2006 hyundai sonata cold start up noise

when i let my hyundai sonata sit for a few hours, on start up there is
a fairly loud rattling/grinding noise coming from the left side of the
engine. It stops after about 3-4 seconds but i was just wondering if
you know what this is or have seen it before.

I am guessing it is a pump of some sort but.....

 

Chances are good that the locking mechanism on one of your timing chain
tensioners has failed. This is a well-known but not all that common
failure. The tensioners are operated by oil pressure, and the lock keeps
the chain tensioned while the car is off. If the lock fails, you hear the
timing chain slapping around until you build up oil pressure.

Take your car to the dealer to be checked.

 

What HT said.

If it's any consolation, I had the same problem and got it fixed. I
was concerned with "collateral damage" on such a major repair job. My
dealer made a clean job of it. There were no dents, paint scratches,
oil or coolant leaks, rattles, or upholstery smudges. What a relief!
-

Bob

 

They'll pull the engine and transmission to do the job. But the good news
is that it comes out fairly easily. Undo the fluid lines, some wire
connectors, and the steering column, you lower the front of the car onto a
table, unbolt the subframe, and simply raise the car up off the
engine/trans assembly.

 

My SM told me it would take all day, and I told him that wasn't too
bad considering he had to pull the engine. He said the engine wouldn't
have to be pulled, but it was still a time consuming job.

They started work at around 10am, gave me a loaner, and called me to
pick it up at 4pm. They fixed the timing chain tensioner, changed the
noisy rear shocks, and changed oil and filter. I was impressed!

-

Bob

 

I understand that some people have done this job without pulling the
engine, but every time I look at what's involved, I figure it can't
possibly be quicker that way. Not nearly enough room for air tools with
the engine still in the car. With the engine on the ground and the car in
the air, there's plenty of room to work. A tech experienced with this
repair will be able to do it in a day, even if the engine is removed.

 

If you own the V6 -- it’s probably something to do with the Timing
Chain tensioner. There is an issue with it, I read it in other places.
You need to get in touch with your dealer

 

Mamamia! Small world!
-

Bob

 

I have mine in for this very thing. Just got a call from the service
center. It is indeed the locking mechanism, it will be a 13 hour job.
Thankfully covered by the warranty (yaay!)