SurryCoPat

good morning ...I'm really hoping someone recognizes the problem I'm having.

2009 GX470 with 144k miles. Very well maintained.

My wife started our GX last Sunday while I was standing close by and I immediately noticed a terrible knocking noise that seemed to be coming mostly from the top end of the motor. We shut it down and called my mechanic to come by and listen to it. He confirmed it was a "bad" noise and something he was concerned about but said he would have to do some research to give us an idea of what it could be. We called a roll back and had it delivered to his shop. He called me a couple of days later as he had a chance to pull it in to his shop and said the noise was there when he started it but by the time he moved it 20 yds into the bay the noise had almost disappeared. After a couple more minutes, he says it was "purring perfectly, just like a Lexus should". He let it idle for 30 minutes watching and listening without anything unusual at all happening.
Now, looking back I believe this is the second time this has happened. We went through a similar experience a year and 14,000 miles ago but wrote it off to carbon deposit. I don't remember the noise being as loud but it was definitely there. My mechanic listened to it and ended up driving it. He said the noise disappeared after just a minute or two and also said he got on the pedal a couple of times pretty hard and open it up. Haven't heard anything unusual at all since until this week.

He believes it is likely an oil starvation causing the noise and is suggesting changing the oil pump but is careful to say it may not be the problem. He says his Lexus parts supplier in Atlanta has sold 6 of these pumps in the past year, so its not unheard of.

I can't get past the problem being intermittent. It doesn't make sense to me. It sounds to me like something may be creating a blockage in an oil path when the GX is cold but I'm no mechanic.

Please help if you have ideas. I hate to spend the $2k he wants to replace the oil pump without knowing it will be the fix to the problem.

thanks!

SurryCoPat

speaking with another mechanic friend of mine, he is suggesting the check valve in the oil pump is sticking due to varnishing. Maybe an oil additive will help to clean that up. I'd be interested in thoughts on successful use of additives

chiph9

When I did my valve cover gaskets the other week, the driver's side had some varnish on it because that's where the EGR valve is. The passenger side was pretty clean.

Have your mechanic use a bore scope down the oil fill (or just remove the valve cover) to see the degree of varnish. So far as products to clean/remove varnish, he would be a better judge of what to use. But he may look at doing a multiple oil + filter change with Marvel Mystery Oil or Seafoam added to the oil. (use additive, drive "with vigor" for about 40-50 miles, do oil+filter change, repeat)

Chip H.

SurryCoPat

thanks for your input Chip. I will definitely suggest we do this.

FrankT

I have had 7m, 2jz and 1uz motors do this at start up only to clear up in less than 1 min maybe 30 seconds.
My 1998 GS400 beater with over 340k miles does this once or twice a year. It always clears up and runs perfect.

Nothing scientific just my personal experience with Toyota cylinder heads.
I attributed this to sticking lifter buckets at the valves; till oil and heat break them loose, then it runs perfect.
I do agree that maybe dirty oil MAY have something to do with this...




Photo taken from https://www.lextreme.com/change-1uzf...er-bucket-sub/

chiph9

SurryCoPat -
Frank's comment reminded me that sometimes the mechanic doesn't actually change the oil + filter (that you paid for).
Pull the dipstick and inspect the oil quality.

Chip H.

SurryCoPat

thanks for the feedback Frank! That seems to be the case with mine too. Very worrisome to hear that kind of racket even for a minute or so.
I am running synthetic oil, changing it more frequently than I probably need to at 5,000 miles. The oil has never looked dirty when drained out so i'm wondering why I may be having varnish issues

SurryCoPat

absolutely...you always have to check behind your mechanics.
In a totally unrelated situation, my wife recently took my son's car to a Firestone shop close to her office r for a state inspection. They suggested we change the serpentine belt and we agreed to the work. One signal light was burnt out and was required to pass the inspection. they billed us for the inspection, the new signal light and replacing the belt but did none of the work. Needless to say, when she took the car back after I found they hadn't done the work they charged for, they refunded all our money and then did the work. I was ready to call the cops...probably should have

SurryCoPat

yes we change the oil every 5k miles with synthetic oil. The oil at 5,000 miles still looks very clean too