speedkar9

Just finished replacing the valve cover gaskets and spark plugs and wires on my brother's Lexus GS300. I haven't found a DIY for the valve cover gaskets yet, so I made a YouTube video on how its done:


As for the spark plugs, there are two write-ups, one has pictures and one doesn't, but they're good for reference:
https://www.clublexus.com/forums/per...-gs300-10.html
https://www.clublexus.com/forums/gs-...-cleaning.html

Here's a few photos of the procedure:

The valve covers are located under the engine covers and intake. Start by removing the covers, and then the intake tube before the throttle body.




The throttle body and part of the intake will have to be removed to access the valve covers and spark plugs underneath.


There are a number of vacuum hoses, electrical connectors and coolant lines to be removed, including a small green vacuum switch behind the intake that's held on by a bolt.







The front coolant line can be removed now, and the rear coolant line will be removed once the throttle body is unbolted.


The throttle cable can then be removed and unbolted from the adjuster.


There are 4 bolts and 2 nuts that hold the intake to the plenum on the drivers side of the car, and two additional 12mm nuts on the passenger side.




The use of a ratcheting wrench is helpful for accessing those nuts under the intake.


Intake removed:


Remove the ignition harness from the coils. Be-careful as they're brittle and will break and you'll need to replace them.


Here you can see how much oil was built up in the spark plug wells due to the leaking valve cover.



Next start unbolting the valve cover, each one has 6 10mm bolts and two 10mm nuts on studs.



Here's what it looks like under the valve cover. This engine hasn't been that well maintained and there is some sludge buildup.




Its also a good time to clean out or change the PCV valve.



Use some engine degreaser to clean up the valve covers.



Take a break! Your half way there now that everything is opened. Time to put things back together.


A Fel-Pro gasket kit was used to replace the valve cover gaskets.


Use some Permatex RTV on the corners of the half-moon shaped parts of the valve cover where it goes over the cam to help it seal better.



Torque down the valve cover gasket bolts to 75 in-lb.

speedkar9

Using a spark plug socket, unscrew the old spark plug and replace them with new ones!


Denso dual electrode spark plugs were used for this engine, since it has waste spark ignition.



Remember those brittle coil pack connectors? Now's a good time to change them.

Here's a DIY on that:
https://www.clublexus.com/forums/gs-...onnectors.html





They can be found on eBay. You should buy 3 in case all three of them break. In this case only the front one disintegrated.
A pin was used to de-pin them from their contacts and the new one slides right in.



An NGK spark plug wire set (blue) was used to replace the original wire set, which was getting hard and brittle.



The brackets were transferred over, and they were plugged into the new coils.





The coils and wires were then installed back into the car, and tidied up - getting ready for the intake to go back on.



Before replacing the intake, its a good idea to run some carb cleaner down the plenum and the back of the throttle body and clean it up with an old tooth brush.
The PCV system in the car always makes the throttle body and intake gummed up with oily deposits that need to be cleared our periodically.







The throttle body to plenum gasket was then replaced.


And the throttle body assembly reinstalled into the car.



The 12 mm nuts on the passenger side were secured to the throttle body bracket.

Replace the throttle cable and electrical connectors.



Replace the coolant lines:


This is where labeling the connectors and hoses come in handy when you were taking things apart.
Double and triple check that everything is connected before starting the car.


Finally once everything is secured, start the vehicle and let it warm up. Check for leaks.



If its hard to start, its probably the throttle body cleaner offsetting the fuel mixture and it will burn off.

The car should run smoother now, with new spark plug and wires, you might even notice the throttle more responsive.
Furthermore there should be no more leaks, which means no more mess on the driveway or burning oil smell as it drips on the exhaust.
Its a good idea to degrease the engine to make it easier to look for leaks and cleanup the mess from the leaky valve covers.

timherb20

Nice write up, with good pics! This should def become a STICKY!!

tiger4life

iTrader: (16)

Great write up. Much appreciated info. Good to see members still contributing given how long the car has been around. How did you find those connectors on Ebay? Got a part number for them?

lexo98

iTrader: (2)

👍👍👍👍......

speedkar9

Thanks all.
Yes the part number is in the DIY below the connector picture:
https://www.clublexus.com/forums/gs-...onnectors.html

Currently dealing with a P0446 code 4 days later. My assumption is a vacuum hose that was disturbed. Gotta do some research.

MattGS300

Thanks, doing this job now and your write up and your video to help and it has been a godsend.

Right now I am stuck with trying to get the old hard gasket out of the cover, but I'll get there.

bruceb58

I suggest doing this when you do the timing belt. Change the plugs, timing belt, cam seals and valve cover gasket all at the same time.