2008 RX400h rear wiper skips/ poor contact with window

Zeus01 · January 29, 2021

My 2008 RX400h has a rear-wiper issue that existed before I bought the vehicle two years ago: The rear wiper does not make sufficient contact with the outer two-thirds of the wiper blade's length. It only smears the water/dirt, making visibility in the main line of sight even worse. It wipes fine at the bottom of the window, but not at the middle and top.

Attempted fixes that failed:

1. replaced wiper blade with new. (well, duh...)
2) replaced wiper blade (again) and replaced wiper arm with new - thinking maybe it was simply a case of a weak wiper arm spring.

Assuming that all rear windows are created equal, the problem must be with the wiper motor mount itself. There is no detectible looseness that might have been caused by a worn mounting surface. But could there be an issue with a removal by the original owner or their shop that was missing a shim or three upon reinstallation? Has anyone else experienced this annoyance?

Any help most appreciated. Thanks in advance, B.

1990LS400 · January 30, 2021

Did you replace the entire wiper blade or just the rubber insert? If you replaced either, did you use OEM parts? Unfortunately, the effectiveness of rear wipers on windows with curvature is sometimes marginal. The rear wiper on our Prius v wagon's flatter rear window works better than the rear wiper on our Sienna van's window that has more curvature. Something else you could try is to thoroughly clean the rear window glass and wiper blade insert with denatured alcohol to remove road film and general crud. I do that several times a year on our vehicles with rear wipers. It's surprising how much crud builds up even when the glass looks clean. Applying water repellent (I use Rain-X) after cleaning the rear windows with alcohol seems to help the wipers function better.

Zeus01 · January 30, 2021

Thanks Jim. I did indeed replace the wiper blade assy (not just the refill) twice, and the entire arm (once). Parts were aftermarket, not OEM.

I'll try the denatured alcohol strategy and quiz one of the Lexus techs about the issue. Looks like I may have to spring for OEM.

Your theory about the curved window makes sense. What does not make sense is the complete lack of complaints by others on any of these forums regarding this problem. If it's a design flaw I'd have expected to reports to be the rule rather than the exception...

1990LS400 · January 30, 2021

You might try reinstalling your original wiper arm and blade if you still have them and replace the rubber blade insert with a new OEM one. It's rare for a wiper arm to wear out. We've kept a number vehicles for from 10 to 14 years and have never needed to replace a front or rear wiper arm.

I don't know what kind of aftermarket blade you bought but some don't have the little spring arms that the OEM blades have that allow them to conform better to curved glass. I tried aftermarket wiper blades on the 2000 LS400 I drove for many years and they didn't begin to conform to its curved glass windshield. I immediately went back to OEM.

You may need your rear wiper more than those of us who live further south.

Zeus01 · February 1, 2021

Yup, we certainly need that rear wiper here, especially in the winter months: snow, ice, road salt, etc.

Too late to reinstall the previous wiper arm, it's now landfill. It did however appear to be the exact same design as the one I replaced it with, complete with spring and spring tension.

On that note, maybe the one I tossed was not the original either(?) Or maybe it was the original, but the spring was no longer strong enough to provide full contact - and it's replacement came with a weaker spring right out of the box? (that one was an Amazon purchase btw).

1990LS400 · February 1, 2021

3 hours ago, Zeus01 said:

Yup, we certainly need that rear wiper here, especially in the winter months: snow, ice, road salt, etc.

Too late to reinstall the previous wiper arm, it's now landfill. It did however appear to be the exact same design as the one I replaced it with, complete with spring and spring tension.

On that note, maybe the one I tossed was not the original either(?) Or maybe it was the original, but the spring was no longer strong enough to provide full contact - and it's replacement came with a weaker spring right out of the box? (that one was an Amazon purchase btw).

My opinion is that the blade is more important than the arm. Your rubber wiper blade insert should have a slot on each side for a metal rib. The metal ribs that fit into the slots are curved. It's important that the curvature of the metal ribs matches the curvature of the window when inserting the metal ribs into the slots in the rubber insert. If the curvature of the metal ribs is reversed, the wiper blade won't contact the glass well through its sweep.

If you purchased an aftermarket wiper blade that doesn't use the two reusable curved metal ribs, then that's likely the problem ... or if the aftermarket blade doesn't have the additional inward spring arms that allow the blade to flex and adapt to the curvature of the glass. Your rear wiper blade should like like the one in the attached image.

Zeus01 · February 3, 2021

Thanks Jim. My blade does look like that one, but I'll need to take a closer look at it to confirm if it deviates in any way from what you've described. When I physically apply pressure (not much) to the blade while it's in motion it wipes just fine. But the spring in the arm just doesn't seem to provide much tension to provide the necessary firm contact with the glass to follow the curvature. One thing I did notice when I replaced the arm and blade last time: for about the first day id did wipe about 90% of the swept area of the window. But by the following day it was back to only the lower 30% as though I hadn't done a thing. Still have to call Lexus, but work keeps getting in the way.

Zeus01 · February 20, 2021

Update: Well Jim, you were correct: The aftermarket rear wiper blades are garbage vs. the genuine article from Lexus. Once temps here finally rose above freezing I was able to remove, clean, lube and reinstall the rear wiper arm and blade assembly - with little to no improvement in effectiveness.

Went to Lexus and purchased a new blade. Both blade assemblies looked exactly the same, but right away I could feel the difference between the two blades as I had both lying on the counter: The after-market blade assembly exhibited stiffness in the joints that support the wiper strip. The Lexus blade had no such stiffness, readily flexing with minimal effort. The new blade now wipes the entire window with no areas of poor contact.

Even the price was not excessive. The blades purchased from Amazon and from Canadian Tire (like Walmart or Pep Boys) were in the neighborhood of $20 . the Lexus blade was $24 taxes in. If those numbers seem excessive it's because nearly everything sold up here is around 30 to 40% higher in price than they are in the US - owing to our Liberal-government-engineered deflated dollar value ($1 Canadian = around 0.72 US) as well as economy of scales - or lack thereof up here.

Thanks again for the guidance, and hopefully this helps others who may be having this issue. Moral of story: don't replace rear wiper blades with after-market garbage. Spring for the Lexus blades.