Trace of oil in coolant reservoir?

Tiny
TAHA YASEEN
  • MEMBER
  • 2014 AUDI Q7
  • 3.5L
  • 6 CYL
  • TURBO
  • AUTOMATIC
  • 192,000 MILES
Hi,

My mechanic asked me to change the oil cooler because there are traces of gear oil in the coolant reservoir.

Any help is highly appreciated
Monday, February 17th, 2025 AT 6:20 AM

6 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Yep, the oil cooler will allow engine oil to enter the cooling system, here is a guide to help you see what's going on and I have included the oil cooler replacement instructions as well.

https://www.2carpros.com/articles/engine-oil-inside-the-radiator

There is also an engine cooler system thermostat which I would change if there were sludge inside the engine, please change the oil and filter once the job is completed as well. Check out the images (below). Let us know if you need anything else.
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Tuesday, February 18th, 2025 AT 10:37 AM
Tiny
TAHA YASEEN
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Thanks for your help, Ken. The mechanic is saying gear oil is mixing with coolant. The solution that you propose is also applicable for gear oil leak?

Chassis number: WA1AGDFEXED011656

Many thanks.
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Wednesday, February 19th, 2025 AT 3:17 AM
Tiny
KEN L
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I am not sure gear oil can get into the cooling system only engine oil. Can you confirm it is gear oil?
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Wednesday, February 19th, 2025 AT 10:25 AM
Tiny
TAHA YASEEN
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Please see the video I have uploaded to YouTube.

https://youtube.com/shorts/Wbz2TSxFyxE?si=lk2vz7mxBjANG46e
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Wednesday, February 26th, 2025 AT 5:12 AM
Tiny
TAHA YASEEN
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Another video sent by the workshop.

https://youtube.com/shorts/p2ubhpMN1U0?si=Xbd8dj_rIdGk6CYC
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Wednesday, February 26th, 2025 AT 5:13 AM
Tiny
KEN L
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The super charger is making noise, and it could be leaking into the cooling system which means you need a new super charger, this is a sealed unit so there is no way to check the oil level.
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Thursday, February 27th, 2025 AT 10:02 AM

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