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Discussion Starter · #1 ·
As you know, there are two intercooler/turbo short hoses on the turbo assembly that nestles in the V between cylinder banks of a '99 Arnage 4.4-litre BMW Cosworth V-8. One of these blew off our car, bringing us to a sputtering halt, and the other was close to going...; both hoses have now been replaced by our Bentley main dealer--but I am concerned that this may happen again in the fullness of time (I drive mainly in Sport Mode for increased responsiveness, which of course generates more heat). Question: beyond the four clamps tightly installed to secure the blasted things, is there a secret to keeping these two short hoses in place under even the most strenuous driving conditions?
 

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I'm not familiar with the blown V8 (although I've owned several BMW's with the M60/M62 engines). I suspect that as with any hose under the hood , it probably failed because the hoses got old and brittle. New ones should be good for years to come.
 

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Discussion Starter · #3 ·
Thank you for responding so swiftly. The hose that blew entirely and the one which was almost entirely off its spout were replaced only last year with new Bentley stock items by my Bentley main dealer--which is why I am paranoid about what the French call la suite....
 

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I would be far more circumspect about your chosen maintenance provider. And I do not say that lightly.

Many main dealers have not a soul on staff that's ever touched a 22-year-old model.
 

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Discussion Starter · #5 ·
Right. Perfectly understandable response, guyslp. However, our old boy's engine was entirely rebuilt last year by this same outfit, a respected Bentley/Rolls main dealer, and specifically by the top mechanic there who was in charge of all marque servicing for over twenty years. But you are of course right that mistakes happen. Only, I wonder if this isn't a weird boost problem that's feeding rather more than they can take in the way of excess pressure into those two hoses, thereby pointing to a problem with the snails themselves.... Again, please be assured that I am grateful for your sensible response. (I was not charged for the replacement hoses, by the way, this over a year after the initial motor work was done.) Finally, we are loyal clients of the place in question, who spent upward of thirty recommissioning the barge in question, this just before Covid crippled our economy, which essentially qualifies us for debile mental status, to continue with the French theme inaugurated by me above.
 

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All I can say is that yours is the first instance of this particular problem that I recall (and, note well, my recall could be a problem here) ever having crossed these pages.

I would hope that if your technician has the expertise you state, that double and triple checking everything this time around would have been part of the process, as a repeat of this within a year, again, would definitely not be a good look.

I would also encourage you to talk to your tech about this if you already have a long-established working relationship. They may be able to put your mind at ease, or, possibly, disquiet it more. And that's not meant, in any way, as a criticism of your having asked here. But if you feel comfortable "going to the source" I'd encourage you to do so.
 

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I'm not familiar with this engine either. Obviously there seems to be too much pressure in the system at certain points in time. Lucky you that the hoses go and not the engine. Probably a smart design.

Possible reasons for a pressure overload in the system could be:
  • (sporadically) stuck waste gate regulators (which is a known issue on the later models, stemming from lack of temperature resistant lubrification after too many washes or rains. Easy to fix: just add ceramic grease or similar on the mechanical parts of the regulator and problem solved. On the later models this issue gives you a check engine light with corresponding OBD code BTW)
  • a clogged charcol canister for the waste gate fumes (if there is such a canister)

Depending on where these items are located on the engine it can be difficult to analyze them, but I would definetly venture in this direction.

Bonne chance, mon ami.
 

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Discussion Starter · #8 · (Edited)
Thank you for your sensible, intelligent responses, guyslp and Grease Donkey (I'm starting to regret my lacklustre choice of a username...). I am Scots, which is another way of stating that resource-management is always a concern, whether skint or flush: we carefully analysed the process that would rehabilitate our beloved old motor, and decided, in spite of his being worth the rough equivalent of a pack of Kools, that going forward full blast was the only way to proceed, and so new Honda Accord money was invested getting him right again with the best possible fellow.

My cousin retired from my old regiment to life in the States, in a place where humidity is largely non-existent. This '99 Arnage does not battle damp weather. But he does occasionally endure my lead foot. I had his two-and-a-half tons pegged to 150 on the speedo for nine miles just two weeks ago, and the only noise came from wind rush around a moving brick. And then this unfortunate release at very low speeds, mercifully just a mile away from his mechanical home (Bentleys are civilised brutes, as you know). The turbos were carefully scrutinised last year, when the engine topside was re-built. But I will ask our reliable--and honourable--mechanic to consider the waste gate regulators as you suggest, GD. Also, guyslp, I have richly explored possible reasons for this shocking malfunction with our much-respected technician; the reason for posting my concerns here had uniquely to do with consulting fellow owners on this forum, where personal experience with Bentley and Rolls-Royce motorcars varies widely. I appreciate your insights.
 

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The first Arnages used the BMW covers over the ignition coils, simply omitting the BMW logo. This meant that the aluminum portion of the turbo pressure duct which connects to the intercooler was only held in place by the hoses. I do not know the max boost pressure but let us assume it is 6 psi. The hoses are about 2.5" diameter so this would put a force of about 30 lb trying to blow the hose off. I assume Bentley or Cosworth realized the potential problem and subsequent cars used new (rather ugly) flat coil covers of 1/4" aluminum with two threaded holes. The aluminum ducts were modified to have two ears so that the ducts could be bolted to the cover. By doing this, the hoses may leak if not tightly clamped but all forces are taken by the bolts. From what you describe your car does not have bolted ducts. The boost max pressure is controlled via a valve on the intercooler which feeds two small hoses, one to each actuator on the turbo wastegates. If these hoses have leaks or the wastegates are frozen there is risk of higher boost pressure but I believe in this case you would get an alarm on the DIP. Check the coil covers. If the ducts are unsecured I recommend you procure the later versions from a salvage yard or modify your existing ones. If you would like some photos I can post.
 

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Discussion Starter · #11 ·
Most helpful response, umtaliman--thank you kindly. And yes, I should be most grateful for an image demonstrating what you so intelligently describe. Our old boy was built in late 1999, but I doubt that he benefits from any of the Green Label upgrades that mildly improved the second batch of 4.4-litre Arnages, those mainly instituted as a by-product of the desperate stiffening that made it possible for Red Label cars to carry the 6.75-litre lump's extra 500 pounds over their front axles (engine bay brace; stiffer transmission tunnel...). I appreciate your keen insight.
 

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Most helpful response, umtaliman--thank you kindly. And yes, I should be most grateful for an image demonstrating what you so intelligently describe. Our old boy was built in late 1999, but I doubt that he benefits from any of the Green Label upgrades that mildly improved the second batch of 4.4-litre Arnages, those mainly instituted as a by-product of the desperate stiffening that made it possible for Red Label cars to carry the 6.75-litre lump's extra 500 pounds over their front axles (engine bay brace; stiffer transmission tunnel...). I appreciate your keen insight.
29722
You can see the flattened pressure duct supported by the two ears to the coil cover. However, the upper 90 degree duct is only supported by the hoses.
1620564308862.png
All the connections are beaded so it is quite difficult for the hoses to blow loose unless the clamps are loose. These clamps need to be tightened quite hard, I use a 1/4" ratchet with socket. Obviously also the hoses must be in good condition and the mating surfaces oil-free. If all this is correct and the hose still blows then you need to check the wastegate operation as Grease Donkey suggests.
 

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Discussion Starter · #13 ·
Very good advice, umtaliman--and thank you for posting these images. I am going to share your response to me from two days ago with our mechanic, who is the sort of civilised fellow who respects and appreciates intelligent contributions to his own vast store of Rolls/Bentley knowledge. Thanks again for taking time to address my concerns.
 

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You are most welcome. This car with the BMW engine is fairly rare and so RR shops do not work on them very often. The engine was actually modified by Mahle in UK working in conjunction with Cosworth. It is all standard BMW M62 except for the turbos, oil return ports on the sump, oil feed ports on the LH engine mount and lower compression pistons.
 

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Discussion Starter · #15 ·
Very interesting about the Mahle connection, umtaliman: first I've heard about it; one does indeed learn something new every day--thank you kindly for that obscure and very worthwhile bit of information. You're a bloody gold mine of useful facts, but then a fellow tends to grow quite sharp working on a massive lump of his own.... I wish you good fortune in your 4.4-litre reconstruction efforts.
 

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It is indeed impressive, unfortunately constrained from its potential horsepower by the torque limitation of the ZF transmission. The Arnage was designed around this powertrain but as you can see, compromises were made and the engine bay is not quite wide enough to accommodate it, hence the flattened ducts. Most maintenance work requires the removable of the entire subframe and this can only be accomplished from the bottom and requires a lift.
 

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Discussion Starter · #20 ·
It is indeed impressive, unfortunately constrained from its potential horsepower by the torque limitation of the ZF transmission. The Arnage was designed around this powertrain but as you can see, compromises were made and the engine bay is not quite wide enough to accommodate it, hence the flattened ducts. Most maintenance work requires the removable of the entire subframe and this can only be accomplished from the bottom and requires a lift.
Quite right, of course, but at least the car was engineered to carry this particular engine, which makes it as good a fit as ever there was for an Arnage--whilst the 6.75-litre is the ultimate shoe horn job, which explains the crank failures and blown head gaskets that afflict so many of those cars. It's offensive to some, I know, but the only Arnage to own is powered by a 4.4-litre BMW Cosworth (and Mahle, as you so cleverly brought-up) Twin-Turbo.

The monster engine cars are front-heavy and not nearly as much fun to drive when the road actually turns. I respect the massive torque of the 6.75 in later Arnage motorcars, but many will be shocked and mildly annoyed to learn that a well-preserved launch edition or Green Label car will keep up with all but the most psychotic Arnage Red Label models over anything besides a screaming straight line. Fifty-fifty balance is the determining factor for me. In a phrase, I could have had any of these cars, and instead chose to spend Final Edition money getting our flying brick into rude health (notwithstanding the occasional irritant, mind...). Finally, please know that I greatly respect what you are doing on your own to get your car up to snuff, umtaliman--most impressive endeavour in every sense.
 
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