When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
When this plastic hose bib broke off, some fluid ran out onto the asphalt until I plugged it. My initial assumption was that this fluid coming out of the plastic ATC thermostat housing would the regular radiator cooling fluid, and it should have dried up on the asphalt. But it didn't dry up, looks like an oil stain on the ground.
So, is this transmission fluid/oil?
How to tell?
Transmission fluid runs trough the cooler so it would be ATF
Currently I envision the flow through the plastic housing of the transmission cooler thermostat and its function as I have drafted it below (but this might be completely wrong, please correct where wrong).
Actually: Please confirm or correct my understanding of the coolant flow versus the transmission oil flow, because I would like to understand for sure, if oil should or should not have come out of the broken-off plastic-bib.
The way I drafted it up, where the hose bibb broke off, only radiator coolant fluid should have run out, but I'm pretty sure it was oil, since it didn't dry up and left a "wet-looking" stain on the asphalt.
If any of the gaskets inside the plastic housings would fail, then only radiator coolant would leak out.
The only way transmission oil could potentially mix with radiator coolant, is, if a separation-wall inside the metal cooler channels would develop a hole, and let the 2 different circuits intermix.
To test that, one would completely take off the transmission oil cooler, clean it out, pressurize one side, and see if it bubbles out on the other side (saw some utube's on that)
Because: If the trani-oil-cooler does Not show any internal cross-leaks, AND oil still came out of the broken-off bibb, then there would be a different fluid-cross-over leak somewhere else in the engine.
On the other hand: I could be completely wrong, it could be completely normal to have transmission oil flowing out of that broken-off bibb, then I would have to understand the flow-diagram correctly.
So basically: I don't know where the oil came from, and would want to find out if there is a potential other problem.
Few Add-on Questions:
It looks to me, when removing the 6 torx screws with the plastic housing of the transmission cooler thermostat, then more of the same fluid (= ATF according to seanjordan20) would run out, correct?
Since this is transmission fluid, then I assume the transmission fluid needs to be topped after reassembly, correct?
And also the radiator fluid? Of flush it?
I would be very grateful if some of you experts out there could correct or confirm my flow-circuit assumptions, any of my other assumptions, correct me where incorrect, and hit us with some insights on my questions.
Last edited by Quetara; Dec 19, 2022 at 09:11 PM.
Reason: (updated, because initial post contained some errors)
So I was pulling the fan out to replace the thermostat (the normal one) and the exact same thing happened when I removed the clip, it sheared the port right off the ATF cooler thermostat. Could someone give me a walk through on replacing it? I ordered the parts already and they should be in shortly.
Same thing happened to me. I have the new part and gasket but I cant find torque specs for the 6 bolts or if I need to use silicone on the gasket or not. Anyone know?
2006 E61 N52 530xi.
Uh just put it on and reasonably tighten it. I changed mine over 10 years ago. Haven't had one issue. I can get the torque specs if you really need them
Uh just put it on and reasonably tighten it. I changed mine over 10 years ago. Haven't had one issue. I can get the torque specs if you really need them.
Isn't 18 ft-lb a good go to torque for lightweight parts?
