This information is specific to high miler M113 engines that have sludge and increased oil consumption.
If you decide to use a proprietary engine flush use a funnel to direct the flush towards the nearest oil return to avoid filling up the valve recesses. If you use ATF you don’t need to worry about this.
The valve recesses are here -
View attachment 2764251
if you decide to remove the valve covers and clean out some of the soft sludge manually with a suitable proprietary spray solvent, you could use kerosine but use it very sparingly, and stuff rags in the oil returns and valve recesses to protect the valve stem oil seals. Don’t let the solvent run into the camshaft/roller rocker journals or down the oil returns. Use suitable rags. A vacuum extractor would also be handy.
The decision to remove sludge deposits by using an engine flush comes down to a balance between the pros and cons.
Page 278 of your owners manual states -
‘
Do not blend oil additives with engine oil. They may be harmful to the engine operation.
Damage or malfunctions resulting from blending oil additives are not covered by the Mercedes-Benz Limited Warranty.’
It is often stated that -
‘
engine flushes can damage your engine. The chemicals in flushing additives can damage engine seals, leading to expensive repairs in the event of an oil leak. These chemicals can also damage engine bearings; (turbochargers) and other oil-lubricated components.’
Counter-argument -
Engine oil that has done 10,000km is laden with hydrocarbons, including gasoline and combustion by-products is also damaging to engine seals, engine bearings and other oil-lubricated components.
In the case regarding the M113, carbon build up around the piston oil control rings in high milers appears to be the main reason for the increase in blow-by, oil consumption, oil sludge, gasoline/hydrocarbon/moisture/acidic contamination of the engine oil.
In the link to Pelican Parts forum duxthe1 posted -
Originally Posted by duxthe1 
In the shop we only sell engine flushes on the new 112, 113 motors when they begin to consume excessive amounts of oil. When the FFS intervals get ignored the engines begin to carbon up the piston rings leading to oil consumption. If flushed before the bores get beat they usually can return to service without issues. |
Some folk are driven by their emotional attachment and will follow the manufacturer’s advice in the owners manual without question and will defend this position convincingly.
However, in the case of the M112/M113 it appears that alternative remedial interventions are probably justified and worth considering.
Regarding your other question ‘After this valve cover job I should see if there is any oil consumption?’. Answer - No. Don’t clean the sludge off the top end unless you also intend to use an engine flush.
Don’t use an engine flush unless the oil consumption has increased significantly. This is the key point.
As I said, if you notice an increase in oil consumption, you should consider using an engine flush during oil changes. The choice comes down to proprietary or ATF as recommended by others.
BEFORE using an engine flush for the first time on YOUR engine (but note what I said two paragraphs above) you should try to clean off as much of the soft carbon sludge as possible using the approach I mentioned in my previous post, simply to minimise the amount of sludge mobilised by the engine flush as a precaution. I imagine that subsequent engine flushes would probably not require this top end cleaning.
As far as what is considered to be an excessive oil consumption in the M113, refer to the link that I provided in my previous post. You ought to read up on the recommended remedial interventions in the class action law suit, and folks here would probably appreciate your feedback.
