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Noise reduction right valve cover ventilation tube
Originally Posted by YODAONE
PCV valves generate noise and so to dampen and block noise Toyota employed a molded foam-like cover.
The original cover was degraded by heat over time and so was a very loose fit and no longer doing its job.
After installing the new part, less noisy PCV valve.
Inexpensive part
....as an aside, our PCV valves are 90 degree tube, so air whooshing through the right angle is noisier than straight tube.
Old vs new Original part hard and brittle...
Inexpensive part...check condition of other ventilation parts.
The right valve cover incorporates a counterpart vent tube that is part of the PCV system.
The tube extends from the valve cover and then abrubtly angles parallel to cover.
Thi transition is not radiused but formed at a sharp 90 angle..as if two pieces of 45 degree tubing were welded together.
But what's the point to this descriptive diatribe?
The volume of airflow through this sharp transition makes noise.
So, because Toyota reasoned the PCV valve would quiet with a foam cover, I repurposed the old foam cover over the right bank valve cover tube.
Image depicting the hard angle of right bank ventilation tube Repurposed PCV valve foam cover installed on right bank. The cover base was trimmed to fit.
The right valve cover incorporates a counterpart vent tube that is part of the PCV system.
The tube extends from the valve cover and then abrubtly angles parallel to cover.
Thi transition is not radiused but formed at a sharp 90 angle..as if two pieces of 45 degree tubing were welded together.
But what's the point to this descriptive diatribe?
The volume of airflow through this sharp transition makes noise.
So, because Toyota reasoned the PCV valve would quiet with a foam cover, I repurposed the old foam cover over the right bank valve cover tube.
Image depicting the hard angle of right bank ventilation tube Repurposed PCV valve foam cover installed on right bank. The cover base was trimmed to fit.
Rummaged through Toyota parts bin and located a new foam cover from another Lexus model to cover the job.
New "Ventilation Cap" # 12235-50020 from Lexus. New Cap installed on right bank valve cover.
Fits like a glove. Sound reduction up close is noticeable, but stand alone, negligible.
However, covering 20 areas requiring treatment makes a discernible difference.
1998 - 2000 LS400 PCV system use sharp 90 degree (mitered).fittings on right valve cover and atop intake manifold that generate noise with airflow.
Toyota covered the PCV valve with a foam barrier/damping cover.
Another Lexus model employs a cover on the fitting on intake fitting....so I purchased two of "Ventilation Cap" P.N. 12235-50020
One installed earlier in this post on the right bank valve cover ventilation fitting, and the second on the intake manifold right angle fitting.
No modification to the cover installed on valve cover fitting, but due to tight quarters, trimming required for intake manifold fitting.
Trimmed foam ventilation cover Foam ventilation cover installed The standard cover is formed with a 45 degree side, so no trimming required to.clear adjacent vacuum hose. Appears stock.
I must inform you guys that those molded foam-like covers are used to avoid icing problems. Toyota have had many complains in colder places that those breath lines were blocked by the ice. Believe it or not, minor icing problems even happen in Tokyo in cold winter days. Those foam-like covers are used as a heat insulator. Toyota would use different material if the sound damping were needed seriously. The hose 12262 does not make any special noise but has a cover because these lines are very critical on icing.
I must inform you guys that those molded foam-like covers are used to avoid icing problems. Toyota have had many complains in colder places that those breath lines were blocked by the ice. Believe it or not, minor icing problems even happen in Tokyo in cold winter days. Those foam-like covers are used as a heat insulator. Toyota would use different material if the sound damping were needed seriously. The hose 12262 does not make any special noise but has a cover because these lines are very critical on icing.
Ask the man who knows....
But airflow through a sharp.transition is audible....however not discernible standing next to your LS400, but if you attenuate noise at 10 or 20 locations it is discernable.
04-17-19, 06:39 PM
Pcv valve molded foam cover
