Rebuild (or rings) on OM617 NA - Page 2 - PeachParts Mercedes-Benz Forum

vstech · #16 08-25-2014, 09:26 AM

Quote:

Originally Posted by leathermang

Many engines have valve rotators built into the system... some engines only put them onto the exhaust valves.. some on both...

In the FSM drawings of the valve and spring assembly for the turbo 617 it is listed as # 69 and called ' rotocap' under the spring.

So if one found that the valve seat was wearing in a non concentric fashion.. that rotocap would need to be replaced... this would be during a head off the engine valve job on the head because that is about the only way to find non concentric wear.

this is true, but if the vehicle was driven with tight clearances, junk gets in the seat area, and can warp the shape of things. manually rotating them, and setting the clearance correct after good friction rotation clears the path, and beds the valve, gives you better compression if that was a problem.

Don M · #17 08-25-2014, 11:12 AM

If the MMO does not free the ring pack there is another good way that the BMW guys use. The EGR systems in BMWs is responsible for many carboned up engines.

AC Delco has a product called upper engine cleaner. Pour a few ounces of it in each cylinder and let it soak overnight. Crank the engine the next morning with the injectors removed. This treatment frees rings very effectively.

BMW has the same product, but it is more money. The same company makes it for both GM and BMW.

This was my next step if the MMO added to the oil did not work for me.

t walgamuth · #18 08-25-2014, 11:25 AM

My old chilton's repair manual says you need 220psi or more to have reliable cold starting, taken on a cold engine.

cooljjay · #19 08-25-2014, 05:16 PM

It is also possible for the lift pump to be sucking oil from the IP and dumping it into the fuel supply..

Douglas.Sherida · #20 08-25-2014, 06:59 PM

Thanks for the responses.

When I got the truck (25,000 km ago) the intake valves were all a bit tight (not too surprising) and the exhaust valves on cylinders 1 and 2 were also tight (~ 0.010"). I have adjusted them a couple times since then and they are spot on at 0.004" and 0.012" for intake and exhaust.

I just checked my factory service manual from 1978 (introductory for the "new" cross country vehicle) and you are correct that the compressions are within normal specs (320 - 350 psi with +/- 45 psi variance between cylinders). I was mistaken thinking that they should be more like 400+ psi.

So, yeah the compression seems decent.

Sluggish starter is an interesting hypothesis for difficult warm starts without a full glow cycle.

Glow plugs are new since I got it (I had a couple bad ones).

I don't think that I'm getting oil dumping into the fuel, as the pre-filter (and the fuel in it) stays nice and clean.

I'm curious about the hypothesis of the vacuum pump dumping oil into the intake, but I can't even see how that would happen. There is no oil in the main vacuum line to the brake booster and no leaks around the pump (or anywhere else). How would I diagnose it?

leathermang · #21 08-25-2014, 07:28 PM

What is the problem with ' a full glow plug cycle ' ? ( which it probably is not )

In the FSM..... it says something like 45 seconds to one minute for max heating.... that seems like a long time when you are just sitting there looking at it...
but see the discussions about starting in the winter... use a clock and time it... the light goes out due to some circuit trying to figure out the relationship between the ambient temperature and the block temp... or something like that... and think about how old those electric components are...
Be glad it will start. Look at the threads of persons whose cars will not start no matter how long they glow.....

Douglas.Sherida · #22 08-25-2014, 07:38 PM

Quote:

Originally Posted by leathermang

What is the problem with ' a full glow plug cycle ' ? ( which it probably is not )

In the FSM..... it says something like 45 seconds to one minute for max heating.... that seems like a long time when you are just sitting there looking at it...
but see the discussions about starting in the winter... use a clock and time it... the light goes out due to some circuit trying to figure out the relationship between the ambient temperature and the block temp... or something like that... and think about how old those electric components are...
Be glad it will start. Look at the threads of persons whose cars will not start no matter how long they glow.....

Its just not what I'm used to from my ex-w123s. Once warmed up I could restart them without a glow cycle.

I'm fully aware of multiple glow cycles in the dead of winter, pouring a pot of boiling water over the engine to get it to start, etc.

I don't mean to confuse the issue, but I was trying to give a full description of the general health of the engine.

The main question is, why is it burning oil?

leathermang · #23 08-25-2014, 10:05 PM

Quote:

Originally Posted by Douglas.Sherida

I'm fully aware of multiple glow cycles in the dead of winter, pouring a pot of boiling water over the engine to get it to start, etc.

That is another miss impression ... multiple glow cycles... taken from the assumption that the glow plug is deactivated at the time the light goes off...

The FSM says to leave it on for something like 45 seconds to a minute... it gives the temperature the glow plug gets to at different lengths of engagement... Just turn on the key and ignore the LIGHT.... wait to turn on the key until the proper amount of time has elapsed....

Pouring a pot of boiling water on the engine is very dangerous... assuming you had enough to effect anything you are taking a chance on cracking the cast iron of the engine... and you are NOT reaching the bores... only heating the water inside the coolant jacket will do that... best done with a block heater plugged into the side of the block...

And even more important ..... you take a chance on RUINING the injector pump.... you should not even wash the injector pump with hot ...or cold water when cleaning the engine... the tolerances inside it are amazing... this warning is also in the FSM....

neumann · #24 08-25-2014, 10:20 PM

Quote:

Originally Posted by Douglas.Sherida

Vehicle: 1980 300GD cabrio, 116,000 km true mileage on the clock, original normally aspirated 617.931 engine and 4 spd manual (all numbers matching), truly rust free original paint and unmolested interior. Does not leak any fluids. All my maintenance is up to date. Runs well, with decent performance (for a non-turbo 617).

Symptoms: Burns ~ 1 liter of oil every 500 km. Poor compression (tested with a cheap harbor freight gauge on a hot engine, #330, #340, #340, #340, #310). Always needs a glow plug cycle to start, even warm.

My guess is that it is either scored cylinder walls or broken rings from having not been exercised a whole lot (average of 3400 km/yr over 34 years!). I have tried the cheap and patient solutions but nothing helped (diesel purge, 2 week marvel mystery oil soak of cylinders, replaced valve stem seals, switched to synthetic oil for the last 15,000 km).

Looking for advice on options to fix it without compromising the originality (not interested in dropping in a 617a, 603...):
Option 1) I've always done all my own work myself, but never dove into the guts of an engine. How crazy would I have to be to take it on myself?
Option 2) I have a local MB specialty independent (Classic Motor Cars in Branford, CT) who I have heard good things about. Its a family owned shop (father and two sons) and has been in business since 1986.
Option 3) Pay through the nose to pull the motor and ship to Metric Motors for complete rebuild.

My primary concern about rebuilding it myself of having a local shop do it, is meeting the required specs (and having the required specialty tools in my case).

I would triple check the glow plug system for the starting issues. I have had new glow plugs test bad right out of the box. Have you tried a water injection system to try and fix the oil useage issue?

leathermang · #25 08-25-2014, 10:31 PM

The starter is easy relative to some of the other things which could be wrong... and it is always nice to have a healthy starter.... the piston needs to travel a certain speed in order to produce the heat needed for combustion..
All the connections to the starter need to be cleaned also... including its connection to the engine.
In addition to the heat... you need the fuel to be dispersed properly... no one likes it when I mention this.... but there are FOUR or so TINY holes pointing radially out of the bottom of the Precombustion chamber.... all of them need to be clean. They are very carefully engineered... and there were changes in them over the years..
So if they are clogged with carbon from the combustion chamber...

OR IF THE PINTLE HAS BROKEN OFF INSIDE ONE OR MORE OF THEM...

you will have starting problems....

Stretch · #26 08-26-2014, 02:10 AM

Quote:

Originally Posted by Douglas.Sherida

...

The main question is, why is it burning oil?

I agree the main concern is the "missing" oil

I didn't think you had said it was burning oil - is that so?

The main culprits for OM617 oil leaks are the valve cover gasket, the front seal on the crankshaft, sometimes the rear crankshaft seal, the vacuum pump and blow-by oil ending up in the take.

If you can't see any obvious leaks on the inside then I think you need to check the crank case breathing system (which is essentially a pipe that runs from the valve cover to the intake on most set ups).

Douglas.Sherida · #27 08-26-2014, 07:06 AM

Quote:

Originally Posted by Stretch

I agree the main concern is the "missing" oil

I didn't think you had said it was burning oil - is that so?

The main culprits for OM617 oil leaks are the valve cover gasket, the front seal on the crankshaft, sometimes the rear crankshaft seal, the vacuum pump and blow-by oil ending up in the take.

If you can't see any obvious leaks on the inside then I think you need to check the crank case breathing system (which is essentially a pipe that runs from the valve cover to the intake on most set ups).

It does not leak a drop of any fluids. Coolant, front and dear differentials, brakes, clutch, front and rear differential locks, transfer case, transmission and engine are all leak free.

Yes, it is burning engine oil. I can see it in the rear view and passenger side mirrors as a gray haze. It smokes a bit at start up and smokes when under load for sure. Seems to smoke more when I let off the throttle to shift, but its tough to be sure about that.

Yes, the crank case breather tube runs straight into the intake manifold and there is always "some" oil inside it, but nothing leaking around the joints to the valve cover or intake manifold. IIRC, there are no baffles inside the chamber in the top of the valve cover leading to the breather tube. I know I've read somewhere about people putting metal pot scrubbers in there to catch more oil and return it to the engine.

If the oil consumption were running through the breather tube, doesn't that implicate excessive combustion gasses leaking past the rings (i.e. blow by which should be diagnosed as poor compression)?

Is there any way for the vacuum pump to leak into the intake? I don't see how those two might be connected.

t walgamuth · #28 08-26-2014, 07:19 AM

I have several good starters available.

leathermang · #29 08-26-2014, 07:28 AM

Put new valve stem seals on it.
Has the symptoms of needing those...

Stretch · #30 08-26-2014, 09:10 AM

Quote:

Originally Posted by Douglas.Sherida

...
If the oil consumption were running through the breather tube, doesn't that implicate excessive combustion gasses leaking past the rings (i.e. blow by which should be diagnosed as poor compression)?

...

Excessive oil in the breather tube is indeed bad and it does indicate that the cylinder is leaking somewhere. (see lower down =>)

Quote:

Originally Posted by Douglas.Sherida

...
Is there any way for the vacuum pump to leak into the intake? I don't see how those two might be connected.

On early OM61X engines there was a connection from the intake to a diaphragm pump. When the diaphragm splits oil gets pushed into the intake as a result of crank case pressure.

If your vacuum pump looks like this =>

Then it is a piston vacuum pump and the connection to the intake manifold doesn't exist

More than you are likely to ever want to know about OM61X piston vacuum pumps

Quote:

Originally Posted by leathermang

Put new valve stem seals on it.
Has the symptoms of needing those...

Indeed - valve stem seals could cause this trouble but the oil consumption is so high I think it might be a combination of several things.

A leak down test might give a better measure of engine health - just applying low pressure compressed air to each cylinder could help identify which part of the cylinder is leaking...

..."more" noise at the exhaust = leaking exhaust valve (not a path for oil consumption though)

..."more" noise at the intake = leaking inlet valve (also not oil consumption path)

..."more" noise at the oil filler cap - possibly valve stem seals but check for noise at dipstick tube

Valves need to be closed for this leak test - to check for different piston heights remove cam followers from the engine. Don't apply so much pressure in the cylinder that you simulate combustion!

#########

I had a similar problem with my non turbo OM617 - although the oil consumption wasn't as bad

OM617 manifold oil = broken valve guide

Lots of oil in the manifolds

Turned out to be a broken valve guide

I'm convinced this happened because a Mercedes "expert" used normal 14mm spanners to adjust valves