My first post. Has just had RX350 2008 for a month. I'm from Australia.
I found the pinky mark on the front grille after getting the car back from serving. Open the bonnet and I found as below image
Does it mean the radiator have to be replaced?
Have not had time to get this back to the shop yet.

 

Yep.
Need a new radiator.
I’d replace the t-stat as well.

 

id also check the water pump as well make sure thats still in good shape and is not leaking while yer in there.

 

How many miles (or kilometers) on your RX?

 

Yep, same thing happened to my old Camry. Crack got so bad when idling it you'd see steam come from the hood. You can lose a lot of coolant from this, get it fixed as soon as you can.

As others mentioned, great time to change the T-stat and hoses if they're in bad shape.

 

do not muck around with radiators. You risk overheating/blowing the engine. Radiators on ebay are ~$200

 

Thanks guys, I will send her to a mechanic to get a quote this Monday. If it's expensive than probably a DYI.
Fyi, it's 180,000 km and according to the service logbook the water pump was replaced in 2016 by Lexus. Hope it's still in a good shape.
You guys mentioned about the t-stat, not sure what is it Car is a completely new area to me.

 

Hi zerox,
since you mentioned it- this is definately a DIY job for most people with only simple tools required.
There is a big price difference between Lexus OEM radiator and a genuine Denso on Rock Auto for only $150.00.

If your mechanic wants to sell you a junky aftermarket radiator for $300 that is NOT a Denso I would order the Denso from Rock Auto and have it Next Day Air shipped in.
PS- There are 2 radiators available depending if you have tow package or not. They both appear to mount using same bracket unlike the RX330 model.