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Toyota/Lexus first gen V6 3.5L Engine Rattle Warning
I wasn't aware of this until I had the issue in GS450H. It is a fairly big job to fix, aside from the cost of parts, the average shop will easily charge $2500-$4000 CAD for this job.
When I first got my 07 JDM GS450h, I noticed it had a bit of a rattle sound of startup. A quick search of Lexus/Toyota forums mainly shows people suggesting "it's the CAM gears and it's no big deal".
The issue seems to mainly be on the right side of the engine with the large intake CAM sprocket having a defect (looking from the interior of the vehicle). The short story is that on startup it creates a lack of lubrication since the actuator doesn't work properly. I have heard of these seizing or spinning freely and then destroying engines. I was surprised to see that it was mainly the small timing chain between the two sprockets that had huge slack, other GS450h owners have reported the main chain being bad.
I solved it by replacing most timing components which included all 3 tensioners, timing chain guides, all 3 timing chains and the intake CAMs on both sides just to be sure. While in there you might as well get the water pump done too.
I would disagree with this as my engine was coming close to being grenaded by the time I did this huge job (much more difficult on a Lexus than say an equivalent 3.5L Toyota as in the GS450h and similar Lexus the timing cover does not come off unless you remove both oil pans which is a real pain!).
In GS450h by the time I noticed it and ordered parts 2 of 3 tensioners were totally seized, the car had a CEL which said something about the cam position being off from the sensor. It progressed from an occasional CEL in the morning that would come and go, to being on full time. If you get the full time CEL you are living on borrowed time. The next stage is that the engine starts up very rough, fuel economy drops significantly, timing is pulled hard and you can hardly accelerate when cold and the engine gets raspy/loud.
How can you avoid this? If you get a car like GS450h and have any startup rattle don't ignore it, if you have lower mileage or not CEL you may be able to get away with what I wanted to do. If this is your case, open up the right cam cover and have a good/skilled mechanic replace the CAM gear and small chain without opening the timing cover and also the relevant tensioner. I believe if I had known what I know now that I wouldn't have had to do such a huge job and order so many parts. If the big/main chain is loose and the timing guides are messed up, you would have to do the full job that I did still, since the timing cover must come off and to do that the engine either has to be removed/jacked and both bottom oil pans must be removed in order to remove the timing cover (this is unfortunately different than the similar Toyota 3.5L engines which don't require this extra huge/annoying step).
I also saved some money on parts which I normally wouldn't do but for example I bought AISIN timing chains, water pump etc...since AISIN IMHO is considered about as good as OEM. But the rest of the parts were all 100% OEM Toyota/Lexus (eg. CAM gears, timing guides, tensioners). For timing components you really don't want to mess around IMHO as there are reports that some of the other aftermarket problems have issues, so it's not worth the risk with the job being so tedious and expensive.
Last edited by jdmvip; 11-26-2024 at 01:29 AM.
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