[beemer100]

Gentlemen, I am doing my 12k service and am wanting to replace the radiator cap. I have searched the forums regarding the cap and wanted to ask if you thought a 1.4 rated cap would be "close enough for government work". The OEM cap is 1.5.

Has anyone ran into problems using a non-BMW issued radiator cap?

Thanks.
James

 

[Cochinosucio]

Found these online.... refers to radiators on cars, however I bet the concept is the same.
A radiator cap pressure ranges from about 14-15 PSI for most modern vehicles, while many aftermarket high pressure radiator caps can increase this pressure to between 18 and 20 PSI. High performance racing radiators may have caps rated at as high as 22-31 PSI, but these should not be used on a factory radiator. It is important to select the pressure rating that is recommended for your vehicle in your owner’s manual. Too low a pressure will decrease a coolant’s boiling point, while an excessively high rating may increase the chances of a coolant leak.

If the coolant cap is bad, the fans may come on but the bike will still tend to overheat. A bad coolant cap will really show itself if you are riding with a good airstream crossing the radiators and the temp is still rising a little.

 

[beemer100]

Thanks for the reply. I had an experience a couple of months ago whereby after I parked the bike in the garage, I immediately had an overflow of coolant seeming to be located under the coolant reservoir near the back of the bike. I filled the reservoir back up and noticed now that it is showing low again as I am doing my service.

The bike didn't seem to be running extraordinarily hot and I am wanting to replace the cap in case it is defective.

James

 

[RonKMiller]

Hmm, you shouldn't have any trouble sourcing the correct bar cap... it is known as a European or Mini-Cap. Mine is a Stant brand that I bought for around 10 bucks.

The conversion is 21.7 psi.

But I don't think you would have any issues with the 1.4. If it runs hotter than before you'll need to up the pressure. Installing one that is too high could potentially cause serious problems.

You can easily have the old cap tested, a lot of times they will have just a very minor leak from an age hardened seal that is hard to detect, so replacing it is a good first start.

 

[andres]

The fans come an at about 220 deg F and I've seen the coolant temperature rise to 230 deg F on my LT. Pure water boils at 233 deg F at 1.5 Bar. Decreasing the radiator cap rating from 1.5 Bar to 1.4 Bar lowers the boiling point by about 5 deg F. The "anti-freeze" increases the boiling point, but I would not risk installing a radiator cap with an incorrect rating.

 

[beemer100]

Thanks for the replies. I guess I will continue my request for the 1.5 cap. I tried several places to date (Auto Zone, O'reilly's, Napa, Pep Boys). I guess someone will have one around here. I was just wanting to bypass the expense and wait for the OEM cap. Dealer wanted 24 dollars and is special order.

James

 

[Cochinosucio]

$22 was the best I found... BMW Chattanooga...
http://www.bmwmcchattanooga.com/pro...00LT/Plug--cover-lid/1025431/17117675523.html
You can try BMW of Denver, 10% discount..303-755-6400

Did you try to have it tested yet?

I bet that's gonna be a specialty item no matter what....