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RG5384 05-26-2001 02:15 AM

worried about my diesel (300SD)
Well i am the proud owner of a 1983 300SD. The engine starts great, seems to run great, but has a couple catches that have me worried. The first thing is that the engine runs at about 102 degrees C when idling, and around 95 when driving(with a/c on). This is after flushing the radiator, i'm thinking of just replacing the thermostat? Second, it has an oil leak that seems to come from EVERYWHERE. I looked at the bottom of the engine and it looks as if everything is leaking. The guy i bought the car from recently had the oil lines replaced as well as the oil pan gasket, so valve covers maybe? I'm worried because i heard that these engines can leak from the block or something? is that true? also, there is a little bit of oil in my air filter housing. Is that normal? The oil leak has also gotten much worse within a couple days time, although it does seem to lessen and get worse intermitantly. If you have any tips or advice on ANY of these things, please let me know. By the way the car has 150k miles on it and seems to run/shift/idle great. Thanks again

Johnson Chan 05-26-2001 04:16 AM

clean the engine first so you can pinpoint the area of the leak.

h2odiesel 05-26-2001 09:29 AM

A good bath will help narrow things down. Oil in the air filter is normal on these fine cars and there is a separator and a drain that returns it to the pan. There is a revised flat baffled breather hose that goes from the valve cover to the air filter that cuts down on drips. The other common sources are the valve cover gasket, the turbo drain line seals the air filter drain line o-ring at the pan. the oil filter housing to block gasket. the IP to block gasket, and the front crank seal. Start at the top and work your way down.

Bob D.

RG5384 05-26-2001 12:04 PM

What/how to you recommend cleaning it? I took it once to that car wash thing and it didn't do much. I don't' want to get water where it's not supposed to be. Also, if it is in fact leaking from the front crank casing is that something even worth fixing, or will it just leak oil forever? I know my valve covers are leaking but I didn't think that they could put down about a 2 inch diameter circle of oil every night, plus I don't see that much "liquid" oil around them, just all over the bottom of the engine. I do see oil stains that seem to go up onto the valve covers, it goes up about 1 inch from the gaskets and then is clean the rest of the way. The only leak that you mentioned there that concerns me is the crank casing because I'm not sure that I could reasonably have that fixed. Thanks for your help

can-do 05-26-2001 12:40 PM

Use a Degreaser

To get a better look at the engine and where the leaks are coming from I'd spray it down with a degreaser let it sit 10 minutes or more and pressure wash the crud, sludge and oil that has built up on the engine. If you are to wild with the pressure washer wand you may want to cover electrical relay boxes etc. under the hood to keep water out. Just one of the uses of used plastic shopping bags, handles tie easily into a knot to keep pressure from blowing them off. Some of the most common leaks will probably be found at the valve cover gasket, (easy fix and cheap to buy from Fastlane) front or rear oil pan to engine seals, (requires lifting engine up with hoist to remove upper pan assembly) lower oil pan seal, once again an easy fix. There are other areas that may seap oil that in most cases can either be tightened or seals replaced. Also look at the oil filter housing to engine connection for possible seal leakage, as well as oil lines that are connected to it and running to the IP. Time and a few hours spent can cure most of your major oil leaks.


Ron Johnstone 05-27-2001 05:38 PM

To clean my engine, I use Gunk foamy, but the critical thing is to NOT do it when the engine is hot. Warm is good, but absolutely not hot. It isn't the Gunk that is bad, it is the cold water you wash it off with. Avoid temperature shock at all costs.

NIC 05-28-2001 10:46 AM

I believe someone mentioned this but check the oil return line under the air cleaner housing. Oil accumulates in the cyclonic thingamabob inside the air cleaner housing and is returned to the engine via a tube under the housing. there is a critical "o" ring there that can be bought for about a dollar. The only leak I had was that one and it got the whole area underneath it oily.

Good luck.

Nic in SC
'85 300CD @ 140k miles

MikeTangas 05-28-2001 01:14 PM

Cold clean for diesels...
or so I've heard. Because of the high heat generated by the vacuum pump, it is best to clean the diesel engine when cold to avoid damaging the pump.

Definitely change the valve cover gasket (you only have one), you'd be amazed at the amount the cover(s) can leak. The valve cover bolts only need something like 8 ft lbs to tighten, so be careful not to over tighten them.

Depending on how much crud has built up on the sides of the block, it may take several degreasing sessions to really knock the crud down.

Robert W. Roe 05-28-2001 01:17 PM

I once "washed" my '77 300D's engine with a can of WD40 and a bunch of paper towels. It was a can that had fallen onto it's nozzle and the nozzle was broken off. I used a can opener to make a tiny opening in the top of the can and let the WD40 drip onto the caked oil all over the engine. It worked pretty well, but I think I still had some oil left after the 16 oz of WD40 was all gone :) Just a suggestion; it did seem like a more controlled method than a car wash or a garden hose.

My current engine has yet to see water, but it doesn't use much oil, so it can't be leaking, right? I've been really tempted to take the SD to Florida when we go to visit the in-laws next, since they have a brand-new concrete driveway, so I can see if my car leaks. My current parking spot has been occupied by three MB diesels in recent years, so it's hard to tell if it's ATF, power steering fluid, oil, or diesel fuel marking up the asphalt.

engatwork 05-28-2001 02:37 PM

don't forget to clean
and lube the throttle linkage connectors after the pressure wash. That pressure wash seems to clean all that out real good too.
I just finished cleaning the 300D and I will get out there and do the lube thing on the throttle linkage sometime this afternoon.
'85 300D
'95 E320
'97 CRV

WoodTA 05-28-2001 09:37 PM

300SD Leak Too
I have also recently purchased a 82 300SD. I consider myself a basic fix it person. I have noticed my driveway is bearing the same mark of the diesel. I have pinpointed my leaks though. One leak was coming from the rubber boot(top of oil pan) where the turbo exhaust tube goes down into the oil pan. I was able to go under the car and lift the tube, twist the boot slightly and then move the tube back down. This seemed to solve this leak. The leak I am fighting now is under the oil filter where the hoses attach to the filter housing (bottom hose). Because of the location, I am having a hard time getting a wrench on this tube to tighten it. The only other problem I have had thus far was diesel leaking from the last fuel line on the injectors. I replaced this and it solved the leak. Good luck with your ventures. I am having a blast working with mine.

whunter 01-29-2005 01:24 AM

Old is not bad. :D

Robert W. Roe 02-04-2005 11:33 PM

My SD turns 21 this month.
And the TE is leaking more than the SD; go figure.

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