5.7 oil cooler changeout

Engines are 2002 5.7 Captain's Choice. I am changing out the oil coolers as preventative maintenance as they are now 15 years old. The engines use the dual (straight though) oil cooler, R147035. Access is terrible so I have been waiting until it was time to do elbows so that I could also take off the exhaust manifold on that side to get at them. Well, the time has now come and I will likely get to it in the next few weeks.

I have never done this job so if there are any shortcuts or tricks to make it easier or less messy or less likely to go wrong I would love to hear them. I would appreciate any suggestions from those that are familiar with the issues. Thanks.

CaboJohn

Well I have the same coolers on my 8.1's and there are no real short cuts. I spent a good 2 hours hanging up side down getting at the starboard side cooler. It could have been worse I suppose it was just very tedious. Make sure you have the absorbing pads to put all over the place under the cooler to catch all of the fluid that is going to leak out when you get the tranny and oil lines off. Also you may want to take a look at how the lines are run. One of mine was easier to leave attached to the cooler but disconnect from the other end.

Good luck

Like matta said, there aren't any shortcuts.....the installation i the hull drives access and I'm sure you are baselined there....

Besides the pads, a good set of flare wrenches will come in handy...

Thanks for the suggestions. I particularly like the one about looking for opportunities to disconnect the lines at the other end. Should be obvious, but likely I would have missed it until too late.

Looking at the new coolers, I see two of the connections were not plugged at painting and have the threads pretty well coated blue. Which brings up the thought; what kind of thread sealant is recommended? I thought I would see hydraulic fittings (no sealant needed) but they don't look that way. I don't see any sealing surface so I presume the thread is the seal and must be taped or gooped somehow.

CaboJohn

The fittings you will need to remove from the old cooler and put them in the new one. I just used pipe dope on the threads. One thought I did have if I had more time when I did it was to look into longer lines and relocate the cooler to a spot that is more convenient. With new raw water hoses and longer hydraulic lines you can put that cooler just about anywhere.

The fittings should be Flare (hose side) to NPT (cooler side) so , PST should be fine for the NPT side.....

I have never done this job so if there are any shortcuts or tricks to make it easier or less messy or less likely to go wrong I would love to hear them.

Click to expand...

Ayuh,..... I've found havin' a Hose Pick, makes takin' water hoses off, much, Much easier,.....

One of those tools, that once ya got one, ya can't figure out just how ya ever got by without it,....

Well, I did manage to get the cooler on the starboard engine replaced. Access is restricted because of a stringer that rises above the level of the cooler and is only an inch or so away. I had to remove the exhaust manifold, the alternator and the left forward motor mount. And even so one of the transmission hoses had to be disconnected at the transmission end because it was impossible to wench in location. The hardest part of the reinstall was to get the small screws holding the clamps that hold the cooler to the engine installed.

Since I would have to reach over the top of the port engine to reach that cooler, and then just with my fingertips, I gave up on installing a new cooler for that engine. I think that maybe I could get at it if I also removed the head on that side but that seems excessive for a preventative maintenance action. Or, of course, I could have the engine pulled.

I believe that in the early stages of oil cooler failure you see a sheen on the exhaust water but salt does not work its way into the engine/transmission and you will not be marooned anywhere. Hopefully this thing will live forever and I will not have to test that theory. For what it's worth, the cooler removed looks perfect inside. It is solid copper with no signs of corrosion, but I suppose it could have been only hours from a pinhole leak.

First time I have plain given up on trying to do something on the engines. Gotta love boating!

You can back flush that cooler to get any dirt out and you can also soak the cooler with Barnacle buster to clean it. It is an awfully stupid place to put it.

My 8.1L Crusader has a closed cooling system. The raw water side is restricted. Looks like it is restricted by zebra mussels. I was planning on removing both the engine and transmission oil coolers to clean out, but looked at the location today. Then read the posts here. Wow what a bad location.
Would barnicle buster disolve zebra mussel shells?
Reverse flushing seems easy enough if it works. The issue may be that the mussels get in when litterally microscopic size then grow to roughly 1/8 to 1/4" size. They could grow inside the coolers screens. What do these coolers look like inside?
Thanks for your help.
John Brock

I see you have opened up one of my old threads. I believe my 5.7 oil cooler has a different form factor than your 8.1 cooler. But construction should be similar which means solid copper classic heat exchanger. Water goes in one end, enters a chamber that feeds a tube bundle, then exits the tube bundle into another chamber that is connected to the outlet. Oil enters from the side, flows around the tubes and exits farther down the side of the exchanger. So if you have mussels, they logically are in one or both of those chambers. If you get an endoscope that attaches to your iPhone you should be able to remove the water hoses and look inside to assess the situation without removing the oil cooler. I used one when I had a blockage in my engine cooling, Pulled the water pump and could look in the head. Great tool!

I did finally change out my port side cooler a year or so after my last post. I had a bad exhaust valve and had to pull the head. As I surmised, once the head is off it is not too hard to get at the oil cooler. But I think you should be able to get an endoscope down there to check it out and confirm whether that actually is your problem before going that far.