RX 400h - Water coming in from somewhere?

rich1068 · November 27, 2018

Noticed these water marks and a run yesterday.

Obviously recent as a paper towel soaked some of it up.

Any ideas? I think due to the location I'm leaning toward the roof bar foot. Any thoughts on this? I can't see how eg rain water could get past the tailgate seal. I did use the rear washer the other day (something I do very rarely) but where I think the washer hose comes through to the tailgate just doesn't fit with where the damp marks are. And I suppose I could exclude that altogether with the use of a hosepipe.

I gave the trim a clean up and the marks haven't returned. Coincidentally, I found the marks investigating a gentle knocking I get from the n/s rear. No idea what's causing that but I'm wondering if it's connected.

oldgreybeard · November 28, 2018

Hi Richard

I have had same problem with water marks in same place and after looking in all the known places ( more than one well known area that leaks) Lexus had the car in and stripped out the rear boot trim and sides only to find water pooled in boot floor pan area. This had been going on so long it had caused corrosion of the rear boot panel at the base that had to be rectified at bodyshop !

Two areas found to be at fault:

1. Small split in boot/tailgate seal- item replaced and sealed.

2. Small fracture/split on welded seam in boot as the side panel starts to turn vertical if that makes sense.

Rear light clusters were checked and seemed ok but had the seals replaced just in case.

Hope that may help a little and good luck

stuart

rich1068 · November 28, 2018

Hi Stuart.

Thanks for the reply.

#2 sound interesting. This might explain the tapping from the rear quarter. I have experience of broken welds on a BMW and the sound is similar. Like popping the side of a Coke can.

I'll have another shufty at the rubber seals too but they looked OK to me.

Prior to purchasing earlier this year I did inspect the boot floor after the worrying stories on here and there was nothing amiss. I'll have another look. Also it was throwing it down last night so I'm going to get it inside and see if the marks have returned.

rich1068 · November 28, 2018

Dismantled the trim around the boot floor and there was a little more water than I'm comfortable with on a 12 year old car but nothing too terrifying.

I've left the two side bins out so I can keep an eye on it and also because I really don't fancy struggling to get them back in again May need some advice on that one...

No closer to knowing how the water is getting in though.

rich1068 · November 28, 2018

Great video here for how to remove the boot floor to access any dampness

Mine wasn't too wet but I'm going to leave everything out for now.

Rutlandlex · November 29, 2018

I don't know if this helps or not but have you had the tailgate open when it's been raining? The reason I ask is because when I had my towbar fitted by a mobile fitter it was pouring with rain and there was a leak coming through the trim in the boot on the driver's side. I found that directly above where the water was seeping through was the bottom of the strut so I think that the water was running down the strut and into the car at the bottom of the strut because it isn't sealed properly. I have since checked the trim after rain many times and not found it to be wet so it only happens with the tailgate open.

Other cars may be different though.

rich1068 · November 29, 2018

Thanks for the tip but no not really. Tbh I haven't tracked down the source of the original leak at all and the car's still in bits!

Jaystar77 · December 1, 2018

I had a leak in exactly the same place as that on my 350:

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.

Jaystar77 · December 1, 2018

Just noticed you mentioned a slight knocking noise too - would you believe I was investigating this as well at the same time as sorting this leak?

There's quite a few rubber bushes on the rear hubs, four or five on each side. My noise was caused by excessive movement on two of the DSR hub bushes. Had one replaced with a cheap eBay which quietened it down a bit but there was still movement in another bush. Could probably have just replaced the rest of them with eBay sourced stuff but I threw the head up - ended up replacing the whole assembly with a new genuine Lexus one. Pricey but at least I knew it was sorted once and for all!

If you crawl under the car with a pry bar and test all the rubber bushes you can see for movement it will hopefully help track the culprit down.

rich1068 · December 1, 2018

2 hours ago, Jaystar77 said:

I had a leak in exactly the same place as that on my 350...

This post couldn't have come at a better time! Absolutely gushed in this morning. Damp patches on the trim and everything. Pretty sure it's related to the roof bar foot or that area as you found. In fact I've noticed it runs out of the fitting for the power boot close thing. I'm parking facing downhill to stop it being quite as bad. Weird how this has only just started. Used the roof bars for a pretty big roof box over the summer, I wonder if this is related?

I've had everything out of the boot but it wasn't practical running the car over the weekend like this so I put everything back. I know I'll have to mop up again and again like you I think some of that dampness is unrelated to the roof. Had the lamps off and everything seemed OK, the seals were dry. So my money's on the two screws either side of the rear bumper just above the plastic protector with the Lexus logo on it.

Great post. Thank you.

rich1068 · December 1, 2018

2 hours ago, Jaystar77 said:

Just noticed you mentioned a slight knocking noise too - would you believe I was investigating this as well at the same time as sorting this leak?

Great minds and all that

I don't think mine is suspension related but I'll check that out.

Jaystar77 · December 1, 2018

I think it's a case of Lexus just wanting to make things interesting for us - the seam welding around the rear panels is a bit substandard to be totally honest. You really wouldn't expect it to happen, I run a gen1 RX and it's built like a tank in comparison!

As you will need to remove the roof bar for access you could grab a fresh set of seals from Lexus (I did this, think they were around a tenner) to fit. Mine were fine but I would rather be looking at them than for them. The end caps pry off and the bars are held on by 2x 12mm bolts at each end. The seals are handy to replace once the bar is out of the way.

rich1068 · December 2, 2018

11 hours ago, Jaystar77 said:

As you will need to remove the roof bar for access you could grab a fresh set of seals from Lexus (I did this, think they were around a tenner) to fit. Mine were fine but I would rather be looking at them than for them. The end caps pry off and the bars are held on by 2x 12mm bolts at each end. The seals are handy to replace once the bar is out of the way.

Thanks.

I looked at removing the bars all together at one point so I'm sure I've got instructions somewhere.

rich1068 · December 3, 2018

Well there's still more bits off the car than on it at the moment!

Roof bar is off and new seals have been ordered. Mastic will go on those too
Black mastic is out and I've done all around the seam mentioned by Jay, removed the tailgate strut, sealed the foot and refitted (not easy on your own!)
Sealed around the seam just above the strut foot
Left the rear lights out for now but I'll probably just pop them back on because I'm not convinced they're leaking. Maybe a squirt of something that's not sealant to be sure
Ordered two new stoppers for the rear bumper fixings on the bottom of the tailgate opening

That last one I'm interested in. The stoppers have a rubber washer on them and both had perished. Their position also matches the run marks on the inside of the rear bulkhead. Convinced now that I'm dealing with two quite separate leaks.

Bit of a bonus. Realised the driver's side sunroof drain was blocked so sorted that too.

Jaystar77 · December 3, 2018

It's like owning a waterpark eh?

😁

rich1068 · December 6, 2018

Bit of an update.

Sealed around the roof bar foot, seam pointed out by Jay (and Lexus bulletins!), tailgate strut, rear bumper fixings and rear lamps. Took it for a wash and so far no leaks. It's raining atm and I've left it facing uphill so we'll see what happens tomorrow.

Close run thing. Nearly fell out with it!

rich1068 · December 7, 2018

Really came down last night and I left it faced uphill. Dry as a bone

I've found the noise too. It's coming from the trim around the tailgate lift, the same area the water was making an appearance. Armed with felt pads and spray grease I'll sort that one this afternoon...

Jaystar77 · December 8, 2018

Good to hear results Richard - nice work!

rich1068 · December 20, 2018

Update after a few weeks.

Everything lovely and dry. Not a drop that I can see (or feel).

Siberpir8 · March 16, 2020

Sorry to revive this thread, I'm having the same issues.

I have already sealed all the places mentioned. Apart from the area rich1068said "two new stoppers for the rear bumper fixings on the bottom of the tailgate opening"

What are these? I managed to stop the leak coming in from the left hand side, but I still have a small leak welling up on the right.

Thanks.

rich1068 · March 16, 2020

Hi Simon. So if you've already done all the big stuff like the roof bar feet, tailgate struts, welds etc or your leaks seem to be coming from around the bumper/light cluster area then see the pic below. I was also happier once I'd taken the rear lights off and had a spray round before refitting.

Siberpir8 · March 17, 2020

Thanks Rich,

I did put some tiger seal, then put the fitting back in. But perhaps it's still leaking a bit.

I have ordered some rubber grommets and I'm just going to block the hole up and leave the bumper fitting out.

If it still leaks.... That's it... I will set it on fire! 😂

stinkerbill · October 9, 2020

I had a similar issue with rain water getting in 'somewhere' around the rear roof area and leaving marks as described by Rich1068, both sides.

Having removed the roof racks and rubber roof rack trim, there were clear cracks in the welding under that area. A bit of CT1 sealant on it and fingers crossed that'll fix it!

I'll report back.

Jpl Plastering · December 20, 2020

Ive be having this trouble soaked carpets & when opening the tailgate water running down A panels at rear.

Dried it all out today removed all boot trim.

Rear lights seals all good

Tailgate seal all good

gas struts letting in water wear joining body,taken of resealed.

Black trim besides each tail light grommets for screws letting in lots of water into boot floor dried up sealed gromets back in with sealant

Water tested for 20mins with a hose hey presto problems solved now water tight again.

Jpl Plastering · December 22, 2020

Update roof rail rubber gasket failure this has solve all water ingress now replaced with rubber washers,heavy rain last night and boot and A panels are bone dry,after a long battle problem is finally solved.

Just as i was going to put a match to it😂😂😂