I have a Brabus 3.6 based on a 300E (M103) which has just had it's head gasket changed, along with new valve guides. The car starts first time from cold as it should holding a high 1200 RPM idle getting progressively slower as expected. The problem is that seemingly the warmer the engine gets the slower it tries to idle. By 85 degrees it wants to idle in drive (i.e. in
traffic) at 500 RPM where it's just about alive but very uneasy, sometimes
dying. Also at this slow RPM oil pressure can dip below 1 bar. I don't
believe there is a prolem with the oil pressure because by 750 RPM it's at
~1.5 bar and at 3 bar by 1500RPM. Additionally the engine idles more
erratically the hotter it gets, lumpily. It does have manual lifters so will
never be silkily smooth I know. If I raise the revs to say, 750RPM the idle
is noticibly smoother & do not believe it would cut out at this speed.
Indeed when it warms I can drive it by left foot braking in traffic if
necessary Engine power does not seem to done although the engine is still
being "run-in" so I dare not stray over 4000RPM.
I have searched forums for answers and the two most prominent are the
overvoltage protection relay (OVP) & the idle control valve (ICV). I rempved
the ICV today, it was clean but I sprayed some WD40 in it none-the-less. I
turned the ignition on and saw it open then shut so it is functioning
properly. The fuse on the OVP is also fine but I'm not sure how to check the
OVP itself. I have also recently changed the air filter, the old one looked
fine anyhow, no signs of the oil I'm used to seeing from the M110 motors.
Any other possibilities? I fear it may be the bottom end, piston rings or
cylinder bore causing a loss of compression but I would have thought this
would be tagged with a loss of power and "smoking" both of which there
aren't signs of.
Thanks for reading & helping if possible. Merry Christmas to all!!!
Sounds like you are having the same problem I am currently having. Read my posts I am going to take her back in to Mercedes in a week to try the injector seals as they have suggested I will post any ansera I get...
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2003 G500 Silver on Gray
1999 Porsche 996 Carrera C2 Silver on grey
2000 CLK430 Silver on Black (sold)
1997 XK8 Coupe Blue on Tan (sold)
1992 300CE Sportline Black on Black (Sold)
From the sound of it, seems like you are fighting a vacuum leak or some sort.. Was the boot under the CIS replaced? W/ age they like to get hard/brittle and are prone to cracking when moved around etc..
An update. Over the last couple of days the car has worsened, it will definitely cut out if I don't right foot accellerate and left foot brake. I decided to buy a cylinder compression tester. The procedure I followed was remove all spark plugs, coil lead and fuel plug relay, then screw in and test cylinder compressions.
The results surprised me as I expected low cylinder compressions. The specced cylinder compression for my engine is 10.1:1 up from the 300's 9.2:1. The actual compressions I read from cylinders 1-6 were: 12.5, 13, 12, 11.5, 12, 10.75. So hopefully Ian was correct when he mentioned the valve clearances as excessive clearences will give higher compression. After the valve's were re-seated the all the clearances became too small so I had to loosen all of them, perhaps all too much. I'll re-check them tomorrow. I would have thought if the valve clearances were out the engine would be noisy though as remember this happening on the M110 engines, my 103 runs fairly quietly. Does anybody know of a site that explains clearly how to get valve clearances 100%?! I have attached a picture of a spark plug that just came out. Unfortunately the picture isn't great but the plug tips look fine however the base of the plug, bottom of the thread is blackened, its smell I cannot make out. Could this be linked to incorrect valve clearences or does it perhaps point to something else?
Thanks & enjoy yourselves tomorrow night!
HAPPY NEW YEAR[:D]
Hi,
most compression testers measure in pounds,not comp ratio's,if your readings are in lbs.then you are really low on compression.Not expert on Mercedes but would expect pressures about 155lbs.but more important that all six are within 5 or so lbs.
good luck
HAPPY NEW YEAR[:D]
Hi,
most compression testers measure in pounds,not comp ratio's,if your readings are in lbs.then you are really low on compression.Not expert on Mercedes but would expect pressures about 155lbs.but more important that all six are within 5 or so lbs.
good luck
Haynes states the minimum acceptable compression of my cylinders to be 8.5bar if it were a 300E, given the uprated Brabus ratio I calculate the minimum for my engine to be 9.3bar. So my previously posted compressions are all okay going by this.
LondonThing, I have checked the ICV. It was clean but I sprayed some WD40 down it anyhow then connected only the electric socket, engaged ignition and it fully opened before moving back to its " shut" position where it is actually 4/5 closed, I'm assuming it doesn't fully close? The fuse on the OVP is fine but I'm unsure about the relay itself. I'm not sure my car has a lamda sensor. I notice you also have an M103 engine, does our engine have one, if so where?
Yesterday I removed the distributor in the process of removing the valve cover to reset the valve clearances. I then saw that the rotor arm was badly burnt & the centre electrode of the distributor cap had burnt "singed" in half. I duly replaced these items only to find a temporary (few minutes) better running & then the same problem again. Tonight I took the car out for a spin & gave it a quick blast. On my way back home I was coming to a standstill expecting RPM to drop to 500 & so engaging my right foot when I noticed it idling happily in drive at 650 RPM. So I took it for a short drive and it was fine. I left it idling for 5 minutes outside my house & when I returned it was idling in neutral at 550RPM, sure enough I dropped it into drive & it sank to 500RPM. It's like the car's teasing me!
Thank you for your replies.
"The actual compressions I read from cylinders 1-6 were: 12.5, 13, 12, 11.5, 12, 10.75."
your compressions are so far from right if the info you've given is correct[:I] 8.5 bar taking a bar to = 14.5 lbs.Haynes are saying according to you a cylinder pressure of 125 lbs.for a 300e.
So if your compression tester measures in Bar or lbs your compressions are rubbish.
12.5 bar= 181lbs
13 bar = 189 lbs (expected)
12 bar = 176 lbs
11.5 bar= 167 lbs
12 bar = 176 lbs
10.75bar= 159 lbs (crap)
compression ratio is physical not altered by any of this,you have a leak on number six cylinder
Haynes also states that up to 1.5bar of deviation between acceptable cylinders is okay. Gregit I only doubt this theory because I've just (I'm talking 200 miles ago) put the head back on. This was after the head had the work done to it; pressure tested, skimmed to spec, new valve guides and stem seals, valves re-seated. If I cannot resolve this problem I will bring it to a renowned Merc independent, George Fraser. I'm sure he'll duly do a cylinder leak down test if he believes it's necessary. Unfortunately I don't have the necessary equipment to do this but from what I've read it's much more useful than a compression test. I notice that many M103 & even M104 engines suffer this most annoying problem with the vast majority being simple repairs as opposed to major engine work. Thanks once again for your reply.
An OVP question. Today I removed the OVP to find it had 89 stamped on it so it's the same one since the car's inception. With the car cold started I removed immediately the idle slowed, roughened and died. Does this mean it's okay or could there be a problem with it which shows up when warm?
Linear Mode
