Did I Blow My Crank Seals?

Yesterday, it was below zero and I started the cj7 up. I went in the shop so it could warm up a bit before driving it. I cam back out to oil leaking out the front and rear crank seals. Once it warmed up some more after driving it, it seemed to go away. Today I started it again and it leaked a little out of the rear. I also undid the oil fill cap. It has a hose that goes down below the engine to vent. I’m assuming that it would have gone to the stock air cleaner originally. It looked like it was full of ice from condensation. Could that have been plugged and caused pressure to build up in the crankcase?

 

It sure sounds like it. The seal areas are the only points of pressure relief when the crankcase ventilation system gets plugged.....ie PCV valve or whatever system you my be using on your engine. Do you get any blowby around your valve cover or filler cap? How many miles are on the engine. Weak seals get weaker when it's cold out.

 

It was rebuilt in 2009/10 and probably has less than 10K miles on it. I started it again today and it is still dripping.

 

Just watched a youtube video. At least they can be replaced without having to pull the crank out.

 

I would be tempted to just drive it some or a day or two and watch it. might stop leaking.

 

Yes. I'm surprised how often things heal themselves.

 

I ordered the seals. I’ll see what happens if I run it for a bit.

 

Crank seals aren’t the toughest thing to replace by any means. But I find it’s among the most uncomfortable jobs I’ve done on a cj. If you find yourself replacing them do yourself a favor and pull the pan, then let it drip for a few days before diving in. I’ve done these twice on my 258 and once on the old 304. I never follow that advice and I’m always covered in oil by the end.

 

At those temps the seals will harden up, the. Add in the vent hose being frosted up it’s possible crankcase pressures simply purged oil past the seals. I’d free up the vent hose, rout it in a more proper fashion so it cannot freeze up again, and see what happens. It’s possible clearing the hose and the seals warming up will help “self fix” the issue.

 

If you are already running a "draft tube" for the venting, perhaps you can find a valve cover vent to replace the oil filler cap. That wouldn't plug.

 

There isn't a provision for a vent on the valve cover. The 360 has an oil fill similar to a 283 or 327 Chevy.

You can see it in this picture just behind the radiator hose.

 

Your oil cap looks to be the stock vented cap, I assume the hose which got frosted up is the hose I see attached to that. Having that hose hanging down below the engine is asking for trouble.

I would buy a new PCV valve, and a new vented cap with the hose going to the air cleaner, which may or may not have a knock out for the purpose of installing the fitting.

I just googled "vented oil cap AMC 360" and got a lot of hits. There are OEM type replacements like what you have, and there are also vented caps which have their own filtering and don't need a hose routed to the air cleaner.

 

As a non fan of gauze air filters, I would suggest you source a stock style air cleaner housing and connect the vent tube up as it was intended. That would keep the end out of the slipstream and free of ice and debris.

The stock filter housing will also help with cold weather running by using the hot air stove and have a cold air intake by hooking up the fresh air inlet.

Might also pop a grommet in that hole in your bulkhead, Brrrrrrrrrrr...........

 

I pulled the rear main out today. Yep, there was no coming back from that. Big chunks missing out of it. At least it came out easy. Really wasn't a bad job. I still have to put the pan on and do the front one.