I noticed that coolant has been leaking from the cap of the OEM reservoir(after a 5 mile drive). However, the cap looks like its in good shape. Coolant level prior was slightly below the max line level.
Is this a common issue?
In the meantime,I ordered an aluminum coolant reservoir to replace the OEM.
Can anyone recommend a replacement cap?

Thanks in advance

 

Check the mid seam around the reservoir. That is a typical failure area. It might not leak out, but under pressure it will seep and leave moisture in the seam area that is very easy to spot.

 

I noticed that it was wet around the mid-seam but it also looked like it was running down & or originating from the cap.

 

some of the metal tanks reuse the oem cap....some use a typical cap...so it depends. i would buy a new oem one if you must use an oem one.

 

having the tank leak, or even split at the seam is common....most just get a new tank, comes with a new cap...caps do fail...but different tan typical radiator caps, so oem is the typical fix.

 

Thanks for the info.
The timing is horrible,I ordered the aluminum replacement(arrives on 4/30) & I now have to buy/install an OEM plastic one(well the shop will).

 

Although the OEM ones are prone to fail, I think the plastic tank is more convenient for regular visual level checks. I just replaced my original tank this weekend with the current OEM tank and noticed that the plastic color is lighter than my original tank. The original was a brownish color, while the new tank is much more white in color. I can easily see the level through the plastic when I shine a flashlight across the tank. I guess with metal tanks, you have to check through the cap looking into the tank?

 

the old tanks were sorta translucent....
mini swapped them out (dealer did mine for free before it leaked years ago) with a less clear milky/darker one....if you don't overfill them past the seam, they seem too last much longer....
changing them out is about a 15 minutes job...a couple clamps for the hose, and a bolt on the firewall....no bleeding needed. if hot...like at a shop, you MIGHT need to wait a bit to let stuff cool off.....
and yes...a flashlight works great with the OEM BLUE coolant for a level check...

 

The tanks can crack/ split at the seam over time. They come with new caps. The Forge Alloy on you need a new cap or transfer your old one.

17137529273

http://www.ecstuning.com/Search/SiteSearch/17137529273/

Genuine Type



Forge Motorsport




&

Cap 17107515499

http://www.ecstuning.com/Search/SiteSearch/17107515499/

 

Common issue on these models. Replace it with the stock unit and be prepared to replace it again. A quality item like the Canton aluminum tank is a great replacement.

http://www.m7tuning.com/r50-r53-alum...lant-tank.html

 

Thanks guys. Appreciate all the info.
I anticipated having to basically change out most if not all components with the car so that I start with a clean slate.
And then moving forward,it will help me with troubleshooting & ultimately I'll feel more confident taking a road trip without fear of something failing

 

Welcome.