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You may want to use that opportunity to clean your throttle body - there's bound to be tons of sooth in there. Also, a pro tip on replacing the gaskets: buy a spray of 3m door trim glue at local parts store and spray the gaskets before inserting them there. That way they won't fall out (impossible to keep in place otherwise, except by pure luck).
That's all that comes to mind. Oh, obviously, air filter, if you want to change it. Shouldn't be more than around $20.- for Denso.
Pcv valve and grommet. Dont forget to replace your throttle body gasket too.👍🏽 take some pictures of the valve cover job as well.
Thanks
Agreed on the PCV valve and grommet, and above on the throttle body cleaning. I did all this on my '91 a few weeks ago.
You'll need some RTV gasket stuff to hit the sharp edges that the VCG's seal against. Half-moon corners, for example.
Depending on how recently things have been apart, there is a good chance you will come across tons of old brittle vacuum hoses and other plastic pieces that will break and need replacement. So having some by-the-foot vacuum hose on hand may be useful.
You'll need some RTV gasket stuff to hit the sharp edges that the VCG's seal against. Half-moon corners, for example.
Hey oldskewel,
Can you give more details on this step you took? Maybe provide a pic of the areas you applied the rtv gasket. Do you think FIPG can be used instead of rtv?
As peterls just suggested. Clean out the throttle body wile you are in there.
This is what mine looked like efter 125000 miles:
Judging from the deposits on your throttle body's wall & butterfly w/ only 125K miles, you're having a serious "coking" problem w/ your engine. You must have a lot of combustion gases slip past or "blow by" the piston rings into the crankcase. Most of these gases are un-burned fuel. They also contain oil droplets & the extreme heat from the engine will bake the gases. Initially, it'll turn the gases into a gummy residue but eventually, the gummy residue will turn into carbon & that's the black, ugly stuffs you see in the photo. This type of harmful carbon deposits will also hurt your vacuum-operated components i.e. power booster, transmission vacuum modulator, distributor vacuum advance diaphragm, etc... due to clogged vacuum ports near the throttle body or inside the intake plenum. It also restricted the incoming air into the combustion chamber & reduce the effectiveness of the TPS & AIT/ACT sensors by sending the wrong electrical signals to the ECU. If you haven't owned the car that long, the previous owner must have neglected the periodic maintenance on the car & that's very unfortunate as the damages may not be reversible. If your car is burning/consuming oil & running poorly, your piston rings & valves maybe shot & eventually the engine may need to be rebuilt. I hope it's not as severe as the photo has indicated. Good luck.
Can you give more details on this step you took? Maybe provide a pic of the areas you applied the rtv gasket. Do you think FIPG can be used instead of rtv?
Thanks
No pics since it's all covered up now. And this is generally true for all cars I know of ...
There will typically be half-moon (semi-circular) cutouts at the ends, aligned with the camshafts. For machining, assembly, etc. Those will have sharp edges at the corners. Also, you may have sharp edges where two separate pieces interface, such as the cylinder head and a timing chain cover (not that on these cars of course). The VCGs can do OK sealing with clean dry smooth surfaces, but have trouble at the sharp half-moon corners and any sharp metal-metal interfaces. These are things that are tiny - like a knife blade small and sharp. Those are where the VCG needs a little help from a gasket-maker type of thing.
Different manufacturers will have their own favorite thing to recommend. E.g., Drei bond 1209 anaerobic sealant, clear RTV, Permatex super black gasket maker, Toyota FIPG part # 08826-00080. Anything you get should be oil resistant and able to withstand temps of ~300*F or so. Many things can do that pretty easily.
On my '91, the half moons were filled in semi-permanently with aluminum plugs, which were semi-permanently sealed to the cylinder heads with the above mentioned FIPG. When I did mine, I left them alone, but it may have been better to remove and reseal with new FIPG. Either way, there is a little seam where the sharp edge of the plug lines up with the rest of the sealing surface, and that needs some help with a FIPG / RTV / etc.
Judging from the deposits on your throttle body's wall & butterfly w/ only 125K miles, you're having a serious "coking" problem w/ your engine. You must have a lot of combustion gases slip past or "blow by" the piston rings into the crankcase. Most of these gases are un-burned fuel. They also contain oil droplets & the extreme heat from the engine will bake the gases. Initially, it'll turn the gases into a gummy residue but eventually, the gummy residue will turn into carbon & that's the black, ugly stuffs you see in the photo. This type of harmful carbon deposits will also hurt your vacuum-operated components i.e. power booster, transmission vacuum modulator, distributor vacuum advance diaphragm, etc... due to clogged vacuum ports near the throttle body or inside the intake plenum. It also restricted the incoming air into the combustion chamber & reduce the effectiveness of the TPS & AIT/ACT sensors by sending the wrong electrical signals to the ECU. If you haven't owned the car that long, the previous owner must have neglected the periodic maintenance on the car & that's very unfortunate as the damages may not be reversible. If your car is burning/consuming oil & running poorly, your piston rings & valves maybe shot & eventually the engine may need to be rebuilt. I hope it's not as severe as the photo has indicated. Good luck.
Yes, you are right and this is good information for a lot of people. The throttle body cooking seams to be a common problem of these engines and as you say, it doesnt mean that the engine is in bad condition. But it could be.
More pics: @lexus.ls400.project on instagram.
My car has pretty good service history where engine oil has been changed ~11 times in 125k miles. (210000km)
Removed the intake with plenum and all from the engine to be able to have a look inside the intake channels in the heads and at the same time clean everything.
The heads looked very good with not much carbon/oil residue, the intake plenum and runners looked a lot better then the throttle body.
After cleaning everything, including egr and pcv valve sytem they look brand new again, inside and out.
Afterwards, the yearly smog test/MOT here in Sweden showed extremely good results. And the engine runs like a dream.
So I'm not worried of having a bad engine in my car.
Toyota has put a lot of emphasis in the design & quality into their luxury brand back in the late 80's. In facts, they've sent their engineers all over the world to study & benchmark other world class automobiles at the time & it took them 6 years in the making before they rolled out the very 1st Lexus LS400 in 1990 so our LS400's engines are built to last. I currently own 2 LS400's, w/ 1 of them being a 97 which I've owned for 21 years. Last year, the starter went out at ~ 240K miles so I pretty much gutted the top half of the engine out in order to get to the starter. The throttle body, the plenum & upper intake manifold were very clean so I was very impressed & please w/ it. Later, I've also replaced the starter on my 2000 LS400 & those parts were also very clean as well. Anyway, continue to take good care of your car by keeping the periodic maintenance up-to-date then it'll serve you well.
05-11-19, 10:27 PM
Changing Valve Cover Gaskets-what else to replace?
