the driver's side, then, exits to the atmosphere.

Do I have it?

If so, I'll bet there is a dedicated tube with proper connections for this part, along with an easily source part number !? (I, of course am running a rubber tube because this part was missing when I started working on the car.)

Thank you.

 

One step at a time.

Part load breather hose.
A very special large diameter corrugated plastic hose with three openings.
Starts at left cam cover. Next opening (ca 2/3 down) connects at throttle body elbow left side large pipe and end opening to purge valve. This hose is the black one pictured in my previous post. Red cicles show where to connect

 

Below is a link to SNG barratt. They have the part load breather hose. Jagbits has it also. If you look at the picture you can see a fitting iin the center. That is where the part load restrictor hose attaches and goes to the throttle body. You would have to send them and inquiry since they don't show that hose. Jagbits show the restrictor hose as out of stock. You could also inquire directly to them for the hose.
I would also recommend that you ask for the availability of the special tool for removing the hoses. It is a U-shaped piece that fits in the coupling for removal.
Having recently done the valley hose replacements I know that the tube exits the cam cover and runs under the intake manifold to the back of the engine. The off shoot fitting for the part load restrictor hose is aligned to the throttle body..

https://www.sngbarratt.com/us/#!/Eng...e-7fb4e26af450

 

I'm going to need the other side of the fitting as well. Someone on the Internets will have it !

Thank you everyone for your help.

 

Do you have cruise control ??

If not - there should be just a "stub" of vacuum pipe on top of the throttle body carbuncle but there won't be a "T" junction in the vacuum line from the inlet elbow at the end of the manifold.

If you DO have CC, you could rule that out of the equation by temporarily blocking that lower vacuum hose and just disconnecting the one on the carbuncle so it is just connected to fresh air !!

There are three vacuum operated solenoids in the front wheel arch which **might** be causing a problem.

(Later cars have electronically operated CC so don't have these pipes)

 

Thank you Devon David. Great to hear from you again and Happy Holidays. Happy Holidays to everyone. I'm glad, David, you picked up the thread...was going to have to start another one for the small vacuum lines. As a matter of fact, I have codes for both Evaporative Emissions (0444) and Cruise Control (1637), and have no (little !?) doubt that improperly routed vacuum lines are the source. Could be those solenoids too.

One a related matter, I'll be checking out SNG Barrett, but since they don't have that one item in stock (part load breather hose), would like another source for hoses (hosiery). Of course I will try to support our advertisers. However, since these parts are scarce, any other ideas for a specialist? I'm missing all sorts of proper connections, having used rubber hose and hose clamps to approximate original equipment. I would imagine these parts (including the small corrugated hose on the intake side, possibly the part load breather and the corrugated hose connections) don't typically wear out. My hose parts apparently took walks, likely to help out other cars in need !

 

If you are missing the part load breather hose or if it is damaged, it should be available from SNG Barrat.

The part load restrictor (the small part that goes down in the cam cover) is hard to get hold at. You may have to get it at a breaker.

 

Step two.

From the small stub on the left side throttle body elbow (fuel tank vacuum and pressure relief valve) to the fuel tank pressure control valve. (Not to be mixed up with the fuel pressure regulator) This valve is located in the aft part of the left front wheel well.
You will have to remove the wheel well plastic liner to get at it. More precise by the charcoal canister wrapped in some kind of sound insulation.

You may use any suitable vacuum hose of the right dimension.

A word of caution. The plastic stubs are fragile after 20 years and break easily It may be better to cut hoses and splice.

 

Wow. This is great information Oyster, and everyone. This car may actually drive someday (on a real road !)

I'm thinking that the vacuum line I see climbing out of the wheel well (unattached at present) comes from this device. Will inspect.

 

Step three.

Brake booster vacuum connection. Large hole in throttle body elbow right side.
In the hole a connector consisting of brass and plastic.
Very tricky to undo to get the vacuum hose out. Push plastic ring in and pull hose out. As it is easy to break, leave it alone if it looks ok.

Hose continues through the bulkhead and further on in an arc to the left and ends up connected to the brake booster.

The brake booster is located in the triangular compartment aft left engine bay.

I think the hose is divided in two parts somewhere along the way.

One more step to go.

 

Step four.

Metal stub on throttle body elbow right side marked Fuel pressure regulator/ Cruise control vacuum.

Thin hose from this via a T-piece to fuel pressure regulator.
From other T-piece stub a long thin hose to right hand wheel well where the cruise control components are located.

It is a similar hose coming back from the wheel well. This can be identified as having a L-piece at the end. This goes on top of your throttle body.

 

Wow, Wow, Wow. That was incredible. I had no idea where all the hoses and such went. It has been a guessing game. Thank you Oyster.

...But just one more question to the group...I've asked before, but still at a loss. When I buy the hoses and such...in particular the part load breather hose...there are the other ends...Oyster said I may have to get the correct fitting at a "breaker." I assume that's Norwegian for junkyard. Then at the other end of the hose are fittings...These fittings, I assume, snap into other fittings that are mounted on tubes. Must these fittings (assuming fittings are necessary) also be sourced at a "breaker" or are there part numbers and online sources for such.

Sorry to be a pain. You've brought me so far, that I would like to do the job right (as opposed to smooshing hoses on metal tubes.)

Whether I can source everything online or at a breaker, I'm immensely grateful for the information.

Happy Holidays Oyster, Devon David, BobRoy, Avern 1, NBCat and all the men, women and children who help out on the Jaguar Forum. This old car will run if I have to drag it down the road, but thanks to your help, it looks like it might run on its own. Hopefully soon !

 

Breaker's yard is used in the UK and other parts of the world to designate a place to source used parts.

Some of the hoses have quick-release fittings that can be GENTLY squeezed to release them; others have fittings with clamps.

If you haven't done so already, download a version of the JEPC so you have images and part numbers to search with.

 

And a Happy Christmas to you as well!

 

Truck Graphics.

Thank you for nice comments.

I don't know which parts you are missing. SNG Barratt has very good diagrams on their website to find part numbers.

Jagrepair.com, Gus' website is also an excellent source of information.

Brake booster connector to throttlebody elbow is not listed under XK8. You will find it attached together with a TSB about the part load restrictor.

Happy Holidays to you and all other friends on the forum.

 

Member Skymark just posted that very often members take the time to provide solutions, but we never find out the result. I like to think this is because members often solve one problem, then move on to others...

Well that's my excuse.

But let me report that my Jaguar now purrs like a kitten thanks to Oyster, Devon David, BobRoy, Avern 1, NBCat and the others who posted here.

The information was great, but I can't claim the credit in implementing the fix. I bought the suggested / required parts on SNG Barrett and handed them over to a new Indie in the neighborhood, along with an edited version of the replies from the forum. (Apparently, I'm better at editing than wrenching.) Not only does the engine run great, but the brake vacuum (and brakes, because I also had them repaired) work, and work well.

The shop is Tony Automotive in the Gaithersburg, MD Airpark. Tony isn't a Jaguar expert per se, but he's owned a couple of them and knows his way around.

As for other things to be repaired (including those I've commented on in the past) with this car, I still have a transmission problem to resolve before the vehicle is truly road worthy. It's getting close!

So thanks again guys and gals that participate in the forum. You've solved my Vacuum Line Shenanigans and like it or not, I'm sure you will be hearing from me soon, hopefully with fewer and fewer problems to solve.