C350 no compression issues
Thread Starter
Newbie
Joined: Oct 2020
Posts: 7
Likes: 0
2005 C350
C350 no compression issues
Good Morning Everyone,
I am new here and yes I did try the search feature. So to my 2005 c350. After a check engine light and a misfire on the motor occurred, I found myself at a Bosch service center. The diagnostic report said no compression on cylinder no 4. The mechanic said that the rocker kept popping out... Now I've built a couple of cars and worked on a couple of engines but never on a MB. My question here is what do you guys think might be the issue and has anyone ever experienced this before? My thoughts are that one of the valves are stuck in the open position.
Any comments will be greatly appreciated.
Regards Philip from South Africa.
I am new here and yes I did try the search feature. So to my 2005 c350. After a check engine light and a misfire on the motor occurred, I found myself at a Bosch service center. The diagnostic report said no compression on cylinder no 4. The mechanic said that the rocker kept popping out... Now I've built a couple of cars and worked on a couple of engines but never on a MB. My question here is what do you guys think might be the issue and has anyone ever experienced this before? My thoughts are that one of the valves are stuck in the open position.
Any comments will be greatly appreciated.
Regards Philip from South Africa.
Thread Starter
Newbie
Joined: Oct 2020
Posts: 7
Likes: 0
2005 C350
To add...
I have checked the spark plugs and cylinder no 4 is always wet. Swopped plugs and coil packs around and the problem still persists. I do believe that the issue is in the head somewhere. Can a valve be so stuck that it pops out the rocker?
I have checked the spark plugs and cylinder no 4 is always wet. Swopped plugs and coil packs around and the problem still persists. I do believe that the issue is in the head somewhere. Can a valve be so stuck that it pops out the rocker?
Thread Starter
Newbie
Joined: Oct 2020
Posts: 7
Likes: 0
2005 C350
Small Update,
I've added some engine flush to the oil to try and loosen up the sticky lifter. Still seems to be missing. I'm going to open up the valve cover and see if the rocker is still in place.
I've added some engine flush to the oil to try and loosen up the sticky lifter. Still seems to be missing. I'm going to open up the valve cover and see if the rocker is still in place.
MBWorld Fanatic!
Joined: Jun 2011
Posts: 1,494
Likes: 131
From: Cape town
not a merc
Possibly the plastic flaps in the intake have broken and has got stuck between the valve and the seat. If the rocker will not stay on then definitely the valve is stuck open. Dont run the the motor! Remove the intake manifold and inspect
Thread Starter
Newbie
Joined: Oct 2020
Posts: 7
Likes: 0
2005 C350
I opened up the valve cover and inspected. I still do not see anything out of place. I rotated the engine by hand and everything looks ok. Nothing that popped out. I'm starting to wonder if it might not be something electronic. Looking at buying one of those OBD2 cables to see what the errors say.
Trending Topics
Thread Starter
Newbie
Joined: Oct 2020
Posts: 7
Likes: 0
2005 C350
Hi,
So I pulled the fuel rail and cleaned out all the injectors. Also swopped 2 of them around to make sure cylinder 4 has a working one. Still the same issue. CEL comes on, rough idle and the following codes. P0304, P0629 and P0637. I got a basic compression tester to test the compression and will be doing that shortly. I'm wondering if this might not be a wiring issue somewhere maybe the wires leading to the injector or the wires going to the coil. Will read up some more and see how to test them. Found lots of info on the site the more I look. Spoke to a mechanic the other day and he mentioned something about a balance shaft and timing. This worries me a bit. Hopefully after the compression test we will have more clarity.
So I pulled the fuel rail and cleaned out all the injectors. Also swopped 2 of them around to make sure cylinder 4 has a working one. Still the same issue. CEL comes on, rough idle and the following codes. P0304, P0629 and P0637. I got a basic compression tester to test the compression and will be doing that shortly. I'm wondering if this might not be a wiring issue somewhere maybe the wires leading to the injector or the wires going to the coil. Will read up some more and see how to test them. Found lots of info on the site the more I look. Spoke to a mechanic the other day and he mentioned something about a balance shaft and timing. This worries me a bit. Hopefully after the compression test we will have more clarity.
MB World Stories
The Best of Mercedes & AMG
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Mercedes Teases Updated EQS With Steer-By-Wire and a Yoke
Verdad Gallardo
8 Mercedes Models With Poor Reliability Records
Verdad Gallardo
Thread Starter
Newbie
Joined: Oct 2020
Posts: 7
Likes: 0
2005 C350
Tested the compression last night and all the cylinders clock in at +-325kPa. Switched the spark plugs between 3 and 4 again and the car actually idled perfectly for about 5 seconds then CEL and misfire again on cylinder 4. I'll have a look at the flaps next. But if there is compression that that should indicate that there is nothing stuck in the valve. Also found a link to check the Balance shaft issues. You set your crank to 305deg and check through the sensors on the heads. if the stamps are clearly visible in the center of the opening then all should be fine. Checked mine and they look perfect. I was wondering if it might not be the wire leading to the injector... But today I will remove intake and inspect from there as you suggested.
Thread Starter
Newbie
Joined: Oct 2020
Posts: 7
Likes: 0
2005 C350
Ok, So i went out an bought a new compression tester. All the cylinders tested 95psi and cylinder 4 only tested in at 30psi. Something is definitely wrong in the head. Pulled the intake manifold out and found that the Left side flap rod was unclipped. Loos like the flaps for cylinder 6 are loose and not connected the rest. will have to order a new intake manifold. Still worried about the compression. i rotated the motor and seems like the intake valves do open. and close. might be something on the exhaust side?
MBWorld Fanatic!
Joined: Jun 2011
Posts: 1,494
Likes: 131
From: Cape town
not a merc
Like I said before.. a cyl leakage test does not lie! Do you think you going to "see" anything looking at a valve. Compression tests don't always give true results. So you know the Compression is low on one cyl.. Next step leakage test. Valve timing and balance shaft will not cause a misfire in a million years. Stick to logic and basics and you will solve your problem. Good luck
