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  #1  
Old 03-26-2002, 02:46 PM
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Engine Questions???

I have a strange knock at idle. It is not there when engine is cold, only when warm and it goes away with even the slightest boost of rpm. Oil pressure is just under 2 bar at warm idle, and oil consumption is next to nothing. It is not loud, sounds more like a click then a knock. I did a search and there is a lot of good information but I'm not clear on how to test if it's an injector knock. Strangely, it idles smooth when cold and develops a slight roughness when warm. I plan on a valve adjustment in the next 4 weeks so all the appropriate timing chain tests will be done then.

Also...I read on this forum that you can test the blowby by plugging the breather hose and counting seconds before engine shutdown. 14 or so for a new engine. Is this test accurate? Will it clog anything or cause other problems? My engine has alot of miles on it so it's not perfect but if you take off the oil cap when idling, there is quite a storm.

It runs fine. Maybe I'm being over protective. Starts up immediately in the morning and uses no oil, I just love my car and want to know how long she has before major illness?
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  #2  
Old 03-26-2002, 03:26 PM
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Since we have a lot of noise in our engine compartments anyway,,, I think we need to find or make an electronic stethoscope to track down some of these kinds of noises.... anyone know how ? Greg
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  #3  
Old 03-26-2002, 04:03 PM
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stethacope?

When I was looking at a 116 SD to buy, I heard a strange (for diesel) knocking sound and asked a mechanic friend of mine if he would take a look at it. When I arrived there was an older man there that I had not seen before. I raised the hood and the olderman revealed a stethascope, "listened" to the engine and told me not to buy the car.. the trouble was deep within and would be a major repair bill. I thanked him and my mechanic friend, took the car back to the owner. It was later that I found out the older man was about to retire as mechanic for the school buses for the county and had his diesel truck repair shop on the side. I guess some people know what to listen for.
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1982 300D (266,001 mi.) looking and running great

Previously owned:
1976 450 SLC
1983 300D
1976 300D
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1982 Jaguar XJ6 (loved, but gone)
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  #4  
Old 03-26-2002, 05:01 PM
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The older man then went to the seller and bought the car for a song. Just kidding.

Sixto
91 300SE
86 300SDL (due soon)
81 300SD (for sale cheap)
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  #5  
Old 03-26-2002, 05:16 PM
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How'd you know that? Serially (sic) I really, really wanted the car and had a hard time taking it back.. I even asked my mechanic friend "how much should I pay for it" and have the engine "rebuilt or whatever it needed" and he just shook his head and sang "um, um um, um, um, um..."

Later
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1982 300D (266,001 mi.) looking and running great

Previously owned:
1976 450 SLC
1983 300D
1976 300D
also
1982 Jaguar XJ6 (loved, but gone)
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  #6  
Old 03-27-2002, 12:27 PM
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Smile

Well I think it was probably injector related. I do mostly city driving, which is notoriously tough on any car. Last night I had to go for a good long highway cruise, about 27 miles each way, and when I got home...no knock, no click, no ping. Just a smooth idle and a nice diesel growl. I'll have to take the highway more often.
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  #7  
Old 03-27-2002, 12:59 PM
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BWatson,
I'm the one who started the thread about the blowby test-- 14 sec for a good engine, etc.

As for harming the engine, all this does is briefly counteract the vacuum that holds the injection pump rack open, and should do no harm.

This only works on turbos--


As for the accuracy of this test, I'd like to invite other members to try it on their cars, and perhaps we can all build some data points so we can come up with some information we all can use when evaluating possible new purchases. As time goes by and the engines we have to choose from get older, this data may be of increasing value to help weed out the really worn out engines when considering our next OM617 puchase.


What are the variables?

1) Total miles on the engine
2) measured oil consumption
3) city / highway driving
4) dino / synthetic oil
--any others worth mentioning?

If we compare the variables with the time it takes for our turbo engines to shut off, we might be able to predict not only good vs. bad engines, but also how much life our oil burners still have left before the $$$ rebuild.

All I personally have is:

14 sec for a new engine,
11 sec for a nice motor with 126k
9 sec for mine, which has 237k accumulating at a rate of 2600 freeway miles per month.

Since I want this motor to see 500k, I have a vested interest in frequent oil changes, valve adjustments, etc.

Any takers?

Cheers,
Nate Stanley
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  #8  
Old 03-27-2002, 04:36 PM
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Thanks for the response Nate! I will check mine out later on. Heres some specifics.
242,000 miles
almost no oil consumption (1/2 qt in 3,000 miles)
20W-50 oil (Castrol)
80% city driving (bummer, I need to get out more)

I have also been told that if you don't consume oil, you don't have a blowby problem. I was only concerned because when I take off the oil cap running, it's quite a storm. My owners manual gives 20W-50 as a choice for warm climates and my mechanic recommends it for high mileage. It gets changed every 3,000 miles and will get a valve adjustment in 2 weeks. I'll bet 11 seconds on the test!!!
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  #9  
Old 03-28-2002, 12:59 PM
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Wink

Well I did it! 9 seconds timed with my watch. I also checked the air filter since I recently got a new breather tube and a new air filter. The verdict is....no signifigant oil build up. A slight film but nothing I would worry about. She runs nice and I feel good about her.

I guess 9 seconds is normal for the mileage????
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  #10  
Old 03-28-2002, 01:35 PM
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So what exactly do you plug to do the test? I'm curious to compare notes. My 81 SD has 293K miles on the clock but supposedly a new engine at 150K miles. Haven't had the car long enough to measure oil consumption, 60/40 city/highway, dino oil.

Sixto
91 300SE
86 300SDL (due soon)
81 300SD (for sale cheap)
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  #11  
Old 03-29-2002, 05:23 AM
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You plug the breather hose on top of the motor. Valve cover to air filter. Either at the air filter or at the valve cover will work.
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  #12  
Old 03-29-2002, 11:09 PM
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Do I not let the air cleaner inhale or not let the valve cover exhale. I presume the only way the engine would die is if I didn't let the valve cover exhale.

Sixto
91 300SE
87 300SDL (correction on year)
81 300SD (for sale cheap)
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  #13  
Old 04-01-2002, 12:21 PM
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You block the valve cover and stop it from exhaling. It will build up pressure and stop the motor.
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  #14  
Old 04-01-2002, 12:36 PM
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Do I do the plugged breather test with engine hot or cold?

P E H
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  #15  
Old 04-01-2002, 03:18 PM
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BWatson,
Sorry I didn't back to you sooner. I was out of comission all weekend--

9 seconds seems right, since mine is at 237K and has the same time. I was hoping a few weeks of good hard freeway miles would blow some carbon out of the ring lands and let the pistons seal better, but that was not to be.

I did an oil change and resealed my valve cover this weekend, and will let all of you know what the real-world consumption is over the next few weeks.
You're probably right about the oil conumption being more important than the huge clouds of blowby that we all have at this mileage.

PEH,
Best to do the test with the engione hot, since cold rings don't seal as well, and cold oil doesnt make as much blowby.


Keep the data points coming!
Nate
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