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  #1  
Old 01-09-2012, 10:08 PM
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Location: Milford, Nebraska
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Oil Leak 300 SDL, Any Ideas?

I've owned this 1987 300SDL for just over a year now, put on about 45,000 very trouble-free miles. This car has been taken good care of since new, and has all the records to show it. It's a very comfortable ride, and looks almost immaculate.

Here's the problem I'm having with it now. It's developed an engine oil leak that I can't seem to locate the source of. It's leaking down the driver's side towards the front of the engine. I've wiped down the oil cooler hoses and they stay dry, wiped the underside of the IP, and it's dry. Everything under the PS pump is wet and covered, especially the AC compressor. Any ideas what's under there that'd leak engine oil? I'll probably start disassembling next weekend, but thought I'd ask you folks if you had any ideas of where to start. I've never needed to add oil between changes (5K on Mobil 1 TDT 5w40), but have added two quarts in the last week, and it's puddling pretty good. Thanks!

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Old 01-09-2012, 11:21 PM
Ron59b
 
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Location: Richmond, Virginia
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Try checking the turbo return oil seal.
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Old 01-10-2012, 12:46 AM
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Front main.

Vac pump
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'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

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Old 01-10-2012, 01:32 AM
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If it's engine oil, where the IP connects to the block. Did you adjust IP timing recently?

If it's PS fluid, either the pump front seal (telltale is oily backside of pulley) or seals between the reservoir and pump body (I've had those fail).

Sixto
87 300D
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Old 01-10-2012, 09:40 AM
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Thanks for the ideas! I'll hopefully have time to investigate it closer this weekend. It's definitely engine oil, and everthing in that area is soaked. It doesn't look like the front main, or the IP o-ring, though I've had them leak on my 190d before. Where does the turbo return line come back to the engine at? I would've thought the other side?
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Old 01-10-2012, 01:31 PM
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Ok ,Ive had your same issues on a 2.2 .,basically the same motor up frt as yours .I took off the vac pump and replaced the gasket with some resolve.I also come across some intersting info on another possible source for leaks,this piece is sealed not by a gasket but a special compound liquid gasket out of a tube.Its somewhat like a timing cover and to remove you have to pull the frt pulley , if you do this you might as well replace the frt seal since its on the piece.I posted a thread last week ,Search This on this forum, Anyone ever had this break?.This was my thread and a search should pull it up.It has a good pick of what Im talking about.You might drain oil and goop some good gasket in a tube to help at the seams of this piece ,it must be very clean and complete if its to hold,also at the dip stick tube were it enters the piece,it just wont be permanent,Ill be trying this at the oil tube on mine to see if this is were Im getting my leak from.Good luck.

Last edited by chasinthesun; 01-10-2012 at 01:44 PM.
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Old 01-10-2012, 01:46 PM
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If you have the old style vacuum pump, the gasket can harden to where the crimped on cover can't hold the seal.

Sixto
87 300D
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  #8  
Old 01-13-2012, 07:40 PM
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Yep, it's the vacuum pump. Up in the air, with the lower panel off, it's dripping pretty good, looks like right out of the pump.

Any trick to replacing? It's the original I'm pretty sure, so I guess I'm glad that an oil leak is forcing replacement rather than it coming apart and getting into the engine.

Peach Parts shows two different brands, though the pictures of each look the same. Should I have a preference of brand?

I appreciate the help!

-Russ
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  #9  
Old 01-13-2012, 08:11 PM
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The serpentine belt and tensioner will have to come off so it's a good time to check the tensioner arm and pulley bearings for smooth quiet operation. A tensioner arm that clicks as it pivots is bad. The tensioner arm is held to the front cover by a bolt that takes a 12mm hex bit. There's a washer between the tensioner arm and front cover that tends to appear an integral part of the tensioner arm and doesn't come with a replacement tensioner arm. Make sure you keep the washer and reinstall it.

Unless you have multi-jointed tools, it helps to remove the power steering pump pulley for clear access to the vacuum pump bolts. Loosen the power steering pump pulley bolts before removing the belt. If you read this too late, use a long screwdriver with a square shaft section to hold a couple of bolts while you loosen one. It'll make sense when you see it.

There are special tools to remove the fan. I get by with an 8mm hex key and a deep socket and breaker bar for the bolt through the fan clutch, and this pulley holder - Pulley Spinning Tool

There is a metal basket in the vacuum pump cavity. Very early engines require a dam gasket which doesn't fit with the basket. Simply remove and discard the basket. Other engines can take either the dam gasket without the basket, or a metal outline gasket or a fiber outline gasket with or without the basket. Are you with me? It's not a fitment issue. You can fit an outline gasket on an early engine and presumably cause problems. Phil should be able to help you or just use a dam gasket if that's what comes with your pump. Or trust Dave M./gsxr like most of us do -



From what I've heard, folks who order the Hella pump get a pump with Pierburg markings. Maybe Phil can enlighten you.

Sixto
87 300D
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  #10  
Old 01-13-2012, 09:33 PM
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Thank you sir! Very good information. I'll call Phil first thing Monday and get parts coming, I'm needing several other things as well.
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  #11  
Old 01-14-2012, 05:19 AM
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Spend the extra cash for the Pierburg unit. I have the same on my SDL.
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'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

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  #12  
Old 01-25-2012, 12:10 PM
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Replaced the vacuum pump, oil leak is gone! Thanks for the tips guys, it was really leaking! The internals looked good, bearings are smooth and all parts were intact. I used the "dam" gasket as that's what came with the new pump, and I removed the basket.

I ordered the Hella unit from Phil, expecting a Pierburg like several of the folks on here have done. I got a Febi pump. Phil says they've been fine, and since Febi is a "Bilstein" company and so many here seem to be in love with Bilstein shocks, I'm hopeful their VPs are good as well. Back to driving one heck of a nice car! Thanks again for the help! Russ
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  #13  
Old 01-25-2012, 12:41 PM
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Did your 'Febi' pump actually have 'Febi' stamped on the body, or was the Febi name just on the box? Most people receive what's shown on the right side of the photo below:



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  #14  
Old 01-25-2012, 03:32 PM
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Mine didn't say Pierburg or have any casting marks or grind marks at all. It had a Febi- Germany sticker on it. The box did say Made in Germany, but who knows for sure. The screws in the top cover definitely looked like better quality than how a chinese screw typically looks- burrs and a general roughness. These were well polished, as was the components inside. I hope it's a good one!
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  #15  
Old 02-15-2012, 09:02 PM
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300SDL Vac pump oil leak

Along the line of this thread, I had an oil leak just like yours, and couldn't tell where it was from. So I just ordered a new front crank seal and a new vacuum pump seal. Replacing the front crank seal made it clear that it hadn't been leaking. Replacing the vacuum pump gasket, I saw that the old one had been leaking. Putting in the new one, I managed to over-torque the bolts and a couple of them snapped off as soon as I started the car. Fixed the problem and torqued them correctly, and used some gasket seal to boot. After all this, the leak is now exactly like it was before I started. It still looks like it's coming from the vacuum pump, but I can see that it's not coming from gasket-sealed seam, but rather looks like it's coming from the metal cover on the front of the pump. Can this be? I didn't think there was any oil in that part of it.

thanks!

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