92 LS400 with a Tapping/Rattle

[dan_t]

I have a 1992 Lexus LS400 thats got around 160k miles on it. It was sat around for a while because the previous owner had issue with it drinking the P/S fluid through the intake. I fixed this the day I got it (Bypased) and it went and passed our emmissions program (AirCare) the day after with decent numbers.

Unfortunately there is a rather loud and annoying sound produced within the engine. It sounds VERY MUCH like a Diesel engine with a RPM specific Rat-Tat-Tat noise. Its gets consistantly faster with RPM, but when reved hard it sort of "buzzes" on the way back down. Its not present on a very COLD start (IE first of the day or several hours 6+ inbetween starts). Seems that its FULLY loud once the startup RPM's drop to there warm idle state.

It sounds as if its coming from the base of the Intake Manifold on passenger side.

I've had a glood listen around using the extention bar to the ear method and it seems impossible to pinpoint. The loudest thing found using that method is the 2 fuel rails. I'm even wondering if it could be a fuel injector itself?

Although it didn't sound as if it was coming from under the valve covers I went ahead and checked clearance anyway and all were within specs.

I'm a little bit lost as to where I can go next...

I hear the EGR cause a noise on these occasionaly but I would imagin that to be a typical exhaust blowing noise rather than a rattle or tap?

Something IN the manifold?

Fuel Injector?

I should say that it drives fine, seems to make good power and MPG is around what I would expect.

Any help greatly appreciated!

Dan

 

[4U2QUIK]

sounds like piston slap or the beginings of rod knock. I'm leaning towards rod knock even though piston slap is more common in these engines.

 

[ak47prince]

.

I guess one side of your cam sliding gears not aligned and jump a tooth difference. maybe it has been removed before by someone. piston slaps and rods are also possible. But please check your cam alignment first. Theres a screw hole that you can look through. If you can't see any screw holes on the cam gears, they're out.

keep us posting. a video will be much better.

 

[dan_t]

Any more details or pics on this gear alignment?

 

[fugly]

Your rattle sounds much like the engine i have just put in my car.
I had to make one engine out of two & didn't think about the cam gear pre load when i was putting the cams back in the swapped heads.
My motor is also rattlier on R/H side of the motor even though i didn't preload either side.
It's a job i have to do soon, L/H side is easy but i have to lift the blower to do the R/H side

 

[dan_t]

On closer inspection - this head has been off the block before as the head bolts are marked.

I don't have a Service Manual so I'm sort of lost on your suggestions right now. Can someone point me to some reference that I can find out more?

 

[dan_t]

I just found this video - http://www.youtube.com/watch?v=hqMDsnRm2aA

Sounds exactly like this...

 

[dan_t]

Spot on guys! Both sides needed doing.

 

[ak47prince]

Sorry

Sorry ,I was busy with my new job as a technician for Lamborghini so i didn't catch up with you dan_T. So .., you spoted the problem? Is it the cam gears?

 

[samsdad]

Got one coming in for that next week. But we have to fit cams with "great big hairy balls" at the same time and he aint looking forward to the bill.. Interestingly enough Mazda had a recall on the KL V6 for the same noise in '96 in NZ as did Toyota on the Camry and 'Rolla. Wasn't noticed on the LS400 due to different fuel and ignition maps in the ECU and we had one of those in today with the complaint that "This f@cking thing is gutless!"

 

[xspsi6]

Any more details or pics on this gear alignment?

I am also curious about this as well.

 

[ak47prince]

hello Sam

Got one coming in for that next week. But we have to fit cams with "great big hairy balls" at the same time and he aint looking forward to the bill.. Interestingly enough Mazda had a recall on the KL V6 for the same noise in '96 in NZ as did Toyota on the Camry and 'Rolla. Wasn't noticed on the LS400 due to different fuel and ignition maps in the ECU and we had one of those in today with the complaint that "This f@cking thing is gutless!"

You mean the engine lost it's gut? the bottom end? Something happen to the crank ? No oil in the sump?

 

[vaki2]

Also interested in this.

-n-

 

[extractors]

Dan, sounds like noisy shim's to me.

You said it was drinking power steer fluid, so have you done a good valve clean yet ? dirty valves can also result in false positives for valve train wear, by increasing clearances, due to valves not seating correctly.

Water meth is great for cleaning, also Amsoil power foam, and Subaru upper engine cleaner. Simple things first.

 

[samsdad]

You mean the engine lost it's gut? the bottom end? Something happen to the crank ? No oil in the sump?

No now that I have a scanner that talks to it there is no communication between the R/H O2 sensor and the ECU yet it doesn't fire any codes so the ECU is detecting the O2 but what we're looking at is degraded wiring in the engine loom which causes a problem once everything reaches operating temp, it has new O2s in it. The owner of the vehicle is a 4th year apprentice mechanic so I told him to go learn how to test a wiring loom and gave him a copy of the diagrams. "How do I read this?" "Find the component on the diagram and where it goes to on the ECU and take note of the wiring colours", "How did you learn how to do that?", "Same way you're going to. By having a go".

I have to agree with extractors, a build up of "crap" on the valves will cause them to "close but not quite close" so a ticking is produced and in worst case a really annoying missfire when the engine is at operating temp (big thanks to extractors for his post as I've been chasing that in mine, another pair of eyes always looks at something differently or "plants a seed")

Wear in the scissor gears can cause the same thing. In the case of the one I put cams in replacing the "Wave washers" and scissor gear springs did shut it up for a bit and all tappet clearances were within spec yet after a while as this was done without head removal the noise did come back. As extractors has said some upper cylinder cleaner will be needed and from my experience I wouldn't use anything other that "Subi spray" (the Subaru stuff). This said nothing like this was a problem back in the days of leaded petrol