Oil change volume, vacuum and valve cover leaks

[hollasboy]

I just changed the oil in my '79 CJ5 (AMC 258 i6 / 4.2l I6) for the first time since I bought it. The TSM said to use 5 qts of oil if you don't change the filter, and 6 quarts if you do.

Well before I changed it, the dipstick was showing full and I only pulled about 3-4 qts out of the drain. So I added 5 qts, AND swapped the filter, the dipstick already showed over full. I ran the engine, let it sit, and rechecked and it showed more than full, so I did not add another quart like the TSM said I should.

One week later, I started to mess with my vacuum tubes which were mostly all severed and left dangling by the PO. The only change I made was to put back a line between the valve cover vacuum port (at the back of the cover, on the firewall side) to the carb air filter port - both ports were open to atmosphere before. I was told on this forum that I was ingesting dirty air into the cover and that it needed to be filtered - since there were already ports on both, it was an easy task to put a tube in there.

Around that time, I started to notice oil dripping under the engine. Oil was everywhere down there, but I could not find a specific source of a leak. I did notice some oil was dripping onto spinning parts and thus slinging it everywhere - that and the engine fan did a real number on spreading it all around. The dipstick still showed above full.

After a few more weeks, even more oil is showing up under the Jeep, especially after driving it around and parking it. I then noticed it was coming from the entire perimeter of the valve cover - leaking from everywhere. I checked the valve cover bolts, and every one of them was loose. I had lost quite a bit of oil by then, maybe a quart, and now the dipstick shows the level exactly at the full mark.

1. What is the correct quantity of oil to do in an oil change? Did I mess that up?

2. Did I overfill the oil and damage the valve cover gasket?

3. Did installing the tube from the vacuum intake to the air filter cause a problem or contribute to this?

 

[Lumpy Grits]

Check the back of the valve cover for leakage.
Make sure your PCV valve is not clogged/plugged up.
Some overfill will not be an issue.
You never said how many miles on your engine.
Might be time to do a compression and leak-down test.
What weight oil you run'n?
Lots of good information here.
Table of Contents

LG

 

[Posi]

1. What is the correct quantity of oil to do in an oil change? Did I mess that up?

2. Did I overfill the oil and damage the valve cover gasket?

3. Did installing the tube from the vacuum intake to the air filter cause a problem or contribute to this?

1. You are correct 5 quarts, 6 with new filter
2 Depends, does your engine have the original oil pan? Do you have the original dip stick?
3. I'm not clear on your question. You should have clean fresh air going into your PCV intake (rear of valve cover). The PCV "valve" should be on the front of the valve cover with a T fitting. One goes to engine vacuum, the other goes to your charcoal canister to purge fuel vapor.

 

[Posi]

3. Did installing the tube from the vacuum intake to the air filter cause a problem or contribute to this?

If you mean the PCV intake hose located at the rear of the valve cover (nearest firewall), that was taking in unfiltered air into the engine, then connecting to a filtered source, then no it wouldn’t contribute to your problem.

Things to check,
Inspect your oil pan and dip stick to make sure it’s the proper size.
PCV valve
Confirm manifold vacuum at the PCV valve
Check for blockage or leaks in vacuum lines on the vacuum side.

 

[hollasboy]

Ok thanks. I was sure I had screwed something up, but sounds like I just have a leaky gasket under my valve cover. Maybe adding more oil than was originally in there just put more volume in there to leak out. Guess I'll be looking into replacing the gasket. I did notice that my oil cap has no rubber gasket in it, and that the PCV tee is somewhat loose (it spins around freely). I'm still not sure about putting 6 qts in there when 5 qts put it well over the full line on the dipstick (yes it's original). Guess I'll just have to trust.

 

[Lumpy Grits]

I have for the last 34+ years I've owned my CJ7 w/258ci engine poured 6qts of oil in with filter change-
Never-ever an issue.
Again I ask--What weight oil are you using?
What's the mileage on the engine?
Did you drain the oil pan on level ground?
LG

 

[hollasboy]

I have for the last 34+ years I've owned my CJ7 w/258ci engine poured 6qts of oil in with filter change-
Never-ever an issue.
Again I ask--What weight oil are you using?
What's the mileage on the engine?
Did you drain the oil pan on level ground?
LG

I put 10W-40 since I'm in central Texas and the TSM recommends that weight for my climate. I have no clue how many miles, this Jeep is on its 3rd odometer - when I got it, the second odometer said 25,000 mi but it was not from this Jeep. The new one I put in started over at 0. It's an old Jeep that has been running since 1979 so I would estimate at least AMC 150 ,000k on the engine - just assuming everything is very old at this point. Yes it was on level ground when I changed it.

 

[TnCJ]

My 1980 CJ5 is the same.
One of the first things I did when I got it home was change all of the fluids.
Per the manual...........6 qts of oil with filter change so that is what I did. But I have the same problem as you as it is showing to be over filled on the dipstick. As far as I can tell it has the original dipstick and oil pan.
I was going to just put in 5 qts next change but on second thought I would rather be a quart over than a quart under so will "probaby" go with 6 quarts.
I too have a leak around the valve cover but I don't think it is because it is over filled with oil.

 

[Lumpy Grits]

I put 10W-40 since I'm in central Texas and the TSM recommends that weight for my climate. I have no clue how many miles, this Jeep is on its 3rd odometer - when I got it, the second odometer said 25,000 mi but it was not from this Jeep. The new one I put in started over at 0. It's an old Jeep that has been running since 1979 so I would estimate at least AMC 150 ,000k on the engine - just assuming everything is very old at this point. Yes it was on level ground when I changed it.

I run 20W-50 Castrol, and have done so since the first oil change.
With the miles you have-Go'n to what I use may not be a bad idea.
LG

 

[Posi]

Ok thanks. I was sure I had screwed something up, but sounds like I just have a leaky gasket under my valve cover. Maybe adding more oil than was originally in there just put more volume in there to leak out. Guess I'll be looking into replacing the gasket. I did notice that my oil cap has no rubber gasket in it, and that the PCV tee is somewhat loose (it spins around freely). I'm still not sure about putting 6 qts in there when 5 qts put it well over the full line on the dipstick (yes it's original). Guess I'll just have to trust.

I would replace both PCV grommets. The vacuum side especially needs a tight seal to draw. Besides the valve cover gasket your most likely needing a timing cover gasket as well. Good time to check the deflection on the timing chain and replace if needed.