Perkins 4-108 Dual Oil Cooler/Heat Exchanger

[amore]

I wonder if anyone out there has had a similar problem. My 4-108 has a dual oil cooler (transmission & engine oil). Recently, my transmission (BW velvet drive) stopped working. Both forward and reverse gears were inoperable. Upon checking my transmission fluid I found it was empty. I had checked it about a month ago and it was fine. I also checked my engine oil and found it was overfull, I'm guessing by a little over a quart. My Perkins is 36 years old and I check oil regularly and never overfill. There is no oil in my bilge and none coming out of exhaust. There is no oil in my cooling system. I'm thinking that the trans. oil cooler has failed and somehow the fluid has been sucked into my engine oil cooler. What I don't understand is how I do not have oil in my antifreeze and if my diagnosis of a faulty cooler is correct. I have owned the boat for 20 years and the lines to the cooler have never been touched. I'm adding this because someone suggested that the lines were crossed.
Any thoughts will be appreciated.

[model 10]

That would be a weird failure. Is trans oil pressure higher than engine oil pressure? There is a casting inside the cooler that holds the 2 little radiators, there must be a crack. Easy enough to pressure test.

[Lepke]

I have a 1972 4108 running a generator. I check the oil & coolant every time I start it.

If you gained oil in the engine and lost oil in the trans and the only thing they have in common is the oil cooler, then start there.

This one is $200: PERKINS MARINE DUEL OIL COOLER #4619

[amore]

Originally Posted by Guy

That would be a weird failure. Is trans oil pressure higher than engine oil pressure? There is a casting inside the cooler that holds the 2 little radiators, there must be a crack. Easy enough to pressure test.

Thank you for your response. I was figuring on a pressure test but I wanted to get some input before I pulled the cooler. It still confuses me why there is no oil in my antifreese

[amore]

Thanks. I saw that cooler on Ebay and it looks good. New one is $335 at MrCooler.com

[leftbrainstuff]

Originally Posted by Guy

That would be a weird failure. Is trans oil pressure higher than engine oil pressure? There is a casting inside the cooler that holds the 2 little radiators, there must be a crack. Easy enough to pressure test.

Indeed.

Take it off and pressure test it. If it has failed as you suggest this test will validate your hypothesis.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[Minggat]

There does seem to be some logic in the illogical failure. But there may also be some coincidence of the high/low oil levels. I would suspect a bad diaphragm in your mechanical fuel lift pump for the high engine oil level, and keep looking for the trams oil escape route.

[topmast]

Assume all this is fresh water cooled?? If on the raw side.you'd hardly notice the small amount of trannie oil in the exhaust over a month. High engine oil may be a separate issue. If bell housing dosen't drain it could hold a trannie full when the front pump seal fails. Check for a well lubricated bendix spring

[lancelot9898]

Looking at that picture of the duel oil cooler, I don't see how the ATF could get into the oil since the picture shows two separate cylinders. The only thing common is the cooling water.

[Osprey83]

Good point. My Perkins 4108 is a 1972 (maybe a 4107) with the same exchanger setup. Last year the oil level rose by 2+ quarts. After replacing fuel lift pump, found the problem to be the seals in HP Injector pump. Both are paths for fuel into the oil system. With a power plant as old as these, I check liquid levels before each start. The oil/transmission cooler (I too have Velvet Drive) is also original with a super thin copper shell that can take very little torque at the hose fittings. (use two wrenches) It has performed without issue for my 33 years on the boat. The problem described seems to be two problems, combined. I would bet that there is no path for transmission fluid to the oil pan and always thought engine fresh water pressure higher than the raw water and oil pressures. (Which failure is worse?) Either way, with engine fresh water cooling two separate oil streams, the oils should be isolated even with tube failures. (your point) A good Perkins Mechanic would know. Ask Mark at Complete Yacht Service in Lauderdale.
Question: Is there a chance that your cooler is using salt water?

[Osprey83]

The front transmission seal failure path, thru the bell housing, is logical. My high high oil level leaked some oil/diesel into the bell housing, from the opposite direction. So if it gets to the bell housing it can end up in the oil pan.

[model 10]

Originally Posted by Osprey83

The front transmission seal failure path, thru the bell housing, is logical. My high high oil level leaked some oil/diesel into the bell housing, from the opposite direction. So if it gets to the bell housing it can end up in the oil pan.

That could be it. Older Perkins use same oil for both engine and trans, so the bell housing can be oil tight. Usually it leaks out the starter or the bottom of the bellhousing . You should be seeing that leak soon and your starter might quit from the oil on the commutator.

[Cheechako]

Incidentally, can you bypass the cooler entirely and try it for a while to see if anything weird occurs again? My 47 footer with a 4-108 had no coolers at all and no problems with it that way. So maybe you could test if it's the cooler that way.

[topmast]

The trannie may unstick its bands and disks but my experience is 'it's toast' The front geroter probably did't survive either and that supplies pressure to the guts to squeeze the friction bits. Then there's the reduction gear and thrust bearings .Be sure you've found the problem so you don't replace the velvet twice.

[amore]

Thanks for all the input. In the next few days when I get back to the boat I'm going to try and determine if there is fuel in engine oil but I kind of doubt it since I think engine would smoke pretty bad and this is not the case. I'm going to pressure test cooler and then possibly send out an engine oil sample. As for front trans seal leaking wouldn't there be trans oil in my bilge?