help!72 250 leaky rear seal any tricks? - PeachParts Mercedes-Benz Forum

chaunsy · #1 12-22-2004, 09:04 PM

Hey guys thanks for having me. Im in need of a qucik response. I have a 72 250 with 53,000 orig miles only problems is that today it started leaking form the rear seal. It looks like i have to take apart the bottom end to put the seal in which would mean big overhaul. Do i have to take aprt the bottom end or is ther a qucik fix? Please let me know becuase the alternative is the rebuild and i need to give my mechanic an answer quick. Thanks

wbain5280 · #2 12-23-2004, 12:48 AM

Take the engine out, remove crankshaft, replace rear rope seal. Replace crank, button engine up, put back in car.

Simple.

chaunsy · #3 12-23-2004, 02:41 AM

my mechanic said id have to change out the bearings is that true?

wbain5280 · #4 12-23-2004, 07:03 AM

It depends on how much the bearings are worn. Your tech will measure thge wear with a plastigauge(sp?) (I always have trouble with gauge). Most likely you will need new bearings, afterall it's apart so it's false economy to keep the same bearings unless there is no wear. You may also need to have the crank ground. While your in there, re-hone the cylinders and replace the rings as well. A new oil pump, chain, guides, assorted gaskets, seals, valves, guides, etc.

ctaylor738 · #5 12-23-2004, 10:49 AM

I would make sure it is in fact a leaking rear seal. This does not seem to me to be a part that would fail suddenly and it's not a widely reported problem.

I would also ask around to see if there is a replacement seal that can go in without dismantling the engine. Try Gernold@sltechw113.com and george_murphy@compuserve.com.

And if worst comes to worst, you may be better off value-wise with a rebuilt short or long block or even a good used engine.

Good luck.

psfred · #6 12-23-2004, 11:59 AM

Try a bottle of engine restore before replacing, it can swell the seal enough to keep it from leaking badly.

You must pull the crank to change the seal (locator pins in the pan and block, can't pull it in), and it's fairly silly not to spend $60 or so on new bearings when you have the old ones out anyway.

Peter

chaunsy · #7 12-25-2004, 04:51 AM

i hear engine restore is bad for these mercedes motors?

psfred · #8 12-25-2004, 11:31 AM

The 72 and later engines aren't a problem, provided they are done to MB specs and not by "Chevy" standards. If put together with excessive clearances, they will wear out again very quickly. If done right, they normally run several hundred thousand miles with minimal wear.

Peter

300SDog · #9 12-25-2004, 11:31 AM

Couple of factors make them tough to build.... tapered bores with high nickel content 'sleeves' mated permanently to the bores at Stuttgart with intense heat process. Also specially weighted piston sets ballanced to the crankshaft. Dunno about turning the crank and using oversized bearings. Never in my life have I heard of MB crank bearings going south.

Recommended poorman's rebuild covers light honing of the bores, then use of special soft alloy Swedish rings designed NOT to cut into the cyl walls. That's all, plus maybe some cyl head work without shaving and planing the head.

The original $700 repair estimate doesnt sound so bad - like 4 hrs out and 4 hrs in for the engine plus gaskets and dropping the sump. I wonder if front suspension rubber bushings would be piece of cake with the engine removed.

joshhol · #10 12-25-2004, 01:30 PM

Quote:

I wonder if front suspension rubber bushings would be piece of cake with the engine removed.

Yes, they could just drop the whole subframe and do all the rubber really easily.

chaunsy · #11 12-26-2004, 05:27 AM

Quote:

Originally Posted by 240DieselDog

Couple of factors make them tough to build.... tapered bores with high nickel content 'sleeves' mated permanently to the bores at Stuttgart with intense heat process. Also specially weighted piston sets ballanced to the crankshaft. Dunno about turning the crank and using oversized bearings. Never in my life have I heard of MB crank bearings going south.

Recommended poorman's rebuild covers light honing of the bores, then use of special soft alloy Swedish rings designed NOT to cut into the cyl walls. That's all, plus maybe some cyl head work without shaving and planing the head.

The original $700 repair estimate doesnt sound so bad - like 4 hrs out and 4 hrs in for the engine plus gaskets and dropping the sump. I wonder if front suspension rubber bushings would be piece of cake with the engine removed.

Ive already done the whole subframe,suspension and steering, all the acc on the engine and the driveshaft and now this happens

joshhol · #12 12-26-2004, 01:38 PM

Can a leaky rear main seal fail catastrophically destroying the engine or is it just a pesky oil leak? I believe I have this type of leak on the 300D, and have had it for some time.

chaunsy I could be in the same boat, not excited about an engine rebuild. I just rebuilt the front end on my 115, have to do the driveshaft next. Did you replace diff mount and rear subframe mounts? I'm about to change those out.

chaunsy · #13 12-27-2004, 10:36 AM

Quote:

Originally Posted by joshhol

Can a leaky rear main seal fail catastrophically destroying the engine or is it just a pesky oil leak? I believe I have this type of leak on the 300D, and have had it for some time.

chaunsy I could be in the same boat, not excited about an engine rebuild. I just rebuilt the front end on my 115, have to do the driveshaft next. Did you replace diff mount and rear subframe mounts? I'm about to change those out.

Yes I did, anything that was rubber on the car has ben changed the only hing that hasnt is the wiring harness

230/8 · #14 12-28-2004, 01:17 PM

If you have checked the cranckcase and confirmed all the bolts are tight, then the rear seal may be your culprit. But with only 53000 miles on the engine, unless it is really pouring out, you can buy a lot of oil for a $700-1000 repair bill.

As to the liquid restorer suggestion, usually these are just cleaners that reduce the varnish that prevents seals from moving about as they seal. The most common brand is Trans-X which states clearly on their website that it does not swell seals. It is only a cleaner, so that the seals can function as originally intended. Also, if the rear seal is a rope, then it will probably not swell up as a rubber seal would.

230/8

300SDog · #15 12-28-2004, 06:11 PM

Quote:

Originally Posted by 230/8

As to the liquid restorer suggestion, usually these are just cleaners that reduce the varnish that prevents seals from moving about as they seal. The most common brand is Trans-X which states clearly on their website that it does not swell seals. It is only a cleaner, so that the seals can function as originally intended. Also, if the rear seal is a rope, then it will probably not swell up as a rubber seal would.

230/8

That's a really good point - Then fatter and dirtier oil such as non-detergent straight 40wt might have more success at blocking pores of a leaky rope seal?

My own experience with rope seals is limitted to the front seal on '65 Finbody that was destroyed by me introducing synthetic oil. And setting the rope seal correctly is tough to do. It took three attempts with brand new seals to set it right.

And it strikes me that you sure as hell dont want to run detergents through the rope, assuming this is actually the type of rear seal used on the '72 114.