coolant / transmission oil mix?

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David Schmidt

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I noticed my engine coolant has gotten "oily" and turned red. Today my tranny started to slip when cold and when I checked oil level it was basically non existant but still shifted fine when warmed up. I just tranned the tranny to put a new filter in. Noticed the fluid looks like a strawberry shake - milky. My radiator is off the shelf autozone or something and probably less than 3 years old. I'm thinking the tranny oil is working its way into the cooling system? Doesn't sound good! Any advice. HELP
 
I hate to bring you any bad news but if the transmission fluid has coolent mixed in there is only one place it can come from. The trans cooler in the radiator has to be leaking into the transmission.
 
Your radiator's failed, allowing coolant and trans fluid to mix. You'll need to replace the radiator and completely flush the transmission and also the engine coolant. You're right - it ain't good.
 
I think the tranny is ok..needs fluid for sure. I think the tranny fluid leaked into the radiator and not the reverse or at least minimum. I drive short distances and has been shifting fine until a day or two ago when I noticed some slipping due to the low fluid level. I drained what I could and put a new filter in. Will fill up tomorrow. The tranny oil was sitting in the top of the radiator and in the resavoir. When I drained the tranny if was all green coolant for a while and then the pink milkshake started. I also got a new radiator - I'm pretty its the problem. Its a Spectra from AutoZone (old and new one). Not even 3 years old but lifetime warranty for $165 dollars. I can't believe it leaked tranny fluid into the coolant. I know the tranny goes into the left side of radiator but for it to connect the two fluids in a failure and do that baffles me. Totally ridiculous and can totally ruin a perfectly good truck.
 
If any leftover coolant is in the trans. The heat will make steam. Then the clutch and band material will turn loose. TQ convertor hold the most fluid.
 
Oil (trans fluid) is lighter than water so that's why you saw it at top of radiator and overflow tank. The radiator has a separate section for the trans fluid to flow through; the wall separating the two sections failed, allowing the two fluids to mix. Good luck with the repair. Let us know what you did and how it worked out.
 
what a mess. everything back together. shifts fine and runs cool. Bottom tranny line into the radiator leaking a bit - always did. Leaks worse now. I'll have to figure something out there. I flushed coolant best I could by cutting heater hose and forcing garden hose into both ends. I dropped the tranny oil cooler lines and drained that dry also. I have prestone coolant cleaner and just water running in it now. Says for deep clean 3-6 hours of driving. I'll drain / flush ( I installed PRestone "T" flush kit)/ drain and fill up with 50/50 in a few days.



Transmission - went to local shop (not Ford dealer) as I wanted to flush it out. They wanted $200 plus tax for all synthetic. I asked for std. MerconV to lower price. They said Ford would only allow full synthetic. Told them truck (2003 sport trac 2 wheel drive) has 178,000 miles on it. They said they won't flush anything over 150,000 as the power flush will cause more damage to it. Best I did for right now is warmed it up in driveway - drained it again (I have a tranny plug installed thank god) and then filled up again a few quarts. Still looks like strawberry milkshake.



I'll probably attempt a poor mans tranny fluid swap using the two lines under the radiator. Does anyone know which line under the cooler sucks and which ones pushes? Basically I'll dump quarts of good clean fluid into a milk jug and stick the sucking hose in that and then the other hose will go into a large oil dump can. Using the tranny pump while engine running to flush - I've done before - works well but you have to watch the fluids carefully and have someone else in the driver seat to cut the engine quickly but I really want to get that strawberry milkshake out of there.
 
Watch this video and you'll see the interface of the transmission cooler within the radiator. In it Brian explains that the trans cooler part is a separate loose tank inside the bottom of the radiator; the quick-connect fittings hold it in place. That tank is surrounded by the circulating engine coolant that absorbs the heat from the transmission fluid. Cleared it up for me on how the two fluids can mix.
 
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2 steps forward, 3 steps back. You'll love this..my new SPECTRA radiator from Autozone. Having issues with maintaining coolant level and reservoir not moving in level. I dug around this morning and found the FACTORY never drilled through the coolant overflow line INTO the radiator neck below the cap. So the radiator has not been breathing in/out for two days as it was SOLID plastic. I was so pissed - took a few pictures and shoved an ice pick in to find hole and took my dremel to it and opened it up - not a huge hole but I hope enough the fluid moves. I REALLY don't want to remove this thing again - especially since I got the tranny lines to stop leaking successfully. So disappointed. Can't believe it would leave the factory like this.
 

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