Help: Need a survey of LX470 owners having any engine noises upon cold starting

[Toylexmods]

Pistons rock as they cross TDC where the thrust load from the rod angularity shifts from one side to the other. This makes noise. Harmless, but it is the source of piston slap in most all situations.

To prevent this, pistons are designed with long, tapered, flexible skirts so that they can be fitted very tight in the bores when the bore and piston is cold. The taper of the skirt and flexibility of the skirt then prevents scuffing when the piston is hot. Also, the piston pin in OEM production pistons is always offset to one side....it is NOT in the middle of the piston. By offsetting the pin in the piston, artificial thrust load is created to control the piston "rocking" as it crosses over TDC.

Unfortunately, all of the above control techniques, common in past model engines to the extreme, create excess piston mass, cause friction and cost power and fuel economy. With the desire to build in as much power and free-revving capability and to improve fuel economy as much as possible thru friction reduction these design features are pushed in the other direction on modern engines.

Piston pin offset has been reduced over the years to a bare minimum today to reduce the thrust load generated and reduce friction. Pistons have been lightened up considerably by shortening the skirts. This creates less rotating/reciprocating mass which is good for power, free revving capability and fuel economy. Light weight pistons are great but the skirts, by necessity, are short making it hard to make them both strong and flexible and the shorter ckirts make them more prone to rocking.

Unfortunately, when the performance or fuel economy oriented pistons are run cold they are very prone to "slap" until they warm up to operating temperature.

The piston designers and development engineers are always treading the fine line between piston slap cold and friction and power/fuel economy loss when the engine is warm.

It is possible that you are hearing piston noise from an engine that is on the "high limit" for piston clearance so that it makes some noise cold. The good news is that the condition is harmless and that engine is probably a little more powerful (due to less friction) than a "quiet" counterpart. The bad news is that...it makes noise cold.

SW,

Yes, I have accepted this condition and Lexus says they will consider any piston failure in the future for poss warranty. We decided not to purchase a new LC/LX or GX and instead will keep this old 99LX and I put a TRD supercharger on it instead. So, if that piston is weak....I will break it or it will be fine. In the end, it saved us money....we didnt purchase a new vehicle nor will we in the future.

 

[SWUtah]

Your not alone, http://www.toyota-4runner.org/showthread.php?s=&threadid=14914&highlight=piston+slap

 

[a990dna]

I wonder if Toyota offers engine block heaters for cold climate situations ?... I personally never ordered a heater on a new vehicle, however if I recall correctly, block heaters are usually offered as an option on most Detroit iron, especially trucks/SUVs.

If Toyota doesn't have a solution, an aftermarket device may be worth looking into.

 

[skopiec]

Just curious here, but do you actually know it's a piston slap issue? Have others actually pulled their engines apart and determined that was the problem (wear signs, etc). I'm curious because if a cylinder was not firing for example, I think that could sound like a piston slap possibly, or a leaky injector (which fixes itself when it gets warm, unlikely I'll admit but never know). If wear was found then a UOA should show that, if the UOA looks good then probably nothing even to see if you pulled it apart.

Just FYI, my sister has a '99 LC, lives in Ohio, she's started it many times below zero (no garage, so vehicle outside) with no knocking of any sort, purrs like a kitten.

Good Luck, I too am surprised in the route Lexus is taking. Always remember the trouble-shooter guys, like Tom Martino and some other ones, several of the Denver news stations have guys that do only that, just find problems and make companies look bad. Certainly can't hurt to have them make some calls.

Good Luck!

I've heard engines with cracked exh manifolds make a pretty good racket - once it warms up, the crack seals up and quiets down. Not an uncommon scenario on LC's as I understand it.

Just something to consider....

 

[FirstToy]

Just curious here, but do you actually know it's a piston slap issue? Have others actually pulled their engines apart and determined that was the problem (wear signs, etc). I'm curious because if a cylinder was not firing for example, I think that could sound like a piston slap possibly, or a leaky injector (which fixes itself when it gets warm, unlikely I'll admit but never know). If wear was found then a UOA should show that, if the UOA looks good then probably nothing even to see if you pulled it apart.


Good Luck!

I agree w/ mabrodis.

I don't think it's good to take assumptions on the internet and see that as a way to diagnose your problem. Assumptions, especially w/ noise from vehicles, can be very wrong.

Your description of the sound and when it happens also sounds like exhaust bouncing off the exhaust manifold. The documented issue is exactly like what you describe (although it may/may not be it in your case). Common on the Prado 120- harmless but the 'knock' is there. I also was told the RX300 had the same issue and they replaced the manifold w/ a thicker one to insulate the noise. FWIW, I've heard it on my friend's 03 Taco too.

Again, I don't know what it is but be careful on taking a bit of assumption and running with it. It's easy to work yourself up into thinking the engine will fail and die when all it is is some air bouncing around the manifold.

 

[SWUtah]

Good point, can't diagnose sounds over the internet. My post was to illustrate that if it was piston slap like some claim, that it really isn't the end of the world and it won't mean their engine will fail. Just a good discussion. LC's rock and I'm not worried about this one in 10K chance of hearing this noise coming from my LC or 4runner, I'm not good at winning at the lottery either.

 

[Coastal]

Sounds very similar to my manifold crack issue- signifiganly worse in cold weather. If you look into it, and its not a cracked manifold..... I would tell Lexus you want their service manger and the Lexas area rep at the dealer one morning at 7:30 and leave the truck parked outside there the night before. Tell them you will come up and start it for them and then let them tell you there is nothing wrong....If they are still sticking to this story claiming it is common and there is no issue, then ask (tell) them to start another new truck or certified pre owned truck on the lot and see if it makes the same noise - when it doesnt then argue like hell with them and tell them you want a new engine.

 

[Toylexmods]

Good point, can't diagnose sounds over the internet. My post was to illustrate that if it was piston slap like some claim, that it really isn't the end of the world and it won't mean their engine will fail. Just a good discussion. LC's rock and I'm not worried about this one in 10K chance of hearing this noise coming from my LC or 4runner, I'm not good at winning at the lottery either.

SW,

Not a whole lot we can do here. Toyota knows about the "noise" and "problem" but will do nothing. Toyota has learned from GM....deny, deny, deny the piston slap issue.

People....I know the difference between an internal engine knock and a exhaust leak.

Tundras have the problem, Seq has the problem, 4runner, LX/LC. Some have it some dont. Most dont...say 95% dont slap. Lexus ran me around the bushes on this and lost any chance of me buying another new Lexus. Ever. Really, it saved me tons of money. I will stick my money into my other business and building up my fun/race cars. Heck, my wife wanted a sedan again and we purchased a mint used LS instead of buying new. I have no need to ever walk into a Lexus dealer and or service department again. Cheers

BTW, I went ahead a stuck the TRD supercharger on our 99LX470. We will see how long those pistons last. I can rebuild if needed.

 

[Aussies]

Engine Noise on my 100 Series

in late 05 we purchased our 100 series and couldnt believe how good a vehicle it was until the weather started cooling down and started to hear this notasable engine nock. The vehicle has 51000 K/M on the clock. The noise and symptoms are exactly the same as Toylexmods and are getting worse with the colder weather 5/10 degree mornings. We recently spent a weekend at Bathurst (Australia) a couple of hours up the mountains from where we live. On start up on a 0 degree morning the engine knock (Piston slap)was heard from 30 meters away by friends inside a house and lasted at least 3 minutes. We have been to our local toyota dealer about the problem and of course they told us it was normal operation. Has any one actually had an engine break a piston and fail from this problem?. In my experience of being an auto mechanic and building race and standard engines this piston noise in not a good noise to have in a standard type engine . The noise appears to only be coming from 1 piston. We are looking at fitting an LPG fuel convertion kit with whitch toyota will voide our engine warranty. Im sure toyota wont be upset if a piston fails after the kit is fitted. We are reluctant to fit the kit untill this problem is corrected but cannot see it happening in the near future. We have heard of piston failures with some incorrectly tuned LPG kits on this engine and dont know if it is related to the exsisting problem. We would like to hear of any new devolpments about this problem.

Hey everyone,

I seem to be having a problem with Lexus and the tech assist department. Can any owners post some documentation please.

99 LX470 with 75,000 miles.

Started last winter in Colorado. Engine knock when started in cold temps. Sounds like a diesel truck....ie knock, knock, knock....lasted for 30 seconds or so. We didnt leave the truck outside that often...but the noise was worse the colder the temps. I really noticed it when I had to move the truck in the driveway after a cold start....it sounded like a diesel. on accel....knock, knock, knock.

Winter 2002 there were no abnormal cold start noises heard...45k on the odometer.

Winter 2003 Our LX sounded like this with around 60k on the odometer. see below

10 degrees....it would make noise even at idle on start up.
20 degrees....less noise but could still hear it.
30 degrees....hard to tell, but if you put it in gear and loaded the engine it would knock.

Ok, fast forward to this year winter 2005 in Oregon with 75k on the odometer.

30 degrees...much, much louder knock....same knock as last year just louder at a warmer temp. Also, the knock will last for 2-3 minutes...or if you drive the truck it sounds like a constant knock, knock with engine speed. You can hear it outside, inside and all around the truck. Stand fifty feet away and listen as the truck takes off. Yes, you hear it just like a diesel truck taking off.

40 degrees....less knock noise that 30 but its very clear and lasts for the same 2-3 minutes.
50 degrees....I heard it this week on a cold start. Put the truck in gear and moved it in the driveway....there it was the diesel knock noise.

So, the trend is getting worse and I made the appt to have it looked/listened to. I had to leave the truck overnight. Got the call...and Lexus techs said could not duplicate. Ok, leave it again....same response. 3rd day I come to pick it up and take the techs out on a 49 degree morning. I start it, put it in gear and there is the knock. Two techs heard it....jumped out and listened. It lasted for about 2 minutes and the techs said they would have to call tech assistance. I told them that the noise was about a 3 on a scale of 1- 10 because it was farily warm that morning. Ok, now the round and around with Lexus customer service. Tech assist says its piston noise and normal. Lexus customer service says that the dealer is saying its normal piston noise. .....round and around general passing the buck.

So, I come to find out that the Tundra/ Sequoia group have been having this problem for a couple of years but on a much higher/ louder scale. Nothing is mentioned in the Landcruiser circles....nor here in the LX40s circles. These are different engines than the Tundra and should not have this clearance issue with the pistons.

Bottom line, noise is wear...and its getting worse. And, its not several pistons...it is just one piston. The knock is one piston, period.

There it is gang, if you can document your LX age, mileage and climate that would be great. Oh, and if your hearing any abnormal knocking when you put the truck in gear and or take off from a cold start. My argument is simple....if this is normal, then any number of similar aged/mileage LX470s will have this noise. Simple, right? Well bring me some trucks that make the noise.

So, post if your hearing the knocking and/or post if your not hearing any noises.
__________________
Cheers,

Dave Hall
99 LX470....special knocking diesel model. We were thinking about a new GX470 but forget it now.
92 SC400
00 LS400

 

[hoser]

As mentioned above, I would look into the possibility of a cracked/warped exhaust manifold. The symtoms you describe sound very much like it and unfortunately is somewhat common. Search "cracked manifold."