ML-430 Frothy Oil Mixture - PeachParts Mercedes-Benz Forum

EPineda · #1 03-12-2007, 06:25 AM

I have a 99 ML-430 with 103,000 miles on it. It's being maintained quite well and had no problem the last 2 years. Synthetic oil (Mobil #1, 0W-40) was always used and replaced with a new fleece filter every 3500-4000 miles.

Lately, I had a tell-tale sign of frothy oil under my oil cap that started to show a few weeks back. This past weekend while checking the oil, it seems there is more frothy oil mixture now than before. I stopped using the car all together to make sure I don't damage the engine until the problem is solved. Although the engine temperature was (I thought) higher than normal (3/4 on the gauge which I think was normal), the engine never overheated.

Are there simple test to determine if I have a 1) blown head gasket, 2) bad EGR, 3) thermostat problem 4) or any kind of problem that can cause this?

I would appreciate any suggestions or tests to determine the cause before I go into an expensive trip to a dealer/independent mechanic.

I appreciate our expert's help on this problem.

Thanks an awful lot!

EPineda · #2 03-13-2007, 03:12 AM

I just want to add that at one time the car was running rough for a few moments and had a CEL light that came on momentarily but did not stay long when the car started running smoothly again. The CEL went away right away after that. I am also losing a little coolant every now and then but not much to be concern about (I thought).

Gilly, any suggestions what to look for? Tests that I could do myself? Is an oil change now in order to prevent bearing problems if I started the car and bring it to a shop? New thermostat, EGR valve & MAF sensor? These seems like little items i could do comparing with the expense of a head gasket replacement - and hopefully not needed.

Thanks again for your kind assistance!

DCF · #3 03-13-2007, 09:47 AM

IS the oil itself contaminated? A pasty, creamy buildup at the oil cap is normal, and not a sign of a problem. If the oil itself is not foamy / "wet", then you have another problem. Have you had the codes scanned? Just b/c the CEL is not on, does not mean the computer is not storing codes. Did you ever change the plugs? If so, did you use OEM style plugs? This could explain the rough idle.

If you want to check it out before driving it more, I would do a simple oil change and see what comes out. Then, when you refill, the car should be fine for a short trip to the shop, if youy cannot diagnose the problem yourself.

supradupe · #4 03-13-2007, 10:21 PM

this creamy/mayo stuff on the oil cap is normal, especially in winter where you live in the snow belt. I see this stuff every winter. Interestingly though, it doesn't happen when I was using the dino oil, before MB mandate that FSS vehicles requires synthetic. But long story short, it's ok to see that. You will notice that in summer time or when the weather gets warmer, that stuff will disappear.

EPineda · #5 03-14-2007, 02:30 AM

Thanks for your replies, DCF & Supradupe.

The weather in the Northeast has been like a roller-coaster. We had a warm January and it did get real cold in the teens last February for almost 3 weeks straight. Yes, I had the plugs replaced about 14 months ago using Bosch Platinum-4's, 2 plugs for each cylinder. The MAF is about 2 years old and may need cleaning or replacement soon. Are the Bosch Platinum-4's considered stock plugs?

The dipstick has no sign of frothy oil mixture, just at the underside of the oil cap. Also, there is no sign of oil contamination on the coolant reservoir as well. You could be right, this may be normal but I am just being cautious I may destroy my engine if there is a leaky head gasket problem. I will try to take picture of the oil cap's underside and try to add it to my post.

First thing I do when I get home is pull out the code(s), replace the oil & filter, clean or replace the MAF, go for a new thermostat and fresh coolant while I'm on it. See what happens from here.

I read that a bad or clogged EGR valve may also cause similar problem. Is this true? Also from a similar posting, they mentioned that the upper radiator hose may get hard fast during engine warm up if the head gasket is leaky as the engine pressure goes to the cooling system. Can you concur on this as well? Any other suggestions or diagnostics measures that can be perform to pinpoint the cause of this frothy oil mixture?

Thanks, and appreciate all the assistance you both are providing. This forum is GREAT.

DCF · #6 03-14-2007, 09:49 AM

The rough running is probably caused by the +4s, they are not OEM. Search the forum for the stock Bosch plugs (I just replaced mine 3 months ago at 80k, got the best price here). The stock ones are not cheap, more than +4s, but as you will see if you search the forum, the +2s and +4s have caused people all kinds of problems. Before you go doing something more expensive like an MAF, I would spend the $150 and get new OEM style plugs.

EPineda · #7 03-15-2007, 02:21 AM

Thanks for the comeback, DCF.

I will certainly follow your advice to use OEM plugs. In the past, I had 'misfiring' episodes occasionally and this could be one of the reason.

Just wandering if you categorize 'misfiring' as/or similar to 'premature detonation'? MB says that this is one major cause of head gasket-related problems. The other is engine overheating. I use 'high test' gas exclusively on my vehicles, never regular grade to prevent engine knock.

Thanks again for your kind assistance.