If you have an older w126 class car, like a 1986-1991 420 or 560 SEL, I highly recommend you have a look inside your oil plan.

I opened mine up, and found the lower portion of the oil pump, which is made of rubber, broken into 2 pieces. The rubber was rock hard. I also found the remenants of a broken chain rail. If you have never replaced the lower portion of your oil pump, at least look at it, because it maybe well overdue for a replacement.

While the pan is off, you may as well replace the 'O' rings on the oil level indicator guage terminal, protruding through the block on the passenger side. The 2 'O' rings become hard and brittle and the inner one begins to pass oil. The rings are cheap, less than $1 each.

It was very easy to replace the lower portion of the oil pump. Just watch out for the 2 nuts, on the AC compressor bracket, which are connected to the pan screws. Remove the nuts first!

Joe

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1989 420 SEL

I am preparing to replace the lower oil pan on my 91 560 SEL. The oil pan is badly bent and there is some seepage at the gasket. I guess my daughter ran over something in the parking lot.

I was wondering if there are anything that I should be cautious about in performing this procedure. You mentioned some rubber on the oil pump and o rings to be replaced as well. Is there anything else?

Do I need gasket maker for the gasket? or just wet with oil?

thx
emmy

My oil pan had a dent in it too. The bottom of the oil pump had to be replaced beacuse it was broken. Yours may need to be replaced too, because the rubber gets very hard and brittle from the heat. The rubber sits snug against the bottom of the oil pan and may have broken upon impact. You may want to be prepared to replace the part, or think of a contingency plan in case the part needs to be replaced. The part is not expensive, less than $20, from the dealer, but it may have to come from a regional warehouse, so it may take a day for delivery.

Next, watchout for the screws on the AC compressor, there are nuts on the reverse side on 2 screws. Remove the nuts first. All screws on the pan are the same size, except for these 2 screws.

I did not lube the gasket. I just put it on dry. I recommend all surfaces contacting the gasket be throughly cleaned. I believe I torqued to 10 nm on the final pass. I put the screws on at 7 NM and made a second pass at 10 NM. Two of the washers split, so you may want to have a couple of washer on-hand. I have had no oil leakage in 2,500 KM.

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1989 420 SEL

Had replaced the oil level sending washers a few years back, so they were good. Used RTV Copper the first time, very thin, and never got a good seal. (in fairness, my ex-wife hit a barrier a few days later, big dent in pan and leaked forevermore) This time, i replaced the pan and sealed the new gasket with (common brand name, not coming to me now) HPF which stands for High Performance Formula. No drips, no runs, no errors. Did the pan a few weeks after finishing chain, rails, head gaskets. Lots of residual "crumbs" in the pan.
Cigar--if You found a bit of rail, have you checked your rails? When my upper left one broke, it also broke a lower rail (found a piece in the oil pan and it had the part number on it which i referenced through FastLane. Closely inspect the piece You found.
Emmy--it's a fairly straight forward job, but don't overtighten the bolts. i think the torque spec on my 560 was only 5 or 6nm, pretty light. i probably am closer to the 10 that Cigar used, but did it by feel.

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Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)

thank you both for your input. I will be ordering asap the oil pan , gasket, and front disc /pads at the same time...yes, i will also be working on my front brakes....my short term weekends are going to be interesting...

Earl:
depending on what I find inside, I may go for chain, tensioner, rail replacement in the near future...you will be hearing from me..i hope you do not mind. my car is at about 150,000 and not sure if the chain has been replaced..( ie i have owned the car for 4 years, and some 30,000 miles ago..)

thx,
emmy

Emmy,
i've only done it once, the hard way--had to remove the cover due to broken lower rail--so i'm by no means an expert. Will offer any info i can though. Shoot, if You are within a 4 or 5 hour drive, i'd come lend a hand. For that matter if You are somewhere warm i'd come just to watch!!
If You've driven her from 120,000 to 150,000, i'd at least pull the left valve cover to get a good lookat the rails on that side. If the valve cover gasket isn't too brittle (and even if it is) it should go back on with no leaks. If the big bolt head on the end of the tensioner has a swab of paint on it, it's probably original.
Good luck on the brakes, i think i'm going to do mine in the spring with a low-dust pad. Not sure what pads yet.

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Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)

Relative to emmydotnet's question - you guys all missed an important but not critical step.

Drain the oil before removing the pan.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

It's not THAT important. If you don't drain it first, it comes right out anyway.
Even after it is drained, there will be a few ounces left in the pan. Good to put the drain plug back in at least finger tight before removing the pan. May save a few drips on the floor.

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Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)