Hi Neil,

Give me a ring when you get a chance. I have to discuss the mode switch with you in more detail.

Satish

Satish,

Yes, I have already replaced the oil filter checkvalve. Unfortunately it made no difference in my case.

However, removing the oil pump relief valve and then reinstalling it (after I determined that the replacement part would not fit in my oil pump) solved the problem (at least for several weeks).

While it did return, it has now dissappeared again.

I detailed in a previous thread somewhere all that I have done so far, but in summary it entails timing chains, tensioner, oil filter checkvalve, and then finally my attempt to change out the oil pump relief valve.

I'll keep everyone posted on the saga as it continues. In the interim, I just keep driving.

Keep up the revs.

Dwight

Great. Let's hope the noise still stays away. Let us know how the valve change goes when you get the correct part.

Satish

Update on my car's racka racka
 

Here's an update on my 92 500E's racka racka at 109K miles:

After I had the oil filter check valve replaced on August 8 (105K miles), the symptoms were greatly reduced, but the engine still occassionally would racka for about half a second upon cold start (well, California cold). Also, there would be occassionally erratic idle oil pressure when warm, that made me speculate that the oil pump pressure relief valve was hanging up. Also the idle oil pressure was dropping to about 1 BAR instead of its usual 1.5BAR, when warm. So I went ahead and had the dealer replace the oil pump pressure relief valve on Nov. 5 (108.8K). While in there, the tech replaced the oil pressure sender unit as well.

Replacing the oil pump pressure relief valve brought NO additional improvement to the frequency or duration of the cold start racka. It still happens occassionally, but still for not more than half a second. The erratic oil pressure has disappeared, however. The oil pressure at idle is still low. I now speculate that this is caused by my switch to Mobil 1 about three changes ago. The dealer uses 0W40 weight Mobil 1 (current Mercedes spec). My older car tends to consume a little and idle at a lower pressure with this lighter-than-original-weight oil. When I top it up with Mobil 1 15W50, it consumes less and idles at 1.5 BAR. Keeping it topped up is the key.

So I'm not sure if I got any real value out of replacing the oil pump pressure relief valve. But with the preventive maintenance I've got peace of mind and pride of ownership, as the current "curator" of this very drivable modern classic!

Have you looked into the possibility of the noise being the rocker arms? I'm not sure about the 124s, but it's common on the 126s. It's constant though, just a more pronounced "racka-racka" when it's cold.

Just a thought...

Rocker arms as in lifter noise? No, I hear a little lifter noise on cold start as well, but that sounds pretty normal to me, comparing it to the usual healthy American V8 cold starting with hydraulic lifters. The racka racka is more like reciprocating sliding steel for a moment, like a clatter rather than a tick. It goes away immediately upon the heads gaining oil pressure, rather than the lifter noise which takes a few seconds longer for the lifters to load up.

Problem fixed!!!!
 

An update on the oil pressure relief valve I installed in October. Since I've installed that $10 part, I've NEVER NEVER EVER again had the startup racka racka clatter from the cam advancers. The updated pressure relief valve with longer "fingers" in it fixed the problem completely.

This forum is great!

Satish

just an update, after all the parts replacements (previously listed) the noise finally intensified and I succumbed to replacing the oil pump (which includes a new checkvalve). Unfortunately the noise was merely lessened for a couple of days and has now returned again.

Hope all is quiet with the rest.

CRash

racka-racka
 

All the racka-racka guys might want to order a Summit Racing catalog. You can find them at www.SummitRacing.com. They have a oil accumulator, one of which can hold 3 quarts of oil. So when you go to start your engine, the electrical impulse to start opens the accumulator vavle and pressurizes the oil system.

There's an even better one in the U.K. that has an oil pump attached to the front of the starter and the starter spins up pressurizing the system and once the correct pressure is acheived the starter engages. Marvelous, but they don't export to this country.

Down with racka-racka!!

Ben

This is the procedure for changing the oil return valve on the 119 engines. The problem of audible noise during cold starts is documented in Tech Service Bulletin AF05-20-U-1400EG. As mentioned eariler, the oil filter return valve becomes leaky. Oil runs out of camshaft adjuster and oil filter housing causing low oil presure during startup - then you get the cold start noise.



Remove engine compartment panel.
Remove generator.
Unplug plug connection (10) of oil pressure sensor (11).
Unbolt oil pressure sensor (11) and remove with seal (12). Tighten to: 15 Nm.
Unbolt oil pipe (8) of air-oil cooler at oil sump.
Unbolt oil lines (7) and (8) of air-to-oil cooler at oil filter (5). Tighten to: 7 Nm.
Replace seals (9).
Unbolt oil filter (5) at crankcase. Tighten to: 25 Nm.
Remove oil filter (6) upward.
Installation Note: Clean sealing surfaces.



Replace gasket (5a).
Install in reverse sequence, observing tightening specifications and the installation note.
Check oil level in engine, adjust to correct level.
Run engine, check for leaks

Remove oil filter.
Pry circlip (17) out with a screwdriver.
Remove valve seat (12), valve cone (14) and compression spring (15).
Install valve seat (12) with extended guide with valve cone (14) and compression spring (15) (2nd version).
NOTE: Standard set oil return check valve with improved sealing properties as of engine no.:
119.970 12 029 923
119.971 12 015 069
119.972 12 002 097
119.974 12 006 973
119.975 12 007 964