AdamSC430

I'm hoping some can help me.
I have a sc430 with 110 miles on it.
Got a timing belt done 1.5 years ago.
No engine noise in the cold or when I drive under 80.
After I take the car over 85 for more than 20 minutes I sometimes hear a knocking - knocking goes away after the car has cooled down.

I brought it in to a service center not lexus and they thought they found the issues. After 600 dollars changing belts etc... the noise is still there.

I also switched to synthetic oil not sure if that was the cause or the timing belt - it's been happening now on and off for over a year.

Not sure what to do. Lexus doesn't want to look at it since i haven't been there in two years and they need to hear the noise.

Should I go back to non synthetic oil, high mileage?

Any ideas would be helpful.

mandyfig

What year is your SC?

The knocking, does it increase in pitch or sound level relative to rpm?

Why don't you bring it back to shop that serviced the car for this "noise?" Is the warranty up on this service you did?

mandyfig

Is the noise coming from the engine bay? Sure it is not tire noise? Or something loose underneath?

Have you tried putting your car in Neutral (try this at your own risk, be very careful) while 80 MPH and see if you can hear the noise still?

AdamSC430

Thank you for your response. It's a 2002, I don't really hear it until I stop the car or slow down after being on the hwy. It sounds like an engine knock low thumping. - I wouldn't be able to hear it while driving at 80. it's not the tires, since the guys at the shop... listen to the engine - it's coming from the engine

mandyfig

If it is cold, you do not hear it. Stopping from a hot engine, running idle you hear it?

And BTW welcome to CL.

AdamSC430

Right, when it's cold I hear nothing... but If I run the car a bit take it on the highway over 80 for around 20 minutes or gun it , put the car in idel and I hear it. It's not a low sound... you get out of the car and know there is a problem. So I let it cool down and then it works fine again. I can make it happen on short drives too lets say i'm driving 80 and need to pass someone.. get it to 100 and then stop the car and the noise is back.

AdamSC430

also to answer the other question:
sound level relative to rpm?
Yes, if i have it in park and give it gas the sound increases relative to the rpm.

robsvdp

Sounds to me like maybe the heat shield making noise? Does the noise go away when you turn the hot car off, or does it continue until it cools down? Revving in neutral could be adding heat hence more ticking.

AdamSC430

It make the noise even if I shut off the car then restart. The car has to cool down then the noise goes away. It's not a high pitch tap, it's a much lower knocking.

mandyfig

What kind of gas do you use? Premium 93 Tier 1?

mandyfig

We have knock sensors so if it were engine knock, you will get a CEL. Did you pass the emission test?

AdamSC430

I use premium 93 , not sure about Tier 1
Yes I passed the emissions test

AdamSC430

Could it be the timing belt? Or the type of Oil? I use synthetic now. You know maybe i'm describing it wrong, the car doesn't make the noise if I drive for an hour on the highway if I baby it and don't go over 3,000 rpms, if I push the car even for short periods it will make the noise and not go away until it cools

mandyfig

The synthetic oil is not the culprit. You checked the oil level right? And it is full?

AdamSC430

yes the oil is full