Hey guys. This is my first post here. I've been lurking on these forums for a while, and I can usually find the answer I need just by searching, except for now...

I have Forge-style aftermarket coolant expansion tank. I noticed that a small amount of coolant seems to drip out of the cap every now and then (as evidenced by stains on the tank). When I first noticed it, I tightened the cap, but I'm seeing a little every few days.

I have ordered a new cap from Way, but I'm wondering if the tank is over filed... Some posts on here say that's an issue with the OEM tank

My question is: how high should I fill the expansion tank? There are no real markings on the tank for reference besides the welded seam.

Thanks

 

Here it's the specific tank I have:
https://www.waymotorworks.com/polish...-tank-r53.html

 

My Forge tank with the stock cap seems to leak, no matter what. It's a bit of a pain as well, since polished tank + hot coolant requires a bit of work to clean.

 

I can't get the stains off. Even tried using silver polish. Now I'm wishing I had ordered the black one Way sells.

 

The OEM plastic tank is filled up to the seam....so about 50%
Looking at most of the aftermarket tanks, the capicity seems higher than the OEM plastic tank....
It seems the OEM caps seem to vent a bit a steam...it then condensed...and leaves a stain..there is only one maker that makes tanks that you can fit an "overflow" tank to catch the steam as it vents, to allow it to condense...what happens with MOST cars. Not 100% sure, but the RMW unit might be the one..could be Colin's, but not sure offhamd....have mixed feelings cause the standard "STANT" caps are actually a higher psi than the OEM spec if I recall...
The desgin difference is the neck on the filler is diffent for the conventional cap, and it has fittings for a tube to the overflow tank rather than just venting.

 

Painting it should not be hard....
Get..strip the tank...use some etching primer (zinc chromate might work if it is polished aluminum)....then paint with flat BBQ or other high temp paint.

 

That's a good idea.

 

For part of your 'dawn patrol' pre-flight walk around (I'm/we're sure you check under the bonnet regularly before hitting the road), just unscrew the cap and stick your finger down the hole 'till it hits the baffle. If there's water on your finger tip, you're good to go.

 

I did read about the higher PSI caps and wasn't too sure about that either...

 

My concern is over filling. That wouldn't really help. I've read it can lead to coolant leaking out, which is the issue I'm having.

 

I replaced my ten year old oem coolant tank with above mentioned metal tank in February as a precaution. I emptied 18 oz. out of the oem tank, which was the level above the baffles and made a note. The metal tank holds 36 oz so the amount in the oem tank was exactly half that of the metal tank. I then took a clear drinking star and found that a full tank measured up four inches on the straw. Marked that with a Sharpie and at two inches for half level. Take the straw, insert it into the tank, put your thumg over the top, remove and view the level. As Flyin Brick stated, the wet digit method works well also. That level has posed no problems since installation this last January. Good luck,

 

Great advice! Thanks!