Had my radiator replaced by Lexus dealer at the end of last summer. Recently started noticing coolant on the driveway and in the under engine tray on the drivers side front left.

Took it to dealer, they pressure tested it and said there is no leak despite me asking a couple times, then how do you explain the coolant in the tray? Couldn't give me an answer and sent me away categorically stating it isn't leaking.

Have done some investigation of my own. Realized there is only a leak on cold start. Start car cold, observe coolant in tray, wipe up, drive to work, no further coolant in tray. Drive home no further coolant in tray. Had the wife start the car in morning so I could try and find the location of leak. Observed and filmed it drip, drip, dripping from what looks like a bolt head to the left of the drainage stopper. It then stops after car gets warm. Luckily I captured this on video and am heading back to the dealer tomorrow but can someone tell me what the actual function and / or name of that bolt head is to the left of the drainage plug. I've attached a picture I found of the lower part of an SC430 radiator for reference and circled the bolt in question in red.

 

I think that's a plug that goes in place of where a temperature sensor used to be. Probably simply needs a new gasket.

 

Anyone have any idea what the part number may be for this bolt / plug and or the gasket or o-ring? My car is a 2005. I intend to attempt to make the dealer make it right but I've already had 3 issues related to poor workmanship at this Lexus dealer and may end up just fixing it myself.

Interestingly, looking at used radiators on eBay, I notice some have a bolt like mine and some have a plastic plug like this...

 

OE parts diagram shows the same thing as above (click to get full part numbers in case you don't know)
http://www.japan-parts.eu/lexus/us/2...r-water-outlet

 

Thanks. That helps a lot.

It looks like they have both options in the diagram. I think...

16467A (16407-7A130) is the plastic plug with o-ring



16400U (90341-16016) is a bolt.

Wonder what the difference is and whether I should switch to the plastic plug.

 

Way I read the diagram is there is a plug then a plug that goes in that. Then another plug. I like to use OEM parts if it was me I'd put back originals and call it day. Or maybe even replace the entire rad if it happens to be original.

 

Radiator is 6 months old and was replaced by Lexus dealer so I expect them to make it right but I’ve already had a bunch of issues with this dealership and their half assed work. Once this is resolved, the car will never go there again.

 

Understandable. Odd that a new rad is leaking.

 

Wanted to close the loop on this one. After determining on my own that the leak only happened when car was cold, took it back to the dealer for the third time and provided my video of the leak. Although it sure looked like it was leaking around the bolt to me, they determined it was leaking down to the bolt from the upper radiator hose which is above the bolt. One new hose and 2 new clamps later, after 3 cold starts, coolant leak appears to be resolved.

 

Thanks for the update. Lesson here is liquids flow, may seem obvious but it's easy to get fooled.