W123 Over-enthusiasm? - Learn from my mistake... - PeachParts Mercedes-Benz Forum

RallyRebel · #1 11-18-2011, 11:55 PM

Here we are some six years or so since I first entered into the realm of the W123 and its kin. This forum and you many who make it what it is have provided me with information and skill to better learn and maintain this fine machine. Of the dozen that have come under my wrench none have been creampuffs, so just parts hulks, but until recently they've all benefitted. Now lets go back about a year... I'd pretty much decided I really wanted a 240D stick with wind-up windows for a daily driver. I wanted simplicity and economy, and that seemed to fit. So, while I was back in school after having been laid off in favor of offshore labor I began the search for the ride to sate my daily 140-mile round trip commute. I can't remember now if it was a craigslist find or an eBay listing but it was near Hattiesburg MS and I had a one-way airline ticket to meet the seller at the airport. He was a restaurant owner who had bought the car off eBay and drove it home from Miami, all intent on recycling his fryer oil into fuel. No worries to me about that at the time, mostly I was concerned with corrosion which was what I most disliked about the W123's currently roadable in my possesion. I looked it over in the parking lot, chit-chatted, exchanged funds, shook hands and headed home for what should have be about a 10 hour trip.

Long story short, it took a LOT LONGER. One, I didn't know the 240D had a smaller fuel tank than the 300D. Two, there was so much crap in the tank I had to stop repeatedly to remove and shake out the secondary fuel filter as I was unable to find one at any of the parts houses along the route. Third, the car literally drank oil. By the gallon.

After finally getting the car home I swapped in a freshly steamed and POR-15 treated tank from a 300D and flushed all the fuel lines and got new filters on everywhere. After some other basic maintenance I started commuting with it to see how consistent the oil consumption would be. It was still staggering and I was here on the forums trying to figure out why. Then I started reading the threads about WVO and oil-rings. About this time while under the car addressing a minor exhaust issue I saw a split in the factory undercoating running parallel to the left rocker, just about where your left butt cheek would sit. Picking at it a little flakes of rust began falling out. More picking and peeling caused a virtual avalance of rust until I could SEE into the car! In the cabin I picked up all the mats and carpet to see what appeared to be a result of either poorly treated or poor quality steel. The floor panel was badly corroded up to the rocker seam. The rocker wasn't too bad except a couple spots where the rust had taken hold across the seam.

At that point I put a backup vehicle into service and sidelined the 240D for repair. I cut out a section of floor about 27" by 3" and based on info from this forum took the opportunity to pull the injectors and fill the combustion chambers with Marvel Mystery Oil in the hopes of freeing what I thought at the time to be stuck oil rings. Life got busy and I couldn't get time to finish up the sheetmetal work but I did keep topping up the Marvel until the engine was full. Not having time to renew the injectors either I ended up sending theme to Hessian for rebuild, balancing and Monark nozzles. So now it's about a year later and the sheetmetal is all welded in and painted, the injectors are back and installed (great work by Hessian by the way!) and after smoking the residue of the Marvel for four miles down the road the 240D is back in service. But...

Oil consumption is still excessive, right around 3 quarts to a gallon every 100 hundred miles. Could the rings still be stuck? I'm generally against "miracles in a can" but tried two cans of Sea Foam in the oil hoping against hope, but no change. So, what else? Valve stem seals? Okay, first compression check. Warm I got the following: Cyl. 1 - 425 psi, Cyl. 2 - 425 psi, Cyl. 3 - 400 psi, Cyl. 4 - 350 psi. I already had new valve springs, jam nuts, cap nuts and valve stem seals so I went ahead and did the job over this past weekend. After the initial valve adjustment another compression check, this time cold, with the following: Cyl. 1 - 340, Cyl. 2 - 300, Cyl. 3 - 400, Cyl. 4 - 340. I wasn't happy with that so went through the valve adjustment again and got new cold numbers: Cyl. 1 - 360, Cyl. 2 - 300, Cyl. 3 - 400, Cyl. 4 - 350. Okay, so now I'm tired of adjusting valves and decide to just drive it a bit and redo valves again after everything settles in a bit.

This car has always started no problems (after new glow plugs) and runs strong, even more so with the Hessian injectors and Monark nozzles. But there's still a steady stream of white smoke coming out the tailpipe. Like I'm working for mosquito control. Well, maybe not that bad, but noticeable. So, on a lark, I disconnect the breather pipe and elbow and stick a new K&N crankcase filter on which I just happen have laying about. Now it seems like even more smoke! And when I check the oil after a 30-mile drive it appears to have used a little more than usual. So I start thinking maybe my shop-made valve stem tool deformed the seals and oil is still getting by, since it's obviously not being injested into the intake via the breather pipe now disconnected, and with no suction to the intake and a valve cover restriction due to the K&N filter perhaps the added pressure, albeit slight but more than previous, is forcing more oil down the valve stems?

After looking at my valve stem seal tool, basically a washer with an ID about the same as the valve stem OD, and comparing it to photos of the factory tool I feel my tool puts too much pressure on the center portion of the seal whereas the factory tool appears to put pressure on the shoulder of the seal. If so I could have deformed each and every one of my seals. Or, they could be fine and the oil rings are well and truly stuck. But due to the change with the breather I'm inclined to think valve stem seals. What are y'all's thoughts? That's an awfully large amount of oil to lose. The coolant is fine, no oil in water or water in oil. The car hasn't ever leaked, and it's been parked long enough in a few spots to show if it did. Sure, it's greasy underneath but nothing is dripping. I'm stumped...

I've got the factory valve stem seal tool on the way, it's not like I won't ever do that job again. So if I need to I'll put a new set of seals on. First inexpensive option for repair. Second inexpensive option is to swap in another OM616 in a $300 240D auto I picked up a few years ago for parts. Ran fine, crap body, but was run on WVO too and I didn't drive it enough to get a feel for oil consumption. Third inexpensive option is to swap in the NA engine from a low-mileage 300D also bought for parts. It's never ran while I've had it, never tried, but simple enough to throw in a battery to check. The 5-cylinder is going to be bit more involved to hook to the 4-speed though I'm thinking!

Hopefully after reading through this novel someone will get something useful from my experiences with this car. It may just end back up on eBay soon too...

Lycoming-8 · #2 11-19-2011, 12:07 AM

Have you checked to see if the vacuum pump is the diaphram type? If so, they can contribute to oil consumption when the diaphram fails.

vstech · #3 11-19-2011, 07:49 AM

two things stand out to me in this story...

1. I find it difficult to comprehend someone with a 140 mile commute would choose a 240D. the cars are quite loud at speeds above 60mph, and even with a manual, they are low on power. the 90-93 300D is FAR more efficient on fuel, and a much nicer highway vehicle.

2. oil consumption from valve stem seals is usually limited to startup ingestion. your description of usage along with the massive difference in compression leads me to believe you have a bad piston/set of rings/cylinder wear in #4 hole. also, #2 cold numbers scare me.

take a look at the compression on your auto 240 motor.

sethza · #4 11-19-2011, 01:43 PM

As far as the 140 mile trip is concerned: get a good stereo system and get used to tailgaters. I love putting miles on my little 240d. One lesson I've learned with my car, never give up! Once you spend a certain amount of money on one of these things, you'll never get it back by selling it. You'll just buy another car with a different laundry list of problems. If I were you, I would put another motor in this thing, and take the old motor apart. You've got a ring or cylinder wear issue here, my gut tells me, but yeah check the vacuum pump first. I've had that problem before and I had oil travelling all over my car via the vacuum lines.

It sounds to me like the lesson here isn't so much to be cautious regarding vintage mercedes, but to do a good inspection on ANY used car your'e buying! I've been burned before, myself. You'll never make the same mistake again, I guarantee it.

RallyRebel · #5 11-19-2011, 02:46 PM

LOL, my personal vehicle tastes are rather eclectic. Sometimes I'll use my M35A2 as a daily driver when I can stand keeping the 50 gallon tank filled! I've also got about half a dozen Merkur XR4Ti's around and also two Isuzu VehiCROSS's, but I enjoy the 240D on the highway as I'm rarely in a hurry like everyone else seems to be. I know where I'm going and I like to enjoy the journey along the way.

I haven't looked at the vacuum pump yet, wasn't really sure if the '81 had a diaphragm thinking that was on the older pumps. The only thing connected right now is brake booster and rack shutoff due to a leak in locking system that hasn't been high on the "to-do" list.

As for the compression numbers I'm still not real happy about my valve adjustment as I always have problems getting the jam nut tightened without changing the clearance. I'm going to set up my aircraft compression tester to get a better idea of what's going on with compression.

RallyRebel · #6 11-20-2011, 02:43 PM

UPDATE: I'm an idiot. While pouring over the shop manual I came across the valve adjustment procedure and about hit my head on the table. It's been years since I last did this on an MB so just double-checked the clearances on the underhood sticker and went to town. What I did wrong was put the feeler gauge between the rocker and valve cap. D'oh! Anyway, just finished adjusting them the PROPER way. Every one was tight which likely caused the low cold compression readings. I'm waiting for my differential compression gauge to come back then I'll retest compression with both my HF diesel gauge and the aircraft differential. I'm pretty sure at this point I've still got one or two worn cylinders the cause of the oil consumption, I just can't see a gallon of oil going through the valve stem seals every 100 miles.

I'll report back after compression testing, hopefully someone will find this thread useful.

Brian Carlton · #7 11-20-2011, 03:22 PM

Quote:

Originally Posted by sethza

Once you spend a certain amount of money on one of these things, you'll never get it back by selling it.

I believe that the "certain amount" is approximately $100.

t walgamuth · #8 11-20-2011, 04:54 PM

If your 300 na motor checks out good, putting that into a 240 makes a sweet car. I have one which I put in a 307 diff from the turboed car and with the four speed it got 30 highway. Now that it has the od five speed it gets 35 with monotonous regularity. The lowered engine speed makes the car a completely different animal on the highway.....very very quiet.

Rick Miley · #9 11-20-2011, 09:01 PM

Now that you've gotten your feet wet in the W123 world and learned a bunch of lessons, you need to upgrade to a better car. I know where you can pick up a Euro 300D with manual everything in pretty good condition.

RallyRebel · #10 11-20-2011, 09:11 PM

Quote:

Originally Posted by Rick Miley

Now that you've gotten your feet wet in the W123 world and learned a bunch of lessons, you need to upgrade to a better car. I know where you can pick up a Euro 300D with manual everything in pretty good condition.

Oh do ya now?

kerry · #11 11-20-2011, 09:44 PM

That's a lot of oil to be pushing by the rings. Did you check the vacuum pump vent line to the air cleaner if it has one.

shadetreemechan · #12 11-20-2011, 10:08 PM

As others have said, check your vacuum pump. You are not burning that much oil past the rings. If you were it would (or will soon) just run away with you.

leathermang · #13 11-20-2011, 10:50 PM

Could the vacuum pump be leaking that much without the brakes and other vacuum things being affected big time ?

47dodge · #14 11-20-2011, 11:20 PM

My vacuum pump was dumping a good bit of oil, about a qt every 100 miles. It did not effect the brakes much, just a slightly harder pedal. Vacuum was a little low, but not too bad. New diaphragm fixed it up. It is still an oil burner but about a qt every 1000 miles now.

As far as highway noise, really depends on what is to much for you. I run mine about 70 on the highway.

leathermang · #15 11-20-2011, 11:25 PM

He is talking Three to Four times that much oil usage....
perhaps a leak mostly when driving... not showing up in driveway ?
Did not seem to be 'that much' smoke in the complaint....