crankcase pressure

[cj77windsor]

My AMC 304 V8 seems to building a lot of crankcase pressure. I noticed that I had a little bit of oil sprayed on the hood but can't really see any leaks. A couple days ago my dipstick tube and oil cap were both missing after a short drive. I replaced the oil cap and still waiting on dipstick tube I just have it plugged for right now. When it is first started the jumps over 80 and than warms up and drops below 20 I know thats sort of normal but I also have a pro lite auto meter for low oil pressure and has never indicated anything wrong before but thats not the case now it automatically comes on when engine is started but turns off when it is rev up any help would be appreciated. Thanks

 

[Rescue Diver]

My AMC 304 V8 seems to building a lot of crankcase pressure. I noticed that I had a little bit of oil sprayed on the hood but can't really see any leaks. A couple days ago my dipstick tube and oil cap were both missing after a short drive. I replaced the oil cap and still waiting on dipstick tube I just have it plugged for right now. When it is first started the jumps over 80 and than warms up and drops below 20 I know thats sort of normal but I also have a pro lite auto meter for low oil pressure and has never indicated anything wrong before but thats not the case now it automatically comes on when engine is started but turns off when it is rev up any help would be appreciated. Thanks

Your oil pressure wouldn't blow off your dipstick and oil cap. A lot of blow by(Combustion) getting past your piston rings is what builds pressure in the crank case. Do you have an oil breather and or a PCV valve?

 

[cj77windsor]

I do have an oil breather on the oil cap that runs into the air filter. I noticed a little oil in the air filter coming through the breather hose. Just seems like a lot of blow by to me. I haven't checked the PCV valve yet could it be no good and how hard of a fix is that?

 

[Rescue Diver]

I do have an oil breather on the oil cap that runs into the air filter. I noticed a little oil in the air filter coming through the breather hose. Just seems like a lot of blow by to me. I haven't checked the PCV valve yet could it be no good and how hard of a fix is that?

It's nothing to change the PCV valve and they only cost a few dollars, but if you have a whole lot of blow by, it's time for an overhaul because your rings are worn out. Hate to be the bearer of bad news.

 

[cj77windsor]

That's kinda what I was worried about maybe after summer I'll tear into it a little Still runs like its brand new so hopefully its just the pcv valve thanks

 

[Rescue Diver]

That's kinda what I was worried about maybe after summer I'll tear into it a little Still runs like its brand new so hopefully its just the pcv valve thanks

No prob. You should replace the breather cap while you're at it. Sounds like it might be clogged. I've never heard of an engine having so much blow by that it built up enough pressure to blow the dip stick out of the tube!

If it's the rings and it's still running good, you might be able to milk a few more miles out of it with some engine resore additive. If you decide to do a rebuild and want to go cheap, just replacing the rings, bearings and timing chain with a good hone of the cylinders will usually give you an engine that'll last for years. Or you might opt for a complete rebuild while you're at it with new pistons and boring the cylinders. It all depends on how much you want to spend and how long you want it to last. Good luck!

 

[Old Dog]

That sounds like a lot of pressure. But the rest sounds like a bad pcv valve. As rescure diver said, change the breather cap also as they work together.

 

[Tommy]

I think Rescue has it right. I have a lot of blow by in my AMC 258 i6 / 4.2l CID. It has blown the dip stick out several times. I've been lucky that it got hung up every time and I didn't loose it. My trusty mechanic that does all my smog work here in California confirmed the bad ring diagnosis. I will do the rebuild one of these days when the funds are there but until then I will keep the revs down. It runs like a top other than that.

Tommy

 

[Cheepjeep85]

I think Rescue has it right. I have a lot of blow by in my AMC 258 i6 / 4.2l CID. It has blown the dip stick out several times. I've been lucky that it got hung up every time and I didn't loose it. My trusty mechanic that does all my smog work here in California confirmed the bad ring diagnosis. I will do the rebuild one of these days when the funds are there but until then I will keep the revs down. It runs like a top other than that.

Tommy

until then you should put a leash on that dipstick

 

[Rollbar]

I to have had the dipstick blow out a little and oil in the air cleaner.

I replaced the PCV and something.

I pulled the PCV while it was still running and had little suction.

Remedy, I moved the PCV vacuum from the base of the carb to the main vacuum on the intake under the EGR (tree) and it solved the problem. Maybe a factory flaw I don't know but now I have no loss of oil.

Works for me.