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Oil in Coolant Reservoir

Tiny
DEADBUG
  • MEMBER
  • 2004 CADILLAC CTS
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 90,000 MILES
Found oil in coolant reservoir when I thought I had a coolant leak. Leak looks like it came out of overflow tube. No water on dip stick or oil cap. Car did not over heat. Engine sound fine. Oil cooler? How do I replace?
Monday, May 10th, 2010 AT 6:04 PM

16 Replies

Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Sounds like the oil cooler is leaking. It is a bit of an undertaking, the cooler is located under the intake manifold, between the cylinder heads. You have to remove the intake manifold to access it.I strongly suggest getting the updated GM kit that should include all parts necessary to change it, the GM is a bit pricey, but is stronger than original.I also suggest taking care of this ASAP, the oil wiull destroy every rubber coolant hose. Have the cooling system pressure flushed to get all of the oil out
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Tuesday, May 11th, 2010 AT 11:17 AM
Tiny
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I was just told by the dealer the 3.6L does not have an oil cooler. I have found a lot of problems with the 3.2L online in the location you described. What is your next best guess? Thanks
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Tuesday, May 11th, 2010 AT 3:50 PM
Tiny
2CARPRO JACK
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If there is no cooler, it is coming from either the head gasket, intake manifold gasket or possibly a front cover.How much oil are we talking about? does the coolant bottle have actual oil in it or was it just what ran out of the overflow tube? has the cooling system ever been serviced? Usually the intake gaskets will do the opposite (Water in oil) since the oil is under higher pressure than the coolant... May need to chemical test the head gasket

Read the guide below, it will help

https://www.2carpros.com/articles/head-gasket-blown-test
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Tuesday, May 11th, 2010 AT 9:29 PM
Tiny
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It sucked up enough oil to overflow the reservoir. When I start the car the level goes up. Very muddy in color. The thing that confuses me is the oil level appears fine on the dip stick. Unless it just leaked out half a qt or less. Could it be transmission fluid? I installed a new water pump about 6mths ago. No other service has been done.
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Wednesday, May 12th, 2010 AT 5:20 AM
Tiny
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Could very well be trans fluid. Check the level of the trans. Sometimes the internal coolers leak and will do that.
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Wednesday, May 12th, 2010 AT 8:07 AM
Tiny
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It is tranny fluid. After warming the car to operating temp. It will not move in D or R. I have read that the tranny cooler lines go through the radiator on this model. My guess is to replace the radiator? Flush cooling system and tranny fluid?
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Saturday, May 15th, 2010 AT 5:15 PM
Tiny
2CARPRO JACK
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Yes, the cooler is mounted inside the radiator, You could find a radiator shop to just repalce the trans cooler if you want to go that route.A radiator shop will also have the equipment to flush the cooling system to get rid of the oil.
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Saturday, May 15th, 2010 AT 9:30 PM
Tiny
ARCHRAED
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  • 3 POSTS
  • 2004 CADILLAC CTS
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 10,000 MILES
I really scared, when I saw white muddy oil in the coolent unit, and I recieve massage ( check coolent level ) in my ctc 04
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Friday, November 30th, 2018 AT 8:25 AM (Merged)
Tiny
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Hello,

Well, Oil in the Coolant is a good sign of a Blown Head Gasket.

To repair can cost $1,500+/- depending on Labor Rate and Parts Cost.

.
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Friday, November 30th, 2018 AT 8:25 AM (Merged)
Tiny
MARK2967
  • MEMBER
  • 2 POSTS
  • 2003 CADILLAC CTS
  • 3.2L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 195,000 MILES
Just recently noticed brown sludge in my coolant reservoir. My car is heating up fast fan is coming on just very shortly after starting the vehicle you. From my research I see that it could be the oil cooler causing the problem or it could be inside the radiator where the transmission fluid lines come in. How do I tell if it is oil from the motor or transmission oil in the radiator coolant? There is a small oil leak that drips to the ground but is very little I was notified of this when I purchased the car.. Not sure if that is relevant but thought I would mention it Other than the car heating up fast it seems to run fine and very strong. Should I begin by replacing the oil cooler or replacing the radiator or the transmission fluid cooling element inside the radiator? How do I tell if it is one problem or the other or if it is both? What needs to be done in hole to fix the problems?
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Friday, November 30th, 2018 AT 8:25 AM (Merged)
Tiny
HMAC300
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Pressure check the coolant system if it's from trans the fluid there will be down but has to be checked by a pro. You would have water in oil if it's a cooler line. If it's dark brown it's either going to be engine oil getting from head gasket rarely from oil cooler.
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Friday, November 30th, 2018 AT 8:25 AM (Merged)
Tiny
MARK2967
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Supposedly the 2003 six-cylinder Audi Motor had problems with the oil cooler malfunctioning and that is what is in the 2003 Cadillac CTS 3.2. That's why I Suspected it could be be the oil cooler. So what is the fix it if its the head gasket just replace the head gasket?
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Friday, November 30th, 2018 AT 8:25 AM (Merged)
Tiny
HMAC300
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Yes replace the head gaskets and check flatness of heads. Besides your oil cooler isn't in the radiator anyhow. It's under intake manifold.
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Friday, November 30th, 2018 AT 8:25 AM (Merged)
Tiny
KENNETH NUTT
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  • 2003 CADILLAC CTS
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 164,000 MILES
I noticed that in the coolant reservoir that there was a little contamination from oil in the coolant. A day later it overheated and there was more contamination. It doesn't appear to have any water in the oil in the crankcase though. Any suggestions as to what is the cause of this.
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Friday, November 30th, 2018 AT 8:25 AM (Merged)
Tiny
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Hi Kenneth,

First - does it look like engine oil or transmission oil

If it looks kinda reddish it is most likely tranny fluid and the tranny oil cooler in the radiator has failed.

If is engine oil then most likely it is a blown head gasket.

.
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Friday, November 30th, 2018 AT 8:25 AM (Merged)
Tiny
ALEXANDERBARREIRO
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It's the oil cooler but in this year the oil cooler is located under the intake not in the radiator
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Friday, November 30th, 2018 AT 8:25 AM (Merged)

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