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Old 07-08-2005, 04:33 PM
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Join Date: Jul 2005
Location: long beach
Posts: 99
Question nasty oil leak

Hello! I am new here. I recently acquired a used 88 300e with 116k miles on it. the problem is that the car has several oil leaks that are hard to locate. there is oil seeping from where the trans meets the block making it seem like a rear main seal. there is a plastic allen plug on the bottom of the trans and I'm wondering if it is really supposed to be there. I cleaned it up to get a better picture of the leaks origin. oil is also leaking down the block and around the trans from the rear passenger side of the motor. I spoke to a mechanic(on the phone) who said it is most likely the head gasket. the puzzling thing is that oil is dripping down the exhaust manifold and the intake manifold also. I removed the valve cover only to notice that it was never tightened down to begin with. I took it off and added some sealant to the gasket and tightened it down. the leak is still there so the valve cover could not be leaking. I'm clueless why oil would be in the exhaust man if this leak is related to the head gasket. any suggestions? where would be a good place to get affordable replacement parts? thanks for your help.

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Old 07-08-2005, 04:39 PM
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Join Date: Jun 2005
Location: NJ
Posts: 1,182
If the torque specs for the cam/valve covers is the same or similar to my 85 v8, then when loosening the bolts you may think they were never tightened. Very little tightening for cam covers.

You may want to degrease your engine to find the source of the leak...when I bought my sel, the seller and I thought the rear main seal was leaking but it turned out to be a valve cover gasket leak.
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Old 07-08-2005, 06:42 PM
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Location: long beach
Posts: 99
I was able to turn them with a nut driver. after I loosened a few, I did the rest with my fingers. I know the leak is from the rear of the motor obviously, its just such a tight spot to get into and look around. the mechanic said to clean it off real good and run the motor and check it. I tried but there seems to be no room to do this (cleaning). I might need to invest in a small telescoping mirror or just start ripping stuff apart to get a better view.
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Old 07-08-2005, 09:14 PM
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Join Date: Feb 2005
Location: Frederick, Md
Posts: 4,540
116K is not unusual for it to need a headgasket. almost EVERY single one I see needs the headgasket replaced, all leak oil at the front and rear on the passenger side of the engine. Do the headgasket and see how much of the leak it fixes.

the plastic allen plug in the trans is just there to keep the torque converter in when the trans is removed from the vehicle.

1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350
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Old 07-10-2005, 03:59 PM
Robert Ryan
Join Date: Mar 2005
Location: Bay Area, CA
Posts: 222
the M103 motor typically develops oil leaks at the "timing cover at top" and at the back of the head from a bad head gasket. The timing cover at top is covered in the DIY section, and is about a 2 hour job for the diy. the head is a different story. oil from the timing cover will run down the engine and flow towards the back. Oil from the head will run down the back where the motor meets the tranny, then turn towards the exhaust manifold and drip onto it.
89 300te 222,222
92 300e 190,000
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Old 07-11-2005, 06:36 PM
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Location: long beach
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I cant seem to understand the idea of oil from the headgasket seeping upwards toward the exhause manifold and running down it. the car is not being driven. I prob have a combination of leaks including a rear main seal. where would be a good place to order gaskets and parts? affordable and oem stuff. thanks much.
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Old 07-12-2005, 05:20 PM
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Location: long beach
Posts: 99

I waste time waiting for a repair manual so I know what tools to get and torque specs to use. this cd is useless. I have to order something else or just wing it. I am going to start disassembly for the head gasket. anybody want to share some torque specs and tips with me? sigh!
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Old 07-12-2005, 07:06 PM
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Join Date: Jul 2002
Posts: 1,141
What cd is useless?

The factory cd is quite good. Head bolts are stretch bolts and you should only buy the headgasket from the dealership so you get the latest version.

On oil leaks, there is also a TSB against rear crank seals. I believe the seal housing has been revised if yours is leaking- you'll need to get the updated housing. Assuming your engine # pre-dates the change.

Do a search to get "headgasket replacement M103".
Should be a bunch of stuff.

Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E
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Old 07-12-2005, 09:19 PM
Join Date: Oct 2004
Location: Johnson City, TN
Posts: 985
If you jack up the car on the passenger side, remove the under-engine sound shield and crawl under there with a flash light while the engine is running you can visually see the join line between head and block. You should be able to determine whether the head gasket is leaking.

Valve cover gasket uses no sealant.

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Old 07-13-2005, 07:06 PM
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Join Date: Jul 2005
Location: long beach
Posts: 99
I see the line. there is oil on the exhaust manifold nuts and such which are above this line. I got the exhaust manifolds off and am taking off the intake manifold. the nut and bolts on the intake man are somewhat hard to get to. you either need to use tiny tools or have very tiny hands to get the bolts on the bottom. I bought a useless manual online (read the thread about ebay manuals). so I'm just winging it.
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Old 07-13-2005, 07:16 PM
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Join Date: Jul 2005
Location: long beach
Posts: 99
some of the studs for the exhaust man came off when I was removing the nuts. do I need a special tool to put these back? also does anybody recommend replacing the timing chain? 116k 88 300e
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Old 07-14-2005, 08:40 PM
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Join Date: Jul 2005
Location: long beach
Posts: 99
I'm having trouble taking off the intake manifold. I got all the bolts out that I can see. I took off the nut towards the center of the manifold, the one blocked by the cold start injector I think. its pulling out towards the front of the engine but the rear wont come loose. I can see the gap when I pull on it. I have the manifold bracket below removed. I cant see what is still holding on. it wiggles and jiggles but wont come loose. helpp meeeee

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