I did a timing belt change with valve cover seal reaplacement about 5000 miles ago. Move to an area with high freeway speeds. Car leaks after being on the freeway with a heavy load -- moving. I can't find the leak, but it ends up between the engine and tranny and sometime burning oil smell from the engine area after being on the freeway. Anybody else with the problem? (oil backing up under the valve cover then leaking valve cover? Over flow? If one of the drains are clogged, how to find and unclog them? Engine flush or too risky? Any fixes.

Usually dino, but did a quick dino oil change then to Mobil 1 with entended oil change now.
I added the extra tranny cooler.

OnTheRoad

 

if it's BETWEEN the engine and tranny i'd suspect the rear main, if by between you literally mean between.

 

Well...it could be the rear main, but I suspect leaky valve covers. It's easy to check...just look to see if there's fresh oil on the cylinder heads after a powerwash. More than likely your engine is already dirty, so the best way to check for an oil leak is to carefully wash your engine and then look at it the next day or after a long drive. I suspect it's the valve covers because it'll leak on the manifolds and burn. A bad rear main seal won't cause a leak on anything to cause a burning oil smell. Both with give you a dirty driveway though.


Speaking of a possible clog (and not to thread jack) When I took a look under my rocker covers this past weekend I noticed that the back right (near cylinder 5) of the engine was a little more dry than the rest and the oil coating the springs and rockers wansn't a nice gold color, but more of a light brown. What could cause that??? I don't want to start another thread when this one is so close to the same topic.

 

The engine is very clean after the engine wash and timing belt change. I can't see any leaking oil. Before the timing belt change, I could only see the oil leak by the dirt on the leaking oil. Not all my valve cover screws are accessible with the air plume in place. A major job to remove the air plume.

Don't worry about stealing a thread and the topic is related. Your changing of color from gold to brown is likely burnt oil, presludge. The temperture rose, possible by a lack of oil or hot spot. Do you know a good way to clean out the in and out lines for the oil? Did you have any sludge (burnt oil that has tarred or gritty)? On my 2003 Toyota with 70000 miles, sludge forms in the oil filler tube becuase of oil pooling and high temp. A design problem. I just cleaned the area to remove the sludge and hope for the best -- sludge not forming in other area. BTW the Fremont, CA Toyota dealer never cleaned out that sludge or noted it.

On another guy said he after oil draining he pours a quart of diesel to dissolve out the sludge from his oil pan and other said he ran is 1950's car with mineral oil for a few minutes. 1950's car has much looser tolerance. I'm afraid both method might destroy a modern car engine. Possible a napthaletic oil with 1000 mile change interval might dissolve a partial clog. The change to a good quality oil to keep it clean. Pennoil advertises that their 100% synthetic is very good in keeping an engine clean. Don't know the oil is better than the other oils. I think it group III type oil. Group III are better than real synthetics (group IV and V) in dissolving oil degradation products.

Anybody try the oil flushing machine? Pumps solvent then oil in by attaching to the oil filter connector.

OnTheRoad

 

Its std procedure on some car maint schedules, good practice (and pricey).

"but did a quick dino oil change then to Mobil 1" ... this is possibly thinner than previous.

U may try the seal swelling additives.

"Not all my valve cover screws are accessible..." ---> they dont care if theyre loose. They just leak. Worktime?

 

Clean your engine and visually inspect it at idle! If you think it's only leaking @ hi-speed that's not the case! Either it leaks or it doesn't! Changing your PCV valve might help you out!

 

The leak only shows up on the floor after high speed driving.
Low speed (<50 mph) no oil on the floor.

Any trick in tightening the valve cover screws without remove the throotle body?

The valve cover seals are new or at least 5000 miles ago. New PCV valves could reduce the pressure under the cover. But my mechanic would of cleaned the PCV valves when the throttle body was removed. He said the cleaned a very dirty throttle body.

OnTheRoad.

 

Run it for 30 minutes @ idle or more, it will leak; You shouldn't have to remove the throttle body just to tighten the screws, use a 1/4 drive rachet with an apex bit. That's why I'm replacing my screws with hex head bolts!

 

I drove it around town <50 mph, then put cardboard under the engine and no drip. I can't see any leaks on top. Any dye to put into the oil?

Matt, where's a good place to get the hex bolts and rubber washers? What the bolt size and length?

 

CMax03: One mechanic said maybe the oil is pooling on top, because some oil drain lines are clogged under the valve covers.

Does anybody know of a good way to clean out the cloges without disassembling the valve covers?

 

What kinda oil are you using? What lines are you referring too? I think you mean drain holes in the head! What does your valvetrain and upper head look like with the valve covers off? Full of oil varnish and build up?

Those grade 8 bolts can be acquired at any bolt specialty store, just take a screw with you so the clerk can match it up!

Does sound like pooling or puddling of oil and running out of the valve cover on to the everything else....You can't see the origin?

 

Ask at McDonalds, what they said?

Blowtorch?

Hard work first, if it wont hlp, then the easy one ? (oil change)

 

ya could be possible some of the oil galleries are clogged up. If there is any type of treatments to do to clean these Id like to know as well. I have a VE and we all know whats happens to VTC when poor oil flow. Had my jdm in for almost 4 years, no clack, i want to keep it that way.

I was thinking of maybe doing a couple of multiple oil changes. topping off with half, maybe even full can of seafoam, running for a few hundred miles, rinse and repeat. I know they have the "engine restore" or engine flush chemicals you can put in...but I heard they are bad for newer cars, but for older cars, they are ok

 

I can't see the origin, but may have found one moist looking spot with a little dust on the manifold, but maybe from the prior leak. I cleaned the spot with brake cleaner and will check if spot returns. The location is right under a rubber hose from the valve cover (clamp is missing).

On the engine cleaner, a bay area Toyota dealer has a BG engine cleanner. With the engine turned off, oil filter off and oil plug out, the machine attached to where the oil filter was, then pumps solvent into the engine, then pumps oil to restore the oil film before engine restarting. I think the cost is $150. I need to find a Nissan dealer who does it (need correct adapter).

OnTheRoad
93 Maxima.

 

See my post above on BG engine cleaning machine. I don't have any experience with it. On the do it yourself cleaner, the cleaners are very stressfull on the engine (especially older ones) because the thining of the oil and oil possible oil starvation, like having a stoke in people. The sludge in the pan is stirred up and gets sucked up into the lines and even cloggs the filter. Too bad the oil pan is not easily removed for cleaning and inspections. Nissan not only did that on the engine, but also did that on the transmission pan.

 

Ridiculous - why do you even go to this guy?

Your oil pump should reach max pressure way below 2000 rpm on an engine in good condition - soon as it reaches max pressure the oil pressure control bypass valve bleeds any additional oil back to the sump directly - Net result is that whether you drive in town or on the highway, once you reach about 2000 rpm, the volume of oil is exactly the same, so it cannot possibly account for causing a leak by pumping "more" at high speed highway driving - this is exactly where the twit "mechanic" should have suggested you start your investigation

I think its pretty simple - you have a crappy gasket/seal somewhere that cannot contain the oil being dumped on it because of engine blow-by )at sustained high-speed driving) causing sump air pressure to rise to a point where the PCV system no longer can cope with the air volume to maintain a slightly lower than atmosphere status in the engine (the PCV valve has a very limited flow capability by design).


I would remove both the PCV hoses from the valve covers and block the PCV valve inlet on the IM - do your town and highway driving for a while, and I am willing to bet that you now, in both cases, will have oil leaks.

The answer is simple - you need to fix the leaky gasket/seal and not stuff around with the internals of the motor. If it turns out that I am wrong, you have way bigger mechanical problems in that motor that you either have not mentioned or are not even aware of.

 

The counselor is moonlightin at Mc Donalds = easy cheap advice?

Cleanup is smtg which dealerships do at regular basis. Good practice, good revenue
The cleanup WILL NOT help in leaks no not in any way.

My engines have never failed b/c of that [not piling steare$hip bill$], few million miles experience. Just swap oil and filter as maint procedures say.

I wonder how ppl cant read: If u swap oil, and it starts to leak --->oil is the culprit. ... And behind that are, loose screws, worn old seals.

What u can do?
1. Swap, tighten all seals
2. Return to oil used previously
3. Use seal expanding additives

One fingertip oil spot on engine? Youre in wrong section, return to cabin.

 

you are making an ASSumption

it is not unheard of for that valve to stick closed and let the oil pressure rise with RPM, which can cause an oil leak at higher RPM. We just had a van in the shop that the valve in the pump stuck closed, and it would build up so much pressure that it would break the oil filter.
swapped in a new pump, and the problem went away.

 

No assumption at all...................

as I said ...........

and from earlier..........

 

my car doesn't usually hit 2500 until it's on the highway, or during the merge onto the highway i'll bump it up to 3000-3500, but around the neighborhood it doesn't usually hit but about 2300. so i guess that's correct for me... but not necessarily true for how everyone drives (throttle-happy ppl)

 

you made an assumption that the pump is functioning 100% correctly.
if the pressure exceeds the level that the seals can handle (which really isn't much) oil will get past them no matter how new they are.

 

 

what i meant is that for me, RPMS stay low until speed goes up because i short-shift. for others, rpm is at its highest around town, b/c they run it up to 4000 rpm before shifting, then just cruise in OD on the highway. so the idea of the oil pressure being higher at higher speed would apply to me, but not to all.

 

Around town the rmp stays usually under 2000 except for short period right before tranny shifts gear. On the fast highway the rpm is steady at 2400 to 3000. On my old MBZ diesel with an oil pressure gauge, the presure goes up to max at highway speeds and about 3/4 at city driving and third way at idle. I don't think the MBZ has a pressure bypassing the engine, it has a temperture bypassing the cooler and pressure bypassing the filter, but the full flow goes to the engine.

As for a new valve cover seal not being able to stop a leak from a moderate pressure build-up, then the solutions appears to be stop the oil from pooling or not allowing the pressure to build-up by fixing the oil pressure, higher viscosity oil to prevent blow-by, or opening enlarging the PCV. I've read of opening the PCV to prevent sludge some Eurocar and Japanese cars, but forgot which ones.

Just got the car painted with 2 coats of paint and 3 coats of clear coat. DuPont Chroma Cat. Clear Coat.

 

Around town the rmp stays usually under 2000 except for short period right before tranny shifts gear. On the fast highway the rpm is steady at 2400 to 3000. On my old MBZ diesel with an oil pressure gauge, the presure goes up to max at highway speeds and about 3/4 at city driving and third way at idle. I don't think the MBZ has a pressure bypassing the engine, it has a temperture bypassing the cooler and pressure bypassing the filter, but the full flow goes to the engine.

As for a new valve cover seal not being able to stop a leak from a moderate pressure build-up, then the solutions appears to be stop the oil from pooling or not allowing the pressure to build-up by fixing the oil pressure, higher viscosity oil to prevent blow-by, or opening enlarging the PCV. If it pressure build up then loosing the oil cap should stop the leak. I've read of opening the PCV to prevent sludge some Eurocar and Japanese cars, but forgot which ones.

Just got the car painted with 2 coats of paint and 3 coats of clear coat. DuPont Chroma Cat. Clear Coat.

 

Man - if you wanna pick a fight, then try one you at least stand a chance of winning.

Please don't tell me what I assumed by selectively choosing which words of mine to quote - I posted what should be the case with a normal motor and then said that the mechanic should have started measurements exactly there before dreaming up a stupid theory without even doing anything.
Again from my unedited post


OnTheRoad

I will grant you that I have not had my hands in every Merc engine ever designed, but those that I did encounter (including all diesels I can remember) all use a fairly std oil pump setup (iirc 3Bar @3000rpm spec'd) not unlike what the Nissans and many other car brands do - ie - positive displacement pump with a pressure control valve either on the pump body itself or elsewhere in the motor to limit max oil pressure. Mechanically its a bad idea to not have such a setup (iow oil pressure increase uncontrolled with engine speed) because of huge mechanical pumping losses, popping of pressed-in gallery plugs, too much oil on rotating members and pistons (rings cant cope) etc etc........

If your MB motor is showing the oil pressure behavior you state, then its obviously seen a lot of use (or abuse ito maintenance) and bearing/journal wear as well as oil-pump gear/vane wear are working together to no longer produce the spec's volume of oil flow.

The PCV system should ideally be able to maintain the inside of engine at a slightly below atmosphere pressure if the motor is in good condition - the idea is to use a small amount of fresh air sucked into the front valve cover cavity from the intake tube to scavenge the blow-by gasses and to then suck it directly into the intake manifold where its fed to the combustion process. When your blow-by starts increasing with engine wear, you don't get a "huge" pressure buildup in the sump, but the slight "vacuum" that should exist is now no longer there, actually forcing blow-by back up the front intake valve cover and into the inlet tube before the TB where its also sucked into the engine for combustion.

There is not much you can or should actually do about changing the oil flow/pooling characteristics of the motor if your oil pressure is normal ............ and as for suspecting that the oil pump's delivery volume at normal pressures can drown a seal - try this:

When you next have to change your oil, drain the oil and leave the sump open with a new clean and fresh container to catch about 5 liters of new oil - now fit a funnel on the valve cover and dump a 5L can of oil as fast as you can into the funnel. My bet is you get that oil going down into the sump (and thus into the new container) just as fast as you can pour it into the motor - the point being your oil-pump cannot deliver a volume of oil to the top of the motor even remotely resembling the volume you can dump out of a can directly into the engine - so if the motor can cope with your canned volume it will surely be able to cope with whatever the oil-pump can deliver no?

Opening the PCV system will cause sludge not prevent it. The PCV system is designed to remove the blow-by gasses etc from the inside of the engine before it can settle into the oil and start reacting with everything it comes in contact with.

Higher viscosity oil is not the answer - it was designed to run with what the owner's manual says without leaking - if its leaking now there is a problem

As I said in my first post - measure the oil-pressure, and if its normal I am willing to bet you have crappy seals/packings somewhere - its as simple as that. Fix that