2006 Sonata Rear Suspension Noise--SOLVED.

Below is a quote from a Web forum member. It sounds plausible, and I
take it as very good news to K-Thunk sufferers!

"My K-thunk is gone...... Today was probably my 6th trip to the dealer
about the K-thunk. Hyundai told them to install a rubber bushing on
top of both rear strut mounts. It worked. I no longer get the sound
that reminded me of a shock that had gone bad. All it took was two
rubber bushing and 1/2 hour labor to make me a happy man. Other than
the K-thunk my LX had been a very satisfactory auto. Those of you who
still have this problem, keep going back, it can be corrected."

Take it with a grain of salt, as this is the only clear-cut case I
have seen where the dealer implemented a fix that was successful.

This is the only real complaint I have with my 06 Sonata. It was very
timely for me, because I have an appointment tomorrow morning (Fri) to
solve the K-Thunk. I will report back tomorrow afternoon. Fingers
crossed!
-

Bob

 

If your receipt has a part number, please let me know what it is.

 

Happy to HT.

Looks like you may get the part no. before me.

They sent me home without a fix, but said the parts were being shipped
from Korea. The part numbers haven't even been assigned yet. My
Service Manager was puzzled that the fellow I mentioned had a fix
already. He said it must have been an experimental fix, because no
official parts exist yet according to Hyundai.

Highest praise go to my SM and Tech. They were very patient and nice,
and very sincere in wanting to resolve the problem. As soon as the
parts come in, they will set me up with a loaner and apply the fix.
Why a loaner for a 30-45 minute fix? My guess is that he wants to have
a show and tell on the procedure with the Techs, and drive the car a
good bit before and after the fix.

Incidentally, the Hyundai Rep. said the problem is specific to the V6.
The I4 has different shocks, as you are aware.

Maybe Hyundai buys the I4 shocks from a different supplier, and that's
why the bushing material (or size) is defective only in the V6 shocks.
All speculation on my part!
-

Bob

 

Right now you're on pretty much the ground floor of an engineering
solution. Someone figures out (or thinks the've figured out) the cause of
a problem and they create a potential repair. Technical assistance usually
gets a small supply of parts for these repairs and sends them out to a few
cases and monitors the results. If it works well, a TSB is typically
issued (after a significant period of time) with repair and part
information. If this solution is still in the experimental stage, it's
somewhat likely that there is not yet a part number, and Hyundai will just
send the parts free of charge to the dealer.

I'd wager that the cause of the issue being present on the V6 and not the
four cylinder is one of the following:
1. The difference in the stiffness of the suspensions makes a difference
in resonance, and/or
2. The four cylinder engine is just loud enough to make the noise less
noticeable.

I think "defective" is probably a strong word. More likely, there's
nothing wrong with the bushing that prevents it from operating properly,
but it's constructed in such a way that it transmits the thumping noise a
little too well for the driver's aural comfort.

 

Funny, nobody told my I4 as it makes a noise in the rear suspension from
time to time. Or is your noise in the front? I'm wondering why the
rear shocks would differ from the I4 to the V6? That doesn't make much
sense as the weight difference at the rear from the 200 lbs or so of
weight different up front would be negligible.

Matt

 

That's exactly what I've been doing for the last 40 years. Requesting
engineering changes, testing the changes, final approval, the whole
process is very familiar to me.

You're right. It could be something as simple as the Durometer in the
rubber or urethane compound. Too soft and it allows too much movement,
too hard and it could transmit noise to the body. It may not even be
the bushing for all I know. It could be a slight mismatch in the shock
profile and the spring rate... which is about what you said.

It could be noise transmission through the shock mount due to lack of
rigidity, aggravated by sudden fast movement of the shock. Don't know
if the shock mounting pads are welded on or bolted on. If bolted on, a
rubber pad under it could help isolate the drumming noise.

Regardless, I'm impressed with my SM and the Hyundai Rep. for coming
up front.
-

Bob

 

I spoke to a Hyundai field engineer today and asked him about this. He
indicated that there were new struts with a different damping coefficient
and new, softer bushings. I got the impression this was phased in for
the '07 model year.

It's possible the retrofit may be for the bushings only to avoid
introducing ride quality complications from changing the damping
coefficient.

 

Is this the specification for the production build now (Korean build for the
UK)?
Any way of finding out when this was introduced?
cheers
nn

 

Thanks for the info HT!

I just got a P/N from the original person (mat22trees) that got the
first fix:

P/N: 3536966
Description: Seal, 1.456"

That doesn't sound like a bushing or pad as Matt first reported. I'll
chalk that up to normal miscommunication.

Bad Matt reports that while the fix improved the K-thunk noise,
it didn't eliminate it.

Good He reported that the noise was reduced enough to satisfy
him.

If it improves around 50%, I'll be satisfied too. I will report back
as soon as I hear something from my dealer.
-

Bob

 

Unfortunately, 3536966 isn't a Hyundai part number. I suspect that the
dealer, like I alluded above, received the parts for free and this was
simply their way of recording them on the repair order with a number
assigned by them.

Hyundai part numbers will have five digits, a dash, and five more digits,
typically. The first five indicate the type of part and the second five
indicate model (loosely) and revisions.