diagnosing an oil leak

[rubiconron]

In the last couple of weeks I have been fighting oil leaks on the truck.

 

I have replaced the rear main seal twice and installed a new oil pan gasket and a new valve cover gasket. I don't think the oil is coming from the pan area. It appears to me to be coming from the top somewhere. I have made no modifications to the OEM oil filter setup. Is there a problem area that I am overlooking?

[Randy in Maine]

Did you buy the the full metal oil pan gasket from the dealer? Worth every nickel. I used a bit of Hylomar to get it used to being on there.

 

I also "spoke shaved" the sharp edges off the block where the rear main oil seal goes in so that it did not "snag" going in.

 

Could it be leaking from the valve cover?

[jaekl]

Check the vacuum lines. If oil seems to be everywhere, chances are the crankcase has positive pressure. Check the line from the valve cover. It's probably clogged.

[Jeepinmanch]

Also check the slave cylinder for the brakes, as mine was the source of another leak. Looked like oil.

[rubiconron]

It appears to be coming from the bolts on the valve cover.

 

Let me provide a little more background:

 

The CCV system is new. I will double check the air filter to see if I'm still dumping oil in the air box, but I don't think that I am because I used to have that problem........oil all down the drivers side frame rail leaking out of the air box.

 

I have upgraded to a 99 style valve cover and gasket.

 

Ron

[jaekl]

This oil leakage/seepage problem pops up quite often. There has been many posts mentioning oil being collected or blow by. Is this a common problem? Yet I don't recall any posts ending with "I got it fixed" It seems to me that most cases have to be an internal engine problem. If it was a easy external fix, where are the solutions? Correct me if I wrong. A working systems brings air thru the filter into the valve cover while pulling the dirty air into the intake. If oil is getting into the air filter, the engine is leaking combustion faster than the vacuum line can take it away so it starts finding ways out like the air filter and any little hole. In a normal engine there isn't oil puddling up there. It leaks right down. Replacing valve cover gasket is only going to move the leak.

In this case he had oil in the air filter until renewing the CCV system and now it is leaking elsewhere. I think he has blow by. What are the successful solutions?

My experience is with the 4 cylinder, but aren't the L6 the same design? My one owner (me) started oozing at abot 16 years and found the vacuum line clogged. Now the engine is almost leakfree again 6 years later. However, my other one was found for sale because of major blow by with a open CCV so oil was blowing out. Turned out to be 2 pistons with holes.

I hope someone has an easy fix for this guy.

[rubiconron]

The truck does not appear to be burning oil though.....just leaking. There is no smoke whatsoever coming from the tailpipe (even at WOT).

 

Thanks,

Ron

[jaekl]

It's time to check compression just to make sure everything inside as fine. You're looking for some major difference, so if you don't have a tester, use your finger while you turning it over. It won't burn oil if there is no combustion in a severely leaking piston. You didn't mention anything about rough running or lack of power, so maybe it's not a bad cylinder. However, I see nobody jumped in with an easy solution. I don't wish you a lot of work, but from my experience I say it's time to eliminate big problems rather than doing all the little repairs.

Be prepare for the worse then anything less severe will be a relief. If it does turn out to be one or two bad pistons and the rest of the engine is okay you have an option of replacing those pistons and honing the cylinder with the engine in place. It may not be the perfect solution but considering all the factors it is an option. It's one of the benefits of doing your own work. A professional can't afford to do a half job because the owner might b*@$£ and moan and he ends up losing and then charging the next customer. Where as the shade tree/hobby mechanic can do the minimum repair at times. Many times it may end up as more work but isn't that the whole point of working on your own. In this case though you may get another 50 to 100K if the rest of the engine is in good health.

I hate to be so gloomy but come on guys where are those simple fixes?

[maddzz1]

Could it be coming out of the distributor and leaking down? (I think jeepco jusy had this problem) Or maybe bad o rings on the oil filter mount.

[Randy in Maine]

I am not familiar with the 99 valve covers, but I ended up using a valve cover gasket and a dusting of Hylomar (my favorite flange dressing) to get mine to seal correctly. A PITA to do as it is a poor design right from the factory..

 

Correct torque on the valve cover bolts is a plus also. The rear ones are awkward to get to. I have to retorque all of them on a regualr basis, but I am not sure if using a LockTite product on them is a good idea or not, so I have not.

[dragonrider477]

if your engine is worn and has excessive crankcase pressure,no amount of "fixes" or "bandaids" will correct the problem.most reputable auto shops will not do oil leak repairs on high mileage cars because of this.no mechanic wants a pissed off customer that just spent hundreds of dollars for a rear main seal or other big dollar oil leak repair, only to find that it still leaks.in some cases,even if the oil leaks are stopped,the car still uses oil.people don't understand that a modern car can burn a quart of oil in 500 miles and not smoke.the catalast does a good job of hiding the smoke.jeep 4.0 engines will run forever but after a while,just like any other engine,will suffer blowby problems.many jeepers give up on the pcv system and just run a "blowby dump hose" off the back of the valve cover.this works but i would'nt want to breathe what comes out of that pipe!cars built before the mid 60's had this type of system. i can remember when i was a kid seeing cars sitting at intersections idling in gear with plumes of blowby smoke coming out of the road draft tube under the car.in most cases,if you have checked the normal pcv stuff and repaired it on your jeep with out success,an engine overhaul/replacement is in order.

[rubiconron]

I got all of the oil leaks fixed. Everything underneath the Jeep is clean and dry.

 

It was the valve cover leaking. Since I did the 99 cover swap, I first tried to use the $40 valve cover gasket from the 88. That did not work. So then I bought the $30 valve cover gasket for the 99 and installed it with the new bolt grommits that came with the gasket (those were cheap and flimsy). And I didn't do a good job of wiping the surfaces off when I installed the new gasket. So I had 2 issues oil leaking around the gasket and oil leaking out of the grommits because the head of the bolt went through the grommit.

 

In the end I took the valve cover back off and cleaned the surfaces reinstalled the OEM grommits and installed the valve cover and torqued it down to the spec 55in lbs.

 

Last night I cleaned everything off to see if I noticed any oil leaks today.

:cheers:

 

NO LEAKS!!!

 

So in the process, I installed a new CCV system with a 99 valve cover on a Renix engine.