LiQiCE

I've noticed lately that when I goto start my car, you hear the car try to turn over, and then after the engine starts up, I also hear what sounds like a "knocking" sound. The car does not do this all the time, only sometimes, it seems like it does it more often when the car is cold, but there is no set pattern to it. Is this normal? The sound is not the anti-lock brake test because it happens before I shift the car out of park and I know what the anti-lock brake noise sounds like. This is much louder than that and happens almost immediately after I let go of the key to put it from the "Start" position to the "On" position or sometimes during the time I still have it in the "Start" position. Any help is appreciated!!


I did a search on the forums and came up empty... sorry if its already been discussed though.

fla-tls

Mine does it as well. From what I understand it's the engine mounts. They are hydraulic and vacuum adjusted, so the engine may flop over once when it's started. Once the engine starts, the mounts adjust like normal. It usually happens when the car hasn't been started in a while.

LiQiCE

fla-tls,

Hmm, this has been happening to me when I start the car even after it has sat for only maybe 8 hours or so inside of a garage... Should I be concerned or do you think its still normal? Thanks for the help though, at least I know it isn't just me!

fla-tls

I wouldn't worry about it. Mine's done it since it was new. If it starts happening on warm starts... then I'd start worrying.

T Ho

We had a discussion about this before. It seems many do it. Mine does, but only after sitting for a time.
It is the engine mounts bottoming. No big deal. It's the price of hydraulic motor mounts.

Todd

Dirk Diggler

Mine does it too, however. If I turn the key to the "on" position and leave it there for a second, then start the car, the noise never happens. I assume I'm giving the motor mounts a moment to adjust or pressurize before I start the engine... See if it works on your car.

Dirk Diggler.

LiQiCE

Hmm, thanks for the suggestion, I'll definitely try leaving the car in the "on" position before starting it and see if that helps. Thanks for the advice!

stiletto

Mine does it also... so I am assuming it is normal. I'll check at Rick Case Acura next time I am around there.

LiQiCE

Just tried Dirk's suggestion, and the car didn't knock at startup. It isn't 100% conclusive since it doesn't always happen when I start the car up normally ... but I think this may just do the trick! I left the car in the "On" position until the fuel gauge came all the way up and then started her up.

hangman

hhmm.. i did not know that our TL-s has hydraulic engine mounts?? Is this true?? btw..Mine does not make the knocking noise.

FTM-1

This is a very very old topic since the days of the old TL boards.
It seems to happen more in the cooler temps like early mourning start. The temps can range in the mid or low 60s or below.
My 2000 TL has done this since day one & thats been almost 3yrs now. I am not sure what the cause is but I have found with the A/C in the on position at start up it happens. With the A/C in the off position it does not happen. If the overnight temps were say 75 & the A/C was in the on position when you turn the car off because it was a hot day you don't have the knock or thunk at start up.
But when say the A/C was in the on position & the overnight temp drops to 60. When you start up the next mourning you may get the thunk/clunk. This can happen when the system was left in the auto mode also. It only deos this in spring,fall or winter never in the summer& only with the A/C in the on positon.If the car has been driven & has not sit for along time like 6 to 8 hours there seems to be no problem at start after 1st start up. I see that some of you are from northern VA area so the temps lately have been in the range I am talking about overnight like D.C. So my question is was your A/C in the on postion when you turned off your car? But there have not been any adverse effects with my car in almost 3yrs of ownership. Try it with the A/C on & the A/C off overnight & see what happens in the cooler overnight temps. Like I say the noise does not happen in the warmer overnight summertime temps.

fla-tls

Hmmm... I live in Orlando, always turn my A/C off before I shut down the car, and just about always get the morning clunk - summer, winter, whenever...

It's no big deal.

chuchu

Just got my car back from the dealer for a 20K service and when I asked them to check that knock/thump, they explained that it is normal for the electronic engine mounts to make that sound after being off for an extended amount of time(i.e. overnight). I believe it had something to do with vacuums in the mounts.

LiQiCE

Yeah I tried the A/C off thing and it did not help. It does seem to help however if you place the car in the "On" position for a few seconds before starting her up ... That has worked consistently for me for the past 5 out of 6 starts or so (one of my last starts I did not use this method to test the A/C theory).

Southbound

I live in southern california, and only get it some mornings. I agree that it seems to only happen if I have the AC on at startup. It sounds like a thump in the compressor or something purging itself rapidly. Maybe there's a noise with both the AC system and the motor mounts. In any case I feel lucky that it only happens every now and then. So somehow weather and/or the AC must factor into the phenomenon.

Bottom line... it sounds like it's just a nusiance that's evidently normal at times.

AegeanTypeS

I was told by 2 local dealers that it was the A/C clutch engaging at startup.

I tried it with the A/C off, but it still did it. It's not exactly cold in Tampa this time of year yet.

It's more of a thud as soon as the engine turns over, rather than a knocking sound.

Is this the same noise?

LiQiCE

Yeah I guess a "thud" is more accurate than a knocking sound ... I really don't know how to describe it, I just noticed that when it got colder around this area the car started to do it ...

However, in the past week or so I've been doing what Dirk suggested and putting the car in the "ON" position, letting the fuel gauge come up and then starting the car ... Haven't had any thuds or knocks (or whatever you want to call it) since!