Sun roof rear drains

Siberpir8 · February 24, 2020

Hi all, I have the infamous leak on the inside of my boot (truck) and I have sealed up the rear lights, seams and strut brackets and I'm still getting some water in the back. I've check the front drain for the sun roof and they are clear. How can I check the rear as I can't see the holes from the roof? And is there anywhere else that the water could come in?

Thanks.

katabrontes · February 24, 2020

I had this problem with my RX350. It was caused by a kink in the tube inside the trim panel at the side of the boot. I fixed it by replacing the last 10cm or so with a piece of copper tubing and have had no more problems since. I think I posted some pictures of this previously which you can probably find in my earlier posts.

welland · February 25, 2020

I don't understand this issue with sunroof drains causing water ingress in the boot. If water cannot flow through the sunroof drain tube how does it end up in the boot? If the tube is punctured, I could understand it. But, when the tube is just blocked i can only see that the problem would cause the drain to overflow.

Siberpir8 · February 26, 2020

I could understand if the exit point was blocked behind the rear bumper as it would then overflow and come out of the fitting. There are also the ventilation flaps that I found to have a very small amount of water on. I will attach some pictures tonight. But I have ran some small plastic tubing back up to the sun roof from the rear and it seams clear. So now I'm running out of options. I will have to lock myself in the car and get the Mrs to pour water over.

Jaystar77 · February 26, 2020

I struggled for access to the rear drains. Ended up feeding a length of thick soldering wire up the tubes from the drain points so as the wire came out in the depths of the sunroof frame. This let me know that at least they were not blocked.

Have you taken the roof rails off? There's a gasket and bolts on each foot which I replaced just to be certain. Also sealed the roof seams whilst it was all off - the seams ended up being the 'real' problem albeit further back around the hatch area.

Siberpir8 · March 5, 2020

On 2/26/2020 at 6:31 PM, Jaystar77 said:

I struggled for access to the rear drains. Ended up feeding a length of thick soldering wire up the tubes from the drain points so as the wire came out in the depths of the sunroof frame. This let me know that at least they were not blocked.

Have you taken the roof rails off? There's a gasket and bolts on each foot which I replaced just to be certain. Also sealed the roof seams whilst it was all off - the seams ended up being the 'real' problem albeit further back around the hatch area.

No I havent take the roof rails off.....yet!

Im really struggling to fin the leaks on both sides. I have put a wire up the rear drain hoses and it gets stuck around the middle of the rear doors on both sides in the tube. I have pushed quite hard but it wont go any further.

As you can see from the pictures it runs down the outer skin (which I cant trace or see any further) then runs down the outside and correct in the corner.

I am at my wits end and it has been constantly raining for about a week so its hard to pinpoint the area by pouring a watering can over.

Old Git · March 5, 2020

I had the exact same leak with RX350 I think I have cured it seems ok for the last week, I put a small amount of body seam sealer on the panel joints above the boot strut and the panel joints at the top the tailgate seam below the hinges I pulled back the boot seal to make sure I could access all of the joint its been a week of rain and all seems ok absolutely dry, the water was seeping in and running down the double skinned boot panel and leaking under the rear lights by the body seam you could see the marks where it had been leaking, I hope this may be of help

Siberpir8 · March 6, 2020

10 hours ago, Old Git said:

I had the exact same leak with RX350 I think I have cured it seems ok for the last week, I put a small amount of body seam sealer on the panel joints above the boot strut and the panel joints at the top the tailgate seam below the hinges I pulled back the boot seal to make sure I could access all of the joint its been a week of rain and all seems ok absolutely dry, the water was seeping in and running down the double skinned boot panel and leaking under the rear lights by the body seam you could see the marks where it had been leaking, I hope this may be of help

Thanks for the info mate, if possible would you be able take some pictures?

Jaystar77 · March 7, 2020

Sounds like the same issue I had too Ray. Here's a post I made at the time, might help :

Had to take the passenger side roof rail off and find the rear most seam on the roof has the slightest of nicks in it. Whenever the rainwater was rolling off the roof into the 'gutter' it was running right over the pinhole creating my issue. I've attached a few pics in case anyone else encounters the same. I checked the driverside and the same thing has happened there although the leak was nowhere near as bad.

It really doesn't look like much but the amount of water that this tiny crack in the seam was letting in was shocking. I applied some seam sealer all along the welded seams that I could find on both sides. A good heavy instant gasket would probably do the same job just make sure everything is dry before application. After sorting this I still have a slight weep from the rear lamp gaskets but that's a side effect of looking for leaks - you always find more!

You should strip the boot floor storage out and clear it of water before it starts to smell too much too. Leave it stripped until you are happy the leak is fixed.

Siberpir8 · March 10, 2020

Ive sealed every hole, grommet and joint behind the bumper and stripped the roof bars and gutter covers off and run a bead of tiger seal down. Sods law it has now stopped raining so I have to leave the boot stripped and wait for the heavens to open again! If this bloody thing still leaks, I'm going to set it on fire!!! 🙂

The only thing next if it is cured is having to strip out all the carpets!😪

Jaystar77 · March 10, 2020

Yep, Sod's law is what I'm used too as well.

I tackled it in the summer so used a spray bottle for testing purposes 🙂

Siberpir8 · March 14, 2020

Son of a bitch! The left hand side is OK now but the right hand is still leaking, although not as bad. I just don't know where is can seal next! 😞

Baldguy · January 19, 2023

An old thread revival - I'm back in a Lexus after a few years and have just bought a 2007 RX350SE-L as a 2nd car with 65k miles and have all the problems above, I'll be stripping the back of the car out to seal everywhere and clear the rear sunroof drains and also removing the roof rails to seal those too. I've cleared the front sunroof drains.

@Siberpir8 Did you finally get to the bottom of all your leaks?

Cheers Greg

Baldguy · January 31, 2023

On 1/19/2023 at 8:40 AM, Baldguy said:

An old thread revival - I'm back in a Lexus after a few years and have just bought a 2007 RX350SE-L as a 2nd car with 65k miles and have all the problems above, I'll be stripping the back of the car out to seal everywhere and clear the rear sunroof drains and also removing the roof rails to seal those too. I've cleared the front sunroof drains.

@Siberpir8 Did you finally get to the bottom of all your leaks?

Cheers Greg

Had the car just over 2 weeks and been working through the water leak areas.... Sealed up the roof bar fitting points, cleaned and blown out front sunroof drains, stripped the rear out tonight and found one severely collapsed rear sunroof drain where I cut about 2" off and refitted.. all good now, the other side was blown out too and both sides fished through with a curtain wire... Pulled Aircon drain tube off and blown that out too.

Sealed the rear roof seams at the top of the tailgate and also rear hatch strut mounts, last job to do tomorrow is remove the rear lights and seal all those up so they don't let any water in or mist up....accomplished allot in the 2 weeks I've had it... Had a full Hunter alignment too...

It's booked in for a Major service, spark plugs and both rocker gaskets as they're leaking plus rear discs (rotors) and pads next week.....

katabrontes · February 1, 2023

Hi Greg

i think the 350 is a good choice. Mine (2005) has been pretty well trouble free since I bought it in 2010 apart from a persisting irritating tendency for the AFS off, and the triple VSC, ABS etc which come on from time to time but haven't caused an MOT problem and no error codes come up. I did have a wet corner in the boot a while ago poole and, like you, found the bottom of the NS drain hose was kinked. I replaced the last 4" or so with copper pipe and it has been fine since. I haven't had any leaks from the roof rail mounts or into the rear lights.

I am reluctant to replace it with a 450 as they seem to have all the same problems as reported on 350s plus a few more mainly related to the standby Battery. I plan to keep it for at least another 5 years unless a major problem develops.

Following the advice of the Car Nut on Utube I replaced ( well about 2/3) the transmission fluid even though Lexus and my garage said it wasn't necessary. As the video says gearboxes are very expensive and this was pretty cheap insurance.

I am sure you will enjoy the car. Apart from the improved design of the door cills and the wing mirror cameras I don't think the near 450 ( 2015+) have much to offer over a 350.