diesel knock update
#1
04-17-2014, 11:06 AM
diesel knock update
this script is a bit long winded but please read on.
R reg 1998 E300 TD, 47000 genuine miles, FMSH.
Owned car since December 2013, in January 2014 decided to give it an oil and filter change using full syn 5w 30 oil. prior to changing oil I used an engine flush as ive always used them in the past, and had no concerns because of the mileage the car has covered. Anyway, since then it has run sweet as a nut, smooth as silk covering 3500 miles.
4 weeks ago it suffered bad starting so I replaced the glow plugs and car now starts first time again. But from that point its developed a knock up to 1250 rpm, revv the engine above this and the knock disappears, as the engine revvs drop to 1250 and below, the knock returns and I think its starting to sound heavier (I could be wrong). I noticed that there was air bubbles travelling along the clear fuel lines from filter to pump so I replaced the fuel lines, fittings and filters using genuine Mercedes parts, started engine and the air was still present in the lines but not as bad. Switch engine off and you can see the fuel drain back an inch or two from the filter. Took car to an indy and they said it sounds like an injector so I had the injectors refurbished, put it all back together again and it is still knocking at 1250 rpm.
I have removed the valve cover to inspect the camshafts but it all looked like brand new showing no signs of wear and all parts were wet with clean oil. Everything was clean, no crud, no sludge, no carbon etc etc.
Now im thinking its a hydraulic lifter so I put a tin of Wynns hydraulic lifter concentrate in the engine and that hasn't made any difference. If you remove the oil filler cap when engine is running you can hear a distinctive knock.
Should I try a thicker oil? could it be the harmonic balancer on the crank transferring a knocking noise through the engine?
There is no loss of power, no smoke when driven hard, starts first time.
Please Help
R reg 1998 E300 TD, 47000 genuine miles, FMSH.
Owned car since December 2013, in January 2014 decided to give it an oil and filter change using full syn 5w 30 oil. prior to changing oil I used an engine flush as ive always used them in the past, and had no concerns because of the mileage the car has covered. Anyway, since then it has run sweet as a nut, smooth as silk covering 3500 miles.
4 weeks ago it suffered bad starting so I replaced the glow plugs and car now starts first time again. But from that point its developed a knock up to 1250 rpm, revv the engine above this and the knock disappears, as the engine revvs drop to 1250 and below, the knock returns and I think its starting to sound heavier (I could be wrong). I noticed that there was air bubbles travelling along the clear fuel lines from filter to pump so I replaced the fuel lines, fittings and filters using genuine Mercedes parts, started engine and the air was still present in the lines but not as bad. Switch engine off and you can see the fuel drain back an inch or two from the filter. Took car to an indy and they said it sounds like an injector so I had the injectors refurbished, put it all back together again and it is still knocking at 1250 rpm.
I have removed the valve cover to inspect the camshafts but it all looked like brand new showing no signs of wear and all parts were wet with clean oil. Everything was clean, no crud, no sludge, no carbon etc etc.
Now im thinking its a hydraulic lifter so I put a tin of Wynns hydraulic lifter concentrate in the engine and that hasn't made any difference. If you remove the oil filler cap when engine is running you can hear a distinctive knock.
Should I try a thicker oil? could it be the harmonic balancer on the crank transferring a knocking noise through the engine?
There is no loss of power, no smoke when driven hard, starts first time.
Please Help
#2
04-20-2014, 03:24 PM
diesel knock update, part 2.
please read my previous post for info.
1998 E300 td, 47000 genuine miles, FMSH
After reading many articles on this problem I am now thinking that the pump timing may be out on the engine as other E 300 td owners have experienced this. If so, how has this happened?.
when the engine was struggling to start prior to replacing the glow plugs, it sounded like it was running on 2 cylinders with a lot of banging and knocking going on. Could this have caused the pump timing to jump a tooth?.
Its going into the garage next week for the timing to be checked. I have yet to replace the oil (5w 30) with 5w 40.
Your thoughts would be appreciated.
1998 E300 td, 47000 genuine miles, FMSH
After reading many articles on this problem I am now thinking that the pump timing may be out on the engine as other E 300 td owners have experienced this. If so, how has this happened?.
when the engine was struggling to start prior to replacing the glow plugs, it sounded like it was running on 2 cylinders with a lot of banging and knocking going on. Could this have caused the pump timing to jump a tooth?.
Its going into the garage next week for the timing to be checked. I have yet to replace the oil (5w 30) with 5w 40.
Your thoughts would be appreciated.
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