scottonfire

Hi guys,
Long time poster, first time reader.

Just kidding. So I'm buying a 2005 C230 and I took it to a mechanic to check it out. It has 80K miles and is in pretty good condition (carfax has it listed as $1,300 above blue book too). So the mechanic found 3 leaks. Vacuum pump (I'll fix that), upper gasket leak (i'll fix that) and Rear main seal (nope).

So, if I don't fix the rear main seal leak, will this hurt the car in any way if I make sure it always has enough oil? What's the worst that could happen? Just catching fire and exploding right? lol.

But seriously, at WHAT POINT does the rear main seal leak become something you NEED/MUST fix? Or do you just run it for another 50,000 miles and pass the problem down the line?

Carsy

A few questions to help the list.

Is it the rear engine or rear gearbox seal ?.

Is the gearbox manual or auto?

How many clix has the car done?

scottonfire

1) It's the rear crankshaft main bearing seal

2) Automatic

3) what?

Carsy

How many miles has the car done?

Rear engine seals leaks only become worse over time. At least it is not leaking into a manual clutch.

If it develops it may affect your yearly inspection & roadworthyness ?

Why not get a quote on the repair & that will make the decision for you.

scottonfire

oh, car has 80,000 miles on it. The quote is $850 which is my current budget beyond the sale price. I would rather put $850 toward fixing the vacuum pump, valve cover gasket seals, upgrade the grille and leather boot, and replacing the engine mounts and deal with this one later. Unless later spells disaster. How could this affect my yearly inspection?

samaritrey

Well my rear main seal has been leaking for going on 100k it gets worse some months and better others I average 1 quart every 1-4k miles depending on highway vs city miles. I drive the car hard which doesn't help the situation. That said I check it very often and always am ready to top it off when needed. That said if you have yet to buy the car try to negotiate price down maybe they can meet you in the middle of the $850 and you can just get it out of the way the mobile 1 0w-40 can get expensive to keep throwing away. You also would want to get the transmission flushed and the rear dif and most importantly timing chain!!
Also remember the golden rule of buying an old Mercedes Don't!! lol but seriously make sure your budget can always handle a $1,000 repair at the drop of a hat as old Mercedes love to do that to most people (except for me Knocking on wood vigorously)

flying_whale

Agreed, except the part about buying an old Benz, I love my old Benz. My rear main seal has been leaking for 10K miles now and I throw in a quart every 2.5K miles. And I drive it hard. You can check the oil level (at least in pre-facelift models) by turning the key all the way WITHOUT starting the car and scrolling through the menu via the steering wheel buttons. Make sure you are on a flat surface, and, ideally, you've warmed up the car and then let it sit enough for the oil to come back to the pan. My C320 also warns me if I need to add oil.

mleskovar

No, if you keep the underside relatively clean and don't let the leaked oil build up on something that it shouldn't...like electrical connectors or rubber bushings/mounts. Manual clutches don't do well with oil and if the leak is bad enough it could contaminate it.

1. When it reaches the street and contaminates the environment or just plain stinks. 2. When it leaks so much that you can't keep up with topping it off.

How much does it leak

scottonfire

I'm buying it tomorrow. From what I could tell, it's not 'leaking' per say, but the rear seal was covered in oil, hence the 'leak.'

For my budget, I think the best option is to stick the rear seal leak on the back burner, blow the dust off this 145 iq and head down the DIY path.

I'll dive in with an air and carbon filter change, replace the vacuum pump, then maybe go for fixing the valve cover gasket leak and replacing the timing chain. Me thinks the tranny flush'll be the only thing I'll have a mechanic do for now.

thx everyone for your input! I'll most likely be lurking about as I learn how to be mechanically self reliant.

samaritrey

If you can do an oil change you can do the transmission flush it is easy. You just need to be able to get the car up enough to get under it and keep it relatively level. If you can do that you are all set. You will need the transmission dipstick which can be found on eBay very cheap and a temperature gauge to keep an eye on fluid temperature so you can get an accurate reading ( I got an IR gauge from newegg for $20)
Once you have her post some pics and if you haven't already run the vin through a vin decoder or pm it to me and you can get the build sheet which is fun to have.

Carsy

In Australia if an oil leak is dripping on to the road endangering fellow road users, it will not be registered. A weep like yours is no problem.

Enjoy your new MB. Nice to hear that you plan to maintain it yourself. It is a satisfying & money saving hobby.

John.

scottonfire

Interesting. I went to pelican parts which rates service difficulty by the number of little wrench icons, and a transmission fluid change had like 6 compared to 2 for an oil change and pretty much every other DYI service, so that's why I was like F that. So going off of what you said, the only logical conclusion I can draw is that a transmission flush is different and less extensive than a transmission fluid change. That or the pelican's full of bird shlt

samaritrey

Just posted this a few days ago
https://mbworld.org/forums/5843195-post4.html
If you do the flush like suggested you drop the pan and change filter (which is the fluid change). Then you flush the system with a few quarts from the cooler line (so the flush if done correctly is more work). It does take time and some preparation but really is easy. The hardest part is getting the car in the air and getting all the under body covers off.

jkowtko

If you had time to check it out, I would suggest cleaning off the oily area and then monitoring it over a few days or weeks to see how it leaks. Make sure it actually is a leaking rear main seal.

Example --a while back the dealership said the parking pawl was leaking on my tranny. $1360 repair estimate. However when I did my tranny fluid change and checked out the area ... first, it was the gear shift lever they were talking about where the shaft enters the transmission housing ... and second it wasn't a leak -- there was just a bunch of dirty fluid residue left over from the electronic plug leak (common problem) that had been fixed by the indy a couple of years prior and they had just not cleaned up the mess entirely. It's been over a year since I did the tranny flush, and whenever I get the car up on ramps I recheck that area ... still clean

If it is leaking, you might consider using high mileage oil or adding a some leak stop a couple of weeks prior to oil changes ... if the problem is a hardened seal treated with dirty oil for most of it's like, you may be able to revive it somewhat.

slammer111

So I just noticed a small weep happening around the 8-10 o'clock positions exactly along the seam between the engine and the transmission. My mechanic friend and I both agree that is engine oil and not transmission fluid. Is this the rear main seal going?

The area directly above is completely dry, so it is definitely not from the infamous leaky vacuum pump. I replaced both pump and gasket and added some sealant recently.

jkowtko

First of all, that doesn't look very wet to me ... I suggest you clean it off and see if it reappears.

I am assuming your under engine covers are dry? No dried oil spots on them?

Do you have the rectangular access covers on the bottom of the tranny bell housing? If so, you should be able to pop those off and have a peek inside to see if there is any oil residue.

I had a small amount of oil seepage through those bottom access covers for a couple of years, which led me to thinking that the rear main seal was starting to go ... however it stopped and for the past couple of years I have seen nothing. I don't know what would cause a "temporary" oil leak ... something that got under the lip of the seal and worked its way out? Oil got excessive dirty one time just before I changed it? A momentary hard acceleration or high rpm spin that adds a bit of excessive crankcase pressure?

slammer111

I've cleaned it off several times over the last few week. In every case, the same part gets wet within a day of driving.

Underbody panels are completely dry. As the photo shows, the "leak" isn't enough to actually cause a full drop to form. Every time I look at the end of the day, it's always just a thin film that isn't even wet to the touch. I'll look again, but the slick is only on the sides of the seam there and not near the bottom.

Yes I've noticed the rectangular plastic covers at the bottom of the transmission bell housing. Do those just pop off? Any special tools required?

jkowtko

You have me stumped. Look at the end of this short video of removing the transmission:


It shows both the inside of the bell housing and the rear of the engine. To me it looks like that area should be dry.

Yes they should just pop off. I can't find a good pic or video online showing this though.

slammer111

Just checked the bottom of the bell housing where those hatches are. The plastic hatches are dry. And sure enough, the oil slick does not extend to the 6-8 o'clock positions. That portion is completely dry.

This might actually be just remnants of old oil seeping out, as my pump was leaking for several years before this. Each time I fiddled with the pump or removed it, a few spoonfuls of oil would drip into that area Back then it got so bad that the hoses underneath would be covered in oily goo. Guess I'll monitor it over the next while and see if it eventually stops.

Thanks for the tips. Greatly appreciated.

slammer111

So after cleaning this off several times, the leak is reappearing at the exact same spot every single time. Ideas?

jkowtko

you sure this is engine oil and not tranny fluid?

I just watched the video again and noted a few things:

* the front of the tranny bell housing shows a dual wall construction. So if oil had leaked in there over time, there could still be oil in the pockets between the dual walls continuing to seep out.

* something was dripping from the bottom of the tranny when they pulled it out ... presumably this was tranny fluid. not sure why there was a drip there ... maybe that is why they removed this one.

* looking at the engine, the top half of the mating surface is dark colored implying it was wet(?), whereas the bottom half was dry.

* looking at the engine, the flywheel looks like it is positioned right on the seam, so any oil that gets onto that flywheel would be flung at a pretty high velocity right into the seam.

If you have access to one of those snake hose fibre optic cameras it might be useful to pop off the rectangular covers again and have a look up into the bell housing to see if the flywheel has any wetness on it, or if there is any wetness on the inside of the bell housing.

Otherwise I would continue to clean off the spot and try to find anything on the outside that could be dripping onto that area. If there was a way to fasten a metal plate above that spot, that would be one way to confirm if something is dripping down or if the seepage is through the seam.

I am very curious to find out what is causing this.

slammer111

Even though I'm 99% sure it's not the vacuum pump, I'm going to replace the gasket again just to make 100% sure.

I'm 90% sure it's engine oil, but because I had the transmission fluid replaced (full flush) less than a month ago, the fluid should be bright red. The stuff that is seeping out is definitely brown (engine oil brown) and not red. I had a mechanic friend check and he agrees it's engine oil and not transmission fluid.

jkowtko

I'll take it that it's engine oil then ... as you say you can definitely tell the difference between the two, especially if the tranny oil is relatively new.

If it's engine oil, then to make sure it isn't coming from up above, wiping around behind the engine iwth a white paper towel should tell you right away if there is anything up there that is seeping oil. I would think you can confirm that it's not the vacuum pump by wiping under it and not having to replace the gasket again. Also double-check valve cover gasket in the rear ... I've never heard about those leaking, but it's a seam.

If the rear main seal were to be leaking, oil seeping onto the flywheel and then getting flung at the inside of the bell housing should create a mess in there, no?. But you said it all looked dry when you peeked through the rectangular covers?

slammer111

So I crawled under the car and popped off the 2 rectangular covers, wiping the inside of the bell housing (whatever I could reach) with a white paper towel. The inside had a film of something but it wasn't dripping. As for the fluid, I honestly cannot tell for sure what it is. All I know is it's not fresh ATF, as it's not red. The fluid is more a light brown.

I also wiped between the vacuum pump and motor with a white paper towel. Completely dry. Not a single trace of oil, new or old.

The part I don't understand is how old ATF would end up inside the bell housing if I had that bad leaky pilot bushing. Can anyone shed some light on this?

In a month or so I'll be due for an oil change, and so will be topping up the entire engine with the full 5.5L of oil. Right now I'm down to 4.2L, but as mentioned, I lost a bunch with the bad vacuum pump gasket in the past. This will be the surest way to tell if oil is going somewhere.

jkowtko

Green is PF fluid ... but there should be no PS hoses anywhere near that area.

Bad pilot bushing would have allowed ATF to leech up the wiring harness, but that's more rearward than the wet spot is, isn't it?

If you are not getting anything on the under engine covers, then whatever is coming out is probably not enough to be worried about. I suggest just monitor and wipe (with white paper towels) periodically, and someday you will either discover a different spot that has wet oil on it, or your initial problem may stop. My oil seepage through the square covers did just that ... I am pretty sure it was rear main seal starting to leak ... but it stopped on it's own after about a year. And I'm not complaining