kgis1

Anyone have any information on the below problem or an idea on how to contact Lexus engineering support?
We have a problem with a 98 GS300. The auto was purchased new and at 3000 miles we noticed what sounded to be a cold start rod knock. At first the noise would only occur after the car set for a few days, now at 30,000 miles it occurs on every cold start. Yes I'm familiar with the sound after racing sport cars in my youth and having owned many direct overhead cam engines, Jaguar's, Mercedes, Maserati, Lotus, etch.
My question being after all this and considering the mileage on the car what could the noise be? The noise has become more consistent, loader sounds somewhat like the old Jaguar timing chain slap, but remember this car has a belt and our noise stops as soon as oil pressure comes up. If it is cold start rod knock Lexus must have the worlds best rod bearings. Yes the car has been returned to the dealers many times for the problem but that is another story in it's self. Any ideas?

DoubleWhoosh

Sounds more like piston slap...not sure if those bastards would do anything for you though! I'm sure it would fall under "normal" whateverwhateverwhatever.

You outta drain all the oil out and run the car for a while and fill it back up for a nice fat warranty short block

kgis1

I thank you for your reply. The difference between piston slap and cold start rod knock is that piston slap noise decreases as the engine heats up, and cold start rod knock stops as soon as oil pressure comes up. the pressurized oil removes the excess clearance of the rod bearing. One good thing though is that Lexus doesn't use short blocks, they replace the entire engine. If and when the thing blows.

DoubleWhoosh

Ahh I hadn't read the post thoroughly and though you said it was knocking until it warmed up =)

Just make sure that any accidents happen before your warranty is up

Grush

I experience the same noise on my '01 GS300 with 10,000 miles. Very sporadic. Usually does it after sitting for more than an hour. Sometimes it doesn't do it 1st thing in the morning. Sounds like tappet noise with a blocked oil passage. I even changed oil at 5000 mi to Mobile 1 with no change. It only knocks 5-7 times before silencing.

My old '99 GS didn't have this problem. When and if you ever get any confirmation as to the problem, please let me know.

Steve

lexasgs400

just a thought, alot of aftermarket filters do not have an anti drainback valve in them letting the oil run out of the filter and back into the pan, this will also cause a momentary oil starvation situation.