How to repair a leaking oil cooler So, I’m changing my oil the other day and I see coolant dripping from the oil cooler. After I freak out for a while I dig in and here’s what I find out: First the good news – there are 2 gaskets separating coolant from oil, with a weep hole in the no man’s land between them, so chances of getting oil in your water or vice versa are almost zero. The bad news I found out is a new oil cooler costs $309 online at Silver State Ford. The other good news is it’s actually pretty easy to repair if necessary. There are several places you can have a leak, so you should confirm exactly where before you pull this stuff apart. Starting at the block, there’s a gasket between the block and the cooler adapter. Both oil and water go through this. AutoZone carries a $5 Fel-Pro gasket for this, but mine wasn’t leaking there, so movin on. Next there are 2 o-rings between the adapter and the cooler as shown in the FordParts.com exploded view. My local dealer sold me these o-rings for $17 and $11 (I was robbed btw). If the big o-ring is bad you’ll leak oil from between the adapter and cooler, if the little one is bad you’ll leak coolant. Next is the cooler itself. Ford sells this as a non-serviceable unit but you CAN take it apart and replace the o-rings. This is what I had to do after wasting time confirming it wasn’t the other 2 I just bought. The cooler is an aluminum housing with a heat exchanger inside, which can be removed. There are 3 o-rings in this unit plus one on the stud. There is a small weep hole on the bottom, so if oil or water is coming out of the weep hole then one of the rear o-rings inside the cooler is bad. If water is leaking out around the oil filter then the outer o-ring inside the cooler is bad. This is where mine leaked coolant from this groove, see finger in picture. Put car on jackstands with plenty of room underneath, and remove driver’s front wheel for better access. Drain all the coolant – I take the 2 10mm bolts out of the thermostat housing. Also drain the oil and remove the filter. Remove the coolant hose going to the cooler – I had to drop the sway bar ½ inch to reach mine but I think if you jack up the front wheel it will drop too. To take the cooler off you need a 1/2in hex head on the oil filter stud. The upper coolant passage o-ring will hold the cooler in place. The best way I found to break it free is to put the oil filter stud about halfway in and use as a handle for leverage. Pull down on stud while pushing on the bottom of the cooler with your other hand. You can then maneuver the cooler out past the steering lines and such – it will fit. Make sure your alternator has the rubber cover protecting the hot lead or disconnect your battery btw. If your leak is oil or water from between the adapter and cooler, then just get the $17 oil o-ring or $11 coolant one and reassemble, and hope you didn’t cause another leak. If you have oil or coolant coming out the weep hole or coolant from around the oil filter keep going. The cooler is only held together by o-ring friction and some RTV. You can probably insert a flat screw driver through the center hole in the rear and pry the heat exchanger from the case – I think this will work. I separated it the hard way: I stuck rubber stoppers in the big water passages, and held in place with clamps, and filled the cooler with water. One stopper had a hollow bolt which I put air into and blew the heat exch out. (I thought was pressed in but after getting apart I saw nothing holding in but o-rings). If you got this far you may as well replace all 3 o-rings. I went to a place that sells seals (Austin Seal) and bought two Viton o-rings for each of the 3 plus the stud o-ring - 8 pcs for $10. They matched size of my old silicon rings with a chart – something you cant do on the internet very well. There is one ring on the rear face of the cooler – see picture. This holds in oil. There are 2 rings, one on each end of the heat exchanger. These hold in water of course. The small o-ring on the stud just separates cool filtered oil from hot dirty oil so probably not crucial. Here are the Viton sizes I used – NOTE: these may not be exactly correct but are apparently close enough. You can just google Viton –xxx and get the details. -237 (3 5/8 in OD) - 233 (3 1/8 in OD) - 019 (15/16 in OD) - 234 (3 ¼ in OD) Before you reassemble you should scrape off all the old RTV and then sand the lands smooth. I used 1200 grit which took a while. 800 is probably plenty fine for aluminum if you have it. Note there is an axial surface AND a redial surface at the back of the cooler. Don’t forget to clean the adapter still bolted to the block. Once cooler is clean and dry you’ll want to tack the rear o-ring in place since it just sits in a shallow groove. I used black RTV since that ring holds oil. Not sure if that is best thing. You have to align the 2 pieces carefully to slide them together – definitely use some silicone grease or some kind of lube on the other o-rings, but be careful not to mess up your RTV. Now the cooler is assembled use some Silicone grease or RTV to hold the o-ring on the back side and maneuver into place. Don’t forget to replace & lube the ring on the coolant adapter. Torque spec for filter stud is 41-53 ft-lbs – I used 50 fwiw. Now you can refill the coolant while the oil ring RTV sets to insure no major leaks. Next day I filled with oil and burped the cooling system. Been several days and just checked and its completely dry. Hope this is helpful.