YODAONE

LS400 cabin filter is 25mm thick while LS430 is 29mm and both 233.5mm X 215mm. (Online info..) so Toyota determined a benefit and need for a higher capacity filter.
An LS400 will not accommodate an LS430 cabin filter. (Yamae)

So am wondering whether substituting the filter cover door and, or filter tray from an LS430 into an LS400 will allow taller filter OEM fitment.

The cover access door holds the filter tray in position: LS400 cover part # 88891-50030 (discontinued) and, LS430 part # 88891-50070.


LS43O/Celsior UCF30/31 HVAC assembly depicting cabin filter tray on left. (Right hand drive parts image)

LS400/Celsior UCF20/21 HVAC assembly depicting filter door, tray and filter on left. (Right hand drive vehicle parts diagram)

Externally both access doors/ mounting appear similar so if so, suggesting the primary difference is filter tray height secured.

YODAONE

McGrath Lexus parts department indulged a few images of LS400 and LS430 cabin filters.
Filters incorporate activated charcoal, so are left in sealed bag until installed.

Same length X width, but as noted earlier, the LS430 filter is much taller.

Significantly more surface/filtering area.

It appears the LS400 filter housing would require modification to fit the larger filter.

The AC intake housing assembly can be extracted without removing the dashboard, but it is a several hour project.

Will.advise...


LS400 cabin filter atop thicker LS430 filter


More to come.

YODAONE

Acquired a cabin filter tray and access panel from an LS430 in an effort to determine whether they would facilitate plug-and-play of LS430's taller filter assembly into the 1999 LS400.

No question the LS430 filter is the way to go to increase capacity, increase system efficiency and reduce back pressure/noise.

For presentation purposes of determining whether feasible, acquired a spare cabin filter/air inlet housing assembly.



LS430 cabin filter tray is taller than LS400 (bottom)

Same length X width.

LS400 cabin filter tray

LS430 filter tray will not insert.

The cleft plastic plate just inside rectangular access will need to be removed. Easy enough.

Image depicting upper and lower section of cabin filter housing. The ramps of LS400 housing will require milling to accommodate the taller LS430 cabin filter..

Upper and lower halves of housing reunited at filter access.

The opposite side of housing does not fully close due to cabin filter tray clearance issues.

The housing sections appear modular, so perhaps an LS430 cabin filter housing section or one from another Toyota model will be more amenable to plug and play. The GS300/GS400 appears to employ same cabin filter access door as LS430..


Here's the rub... The cabin filter access panels on the LS430 (left) and LS400 differ. Orientation of locking tabs are identical, however the opposing positioning tabs are different. The LS430 panel is necessary to accommodate and hold the wider filter tray in place.(!!!)

The modification to allow use of wider filter can be made to work, but at least a modest amount of fabrication to do it correctly. I notice that the JDM Celsiors optioned with rear air purifiers/ozonizers use a wider filter, so perhaps parts exist to make this work.

Honestly appears more work than swapping out an engine.