alinour

Hi all,
I recently bought a 2011 rx350 private party and I’ve noticed this coolant leak coming from the radiator (see image). It’s not coming from the actual radiator cap, just this little circular part that sits under and behind it. Any clue what’s happening or how to fix it? Any advice helps.

Thanks!

Roscol

Looks like it’s old dried up coolant residue. Is it actively leaking? Right after a drive is it wet or do you have drips on the ground?

alinour

It only gets wet around the circular part after driving for a few minutes, otherwise it doesn't leak. Seems like it's just a slow seep because there are never big drips that I see. All I see happen is that crust gets moist on that circular part (where the red is darker). I don't see drips on the floor either.

carguy75

I did not know that our radiator had that side cap. Here is a video that show how to fix(or maybe correct) the issue on our model RX350 at the beginning by tightening the side cap with pliers. Your cap looks like it has an 10mm hex socket. The cap may also have an o-ring that can be replaced. I have to check mine as well to see if I have any leakage from that cap.

RX in NC

Thanks for posting that video. As you said, something else we all need to check on a regular basis as these vehicles continue to age. Man, how I despise plastic components in cooling systems. If you twist that plastic cap too hard or too far with your needlenose pliers, I bet it will crack and crumble right before your eyes. That entire assembly should be METAL, not plastic....

carguy75

No problem.

Personally, I would only tighten the coolant cap snug enough just to put a band aid on the leak, however if it stops the leak I would still replace the cap or o-ring if possible. I think the 2011 and newer RX models has a radiator side cap with a hex fitting like in the OP picture, so you may only need a hex key to snug it up.

Note:I just checked my 2015 radiator with no leaks in that area and I have the same side radiator cap as the guy in the video. The OP must have a Hybrid or maybe aftermarket radiator with the hex nut cap.