240d blowby - PeachParts Mercedes-Benz Forum

2ruble · #1 06-27-2013, 11:54 AM

Getting significant blow by in my 74 240d... Recommendations? There is blowing passed the oil cap also oil filling up in the air filter housing

barry12345 · #2 06-27-2013, 12:14 PM

Run straight 40 grade oil for the summer. Should cut it down. Add a quart of miracle mystery oil to the oil change as well not overfillng the oil level. You want to see if the rings can be cleaned up a little. Or if it is too late. If the engine has been run on wvo I wouldd suggest a more aggressive treatment.

2ruble · #3 06-27-2013, 12:17 PM

That'll help reduce the symptoms but not really solve the problem.... Thanks for that recommendation, and I'll do that today, but any ideas on solving it?

AwfulMechanic · #4 06-27-2013, 12:24 PM

I'd like to start by saying I'm new here, so take my advice with a grain of salt. If it's pooling in the air filter housing that's pretty bad haha. The only way really to fix this is an engine overhaul, but financially you're better off finding a junkyard engine. If you are up to the challenge you could just throw some piston rings in it, but you get out what you put , so it's not a real fix. You should do everything if your going to bother. In the mean time use a few bottles of Lucas oil stabilizer and thicker motor oil. Replace oil cap gasket, less mess lol.

2ruble · #5 06-27-2013, 12:34 PM

Lol... Thanks... So the consensus is to use thicker oil until I take the top end apart basically..

ah-kay · #6 06-27-2013, 12:59 PM

You need to measure the compression to see how bad or otherwise is the engine. Blow by normally is caused by low compression; worn cylinder or coking of the rings. Soaking with MMO is not going to cut it if the coking is bad, definitely not with worn cylinder. Thicker/heavy oil is a band-aid.

I have rehabilitated a OM603 engine with terrible blowby by removing the head and oil pan, pushed out the pistons from the bottom. Soaked the piston in solvent to remove all the carbon coking. Lightly honed the cylinders and then put the rings back in. I replaced all the oil rings as some were broken when I pushed the piston out. I reused the top rings. The compression was 50psi before and they were 260-300psi ( measured cold ) across all cylinders after the mini overhaul. It was all done with the engine in car. I have done 7K miles on the engine after the overhaul and it is running like a champ. No blow by to speak of. It is using a quart of oil per 1K mile. It is acceptable to me as the engine has 349K miles. I could not have done it without the help of this forum as I am not a heavy duty engine guy. It is a lot of work but it was a fun project for me. It does not beat playing golf but the satisfaction you get after fixing the engine is priceless. This is my experience and it works out well for me.

Good luck.

Skippy · #7 06-27-2013, 05:51 PM

Quote:

Originally Posted by 2ruble

Getting significant blow by in my 74 240d... Recommendations? There is blowing passed the oil cap also oil filling up in the air filter housing

Are you sure it's all blowby? When my 240D started putting oil in the air filter housing, the cause was a perforated diaphragm in the vacuum pump. It was pumping oil into the air filter housing for a while before the brakes started feeling hard.

kerry · #8 06-27-2013, 09:23 PM

Need a video to give meaningful advice. But I agree it could the vacuum pump.

Diesel911 · #9 06-27-2013, 09:26 PM

Before you change the Oil you can dump something like Marvel Mystery Oil into the Cylinders (on by way of the Glow Plugs or Injector holes; if the Injectors you can pool more inside but have to replace the Heat Shields) and let it soak for a week. Rotate the Engine and repeat.

Crank the Engine an blow out any excess left in the Cylinders. Do the Oil Change and go for a hard rid on the Freeway. If load up with some of your heavier weighted Friends for the ride.
The Goal is to free up any sticking Piston Rings.

Others have said that switching to synthetic Motor Oil will do that same after about but it take about 200-300 miles to get the results. Again, this only works if sticking Piston Rings are the cause.

Other wise Blow-by is just nuisance unless so much pressure builds up that it effects the Vacuum Shutoff of your Fuel Injection Pump or blows out a Seal

cooljjay · #10 06-27-2013, 10:14 PM

Also do a valve adjustment and start driving hard....adjust the valves again....drive hard again and keep repeating.....a lack of valve adjustments in the life of the vehicle can cause blow by......my theory is that when the car doesn't receive the recommended valve adjustment carbon builds up on the valves....thus the valve can't seal thus allowing compression to escape....becomes blow by....once the carbon starts chipping away the valves become tight....I have been doing a lot of valve adjustments on my car sometimes only after a couple hundred miles....the exhaust valves are always tight and the intake loose....

barry12345 · #11 06-28-2013, 12:17 PM

Quote:

Originally Posted by AwfulMechanic

I'd like to start by saying I'm new here, so take my advice with a grain of salt. If it's pooling in the air filter housing that's pretty bad haha. The only way really to fix this is an engine overhaul, but financially you're better off finding a junkyard engine. If you are up to the challenge you could just throw some piston rings in it, but you get out what you put , so it's not a real fix. You should do everything if your going to bother. In the mean time use a few bottles of Lucas oil stabilizer and thicker motor oil. Replace oil cap gasket, less mess lol.

That you are probably right is almost certain. Still some effort to see if the rings are sticking is worth a try. That's why the miracle mystery oil in the base. It usually takes some time for the solvent to work on the rings.

I also agree that a good used junkyard engine is a better and cheaper option usually than really getting into these engines seriously. That's unless the rings are just stuck. It usually takes some time and miles if the solvent is going to have any effect. Still the solvent may loosen them back up over time if they are compromised in that way. Nothing simple of course is going to undo serious wear issues.

ah-kay · #12 06-28-2013, 12:50 PM

Quote:

Originally Posted by cooljjay

Also do a valve adjustment and start driving hard....adjust the valves again....drive hard again and keep repeating.....a lack of valve adjustments in the life of the vehicle can cause blow by......my theory is that when the car doesn't receive the recommended valve adjustment carbon builds up on the valves....thus the valve can't seal thus allowing compression to escape....becomes blow by....once the carbon starts chipping away the valves become tight....I have been doing a lot of valve adjustments on my car sometimes only after a couple hundred miles....the exhaust valves are always tight and the intake loose....

I wish valve adjustment can fix blow-by. How about cars using hydraulic lifters which do not need to be adjusted? It ain't going to work!

Diesel911 · #13 06-28-2013, 04:18 PM

I can see where cooljjay is coming from. If you believe poor combustion causes sticking Piston Rings then keeping the Valves Adjusted correctly supports good combustion and helps prevent sticking rings.

Replacing bad Hydraulic Lifters on Engines that have them is the analogy to adjusting the Valves.

Shortsguy1 · #14 06-28-2013, 04:50 PM

Quote:

Originally Posted by 2ruble

... also oil filling up in the air filter housing

If your air filter is like mine (1968 220d), it is supposed to have oil in it. Is your air filter housing actually "filling up" with oil or just has some oil at the bottom? If it is truly filling up, that is too much oil to come from blowby, but probably means you have a busted vacuum pump diaphragm or a busted injection pump diaphragm.

cooljjay · #15 06-28-2013, 05:03 PM

Quote:

Originally Posted by Diesel911

I can see where cooljjay is coming from. If you believe poor combustion causes sticking Piston Rings then keeping the Valves Adjusted correctly supports good combustion and helps prevent sticking rings.

Replacing bad Hydraulic Lifters on Engines that have them is the analogy to adjusting the Valves.

On my current car, I can tell a huge difference when the valves are adjust and a fresh oil change....I always see my horse power increase.....this tells me that the engine is extremely clogged with carbon and slowly its coming back to heath...

On my euro, I actually managed to cure the blow by....by doing repeated oil changes and valve adjustments....I was shocked to open the oil cap and see no smoke...

I am glad some else is seeing my theory....