The caps are in stock after being out of stock for months. If everyone here orders new ones, they may sell out again. :rofl:
Don't forget that brass plug too! :thumbup:

Out of curiosity, I had to look.... I paid $14.04 for it on Amazon just over 4 years ago. I don't recall how much the aluminum cap was at that time, but the price difference was probably more significant than now.

I'm more in the camp of liking to keep things looking OE - the way God intended! ;)

AM.

Me too, but only because the wife would notice a supercharger sticking out of the hood...[emoji1787]

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Has anyone compared the vacuum valves on the different caps?? Are any less likely to collapse the hoses?

I'm curious, has anyone done any towing with the lower pressure cap?

Yes, I towed our 26' travel trailer from CO Spgs to Big Sky, MT with our E53 3.0. It worked very hard, but absolutely no issues with the cooling system running the 1.4 bar cap.

AM.

impressive towing for a 6
 

I've towed some trailers with under-powered trucks before, and always tried to upgrade them before the next long-haul tow (drag car on a tandem axle trailer). Examples, towing the same trailer, about 6000 lbs (3800 lb car + 2200 lb trailer), with three different trucks (each with 1000 lb booster springs installed), :

• 1a) 1969 Chevy C-10, (3600 lb), with a 355 high perf engine with 272 degree cam/350 hp/3.07 rear axle,then
• 1b) same truck, with a better 3.73 rear gear, and
• 2) 1975 Chevy C-10, (3900 lb), with a 358 high-torque engine with 224 degree cam/<300 hp/3.40 rear axle, followed by
• 3) 2004 Chevy 2500HD WT, (5800 lbs), with a 6.0L engine/300hp/360 lb.ft. torque/4.10 rear axle

What I learned from improving the towing vehicle to better tow the basically same load, was that more is better. More weight, more torque, more gearing.

I got the X5 after I quit racing and started camping, so the load to be towed isn't the same. Though my home-built trailer is heavy for its' size (2225 lbs, 4x8 cabin on a 12 ft long trailer), my '04 truck is way more than a match for it. But, I'm wary of using my 6-cylindered 21-year-old X5 to haul the trailer, on long trips (500+ miles).

I know it is rated for 6k lbs, but it is very old (though with a well-maintained engine, and rebuilt suspension), even older than my truck, with 210k miles vs 140k miles on the HD truck, so I'm hesitant to use the X5. Plus, I've only got a 4-way connector on the X5, and can't utilize the brakes on my trailer.

But, I'm encouraged by your 800+ mile trip thru mountainous country, using your 3.0 X5, especially since your trailer probably weighed around 3x what mine does. Maybe I'll try it on a short trip, soon, to a campsite within 200 miles (and over Texas' non-mountainous terrain).

I upgraded mine too..... to an E70 35d! ;)

I haven't weighed my trailer, but the mfgr. listed the dry weight at about 3500 lbs. I partially chose it based on its light weight. Still, I imagine it's likely around 5000 lbs. by the time we hit the road.

I could not maintain speed climbing mountain passes, but it wasn't terrible - maybe 45 mph. or so. Again, it was working hard, but the M54 can withstand working hard.

The OE hitch on the E53 is a work of art - much better than the aftermarket hitch I have on my E70. But the 35d pulls it much more easily.

I wired up a Prodigy brake controller on mine. It worked, but was never quite right. The signal wire I tapped into in the LCM delivered a weak signal that made the display on my Prodigy "spaz" out. It still worked, though. A friend who is a PhD in EE suggested I wire up a relay and pull the power from a stronger source - only using the signal wire from the LCM to trip the relay. Had I opted to keep towing with the E53, I would have done that.

The E70 has circuitry to accept the Prodigy, so it works flawlessly in it.

In TX, I think it will tow your trailer better than you might think. You'll have flatter terrain and slightly more power due to lower elevation. Two of my adult sons were with me on the trip to Big Sky (both are mechanical engineers) and one commented that, although the engine was working hard, it sounded as if it could "take it" better than a lot of engines. I would agree. I think we would all agree that BMW engines are one of their strongest points.

AM.

Already have the brass plug. :D

I'm not quite that level of purist. But I get where you are coming from. ;) Honestly, I have so many BMW caps sitting around I probably have a lower bar cap somewhere in my collection. Have at least 3 or 4 E30 caps floating around...

Thanks, that's what I was curious about, whether it performed adequately or whether it puked out any extra coolant. I've never spent 10 straight minutes at WOT (in third or fourth nonetheless) in a vehicle that wasn't towing. It stresses the vehicle out in a way that you can't do in any other way.