diesel knock 602 2,5 turbo

[owain]

Folks i need some advise, i have a 1990 300E 2.5 turbo, I just purchased knowing the diesel knock was not much to worry about. I had read all the posts ref this concern & as the car has 165000 i thought new injector nozzles "Bosio" would cure the problem.
Replaced them yesterday, engine was much smother but still has the nasty diesel knock just a little more uniform now. there is no smoke and car has all the power, turbo works fine, no blow from the valve cover. it also seems the # 5 cylinder is not running as strong as the others, " i crack the fuel line with not much change in sound or rpm".
this is my first diesel Mercedes, i am a competent master tech but have not much experience with diesels.
I had a thought & wondered if maybe the hyd valve lifters may have collapsed, the engine runs very smooth when cold " all cylinders seem equal " the running deteriorates on # 5 when correct eng temp is reached. diesel knock is always there until engine is brought of idle, also # 5 cyl is ok after approx 1700rpm.

all problems are at idle only, i was very surprised at the great performance from a 2.5 diesel, i get approx 40mpg with ac on.

any help would be much appreciated.

thanks very much.

[Diesel911]

Originally Posted by owain

Folks i need some advise, i have a 1990 300E 2.5 turbo, I just purchased knowing the diesel knock was not much to worry about. I had read all the posts ref this concern & as the car has 165000 i thought new injector nozzles "Bosio" would cure the problem.
Replaced them yesterday, engine was much smother but still has the nasty diesel knock just a little more uniform now. there is no smoke and car has all the power, turbo works fine, no blow from the valve cover. it also seems the # 5 cylinder is not running as strong as the others, " i crack the fuel line with not much change in sound or rpm".
this is my first diesel Mercedes, i am a competent master tech but have not much experience with diesels.
I had a thought & wondered if maybe the hyd valve lifters may have collapsed, the engine runs very smooth when cold " all cylinders seem equal " the running deteriorates on # 5 when correct eng temp is reached. diesel knock is always there until engine is brought of idle, also # 5 cyl is ok after approx 1700rpm.

all problems are at idle only, i was very surprised at the great performance from a 2.5 diesel, i get approx 40mpg with ac on.

any help would be much appreciated.

thanks very much.

That is sort of the symptoms of a Hydraulic Lifter issue; if it taps after Engine is hot.
I only have experience on Old American Cars concerning that.

Bosi Injector Nozzles are said to make a little more noise at idle speed.

It would not hurt to adjust the Fuel Injection Pump Timing but but for the most part Nailing caused by late time decreaes when the Engine is Hot.

"Loud noise at normal operating temperature only. If a lifter develops a loud noise when engine is at normal operating temperature, but is quiet when engine is below normal temperature, it indicates an excessively fast leak down rate or scored lifter plunger. Recondition or replace lifter."

From section B of the below site:
Noisy Valve Lifters

[owain]

thanks for the info, my next action was to have the pump timing checked / adjusted, did not want to try this myself as i dont have the needed tools. also looks like the factory pump setting marks have not been moved. no bolts have had a wrench on them.
what would the cost be to have the timing checked / adjusted.

thanks.

[Brian Carlton]

Originally Posted by owain

it also seems the # 5 cylinder is not running as strong as the others, " i crack the fuel line with not much change in sound or rpm".

If you're attempting to make the conclusion that #5 is the culprit for injection knock, cracking the injector line and preventing the injector from getting fuel would completely eliminate that condition.

Injector knock and ticking valve lifters are two completely different sounds. I'd suggest you make a short sound bite of this engine at idle and post it. Anything that folks post regarding any noise is just a WAG based on facts that are nebulous at best.

[Brian Carlton]

Originally Posted by owain

thanks for the info, my next action was to have the pump timing checked / adjusted, did not want to try this myself as i dont have the needed tools. also looks like the factory pump setting marks have not been moved. no bolts have had a wrench on them.
what would the cost be to have the timing checked / adjusted.

thanks.

Adjusting the IP timing by a couple of degrees is not going to affect the injector knock in any way...............if you actually have injector knock.

With the posted fuel economy, I highly doubt the engine is far from optimal timing.

[Diesel911]

As far as WAGging goes the OP is trying to gather information to narrow down the possibles.

I think the OP is also assuming that because the Injectors were rebuilt they are working OK.

He did say "it also seems the # 5 cylinder is not running as strong as the others" so perhaps it would be a good idea to swap the #5 Injector with another Injector on the other end of the Engine and see if the Weak Cylinder follows what was the #5 Injector.

For the timing you could use the Timing/Locking Pin; see Pic. Faslane sells it and there are other places to buy it.
Ther should be some info on how to use it in the DIY section.

DIY Repair Links
http://www.peachparts.com/shopforum/diy-links-parts-category/

http://www.peachparts.com/Wikka/DoItYourSelf

[owain]

the latest news is: after readiing some further info on replacing nozzles one of the posts said "Nozzle bedding in time " they said to drive for at least 30 miles.
this has been done and most of the knocking has gone, i still have the miss at idle on number 5 cyl. I have already ordered a new Injector, " seems folks dont have much good to say on these as they are now made in India. I will replace & report back with results.
i still seem to think the valves are not opening fully, easyier to replace injector first before removing camshaft to replace lifters.

thanks everybody for the help.

cheers.

[Diesel911]

Originally Posted by owain

the latest news is: after readiing some further info on replacing nozzles one of the posts said "Nozzle bedding in time " they said to drive for at least 30 miles.
this has been done and most of the knocking has gone, i still have the miss at idle on number 5 cyl. I have already ordered a new Injector, " seems folks dont have much good to say on these as they are now made in India. I will replace & report back with results.
i still seem to think the valves are not opening fully, easyier to replace injector first before removing camshaft to replace lifters.

thanks everybody for the help.

cheers.

I bought some Injectors On eBay and one of the Injectors was a Rebuilt with the Indian Nozzle. It was other wise new.
The guy I bought it from said He bought it on the Internet from a Normal Parts seller and when he had a problem they warranted it by sending Him another rebuilt and just gave him bad one.

I took it apart and found there was a big casting bump on the middle Plate that was entirely obvious and should never been assembled.

I am thinking that the rebuilt Injectors are also rebuilt overseas some where.
It is clear that who ever put the Injector I have together had no idea that the part was no good; or, did not care.

On the other end of it a tiny piece of dirt inside an Injector can cause a miss.

[owain]

all fixed after replacing IP, yes the pump had bad delivery valves on # 5 & weak on others.
runs great now. lol, only spent approx $1,700 . worth doing as the car is very very clean. great daily driver.

[300D-91]

owain glad to read you got your problems sorted. I'm adding some info for future readers who may find this thread via a search engine.

After doing work to my OM602 (91 300D) that included replacing my engine mounts and having the injectors rebuilt (by a local Bosch certified service center that does tractor trailers) the nailing noise had only decreased slightly.

I pulled the service manual and followed it to set the idle speed. It's now idling at ~800 RPM vs ~550 RPM and my nailing noises are 90% gone. An unexpected benefit is an increase in power to boot.