Rads,
The Isolation tape was a good idea and I still wrap my coils in kapton tape.
However the cheap coils fail internally in any case so I have purchased expensive coils and have had no more problems. The question about the outer can being grounded: I'm not sure. I didn't carefully peal the entire coil apart 1 layer at a time I just cut it in pieces with a dremmel. So I could have missed a connection. However I found no evidence of the outer metal can being grounded which is why I made the comments about it acting like a capacitor. The layers of a Capacitors act in series without being directly connected. I did also put in a new battery. I found that the 96 vdp battery was smaller than the 97 XJ6L (which I also have) battery. So when I replaced the battery in my 96 I opted for a larger battery like in the 97. So with a combination of new good coils, kapton tape, and bigger battery (which might be nothing) I have had no more problems with coils sparking through the walls to my valve cover.
Good luck with your Jag! I still love mine in spite of the fact that they are aging. I'm not sure what I'm going to do when they finally die. There are no other cars out there I like at the moment.

 

Having the same issue with 1997 VDP - on the same cylinder! Put in all new (cheap) coils and new plugs, put in new crankshaft position sensor, I was about to go replace O2 sensors when I saw this thread. Went and looked at the plug well of cyl 4, and sure enough, there is significant pitting from arcs. Two areas the melted magnesium below the arc pit was protruding enough to touch the coil, creating another area for easy arc. I used a mototool to grind that back down so there is a gap between the wall and the coil, and tried layers of Kapton tape - still an intermittent miss but longer time period before it turns on the MIL. Always the miss is on cyl 4. I'll try another plug and maybe gapping a little closer, but this very frustrating. I'm thinking about finding some old-style spark plug cables to see if I can "remote" the coil out of the well as a test. If that works, then I may look for a good used valve cover -- tho they are hard to find.

 

Success! After grinding down the arc pits in cyl 4 spark plug well, using applying Kapton tape on the coils in the two positions that had arced, and put everything back together with Champion RC9YC4 plugs, no more codes or "Check Engine" light, and Miss Kitty is purring again! The magnesium valve cover seems to be a problem for everyone after a while. I didn't think to take pictures of "before," esp. the worst arc pit and magnesium mound that actually touched the coil, but I did take some pics that might help someone else with the same issue.

Obviously, if you are going to grind with the valve cover in situ, you need to keep the powder from entering the engine -- so I left a plug installed and packed the well with plastic wrap to catch the powdered magnesium and paint flakes. when finished, I then sprayed light oil -- all the waste stuck thoroughly to the plastic wrap and came out clean, no particles left in the well. If you have to do a lot of this, though, it would be better to take the cover off.




Pitting in cylinder 4 spark plug well from arcing.



Grinding the protruding melted magnesium with a mototool. Packed the well with plastic to catch mag powder and chips, then sprayed light oil so the residue stuck to the plastic for removal. Not a bit left in the well.



After grinding.



The worst pitted area was at the shoulder, which had developed a protrusion of melted magnesium that actually touched the coil. This is after grinding.



Not the neatest job ever, but the coil is wrapped in several layers of Kapton insulating tape.

 

Hi,
Yes the inside of the valve cover looks just like mine did.
After much testing I finally found that even the kapton tape was not enough.
Even when it stopped sparking through to the coil, the cheap Chinese coils failed internally leaving the same irritating miss or dashboard flashing problems. My only final solution was to buy the expensive coils. Since I put them in I have had no more sparking problems or missing or flashing lights in dashboard. I drove the cheap coils with the kapon tape for a long time and it worked great till it didn't.... I only got about 5000 miles out of the cheap coils before the missing started again by another 5000 they were failing completely. cheap crap. sorry to deliver the bad news but just buy the good coils.
Steve

 

Steve, where did you get the "expensive" coils? It looks like JagBits has some OEM for $99 and SNG Barrett has some on ebay with "Made in Japan" label about the same price. Several other places have coils in the $60 range but not enough info to see if they are from Japan or China.

Currently also looking around for a lower mileage X300 valve cover - if anyone has one for sale!

 

Well, sad to report that indeed the Chinese coils started zapping in other cylinders. Concerned that the deteriorating valve cover is sort of a "death sentence" for these cars -- sad an aftermarket manufacturer hasn't come up with a replacement, but prob not enough of a market to make it worthwhile, So I spent the last few weeks looking for a good used valve (cam) cover. Coventry West had some they were not enthusiastic about, Welsh had one in "acceptable" shape. But I lucked out -- found one from a really low-mileage 1997 in Canada. The fellow (who works on Lexus mainly) didn't have the exact mileage of the car (and he's sold the ECU) but his recollection was that it was 50,000 km - about 31,000 miles! Held my breath until the cover actually arrived -- and it's better than I had hoped! PLUS - it came with the original coils still installed!!!!!!! Going to put it in this week -- hoping that this will extend the life of the car quite a bit!

 

The near-pristine spark plug well -- with original coil gasket, still looking like fresh from the dealer! The paint "bubbling" so common on these magnesium covers has just barely begun.

 

That was a great buy, cover looks in excellent condition!

What brand of Chinese coils failed on you and how long did they last?

 

Great find, John!

That may be one of the best cam covers in existence, and what a bonus to get the original coils!

Cheers,

Don

 

The last batch were labelled "ECCPP" for what it's worth and they started messing up after a couple of months. But I think it is a symbiosis between the coils and the cover.

 

Bump

 

Given how crucial the cam cover is to extended life of these wonderful cars, I started wondering if there was a way to produce a run of them -- wonder if Jag still has the molds? Then I started wondering if they could be 3D printed with hi-temp carbon fiber. Wondering what temp they need to sustain, since many valve covers on modern cars are being produced out of hi-temp plastic. I wonder if XJRengineer has any thoughts on this subject?

 

I happen to own a cover, unused, never used, still in Jaguar's original crate! Although I was saving it for when my camcover deteriorated past any servicable use, if it could indeed be used to create a mold, I would consider sharing it.

What if I laid down a strip of rubber along the recessed portion where the coils rest? Couldn't that isolate the magnesium?

 

90,000 X300s were built and most of these had AJ16 engines, so I think that there will be a reasonable supply of used parts for many years.


I have no experiencing of 3D printing in a material that would be suitable for such an application (exposed to engine oil at 130degC). The part is also quite large. Many machines won't be able to print such a large part.


I think it would be easier to use an original part as a pattern from which to cast another part in aluminium and then machine it. Alternatively it could be machined from solid from a STEP file generated by scanning the part. Both solutions are possible, but both would be expensive.

 

The problem is that many of the used covers are in deteriorated condition due to the magnesium. In calling around to various Jag parts yards here in the US, it turns out that magnesium covers in good condition are few and far between these days. Lots of pitted, arc-damaged, bubbling ones -- and the middle spark plug wells appear to warp with age and leak.

 

I am not an expert on manufacturing techniques but I was wondering if the company that made the original cam cover still had the original tooling available.

If the original mold could be used with aluminum instead of magnesium that would be quite a cost savings. I don't know if different metals require different or modified molds.

Does anyone know if Jaguar actually made these covers or was this farmed out to a sub contracter?

 

It's possible, but unlikely. The casting patterns were probably made of aluminum, and once it was determined that Jaguar would not be ordering any more cam covers and the aftermarket demand was small, the aluminum was probably recycled.

Metals contract as they cool, which is why we couldn't use an existing cam cover as a casting pattern. The resulting copy would be some percentage smaller than the original. Rates of contraction vary by metal, but those of aluminum and magnesium are essentially identical at about 1.8%. This means that if an original cam cover is about 30 inches long (total guess - I'm too tired to go measure one), an aluminum copy made directly from that original cover would be about 0.54 inches too short and a similar percentage too narrow.

Magnesium and aluminum also have very similar melting points, and I understand that casting aluminum is potentially less hazardous than casting magnesium, so at least that would be in our favor.

It's possible that Jaguar cast the cam covers in their engine foundry, but it's probably more likely that the work was done by a specialist subcontractor like U.S.-based JL French Automotive Castings, which supplies castings to U.S. makers (such as Ford) as well as Jaguar and other Western-European makers; or Hungary-based Csaba Metál ZRt, which supplies castings for Jaguar, BMW, Mercedes, Porsche and many other automakers:

Article about JL French

Csaba Metál ZRt English Home Page

For an idea of how much work is involved in producing just one cam cover, see the video at the link below. It's a little long, so I've listed some highlight points below.


0:00 One side of the casting pattern is prepped in the "cope," or upper half of the two-part metal form or "flask." The pattern is covered with sifted sand and tamped to just the right degree of firmness;

3:50 The cask is flipped and the underside of the pattern is prepped via the lower half of the flask, or "drag";

9:40 The cope and drag are separated;

10:50 The aluminum pattern is removed from the completed sand mold;

12:35 Clamps on the flask are loosened so the flask can be lifted off of the sand mold; the flask and pattern are reassembled in preparation for creating the next mold;

14:40 Ladles of molten metal are drawn from the furnace and visible impurities are scooped out;

15:15 The molten metal is poured into the mold via a series of holes and passages called pouring cups, sprues, gates, risers/feeders, runners, etc. Note that the foundrymen pour into cups on both sides of the mold simultaneously. If they poured from one side only there would be a greater risk of the metal cooling before it filled the opposite side of the mold.

18:05 A foundryman breaks up a sand mold to release the cooled casting. The tall cylinders of aluminum alongside the cam cover casting are called riser/feeders, which serve to provide additional molten metal to the cam cover as it contracts during cooling, reducing the occurrence of voids and other defects.

In a modern factory such as that of JL French or Csaba Metál, some or many of these processes would be automated for increased productivity.

Cheers,

Don

 

Hi Vee,

Your unused cam cover is a truly desirable part!

We would have to do some research, but it seems possible that it could be used to create a mold for making new covers from a high-temperature casting resin that cures without contracting so the copies would be the correct original size. I believe there are some aluminum-filled resins that might work. We'd need a resin with good resistance to motor oil and a deflection temperature of probably 300F or higher.

As I mentioned in my previous post, metals contract as they cool, so copies cast from your cover would be too small. But since most automakers, including Jaguar, have transitioned to plastic cam covers, I think it's quite possible that resin copies of your cover could work for X300s. Maybe you've just discovered a great new business opportunity!

Cheers,

Don

 

I think a non conductive valve cover and one that would not bubble would be a great idea! Like you said some kind of plastic or resin.

 

If anyone produces such a thing I'll buy two. (I have 2 96's)

I still use the Kapon tape even on my new expensive coils. I get all my parts from WELSH. They were the ones who first warned me about the cheap coils. (I didn't listen). I do believe after experimentation that the kapon (multiple layers) tape reduces sparking however the coils and tape do make a capacitor with the cam cover and that capacitor will make the coils fail internally (with the cheap coils).

And for that matter since both my engines are over 170k miles and I'm looking at rebuilds soon I'll buy any good cam covers I can get my hands on. So if anyone knows of any please let me know.