oil pump change M102.980 - PeachParts Mercedes-Benz Forum

emilo · #1 05-05-2004, 09:20 AM

Hi all.

Something has happened to my '84 230CE. The oil pressure is very low ie zip at idle and 1,5 at most while driving. The gauge is a manometer so I don't think it's some kind of sensor.

At my best knowlede that leaves the oil pump or maybe the "vent to prevent over pressure". Has anyone changed the oil pump on a M102?? Is it hard?? I understand it's found in the lower oil pan - Is this correct?? Anyone has any input to this and the proceedure??

Thanks - Emil

emilo · #2 05-06-2004, 04:59 AM

Anyone??

#3 05-06-2004, 08:14 AM

I hate to sound discouraging here, but you should be aware.

When an engine gets low oil pressure it is quite common and sounds quite natural to blame it on the oil pump. Unless the oil pump is completely broken, replacing it will rarely, if ever bring the oil pressure back up.

When oil pressure is low it is almost always caused by worn engine bearings. When they get too loose the restriction to oil flow decreases and thus the oil pressure decreases.

In this case it is worth checking the gauge by connecting a mechanical gauge temporarily. If the mechanical gauge agrees with the in car gauge then it is time for overhaul or at minimum exploratory surgery.

I hope you're not one to shoot the messenger.

Best of luck,

emilo · #4 05-06-2004, 09:45 AM

Thanks LarryBible, ,,

To start with - I'm not gonna shoot you

Any messenger is welcome in this case.

At which point do I temporarily install the mechanical gauge - at the instrument cluster where the ordinary gauge normaly is attached or at the point where it's connected to the engine??

I understand that there are two "over pressure vents" (don't know the correct term - sorry) as well. I guess that they will open when the pressure reaches a sertain level and that they are mechanical with some kind of spring?! Could they be faulty in any way and cause this pressure problem??

// Emil

#5 05-06-2004, 10:08 AM

Install the gauge at the engine. If you install it at the gauge, you are not eliminating all elements of the gauge that could be giving trouble.

Yes, at least on earlier engines thare are some over pressure relief valves. They are nothing more than a spring and it would be very unlikely that the spring would get weak and allow pressure to be dumped that far too low.

In the earlier engines, this relief valve was at the front of the engine in the timing chain area. There was a plug on the outside that you removed to get a socket onto the valve itself so you can remove it. You need to get some detailed prints on your engine to determine where it is.

Good luck,

emilo · #6 05-06-2004, 10:19 AM

OK,, , I'll start by messuring the oil pressure with a mechanical gauge and present the result here and then perhaps you can give me "further instructions"

Thanks again

// Emil

emilo · #7 05-12-2004, 10:56 AM

OK Larry, ,, Here's the story

I talked to a mechanic about borrowing his mechanical gauge today but he had it lend out but suggested a quick swap of instrument clusters between my 230CE(with the low oil pressure) and 230E. Just to rule out the gauge itself. When trying to start the coupé the start engine couldn't move the engine. Therefor I will tell the story from the beginning - at least try, despite my poor english. .. Please ask if something is unclear

I have, for just over a mounth, noticed that the oil pressure gauge didn't peg when the engine was started cold ,, It always has. When the RPM was higher it pegged though, (I have no RPM gauge so I can't tell the exact value) but when it shifted gears it fell to 2 and then back up to 3, following the RPM. I scheduled an oil service and told him about the oil pressure and he thought it would be ok after the service. It didn't help. However I continued driving the car dayly. The engine sounded OK exept for one or two times when it wisseled right after I started it up and I had to rew the engine so it wouldn't stop - OK again after a minute or so. .. I don't know where sound came from but it sounded lika a slipping belt or something.

Then about a week ago when I was to leave work the car didn't start. When I turned the ignition key noting happened. I heard the start engine but it sounded as if the engine was stuck and the start engine couldn't move it (or it self for that matter). Noting wrong with the battery. I tried several times but it was the same thing. After sitting in the car for a while thinking over how to get home I tried to crank the engine one last time - It started immediately (with the same wisseling noice I described above). Now the oil pressure had decreased even more. It was just above 1 bar when driving and fell to 0 at idle. I drove home and the car hasn't been started since. And today, as I said, the same thing happened - I didn't try to crank the engine again this time, afraid of making things worse.

Please help. ..

emilo · #8 05-13-2004, 10:22 AM

After a lot of thinking and discussing with other people who, just like me, haven't got a clue about this - I've got a new theory about what has happened

Larry wrote that "if the oil pump isn't completely broken. .." but what if it is?! The engine has almost 400 000 km on it. My thought is that when the car wouldn't start at all the oil pump was completely broken and wouldn't move. My guess is that the oil pump is driven by some kind of chain and if the chain is still there and the oil pump can't move - so can't the engine!

Am I completely out of target??

Anyone??