Timing chain rattling at cold start?

2010 KIA BORREGO

162,000 MILES • 3.8L • V6 • 4WD • AUTOMATIC

CPINZARU

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Last year I noticed the rattling noise when I started the car with the cold engine. I took the vehicle to a repair shop, and they replaced the timing parts with a kit from Cloyes. No sprockets in the kit. Also, the water pump was replaced as well. After the repair, it still makes the same noise when the car starts at cold. From 5 starts it does it 3,4 times, as it did before the repair.
I took the car to Kia for a diagnostic and I was told that the cause was the hydraulic tensioner.
I took the car to another shop and the mechanic told me that I need to change the VVT intake / exhaust sprockets and all 4 VVT solenoids. He said that one of the VVT sprockets was almost failing and one of the VVT solenoids was leaking oil. The problem now is that the intake VVT sprockets can't be found nowhere for the car model I have, being discontinued.
I would like to mention that the car did not have the engine light coming on, and didn't have oil/ fuel consumption, the running was normal at low and high RPMs.

Jul 30, 2023 at 9:55 AM

BORIS K

CERTIFIED EXPERT
836 POSTS

Hello,

The 3.8 V6 engine is a common engine fitted to various KIA and Hyundai models of that era.
Your vehicle is equipped with the G6DA engine.
While individual timing gears might not be available timing gear sets can be purchased.
The timing chain rattle is caused by slack in the timing chains on startup when the engine oil pressure still has to build up. The timing chain tensioners, there are 2, are then gradually extended to take up the slack in either chain.

A worn timing gear certainly can add to excessive timing chain slack and should be replaced if found to be worn.

A good video of a failed timing chain tensioner is below.
https://youtu.be/kTCBIvTBjOM

The tensioners have a ratchet type adjuster to take up the initial slack and are then fully extended once oil pressure has build up. If this ratchet mechanism fails to engage the tensioner piston, as shown in the video, then you will have a timing chain rattle as the chain remains slack until there is sufficient oil pressure. See image 1.

Has the mechanic checked that the engine oil is clean and of correct viscosity/grade? Also check that the engine has no excessive sludge build up. See image 2.

Sludge can cause a delay in oil pressure build.

Cheers, Boris

Images (Click to enlarge)

Jul 31, 2023 at 3:26 AM