Why? Was it simply ignorance by the engineers about the plastics properties in an attempt to save weight? or was it simply being cheap and trying to boost the bottom line for Jaguar? I just can't imagine that a company selling exclusive cars for those original prices doesn't have better minds working for them.

Jaguar has probably lost in the tens of millions of dollars in sales because of their reputation over the last 30+ years so I just can't imagine what they were thinking over there! The philosophy of Jaguar seems to be make it as complex, expensive and difficult to fix as possible! The depreciation of these cars speaks pretty loudly as to their design, etc. Are the newer XK's faring better?

 

If you want to see BAD!!!! Plastic ....have a good look around the Interior of a 1st Gen Dodge Caliber , Jeep Patriot , & Dodge Avenger . Good build quality let down by recycled CD case interiors . I quite enjoyed mine cos noo one else near me had one BUT the rest of the UK just laughed !!. No wonder Dodge pulled back out of UK after a 2yr struggle to gain a foot hold .So much for American automobile engineering !!

 

the plastics in the XK's, XJ's.....and even older S-Types and X-Types were no where NEAR as bad as the cheaper american/japanese cars. holy cow was that cheap

 

Hi, I think there's some misunderstanding here, this is in reference to the engine and other unseen CRITICAL components, not interior I have had no real problems with the fit and finish of my jag interior. I'm not denigrating English manufacturing specifically, I'm sure there are plenty of problems with American and other nations indigenous manufacturing. This is a specific question about Jaguar.

 

...and then there are those of us who have owned Italian cars. Ever looked into the engine bay of a 15 year old Fiat or Alfa? Sometimes it seems EVERY critical part is either cracked, broken or leaking...sometimes all three.

 

Someone thought making the casings of the cam-belt tensioners out of plastic was a good idea....

Best wishes, Colin

 

In our business the plastic manufacturers have made numerous promises of the reliability, fading, and durability. Vinyls have a life expectancy between four to eight years. none will actually last that long.
One of our customers The largest agricultural machinery manufacturer uses a yellow polyethylene on there headers. we also use a yellow polyethylene sign board, which they have tested in their lab. Both fade under direct UV sun light. fading also breaks it down, but when tested in there labs under simulated UV test they do not. They test this plastic 24/7 in a sped up environment. The manufacturers promise no fading or break down. I can imagine that Jaguar engineers have been told basically the same B.S. They can test these under the simulated test and they probably hold up, but not in real life situations. Of course you have the bean counters always trying to find the cheapest part.

 

I would chalk it up to: "seemed like a good idea at the time".

With respect to things like the plastic tensioners, as I recall, the early Northstar GM V8s has a similar problem, whereas the Ford modular series used metal tensioners.

You'd be surprised how many engineering choices like that come down to what the particular engineer that filled in that box in the FMEA felt like at the time. People estimate risk all the time, and sometimes they get it wrong.

What makes something like the tensioners so difficult an engineering problem is that the failures are not early in the life of the product, they come much, much later. Accelerated life testing is a black art of sorts and doesn't always do a good job of predicting the future.

So that is my opinion of it, that the engineers overestimated the material properties a little bit and underestimated the harshness of the conditions they would see a little bit and ended up with something that would fail.

And once it was in production, it is really really hard to change, both in the sense that re-qualifying a product is a lot of work and also in he legal sense, that when you admit there is a problem, you are on the hook for fixing it for all those people out there who bought the "bad" one, even when the problem only shows up at the way far tail of the distribution.

Same with Nikasil. Nothing wrong with it in principle, but there was an unforeseen interaction once you introduced the variability of gasoline quality that caused a very big problem.

 

It was just Jag all the car manufactures, it was cheaper easier to mold to obtain the desired looks that we have grown to love. Find a Dodge, Chevy, Ford etc the same age or older and see how the are holding up. Mine is 13 years old and still looks great. Did it save money the simple answer is yes, did it hold up to the there required life expectancies yes. Are the new xk's better then the xk8's? The 2007 that I test drove had far more issues with plastic parts failing then my 2000. I personal feel our models will out life the new models. Thank god for JB Weld an other products, sooner than later the parts well will run dry. We will have to continue to be creative and network our ideas to continue to maintain these beautiful machines. Jim

 

Come over to BenzWorld sometime and read up in the CL forum. These cars cost between $100K and $200K when new and--you guessed it--plastic all over the place. Even working parts, even in the engine compartment. Nothing as egregious as timing chain tensioners but they make up for that with a disastrous electro-hydraulic suspension system (ABC).

Engineers are always trying to outdo one another with additional complexity. Bragging rights and also it helps to justify the outlandish MSRP when new. Relatively few components fail during the warranty period. One reason I bought my XK8 is that it's relatively straightforward from an engineering standpoint. I don't think I'll ever buy another car with an 'active suspension'...unless maybe I win the lottery.

Plastic, meanwhile, ye will always have with ye.

Until ye replace it with aluminum

 

With the introduction of the 3D printer, parts needed in the future will be easier to get especially the plastic ones. The latest Hemmings has a pretty good article on these printers. We already have a couple of businesses using them.

 

Our BMW 325i had a failed plastic header tank at 40,000mi. Dealer wanted $425 to replace it. The PCV system uses the same type plastic hoses as our Jags that become brittle from the heat and time, causing all kinds of vacuum and oil leaks. The actual valve is a common failure point and it is......plastic! Oil filter housing, etc. all plastic. So it goes. When it's all about performance vs. mpg, weight matters. And cost.

 

had many cars in my 69 years on this planet and jaguar plastics are better than most.except chain tentioners..had a vauxhall with plastic timing belt..snapped..goodbye engine

 

Well there is also the thermostat housing as well as another big one: the coolant pump. And it's also just the overall overcomplexity of the car(electrical, sensors, etc). I read somewhere that Jag designs cars from an intellectual POV and say Toyota does it from an agricultural POV. Make what you will of that.

Still the biggest point I'm making is that Jaguar SHOULD have been aware of it's relatively bad reputation at least here in the USA and proceeded accordingly. I don't think anyone can deny that Jaguar has probably one of the worst reputations, and even if you don't the market has done it for you as far as depreciation and resale values.

I think the XKR's were built more robustly because of the added stress of the supercharger so this is mostly about the XK8's, XJ8's etc.

 

I have no worries about it never ever gave me any problems.

 

Mostly a cost-savings issue with a touch of weight reduction thrown in for good measure....

And no, the issue is not confined to only the plastics in the engine bay. I've had to replace a number of plastic fasteners as well, though I must admit that our S-Type seems to be more prone to plastic part failure thus far than our XK8 is. Both were built in May 2005, so additional time and mileage on both of them will tell....

Quality and durability of general plastic parts is much better on my 1999 Dodge Ram pickup. Same was true for my wife's previous 2004 Lexus RX330 SUV....

 

Well, this is really plumbing the bottom of useless polls. Nothing better to do?

Jim

 

All cars are pretty much the same under the skin once you peel away the trim. I recall how disappointed I was the first time I removed the inner door panel on my XKR and saw that what was underneath looked the same as any budget bucket you could buy. I don't know what I expected but the basic nitty gritty pieces are the basically same whether a Ferrari or a Yugo.

Doug

 

Kinda.

 

What you find generally happens a manufacturer designs a car that is nigh on perfect, all the suppliers come along and offer there best materials, and the car is pheonominal.....

Then the accountants get a hold of it and start whittling it down, does this need to be this thick, if we go .5mm thinner on this wishbone this will save us $?00000000 on the production run, does this plastic have to be this quality can we use something cheaper...... And there you go... you get what we all drive in today...

Of course the knock on effect is the after sales spares they have to supply, what they do is make sure that the materials used as a minimum last the warranty period...

Win win for them lose lose for us.... and thats basically is it in a nutshell!