OM617 idles very bad - Page 2 - PeachParts Mercedes-Benz Forum

ImBroke · #16 09-25-2010, 08:03 AM

Needs motor mounts for sure, look at how that thing is moving around. You may be surprised at how motor mounts will "fix" certain apparent issues. I know I was. Engine almost sounded like it had a knock, and was moving all over the place. Replaced mount, all is well and smooth.

E_S · #17 09-28-2010, 07:45 AM

Yeah, the mounts are pretty much shot, I know.. Will be replaced, but first I have to sort out the engine problems - if the engine is bad, I will consider dropping in an OM603 instead..

I did a compression test today. Engine warmed up, but pulling the injector lines and injectors took some time, so I guess the engine was warm, not hot while testing.

The test was done with some cheap compression tester, so the numbers may be somewhat off, but the difference between the cylinders should be more or less correct.

Results:
#1: 300 psi
#2: 295 psi
#3: 350 psi
#4: 240 psi
#5: 150 psi

Specs say minimum 220 psi.

I guess this pretty much "tells the truth", but the engine will start cold without any problems and actually get worse as it warms up.. It smokes pretty bad grey while idling, but when doing normal driving, it does not smoke at all.

I adjusted the valves a few weeks ago for the first time (haven't had the car for long), they were all far too tight. Will recheck them.

As it looks now, this engine looks like it's pretty much done. Any ideas?

vstech · #18 09-28-2010, 08:58 AM

could still be valves or cam causing the low compression. focus on #s 4 and 5 and see what the lobes look like, and re adjust the valves.

barry123400 · #19 09-28-2010, 09:31 AM

Could be a breech in the head gasket between 4&5. As engine warms it gets worse for whatever reason. Check the head bolts in that area. Do not go crazy just check for being far below torque specs.

Also add a small amount of oil and check that 140 pound cylinder again. If pressure does not rise substantially do an air injection or leakdown test.

Could just be a valve as well. I would not give up on this engine yet.

E_S · #20 09-29-2010, 09:36 AM

I rechecked the valve clearance today. Two a bit too tight, three a bit too loose, but not any big differences. Redid a compression test, now with engine cold (outside temperature 5 degrees Celcius) as I have pulled the injectors. #5 still at 150 psi while #3 (the strongest) now was at 230 psi. The compression gauge (cheap Ebay thing) is kinda flaky, but at least the difference is a lot smaller.

Hope it's not the head gasket, but I'll try one more old-school trick: Fill some ATF through the injector holes to soak the piston ring area and loosen up any soot. If the engine was operated like this and with poor maintenance, I guess stuck piston rings can be something to consider, and anyways, the ATF treatment does not harm anything.

I took a look at the chain stretch too. I don't have a micrometer, so I just put the cam on TDC and looked at the crank. Looked like 4-5 degrees off, but hard to see 100%.

The car is with me here in the town I study, but I have most of my tools at home. Going back home a few days next week, will bring the tools to check the head bolts.

chasinthesun · #21 09-29-2010, 10:18 AM

It was like that with a diesel 300cd I had bought ,it was a parker with no records.After numerous times trying to get it to run I finally got some numbers from the compression check .tHE #2 AND #5 cylinder were under 200.It made no differences accept when I added a rislone product called compression repair,lines the walls with somewhat of an oiley glaze.I mixed with new oil and drained the old .Then rechecked the numbers ,improved some 20% .It ran for about a year longer before a head gasket gave way ,but it still kept it going .Maybe a quick fix for you if its not a daily driver.

winmutt · #22 09-29-2010, 11:19 AM

Quote:

Originally Posted by E_S

Yeah, the mounts are pretty much shot, I know.. Will be replaced, but first I have to sort out the engine problems - if the engine is bad, I will consider dropping in an OM603 instead..

I did a compression test today. Engine warmed up, but pulling the injector lines and injectors took some time, so I guess the engine was warm, not hot while testing.

The test was done with some cheap compression tester, so the numbers may be somewhat off, but the difference between the cylinders should be more or less correct.

Results:
#1: 300 psi
#2: 295 psi
#3: 350 psi
#4: 240 psi
#5: 150 psi

Specs say minimum 220 psi.

I guess this pretty much "tells the truth", but the engine will start cold without any problems and actually get worse as it warms up.. It smokes pretty bad grey while idling, but when doing normal driving, it does not smoke at all.

I adjusted the valves a few weeks ago for the first time (haven't had the car for long), they were all far too tight. Will recheck them.

As it looks now, this engine looks like it's pretty much done. Any ideas?

Pretty sure the min usable spec is above 220, either way those are horrible numbers. I would be looking for a TD engine or better yet a 602/603/606.

E_S · #23 09-30-2010, 03:41 AM

Yeah, the numbers are horrible, I know. It looks like the engine has been operating with close to zero valve clearance, so there is a possibility for burnt valve(s). Will try a simple leakdown test and see if cylinder pressure escapes through the crankcase ventilation. If so, it looks like a OM603/606 replacement is something to consider.

603/606 pros:
+ Much more modern engine design
+ Increased fuel mileage
+ Runs a lot smoother and more silent
+ No more valve adjustment

603/606 cons:
- Need a lot of expen$ive parts to fit into a W460
- Have to change the transmission due to starter relocating
- Kinda pricey at $1000 up for an used NA engine here in Norway/Sweden

E_S · #24 09-30-2010, 03:57 PM

I borrowed a small compressor from a friend at work and will try pressurizing the cylinders and listen/feel for air escaping through the crankcase ventilation. If I find air escaping through the intake/exhaust, I know it's a valve problem.

Pulling the head and overhauling it will be no problem for me to do, but if the problem lies in the bottom end, a new engine will be considered.

I was thinking that if the "leakdown test" shows pressure escaping through leaky valves, I will soak the cylinders in ATF while the head is off to loosen carbon buildup. Will of course check the cylinders for scoring and any abnormal wear signs after pulling the head before dropping any more money into the engine.

I have no idea of the mileage of the engine, but problem is finding an OM617 turbo here in good shape, not very easy, and doing an OM603/606 transplant demands lots of additional work and expen$ive parts..

Also - I will do a simple leakdown test - then pull the head. If the leakdown test shows valve(s) leaking, I will do a head overhaul. If not, I will pull the head just to take a look if I see something abnormal, as the engine anyway is "useless" as it runs now, with serious smoking, missing and not passing inspection due to this. The fuel mileage is crap too..

E_S · #25 10-08-2010, 10:36 AM

I tried a few tricks, but none really helped. The compression got a little better, but far too low and uneven.

Looked through the ads in my area and found an OM617.952 that had been sitting for 2-3 years. Went to take a look, we got it started, ran it to operating temperature and checked the compression - the results were 390, 390, 390, 400, 390. Bought this engine and will swap it with the worn out one in a few weeks.

Thanks for all your advice!