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Discussion Starter #1
Hi guys,

My 1970 220 (115.920) has a lot of blow by (the port on the intake manifold cant suck up all the blow by so some ends up going into the air inlet downstream of the carb, with some oil too). When I open up the oil cap in the valve cover, a bunch of white gas comes out (more than what looks like should be in there based upon what is circulating through the tubes back to the intake manifold). I believe the car also has a slight leak on the head gasket (get some white smoke for the first few seconds after starting, only after letting the car sit for about 10min after driving only.. not after sitting the car overnight and starting). Getting the car started after letting it sit for about 10min after driving is also tough (it takes several cranks), and then you get white smoke for a few seconds after it starts. I know the carb is totally off too (running too rich in general, and doesnt choke properly so she doesnt idle well on a cold engine). So a lot of problems, but the car still runs decent, but seems a bit weak on power (but I have nothing to compare to). Just ran a full tank of gas and got about 16.5mpg average, which seems rather poor for mostly highway driving.

Anyways, I'm contemplating a full rebuild (rather than just the head gasket alone). I see engine parts readily available for the simple stuff. I was wondering if I did need to bore the block somewhat, and needed oversize pistons, where do I get them for the 220? I find a lot of parts for the diesel engine, but the gas 220 seems to be a "forgotten" model. I cant even locate standard size pistons for this engine. I've seen Hastings makes a standard size piston ring set, which is encouraging. I'm just trying to prepare for the worst case that the engine would need to be bored. I believe the car has an original 92.5k miles on it, so I'm not sure what the likelihood is of needing a bore rather than a simple hone and new rings. I dont believe the car has been driven more than 5k miles in the last 9yrs (based upon some service history), so she's been sitting mostly. I'm planning on getting some compression and/or leak down numbers and trying some type of solvent to see if some of the rings aren't seating properly. I know the test results should show the faulty head gasket on one of the cylinders though. As far as I can tell, the car doesnt seem to be burning oil (through the tail pipe) or by looking at the dipstick. Seems the owner's manual specifies oil burn at a rate of about 3 qts per 1k miles.. that seems ridicously high! I dont know if the owner's manual is a typo, or if the oil ring is really that bad! I already put 300 miles on the car, and it doesnt appear to be even needing 1qt of oil, despite a constant leak from either the oil pan or rear main seal (which seems to defy the owner's manual for oil consumption rate).

Also just a general question.. where do you guys go for parts for doing a rebuild on a vintage MB? I'm not looking to hot rod up the engine.. just to freshen it back up so that it runs like new. I'm looking for reasonable quality parts (which will last), but at a reasonable price.

Thanks for everyone's help in advance!
 

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73 280SE 4.5, 71 300SEL, 03 BMW Z4, 72 Fiat 850, 80 Triumph TR7, 85 Porsche 911
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Peachparts.com is always suggested, as is the Classic center. I like adsitco.com, and I've always had luck with Napa Autoparts.

Try a general internet search on parts for your car, and you'll find a lot of options. Even the 115 engines are still supported...
 

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64' 220SEc, 72' 300SEL 6.3, lots of parts
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The best thing about Mercedes is the parts support. And the longevity of the parts.

Sounds like a ring, valve, and reseal is in your future.
Sounds like the rings are carbon caked stuck from low usage.
I've seen Mercedes motors with over 200k with perfect bores.
All parts are available.
 

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Discussion Starter #4
Thanks guys.

Grubeguy, thanks for the tip on adsitco. I wasn't aware of that one before.

I agree 115 engines are supported, but apparently not so much the 2.2L gas engine. The 2.2L gas seems to be the hardest to find parts for. I've tried searching all of the places you mentioned, and more, and still no luck finding pistons for this engine. If I cant find standard size pistons, so I figure "good luck" finding oversize pistons.. But, since I'm new with all of this, I'm sure as you guys say there are places to find these parts, and I'm hoping someone might point me to the holy grail for parts on my specific model. Any more ideas?

Bostosh, thanks for the vote of confidence on the bores. I hope what you've seen regarding MB cylinder wall wear holds true for my car. If so, I may not need a bore and new rings will do just fine.. I really hope so. That would save tremendously on the cost of the rebuild. I dont think much else is wrong. No noises, slapping, or any other clue suggesting bearing damage. Is that what most owners of these cars end up doing for a rebuild (re-ring only without oversizing the bore?)

I plan to try loosening up the rings with GM Top Cleaner before I take leak down or compression measurements. The bad HG will show up somewhere, but I'm assuming all of my pistons are showing a lot of blow-by due to the crud build up on the rings. The fact that the carb is running real rich is probably not helping the situation either.

Here is another example of something I cant find. I believe my water temp sensor (single wire, mounted on the thermostat housing?) is bad.. I dont know if this is the right sensor, but it is in water. The sensor reads an open circuit at all temps. I found a bunch of 2-wire temp sensors for sale online, but not the exact one which should fit for this car. Any ideas? Seems like most of what I need I cant find :confused:

On a side note, I just put in a full tank of gas yesterday, and soon found the gas tank dripping out all of my gas. Thats weird because I just filled her up not more than a week prior with no issues. I think the gas tank was worked on or replaced a few years ago. Car came from AZ, and then spent some time in CA, before coming to TX, so (exterior) rust is a non-issue. I wonder if the same could be said for the interior of the tank, assuming its been sitting around mostly. I didnt see any immediate gas tank offerings for this car, so I assume I have to seal/repair mine somehow..
 

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73 280SE 4.5, 71 300SEL, 03 BMW Z4, 72 Fiat 850, 80 Triumph TR7, 85 Porsche 911
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Gas tanks are a dime a dozen - see what's available at the local pickapart and replace it. Before you do though, be sure the tank really is bad. There are rubber hoses that connect the tank to the fuel lines - perhaps you have a failing hose.

Your one wire temp sensor is a thermistor. It'll "close" when the temp gets above 212 degrees - it provides a ground to the aux fan which then turns on to prevent the car from overheating. Are you getting no water temp readings at your instrument cluster?
 

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Discussion Starter #6
hey Grubeguy, thanks for the help. The gas tank seems to be leaking only when I top off with the last 2.5 gallons or so. The leak stops after that amount of gas is gone. I havent pulled it down yet to see whats going on (will wait until the tank is near empty first), but the leak appears to be coming from the top half of the tank shell, in the area closest to the front of the car. Its up above where the fuel and return lines come in, where I cant see. Interestingly, the tank seems to be sealed tight, because when I open the gas cap, it lets out a bunch of air. So its hard to imagine the tank itself has a hole in it, otherwise it shouldnt hold air, right? I dont know how the gas gauge is getting its signal from the sending unit (I havent seen any wiring in that area), but maybe thats the area where the leak is?

About the temp sensor gauge. Where is the "aux fan"? As far as I know, the car only has one fan driven off the engine belts, and I'm guessing it has a thermostatically loaded clutch. I dont have any electric fans on the car. My in dash gauge always reads between 125-150 max.. usually so low the needle is almost at the bottom of the gauge. I already replaced the thermostat with a 175F unit, but I get the same result. The thermostat in the car was just fine, and the engine seems to be heating up before the thermostat opens (as it should). This is why I just assumed it was the sensor which was not sending the proper signal to the gauge. Which sensor feeds the gauge, if not this thermistor located on the water pump outlet cover?

I guess still no luck on finding pistons for the 115.920 engine..
 

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1971 280SE 3.5 Coupe
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Have you tried looking them up in EPC and then searching at a online MB parts store? Or contact Tom Hanson at the Classic Center. If you do find them they will not be inexpensive. Pistons are $300+ X8 for mine. You might be better off finding another engine if you can't get away with rings.
 

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64' 220SEc, 72' 300SEL 6.3, lots of parts
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Don't sweat the pistons yet, (ouch at $300/each) They must be removed, cleaned, and inspected. Chances are good that they are OK, The pins have pressurized oil and usually are OK. The top ring slot can get badly beat-up oversize, out of tolerance. I have had a set of six, upper slot re-machined to a wider slot nominal-1.5 to 2.0mm ($130) and a set of custom rings made to suit ($85). (Deves Piston rings)

The engine doesn't know the difference.
Dimensions are dimensions,
Clearances are the critical factor....
 

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That's good info about machining the ring groove for a wider ring. I will be tearing my engine down for inspection soon and can hopefully get by with rings not need boring/oversized pistons.
 

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Thanks guys. But what is the benefit of opening up the slot width on a piston ring? I thought the gap was set to allow for thermal expansion. If set too wide (especially on the top ring), wont you get more compression leakage? If not bored, why not use the standard size gap for the standard size ring? I'm missing something here.

I'm hoping I dont need pistons, but I was just preparing for the worst case, if the motor needs to be bored. I'm still planning on trying some GM Top Cleaner to flush out the rings a little bit and see what happens.

Tony, how many miles does your car have? What kind of compression are you getting to necessitate a rebuild? I dont have the gauges yet to measure.. all my gauges are on order.
 
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