Oil spots on air filter

Oil is blowing into the air filter from the crankcase breather tube that's attached to the motor's valve cover. Either the motor is showing signs of wear - piston rings allowing blow-by or, if it has a vacuum pump, a leak somewhere in the car's vacuum system is dumping air into the motor (vacuum pump exhausts into the motor in many cases) that air then needs to be expelled - into the air cleaner.

If the motor has done > 250,000 miles the rings become quite suspect except if you KNOW there's a vacuum leak(s) in the car.

-->> T.G. Lambach that's attached to the motor's valve cover. Either the motor is showing

Thank you T.G.L.

The car has a mere 90,200 miles on it

-->> T.G. Lambach that's attached to the motor's valve cover. Either the motor is showing

Thank you T.G.L.

The car has a mere 90,200 miles on it and the oil has been checked and changed regularly, so there should be little wear. I'll have to look for that vacuum pump and its lines. At one point a few years ago I did have to change a small plastic piece that was supposed to be part of a vacuum system.

The part I replaced was the Vacuum Control Unit

I can't help you on the vacuum system's details but the theory is that a leak somewhere allows air to be pumped into the motor (via the pump) and that excess air blows lube oil into the air filter. A Mity-Vac (or similar name) vacuum pump can be used to find vacuum leaks.

I (eventually) found that my 617.950 engine blows oil up the air cleaner's oil drain pipe on hard acceleration, staining the paper air filter, whenever the oil level was too high due to careless repair shop overfilling on an oil change.

-->> T.G. Lambach leak somewhere allows air to be pumped into the motor (via the pump) and

A belated thanks TGL for the info. I have been bogged down with other things recently and will be looking at this problem again soon.

This is the first time I have seen lots of discrete oil drops. The filter normally has a uniformly sprayed look in places and moderately clean at others.

I finally got around to this problem in which my '83 240D's air filter is becoming very spattered.

The oil level in the engine is about 1/4" down from the max level. As T G Lambach (thank you TGL) suggested, I have acquired a vacuum pump and now I have to figure how to apply it. I lifted the cover of the air filter and there were several large drops of oil at the mouth of the incoming pipe from the cylinder head cover and the filter was more spattered than a week ago.

Most fortunately I chose a car with the least possible complications and, as a result, I have a very simple vacuum system. There is a single white line about 3/8" diameter going from the vacuum pump to brake unit. About a foot short of the brake unit there is a T junction off the 3/8" line which then splits into two small pipes - one light brown and one dark brown. Both of those go through the firewall, possibly to the steering lock. Another light brown pipe, of the same size as that small pair, comes back out of the firewall and connects to the valve (a check valve?) on top of the injection pump. I don't yet know how the three are connected in the dash area. My 3 big fat manuals seem to have no diagram of this vac system. They do have several for the later EGR system. I believe there are line diagrams in the manuals for the vacuum but I couldn't find it. Looking for something in those manuals is like going down a great black hole.

I propose to pull the two small pipes off the T, plug the hole with a golf tee, and then measure the pump pressure.

Then I guess I could apply the pump to the two light+dark tubes and see if the car key position makes a difference.

Finally, and this one has me stumped, the connection to the injection pump. Is the function of this to lower the pressure in the pump so that the suction speeds the fuel into the pump, and to provide a check valve to keep the fuel from getting onto the vacuum lines?

TIA

The vac line to the injection pump activates a bellows that shuts of the fuel flow and hence stops the engine. It's activated from a vac valve on the ignition switch. If that line develops leaks, the car will start to take longer to stop when the key is turned off. If it leaks real bad, the car will not stop at all.

I'd check where the vac lines go through the firewall. On my 300SD I had two fail right at that point. Not sure why, it wasn't a sharp bend or anything. Could be vibration perhaps. When trying to find the leak, I just wiggled them a bit and the bad one broke right off.

The task is to determine IF there's a vacuum leak - somewhere in the car. The engine's vacuum pump provides the vacuum for the power brake, the engine's controls and the "comfort system" (door locks & climate control). That comfort system is the prime suspect for a vacuum leak, IMHO.

My '80 300SD has two vacuum connections to its vacuum pump: the large one for the power brake etc and a small line for its "comfort system". IMHO you need to find the source connection for your car's comfort system and put the tester onto that line. If there's a leak then the door locks are the next suspect to be checked.

My 300SD has a white vacuum control valve on the top rear of its injection pump; its function is to regulate the vacuum to the automatic transmission's shift modulator based on the throttle's position; your

240D may be the same. Don't touch this valve, its not adjustable and quite expensive to replace if damaged.

The engine shut down device is located on the aft end of the injection pump, facing the oil filter; it has one vacuum line attached, it's probably dark brown.

Hope this helps you.

Thank you Trader4 for the info.

I traced the lines I mentioned in the last post and found that the dark brown tube is redundant and plugged. One of the light brown lines goes from the T on the 3/8" line to the steering lock and then back to the injection pump - the return leg has a faint bluish stripe in it. The tubes pass through a rubber grommet in the firewall and they are well protected there. They look almost like new.

Yesterday I tried to start the car, after a week of being idle, and it was slow to start, so I bled a litttle more air from the fuel line. In the previous week I replaced a gasket between the injection pump and the engine block, so I had to take out the pump and all the fuel lines around it. Yesterday after it started I drove around the block. Finally I turned off the ignition and the engine stopped immediately, so I guess the vac line to the pump is working ok. It seems to me that this doesn't solve the problem of the spatters on the air filter.

Tomorrow I will start the engine and check the vacuum level in the 3/8" line with it attached to the brake unit and with it disconnected. I don't like the noise the engine makes in this quiet neighborhood and tomorrow, Monday, is a better day.

Have a great week :-)

Thank you TG for your effort.

-->> T.G. Lambach the engine's controls and the "comfort system" (door locks & climate

We are agreed on the task ahead. The car was deliberately "designed" by me and ordered about 6 months in advance. There is NO "comfort" system. I am a mechanical engineer and am a great believer in simplicity. I intended to live near the west coast and again deliberately avoided A.C. Any forays inland are restricted to the cooler times of the year.

The large and small connections are the same as on mine, except that the small connection goes to the steering lock only. There is no vacuum lock system on mine.

Again I have NO auto transmission. I was acutely aware that the mechanical gearbox requires almost no maintenance in stark contrast to the auto transmission and requires less juice. Besides all that, having to change gears while driving, helps to keep me from falling asleep :-)

I know about that unit now - the injection pump is the M / RSF type. The device is 1.5" diameter x about 3/4" deep, located on top of the pump - just behind the rear injector - and the center is about 4" from the rear of the injection pump. On mine the line is light brown color.

It does help. Thanks.

So you have a real "simplex," a manual shift 240D. In that case the only vacuum leak possibilities are the brake booster and vacuum reservoir. Either of those, however, would have a massive vacuum leak that would manifest itself in a very "hard" brake pedal for lack of power boost.

Back to the original question of oil spots from blow-by; how many miles on this engine?

Thanks TGL.

-->> T.G. Lambach In that case the only vacuum leak possibilities are the brake booster and vacuum reservoir.

It seems like there is no leak. I attached the vacuum pump to a redundant line inside the car that branched off from the main line from pump to brake booster and, with the engine running of course, the vacuum was 23".

I drove the car recently after replacing the gasket between the engine block and the injection pump and the brakes were quite normal. They are now too. In case my air filter was too plugged up, I replaced it with a new one but it was no help.

90,280

While the engine was running I noticed much more smoke than usual from the exhaust and it seemed that the engine was noisier than usual. I had to make a few attempts to start it. Normally, at least 90% of the time it runs on the first attempt

This is getting deeper and deeper and I am clinging onto the brim :-)

When you reinstalled the injection pump how did you time the injection?

The reason I ask is the engine noise that you mention and the smoky exhaust. I suspect the injection timing is too early (advanced) which would account for the noise, hard starting and possibly the smoke.

Did you align the intentionally missing tooth of the injection pump's gear with the mark cut into the flange in the pump?

Remember those slots in the injection pump's mounting flange? They allow the pump to be turned - moving its top toward the motor advances the timing, away retards the timing. It doesn't have to be perfect but ought to be close.

If you didn't time it there are various "how to" posts on the internet that you can review.

-->> T.G. Lambach

Thanks again TGL.

I did not rotate the shaft in the pump. I did pull off the sleeve that covers the gear on the end of the shaft to inspect the o-ring for damage. There was no alignment mark on that sleeve but there was one on the pump shaft or a gear and on the pump body and they were NOT aligned. As I just wrote, I did not rotate the pump axle, so it went back into same place in the car engine that it came out of. I doubt that it would be physically possible to rotate the pump by hand. Of course the car engine did not rotate either.

There is a small section in the manuals about that alignment - the engine crankshaft is rotated to a certain angle and then the mark on the pump gear or axle is aligned with a mark on its body. Finally, they are "mated." :-) This description was intended for REPLACEMENT pumps.

You're right. So long as neither the IP shaft or the crankshaft was moved the basic timing was preserved.

Now, did you reinstall the IP exactly as it came out (using scribed marks on its slotted mounts)? If not, then the injection timing is somewhat "off"; by your description it's probably a bit too advanced.

You could retard the injection a bit to see if you note any difference. A retarded engine starts easier, is quieter but, if way too retarded, will lack power.

-->> T.G. Lambach You could retard the injection a bit to see if you note any difference.

I guess that means aligning the engine crankshaft and then taking off the cylinder head cover and doing another alignment there?

Today I replaced the main fuel filter and, while priming it, noticed a stream of fuel flowing down. It seems like the washer in that manual pump is failing. The movement of the pump cap up and down was less than + or - 1/4".

Thanks again TGL for your help :-)

I guess that means aligning the engine crankshaft and then taking off the cylinder head cover and doing another alignment there?

No. I mean to retard the installed injection pump - its top should be turned away from the engine. That's IF the injection timing is too advanced. Read about how to check that with a "drip tube" or other method. Then you'll know for sure if it's right.

You can get a replacement hand prime pump, they are inexpensive, mabye $20.