# Oil in my overflow tank **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [April 1, 2013, 7:23pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393 "2013-04-01T19:23:24Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![thumper2000](https://avatars.discourse-cdn.com/v4/letter/t/97f17d/32.png) [@thumper2000](https://community.cartalk.com/u/thumper2000)\ **Post date:** [April 1, 2013, 7:23pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393/1 "2013-04-01T19:23:24Z")
I would like to find out why I have oil in my puke tank ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [April 1, 2013, 7:30pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393/2 "2013-04-01T19:30:05Z")
I would like to find out what the year, make, and model of your car is, as well as how many miles it has on it and whether it has a turbo, And if you’ve been having other operating problems. The only way a typical engine would be able to get oil in the coolant is through a headgasket breech between the water jacket and an oil channel. Typicallly a breech like that would definitely also involve the combustion chamber. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [April 1, 2013, 7:52pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393/3 "2013-04-01T19:52:31Z")
If it has an automatic transmission what you might be seeing is transmission fluid. The transmission fluid cooler is in the radiator. Tester ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [April 1, 2013, 7:59pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393/4 "2013-04-01T19:59:06Z")
Good point, Tester. ---
**Author:** ![Docnick](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Docnick](https://community.cartalk.com/u/Docnick)\ **Post date:** [April 1, 2013, 8:37pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393/5 "2013-04-01T20:37:00Z")
@mountainbike Agree, it’s likely to be transmission fluid. It is hard for oil to get into a prrssurized cooling system from an unpressurised crankcase. ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [April 1, 2013, 8:40pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393/6 "2013-04-01T20:40:43Z")
Docnick. oil is pumped from the block to the head at 40+ psi. It goes through a hole in the head gasket. If the head gasket were to breach around this hole, 40 psi from the oil pump would trump the 15 psi of the cooling system. But I would surely want to check that transmission too. ---
**Author:** ![Docnick](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Docnick](https://community.cartalk.com/u/Docnick)\ **Post date:** [April 1, 2013, 8:50pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393/7 "2013-04-01T20:50:04Z")
@keith Thanks, but I discounted the low probability. However, a good mechanic would look at all possibilities. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [April 1, 2013, 9:09pm UTC](https://community.cartalk.com/t/oil-in-my-overflow-tank/78393/8 "2013-04-01T21:09:11Z")
If it were a headgasket, the vacuum from the intake stroke and the blast from the combustion would cause things to mix anyway…and oil return lines come through the headgasket too…unpressurized oil. But anyway, I think Tester is probbaly right. It’s more likely tranny fluid. For the OP’s reference, I’lll point out that it’s common for cars to use a two-part radiator, the top part dissipating heat from the coolant and the bottom part dissipating heat from the tranny fluid. In these cases, it isn’t unheard of for the radiator to leak between the two and mix the coolant and the tranny fluid.