Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

LinkBack Thread Tools Display Modes
Old 08-21-2017, 11:26 AM
Registered User
Join Date: Jul 2015
Location: King George, VA.
Posts: 148
New owner maintenance 1991 300SE

Hello all,

Yesterday I purchased a 1991 300SE. In great shape, 181K miles with service history at the local Mercedes dealer going back to when it was purchased new.

The fuel pump is very noisy and i think a replacement might be in order pretty soon, and after driving if it sits for about 30 minutes or longer it can take a couple tries to start. From what Iíve read that may be linked to injectors leaking down?

As with all new (old) purchases i will get maintenance items up to date.
Aside from basic stuff like fluids and filters is there anything this car / engine (M103) could need that might be overlooked?


Attached Thumbnails
New owner maintenance 1991 300SE-00y0y_bfioc6kcmko_600x450.jpg   New owner maintenance 1991 300SE-20170820_152719.jpg   New owner maintenance 1991 300SE-20170820_152740.jpg   New owner maintenance 1991 300SE-00d0d_5iqvzeuyj4u_1200x900.jpg  
"It's what non-car people don't get. They see all cars as just ton-and-a-half, two tons of wires, glass, metal and rubber. That's all they see. People like you or I know, we have an unshakable belief that cars are living entities..... You can develop a relationship with a car, and thatís just what non-car people don't get."
-Jeremy Clarkson
Reply With Quote
Old 08-21-2017, 12:10 PM
ps2cho's Avatar
Registered User
Join Date: Jun 2006
Location: Chandler, Arizona
Posts: 3,523
Trouble starting after some time sitting can be a number of things - likely residual fuel pressure related. You'll need to get a fuel pressure gauge to help diagnose. It could be a half dozen things...fuel pump check valves, accumulator, cold start valve, injectors, fuel pressure regulator, eha/seals etc. The Harbor Freight "master" fuel kit comes with CIS-E adapters.
2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k
Reply With Quote
Old 08-21-2017, 12:22 PM
oldsinner111's Avatar
love all animals
Join Date: Nov 2008
Location: bristol,tn
Posts: 5,716
beautiful,don't over look flex disk
seems there is hope after all when folks come together
Reply With Quote
Old 08-21-2017, 12:53 PM
TX76513's Avatar
Platinum Member
Join Date: Apr 2003
Location: Brandon, Mississippi
Posts: 5,203
A non conventional approach to a newly acquired used vehicle is to source common problems with "Year/Make/Model" and see what pops up. Auto MD is a good source or you can simply Google those terms and compare the know problems with service records - if you are proactive. Also the maintenance manual from MB is online.
15 VW Passat TDI
00 E420
98 E300 DT
97 E420 Donor Car - NEED PARTS? PM ME!
97 S500
97 E300D
86 Holden Jackaroo Turbo D
86 300SDL
Reply With Quote
Old 08-21-2017, 03:54 PM
Home appliance genius
Join Date: Jul 2009
Location: cleveland
Posts: 1,160
1. High quality ignition tune up. Plugs wires cap rotor. If you want to be bold pop a new ignition coil in too. Bosch or genuine parts only.
2. Look at flex discs
3. Try a bottle or 3 of redline fuel system cleaner. It's good stuff. If that makes no difference buy all new injectors.

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2
Reply With Quote
Old 08-21-2017, 04:37 PM
Hit Man X's Avatar
Join Date: Sep 2004
Posts: 9,086
Thumbs up

When was the last time anything was done to it? Does the odometer still work?

I would start with all rotational accessories as they wear pretty quick. Idlers, tensioner probably (100k is a good life from it), fan bearing bracket (mind that o-ring!), and a fan belt. Maybe a water pump if you have to do the tensioner. Sachs are the only fan clutches that work worth a damn. Then at least spark plugs, but give that cap and rotor a good eyeball. Service all fluids.

Inspect the rubber related to the CIS system closely. $100 and you can reseal it all in an afternoon. Stick with OE only, all else is crap. Same with the breather hoses and valve cover gasket.

Tint the glass to preserve the interior. Condition the leather big time.

BTW, car looks great!
I'm not a doctor, but I'll have a look.

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

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.
Reply With Quote
Old 08-21-2017, 06:37 PM
85 DSEL's Avatar
Documented User
Join Date: Oct 2006
Location: Dayton, Ohio
Posts: 1,027
For me, I found THIS VIDEO very helpful as well as pretty much on the money for mine. Worth a look...hope it helps point to a solution! All the previous posts are helpful as well.

EDIT: This may or may not be pertinent to your FI system. This is for the CIS style.
1995 W124 Wagon


1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
2006 BMW 330Ci 110K - SOLD
Reply With Quote
Old 08-24-2017, 02:59 PM
Registered User
Join Date: Nov 2006
Location: Houston Texas
Posts: 2
Apart from the obvious (all fluids, plugs, leads, dist cap and coil) I would suggest Leatherique Restoration Products for the seats - get their Prestine Clean and Rejuvinator, it is really great stuff - and if the tires are even vaguely questionable get some Michelin's - if cheaper tires have been fitted you will notice a huge difference with decent tires.

Last edited by Luccia at Pelican Parts; 08-25-2017 at 01:12 PM.
Reply With Quote
Old 08-26-2017, 01:36 AM
Registered User
Join Date: Jul 2014
Posts: 8
Fitts07--- yeah, it's probly not worth your time and $$. I'll just take it off your hands for, hmmm, $1000 ?

Just kidn, enjoy your great find !!
Reply With Quote
Old 08-31-2017, 11:30 PM
Registered User
Join Date: Jul 2015
Location: King George, VA.
Posts: 148

Thanks for the kind words and pointers. I started with the basics; oil/filter change, air filter, an OE expansion tank cap and I got a new hood ornament.
Also started cleaning out all the leaves from down in the false firewall. I was surprised with how quick it is at interstate speeds.

Some things I noticed-
-the threaded freeze plug on the passenger side (USA) of the engine is leaking coolant. It looks like itís been leaking for a while. Iíve done some research on it and it looks like id have to pull the rear exhaust manifold then replace the freeze plug and O-ring. The PO put green coolant in it, and the water pump I think is weeping around the pulley shaft seal.
-it constantly smells like burnt oil, no apparent leaks at the valve cover. The underside of the engine is very wet with oil along with the bottom of all the accessories (alternator and whatnot), it looks like it comes down from behind the harmonic balancer then all over the oil pan. I donít know if that would be the timing cover, the front main seal or both. It doesnít drip oil in the driveway, maybe a very small spot if it sits over the weekend.
-all the under engine plastic pans are missing.
"It's what non-car people don't get. They see all cars as just ton-and-a-half, two tons of wires, glass, metal and rubber. That's all they see. People like you or I know, we have an unshakable belief that cars are living entities..... You can develop a relationship with a car, and thatís just what non-car people don't get."
-Jeremy Clarkson
Reply With Quote
Old 09-01-2017, 06:03 AM
Registered User
Join Date: Aug 2002
Location: Southeastern PA
Posts: 3,035
Fitts07, if the PO had this vehicle serviced at a MB dealer then their recommended maintenance was ignored ... likely to save money. No MB Service Department would use other than MB coolant (now blue, instead of the previous amber color), nor would they ignore weeping freeze plug. It's likely the timing chain cover is leaking oil which coats the front of the engine and the oil pan. If the engine isn't burning oil outright, the burning oil smell is due to leaking oil on the hot engine. It's likely that new valve stem seals are needed. As you mentioned in your first post the engine likely needs new fuel injectors. Very few owners are selling well-maintained vehicles with absolutely no problems. A pending major repair encourages a sale. Check a local salvage yard for a sound encapsulation panel that belongs under the engine compartment. The former one was probably a mess from dripping oil and the PO tossed it. Recommend buying a rebuilt water pump from your local MB dealer.
Fred Hoelzle
Reply With Quote
Old 09-01-2017, 06:27 AM
Registered User
Join Date: Jul 2015
Location: King George, VA.
Posts: 148

It actually has maintenance history from the dealer all the way up to 150k miles. Including 2 head jobs, one at 40k and the next one at 147k. The one at 147k included guides and seals. I really think it's just leaking oil, even still it's only down a hair from full at 600 miles on this oil change. At is current rate of drop I think I could make it to about 2k miles on this oil change before getting to the min mark and having to add. I'll put mercedes coolant back in it after I do a citrus flush and replace that freeze plug. I might gut the cats while I have the manifolds off.

I've done some reading / research and it does sound like it's the timing cover. I feel like that's a pretty easy fix.

Are the encapsulation panels just for sound? Do they serve any other purpose?
Reply With Quote
Old 09-02-2017, 10:41 AM
Registered User
Join Date: Jan 2003
Location: Dallas
Posts: 787
The oil leak is VERY likely the little U-shaped seal just under the small upper front timing cover. this is the number 1 spot for oil leaks on the M103 - replaced mine maybe 6-7 times in the last 26 years. The head gasket can leak oil from the pressurized oil passage near the front exhaust side; and it's hard to tell which is the culprit; but obviously do the $3 little seal first - do a search here for details, not a big job. Valve cover gasket runs down the rear when it oozes - piece of cake, replace on principle. My front crank seal has never leaked.
If the freeze plug you mentioned is the plug with a hose nipple for draining the coolant, then it's just screwed in, no gasket or o-ring. They can get really tight, but can be easily sealed with gasket goop.
Zerex G-05 coolant, still pretty easy to find. drain the rad by removing lower heater hose; drain block thru the above mentioned plug. water pump replacement requires a certain "agility".

Mine has ALWAYS had a warm starting glitch - let it sit more than 20 minutes and it will not hit on the first try, but always on the 2nd. I just hit it for about 1 second, turn it off and hit it again and it fires right up. In my humble opinion, this problem cannot be solved; the dealer worked it unsuccessfully about 25 years ago, and I've fiddled with it periodically ever since then, maybe 100 times; injectors, pump. filters, pressure, ignition, CIS, EHA; yadda yadda. Never gotten worse or better.

Oh, check the right motor mount, they collapse; should be able to put a finger between the heat shield and the lower metal section of the mount.
Cheap ones last two-six weeks!!!!! OEM are hard to find and cost $100.

Upper control arm bearings are the squeak monsters - Aftermarket ones last about a month, unless you take them apart and grease the heck out of them - then you can get a year or two.

Put the car in reverse and see how long it takes for the shift to take place. If it's longer than 2 seconds, prepare for tranny clutch plates - ouch!

Ah, old memories, but I've forgotten much more than I've learned in 26 years with my old '91. But it's all in here, lots of good search material.

Enjoy it; pretty good old cars.

Reply With Quote
Old 09-02-2017, 01:59 PM
Jorn's Avatar
Registered User
Join Date: Nov 2003
Location: TheFlyingDutchManInHollywood
Posts: 5,498
And lube the sunroof with proper Mercedes grease if you want to enjoy it for the coming years. It was the first thing I did, before all that's mentioned above and more. I've spent close to $2000 just in parts in the last year after I purchased it and I'm sure I have an other two grand to go...
Black on Black 1979 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE
Reply With Quote
Old 10-15-2017, 06:41 PM
Registered User
Join Date: Jul 2015
Location: King George, VA.
Posts: 148
Hey all,

Thought I would update the thread.

I got the car caught up on maintenance.
So far I have:
Greased throttle linkage
Installed new fog light lenses
Painted the grill
Buffed some of the car out
Disabled the egr (it was broken )
Clear turn signal lenses
Replaced the leaking freeze plug
Flushed coolant with citrus
New G05 coolant
New expansion tank and cap
Rebuilt the windshield washer resivior (all rubber bits )
Changed the oil and filter
New battery
Replaced air filter
Painted air cleaner housing
Painted the valve cover
Changed valve cover gasket
New plugs and wires
Replaced upper timing cover seal
Cleaned leaves out of false fire wall
Replaced injector seals
Replaced fuel filter and pump
Changed transmission fluid and filter
New modulator cap
New transmission cooler hoses
Cleaned rear axle vent
Changed rear axle oil
Cleaned / oiled wiper drive linkage
Refinished shifter console wood
Replaced gears in the odometer
Greased sunroof tracks
General cleaning inside and underhood
Replaced flood lights under doors

I still need to get new tires, but I broke a lug nut off on the driverside front and rear wheel. Once I get that figured out I'll take a look at the brakes. Motor mounts, and flex discs are on the list too. My defroster vacuum pod needs to be replaced also.

Great car, runs good. I get about 23 mpg highway commuting to work.

"It's what non-car people don't get. They see all cars as just ton-and-a-half, two tons of wires, glass, metal and rubber. That's all they see. People like you or I know, we have an unshakable belief that cars are living entities..... You can develop a relationship with a car, and thatís just what non-car people don't get."
-Jeremy Clarkson
Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 02:24 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page