I have 180 to 190 psi compression in each cylinder...all spark plugs out, no oil added, ten compression strokes with gas pedal wide open. Should I check the compression gauge after fewer strokes? I'm burning a qt/700 miles.

Spark plug electrodes and insulators are burning clean and light tan but the metal ends that is in the combustion chambers have a black coating on them.

No oil anywhere near the cam housing plugs.

no black or oily deposits on the air cleaners.

With that good of compression I'm assuming the rings are good and the valves are sealing so oil must be getting buy the valve guides and or valve stem seals, right?

 

Are you sure you don't have a leak somewhere?

 

I can't find any leaks, i.e. never a drop of oil on my garage floor.

After looking on Ebay for valve stem seals, which are readily available meaning they must sell a few, and after viewing a couple of vids on Youtube I'm becoming convinced that the seals are my problem and they can be replaced without removing the cams, heads or any other major components. Pressurize each cylinder at top dead center, use a special valve spring compressor and swap the seals out.

Does the '07 GL450 have four valves per cylinder? If so, 32 would take a while. The scariest part would be if the engine got slightly off TDC while doing the job on one cylinder because the valve you were working on at the time would end up in the combustion chamber necessitating removal of the head. That would ruin my day for sure.

 

I thought your compression was in the 120s. Sounds like your motor is just like mine.

Valve guides would really surprise me. MB makes good motors.

Saw your other thread asking about the crankcase ventilation. It's supposed to be the most likely culprit.

It's not an expensive fix ($100 in parts, including the plugs), and you'll note I pointed out the separator looked mighty distressed.

If I was you I'd do that fix. You've posted a dozen inquiries about this. It's dangerous to throw parts at a problem, but this is not a big fix.

 

When I checked the compression a couple of months ago I did get 115 to 120 psi but I now know I didn't have a good O ring on the end of the hose I screwed into the spark plug hole so I got a false low reading.

I ordered the cam housing plugs and PCV valve on eBay for about $25. I'll see if that helps.

Is the separator the device on the front of the engine towards the passenger side that has a hose going into the air cleaner housing? Does it just require cleaning? Do I need to remove it to service it?

Sorry for all of the posting on the same basic issue but this is driving me nuts and this car fits my needs perfectly so I am not going to give it up without a good fight.

 

It's great news about the motor, of course.

Something is wrong with your purchase of the housing plugs. The OEM plugs alone should set you back $40. The cheapest OEM separator I found was on Ebay for $75.

All those parts are on the back of the motor. Take off the crossbar and air filter housing to get at them. Check my thread on this.


I feel ya - good knowledge is hard to come by. I would think that if there were such a simple fix to such a terrible problem everyone would know about it. Possibly because so many get their work done at the dealership, the knowledge remains hidden.

Another example of weird: The cost difference between legit aftermarket and OEM parts is staggering. The housing plugs, for example: OEM plugs are 3x the cost. The OEM secondary air pump is about $600; Bosch is 1/4 that. This is a 12V air pump, not a rocket engine.

There's also a cult of mystique. Turns out 87 octane gas just fine. Suggest it, though: "If you can't afford twenty cents a gallon more for gas, you shouldn't drive a MERCEDES." Ditto for straying outside the motor oil demands.

"If you're going to nickel and dime on saving $1,500 on a tranny, you shouldn't drive a MERCEDES"

 

I didn't buy a separator. I bought a PCV valve and the three pugs for $25 all of which I know are on the back of the motor.

Didn't nickel dime on the the new tranny. It was an $8000 bill at the dealer fortunately paid by the previous owner at 100k.

Arnott Airmatic air pump was $499.

What and where is the separator and how it it serviced? Do I have to replace it? Can it contribute to oil consumption?

 

Man, you really should read more posts. I talked about the tranny at length. The $8grand is for realz? I just guessed the figure. I got mine installed for $5k even.

I'm talking about the "secondary air pump". It's a low pressure smog air pump used at startup.

The separator is upper rear passenger side of the motor. Highly recommend you change that, as it's easy, especially while you're in there changing out the plugs and my mechanic immediately suggested it as a candidate for oil consumption. See my post on changing the plugs and separator for a couple of tips.

 

What is the device on the upper front of the motor towards the passenger side that has about a 1" hose going into the air cleaner housing?

The PCV valve is the one on the back, upper, passenger side of the engine, isn't it?

 

After viewing a Youtube video about replacing the PCV valve and the three cam housing plugs I ordered the parts on Ebay. I just viewed another Youtube video which seemed like it is some type of official German Mercedes video which refers to cam chains. In it the part on the upper back of the engine on the passenger side which I am calling the PCV valve is referred to as the separator. It's held on by four torx screws.

So, is there a PCV valve or is the only part which provides that function actually the centrifugal separator on the upper back passenger side of the engine?

Is the device on the upper front, slightly to the passenger side, which has a hose running into the air cleaner housing a smog pump?

 

1x, before you start tearing apart your engine to change the valve seal, I would really suggest that you try to track down where the leak might be coming from. Google leak down test. you be able to possibly track down the leak better with this. You might have to watch a few videos of this. It will also make you a better mechanic. I think there is also a video on how to make one if you don't want to buy one. (I decided to edit this post and put up links for leak down to make it easier) As a side note, you have to know the engine. You will need to know how to put the motor to top dead center(TDC). There are a few ways to do this. You will also need to look for the TDC mark on the engine. This is at a very difficult spot to see and you will need a mirror to find it. Even then, you might not be able to find the mark. You can use a simple tool like a screwdriver down the spark plug hole to find TDC. If you need to know more about this, just ask because I wont write it down if you are not going to go down this route. (edit) I attached another video from eric the car guy. go to about 20:43. You can actually do a poor man leak down. Its basically just hooking up a hose to the cylinder without the gauges. You will still need to find TDC. As far as checking the radiator as per the instructions, you can pretty much rule this out. This really pertains to warped heads/ blown head gaskets. You would be able to see a oil mixture like a milk shake in the coolant reservoir.

https://mobiloil.com/en/article/car-...-leakdown-test



As far as doing the valve seal; you will need to remove the cams and rocker arms. I'm assuming the videos that you watched were not of dual OHC benz motors. I will try to attach pictures on what the top of the heads look like. You will also see that on the exhaust side, there is burnt oil from leaky valve guides which will also be a big indicator of a leaky guide/seal. If its on the intake side, you will see oil covering the valves. If you ran it low on oil, it can be possible that you also wore out the valve guides. If I remember correctly, If you run it low on oil, I think there are a couple of cylinders that the valve guide wear out more quickly then the others. Is there any smoke coming from the tail pipes? Check to see if you have black soot on your rear bumper above the tail pipes or just around the chome at the tile pipe. If it is only coming from one bank of the engine, you will be able to tell if there is an unusual amount of soot by comparing both tail pipes. (Bank 1 being the passenger side and bank 2 being the driver's side).

Also, If you let the leak go long enough, your cats can suffer as the burnt oil deposits will slowly clog the honeycombed platinum that is inside.

 

I'm pretty sure the OP is off his "rocker", thank god.

Is there any track record of MB engines leaking oil out the valve guides?

 

The device is the secondary air pump. It's a smog pump but only for when the motor is cold. Curiously it seems to be integrated with the PCV system. I will research it and report back.

 

Eric, I read it somewhere on the internet so, it has to be true. Anyway, I don't know if there is a track record. Mine was leaking on 2 cylinders. One on each bank

 

lol
how many miles did the motor have on it?
how fast (qts / mi) was it burning?

 

170K miles. I don't know exactly how much oil in a certain amount of time. I know it was loosing oil as wife would tell me the oil dummy light would be on. Wife drives the car as her daily driver. I think the main cause of the oil loss was the rear cam plugs. from there, it got worse since I'm sure parts were being worn out due to oil loss. Then I knew things were bad when it looked like a steam engine was going down the street. At start up, a huge plume of smoke would come from the tail pipes.

 

whoa - sad end to a fine motor. Or are the rings and bearings okay?

OP and I are getting oil consumption with no tailpipe smoke, no drips, and no motor smoke. Pretty sure the PCV system is letting oil mist into the manifold.

 

If you are indeed loosing as much oil as 1X, I would think you would be burning it even though you might not notice any smoke. In 7000 miles, that's 10 quarts. There really isn't any place in the motor that would hold that much oil so I would assume that you are burning it. Maybe you can invest in something like this

http://nmdminishop.com/ridgid-micro-...ection-camera/

It is a bore scope with what looks like a mirror attachment and an LED. since its a rigid, I'm sure its at home depot and if it doesn't work for you, I'm sure you can return it. You can shove it down your spark plug hole and see for sure which cylinder is burning the oil

 

Since all cylinders have excellent and even compression why would I want to do a leak down test or look into any cylinder? I'm not trying to diagnose a bad valve, bad rings etc., as, like I said, compression is very good in all cylinders and all spark plugs look good and the same.

 

1x, I suggested doing a leak down because that is an awful lot of oil to be loosing through the seals. Does it have blue smoke on start up? That is an indication of leaking oil seals. The leak down can determine what issues might possibly be present since you say there is no oil on the ground. Also, if there is oil leaking into the cylinders from the seals, that can cause the rings to have good compression so it is possible to have bad rings also.

What ever the case, that is an usually large amount of oil to be lost. again, 10 quarts of oil every 7000 miles, is basically an oil change and all you would have to do is change the oil filter on the next interval. I was probably burning that amount of oil on my GL. But, I was able to see it being burned because as it sat at idle, there was always a plume of smoke.

As far as looking in the cylinder with a bore scope, I was just trying to have you get a better look at the cylinder to see if you can see the valves since you said the plugs looked fine. If it looks like the one in the picture, 2nd from the left, you can count on your motor leaking oil into the cylinders from somewhere.

I see that you bought the cam plugs and oil separator. You had also mentioned that they were not leaking also. Are they now leaking and is it possible that this is where the loss of oil is coming from? At some point, if it is leaking from the cam plugs or oil separator, it will eventually start oil puddles on the ground. So, having said that, you can possibly have multiple problems. Hopefully it is not serious or best case, just the cam plugs.

Good luck

 

I'm sure you'll find 1,001 household uses for a borescope. I was tempted to get one to peer inside my teenager's head.

 

Eric, HAHA> I never thought about that one! Thanks for the insight. I will use it tonight

 

Is it imperative that the camshafts be removed to replace the valve stem seals on a 2007 GL?

 

1x, Yes. along with the rockers. But to remove those, you also have to remove the cam shaft timing gears. Before you do this, please read up as much info on this and watch a few videos. You will also need a descent set of tools and not just one of those 100 piece craftsman tool kits. Make sure you search around for the torque and torque sequence for the cam shaft cover and be careful when storing and replacing. the do not have cam bearings. The valve cover and the head are the cam bearing so if you remove and replace the cam shaft cover out of sequence, you can warp the cover.

In the pic, you will see the cams sitting on top of the rockers/valve guide seals