oofer

Wondering what your LS sounds like when you start it up.Mine makes a thump or knock just after I turn the key. It happens when the engine is engaged just after the initial turn.Otherwise, she' s whisper quiet. I recently checked both engine and trans mounts and both were ok. Any ideas or is this normal?

LiCelsior

iTrader: (32)

all the time or randomly?? i get some thump when i turn the car over but its random.

oofer

Pretty much all the time.

cjmeyer

My 95 makes no noise when I start it.

Bradster

Just an observation...Although the mounts maybe functioning properly you'd be surprised how much less rubber is left on them when compared to a brand new mount especially after 10 years and all the miles accumulated in that time...Mine were "fine" but what a difference when i replaced all 3!

jtmosca

Hi, I have a 93 LS400 that I just bought and it appears to be doing the exact same thing. The knock/thump is random on mine. I've previously owned a 90 LS400 and it did not do it all. My immediate thoughts were motor mounts, however the randomness of this confused me. Does anyone know how this played out? (I realize that this thread is 2+ yrs old) Oofer, did you ever get this fixed?

PureDrifter

iTrader: (10)

no idea but thank you for SEARCHING

Marklouis

mine also does this random thump at startup, but after reading threads from both CL and LOC on this issue it is definately a result of weakend engine mounts - when I get the budget up will be replacing mine for sure. Amazing difference after just replacing the one Tranny mount.

Good luck!

JimsGX

Check your exhaust system bolts. Especially where the Y pipe connects to each of the catalytic converters up front. I think the torque on those bolts is 43 ft. lbs

jtmosca

Thanks for the reply. I will definitely keep checking my mounts. However, one of the tests for a bad motor mount is to put the car in gear, press firmly down on the brake and then give the engine some gas. This typically "torques" the engine and if a bad mount is present, it should create a similar knock under that scenario...right? When I tried this today, I got nothing. ??? This is not to say that it is not the mounts, but I seem to be having trouble getting confirmation. Anyhow, thanks again for the reply.

jtmosca

Thanks JimsGX! In addition to investigating the mounts, I will also check out the Y pipe as you suggested.

jtmosca

So I ran the vin# for the car at the dealership to pull the service history. (I live in NC and the car spent most of it's life in Ohio. Most of you probably already know that the Lexus dealer's computers are all tied in together). Turns out that sometime last year, the previous owner brought in for this noise, and the dealer also diagnosed it as a motor mount issue. ...so I think I tackle them soon. It looks like the trans mount is pretty easy to change. And suggestions on the others? (I will of course check the forums to see what else I can find) Thanks again for everyone's input!

RAINBOW

My 93 does the same thing. It's not a good sound.What I do now before I start, is turn the key on, buckle my seatbelt, then turn the key to crank. That 10 sec. pause with the igni. on before cranking seems to stop the clunk, bang, booom, which blows the motor mount theory. I replaced the trans mount (very easy) did it in front of the house without jacking the car up. Made zero difference. I would check the engine mounts first, they're probably the cause of most harshness/vibration.

sdls

How about the oil filter? It might be plugged up and starving the engine of oil when cold.