Arnage T Engine - Camshafts-Tappets

[David Hill]

I have a lovely 2005 Arnage T facelift. No problems whatsoever to speak of.

I am indeed a Bentley lover, and after many older (and indeed newer) cars, eventually elected to buy an Arnage T, some 5 years ago, to simply satisfy the need to own a Bentley, that could be used and relied on when needed. The other reason was that the Arnage is a complete bargain . The car has 35K miles and me being an engineer, I have already sorted all the numerous little faults found and indeed made some significant upgrades.

These cars had the GM LE 4-speed gearbox fitted and this is a good choice in many respects, as it's a very well made, plentiful and strong item. The only real letdown is the straight cut gears that can cause it to whine in 1st and sometimes 2nd gear. It's nothing, but everything, if you understand and I am going to replace/modify my gearbox at some stage, because I want rid of a 1st gear whine that in truth, 99.9% of people wouldn't even know was there.

In the search for a car, every single buyers guide that could be found, mentioned "camshaft failure, tappet failure, new engine cost...avoid,avoid avoid" and it is my belief this is a major issue in relation to the low used value of the Arnage today being that most of the cars for sale are in the range of problems. Some report the problems don't exist with the "R" and only the "T" which doesn't make any sense at all.

And so, hopefully some of you can answer my questions....

Does anybody know the true story of the Arnage camshaft. Were the camshafts soft? why did some fail and some not? When Bentley replaced them when the cars were new, did the specification of the replacement part change and indeed, the replacement camshafts available today; are they harder material?

Although much is negatively reported about the cam failure issue, does anyone actually know the true percentage of failures. Jack Barclay say they have replaced a "few" only, so why the numerous reports damning all the 2002/2006 cars because of this?

Thus here is my dilema..

If I am doing other work, do I change the cams now, while there is nothing wrong with them, or do I just leave them be? It would seem stupid to change the cams and tappets for a new set of the same unless I knew there was actually a fault with some of the original ones fitted that caused the problem that was rectified in later producton of the part(s).

Did Bentley have a truthful and official line on the problem? Surely Bentley should have made a comment if this was the serious issue it is being made out to be, or is it actually just a couple of cars fitted with sub-standard camshafts (soft) that have caused the issue to be blown out of proportion.

On the other hand, Bentley had many years to recognise there was a serious design defect with the engine that they should have accepted. What did Bentley say was the cause of the failures?

Any help from fellow members would be most gratefully received..

[Christopher Carnley]

The V8 always had camshaft and tappet problems from the word go,as with all flat tappet engines,the source being inadequate lubrication and not "solved" until a flat was ground up the side of the tappet.
It would surprise to to know how many pitted tappets were passed for service!

There is nothing really wrong with the materials, it is the use and servicing that is the culprit, and expectations of consistent high mileages with minimal attention to the engine, not helped by the reduction in ZDDP anti scuff additives which have a much shorter life in soaked, hammered engines . Replacing the cam shaft and tappets is a major job and very expensive,which is the down side to "trickle down" ownership.
A decision was made to revise the system for the 2007 on Arnage, by reverting to the pre-war type of roller tappet and induction hardened cams, as some cars "seemed to chew camshafts, however neglected maintenance was suspected.
There are lots of Arnages out there with quiet engines, so enjoy the car and ignore the slight gear whine as you won,t get rid of it.

[David Hill]

Thanks for your reply Chris, very appreciated. Do you know when they started to grind a flat up the side of the tappet. I am imagining this was to allow oil flow?

I think you may be right in relation to secondary ownership. Unfortunately many of these cars end up in the hands of people that have no chance of maintaining them appropriately, hence low/old/wrong grade oil could very well be the exact reason behind it. I actually bought this car from a dealer with serious airbag faults. They "fully serviced" the car using the cheapest oil they could have possibly used. They are an independent dealer in Ferrari's Lambo etc etc, and proudly told me they use this oil for everything....so should be fine for and old Bentley.

I bought the car at a very good price because two Bentley main dealers said it needed airbags replaced together with the control unit. I have the estimates of £13K to rectify...! I am an electronics design engineer, hence I took a punt that nothing electronic cannot be repaired. The actual fault was found to be hilarious......

The previous lady owner, was very petit, thus had to have seat extensions(1.5 inch riser shims) fitted. When the car was sold these inserts were removed by a careless fitter that managed to replace the seat directly onto the loom, crushing 3 wires. A soldering iron and 30 minutes of work and all lights went out. A result indeed....

Unfortunately, I don't trust the main dealers simply because they know very little about these cars. I spent £3K at a dealer to resolve another problem that in the end they failed at. I had to work out the problem myself. It is a simple bit of logic. If your computer failed, would you trust a mechanic to fix it? Modern cars are mostly electronics.

Gearbox...yes I hear you, but I have some good friends in the US that know these gearboxes very well. Apparently there is a way to rid us of the 1st gear whine and retain the strength by some particular machining of the gears. whether I will ever get to doing it is another thing, but I do love a project.

Back to the cams quickly, do you think a different grade of oil 0-50 instead of 0-40, would help or hinder?

Thanks again
Kindest Regards

David

[David Hill]

Well I researched......ZDDP is in fact available to buy as an additive from many sources. The Hot rodder's in the US, who live and breath flat tappets couldn't live without it apparently because of the CAM profiles and loading. Where many consider it important for a new cam break-in, I can see no reason why a bottle cannot be added at oil change to up the level in modern oil. The recommended oil for these cars only has 1000ppm, where to original minimum for flat cams was 1300ppm. Specialist Oils in the US can be bought easily with concentrations of 2000ppm.

Too much is bad for a host of reasons including some negative oxidization properties,but more importantly if it can blow by the rings, as it can then damage the CAT, but I am going to take that chance, especially as if it can protect the CAM and tappets, a new CAT surely is much cheaper.

ZDDP will not repair any engine with damage, but it could go a long way to prevent further wear. ZDDP was an additive deliberatly added to oil to protect flat tappets, something we all have I believe. It forms a layer on the metal that effectively cushions and stops metal to metal contact.

Comments please?

Regards

David