My 94 SL500 suddenly has no oil pressure on the gauge at idle, It goes up with engine rpm and at 1,000 rpm the gauge is on 1, at 3,000 rpm it is at 3 The engine sounds and runs fine. It is looking at 200,000 miles. Has anyone experienced this problem?

 

the best we can hope for is the oil pressure switch. start there. unless she has been abused, like 50k interval oil changes. everything else can go wrong ON the engine, but inside, I doubt mechanically there is anything wrong including the oil pump and bearings (a maybe). except for the timing chain, seals she's pretty darn great. good luck on all other convenience features.

 

I have no knowledge of the history of this car. I bought it recently as a project car only because I got it real cheap. I am not opposed to pulling the engine and going through it but NOT if it is not needed. As stated the engine makes no unusual noises and does not have excessive blow by when you remove the oil fill cap. Is there a low oil pressure cut off because when the oil pressure dropped the engine quit. It started right up and I went straight home and it hasn't moved since. I grew up in my fathers auto repair shop but quit that business in '77. I have no Mercedes experience so do not know their quirks. When completed it will be used often for trips around the western states and I do not want any road trouble. Is there anything in this engine that is subject to sudden failure at this mileage? I am thinking in particular of valve train as it appears that there is probably a lot of chain and sprockets in there. The car needs much work, is there somewhere I can obtain a complete factory repair manual without selling my first born into indentured servitude? I would love to have the whole thing steam cleaned top and bottom but do not know what effect that might have on the wiring and sensors. Any insight into these things would be GREATLY appreciated.

 

steam cleaning makes me nervous, clean by hand. I don't think the rig dying is oil pressure related. check for vacuum leaks by spraying carburetor cleaner around injectors and hoses while car is running. a change of idle indicates a vacuum leak. don't spray into the air intake. www.alldata.com can help with repairs. check with www.autohausaz.com for oil pressure switch for price and what it looks like. the switch is usually found at the back of the block. kind of a tight spot but it just unscrews and has a single 2 pin wire going to it. mine is just below the oil filter and cost through autohaus about $26, lists for 100. that will be the cheapest fix. you might want to take it to a shop to get the oil pressure checked first to make sure. the diagnostic will cost from 80 to 120, for what the switch will cost ($26) you might just roll the dice. they don't charge freight if you buy over $50.00 so get some oil filters and or check your air cleaner. timing chain and chain guides are most likely in need of replacement get prices on those too.. I don't think your bearings or oil pump are bad but it is possible. if she running good I don't think you have valve problems, if she uses oil that could be valve stem seals or oil rings. if she uses oil try using a quart of transmission fluid at your next oil change or when you need a quart. run that for about 4 or 5k, it cleans out the varnish around your oil rings without plugging up the oil ports. DO NOT use an engine flush. start simple first, check for vacuum leaks.

 

btw the carburetor cleaner not only works for finding vacuum leaks it is also good for cleaning engine areas that are hard to get at, linkages, etc. steam cleaning is ok under the car or away from the motors electrical system.