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1990-1994 LS400.used an Aluminum Mass Airflow Sensor/Venturi housing Assembly.
Well made but expen$ive to replace.
It was also quieter (noisy airflow through venturi and sensor) than the plastic housing used starting 1995.
Plastic can shrink.or distort slightly with age,.
On 1999 LS400 observed movement of the tapped c-bracket used on the air cleaner assembly for fixing shoulder bolts clamping Mass Airflow Sensor to the housing.
More pronounced gap between the MAF and housing thus rubber sealing ring was not properly compressed.
The special flange head shoulder bolts are designed to bottom out on the shoulder to prevent over tightening the MAF and Housing..
However this mounting scheme is problematic if plastic distorts or shrinks and further tightening is not possible to properly compress the rubber sealing gasket.
A simple fix..
Used 1/32" thick raw Teflon sheet stock to fabricate washers.
.312" I.D. and .5625 O.D.
Teflon was used for slippage and conformability.
Teflon washers were placed under the bolt heads so the shoulder bolt does not bottom out before adequately clamping and sealing the MAF to the housing.
Several images:
MAF mounted to plastic Air Cleaner Housing. The tapped c-shaped metal bracket used for fastening MAF bolts... OEM elected not to insert mold nuts into the housing... Tapped bracket depicted. Used this hole template for measuring shoulder bolt and recess diameter in the MAF where the bolt flange nestles. Shoulder bolts depicted here. They bottom out before adequately clamping MAF to air filter housing...as evidenced by easy movement of bracket and gap between housing and MAF. The solution..employed Teflon because it will not abrade or gouge the plastic in the MAF and will compress to accommodate distortions between the flange bolt and plastic MAF mouting area recess.
Gasket between MAF and Air Cleaner Housing now seals more fully and uniformly.
Interesting. I'll have to inspect mine. I have some phenolic fiber spacer that has varying thickness and has reasonable heat resistance properties. I've used it for similar in the engine bay for spacer material.
05-06-20, 07:56 AM
Mass airflow sensor leaks
