Not my car, but could be - a test drive today: 81 300TD, with about 250k on car - unknown for sure mileage on engine (says engine blew years ago when his dad had it, driving home from Vegas - did it get rebuilt, or replaced with a used unit, he didn't seem to know).

Anyway, nice straight car - garage kept claim, and rubber at base of side windows, beautiful paint, etc, back up the claim...

So, the test drive. Now, my current driver is a 365k 82 300TD, oil burner, blow-by master, and hard cold weather starter, and it's oil pressure hot at idle is 1.5 on the gauge, and jumps immediately to max as soon as I depress the pedal (at all) - so to me this would be 'normal'.

Well, the car I drove today shows oil pressure, warm at idle, just kind of wobbling around in the .5 to 1 or perhaps 1.5 range, and although there is no tach, bringing the engine speed up (no load), I guessed I had to put at least 1500 if not 1800rpm to lift the needle to 3...

It does a much more random wander, and over a much wider range than the gauge in the video here: http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1531707-1981-300-td-chattering-oil-pressure.html

I mentioned it, and the current owner said with the engine good and warm (after higher speed driving) the idle oil pressure often registers zero.

Crap - I also listened to the engine idle with the hood up, and it seemed too smooth; I like to hear some real rattle (good compression).

So, I got real excited to go drive her, and it was kind of a let down - oil pressure only 'real' concern. He also did not offer any records or receipts, or seem to know of valve adjustments, etc - strange for a car that has supposedly been in the family for a long time - harrumph!

So, what of the oil pressure? I've read lots of post this evening - if it were already mine, I'd check the filter housing o-rings, but I'm suspicious there is something more going on here... And not a situation where I can go bolting on aftermarket gauges.

Thoughts?

Ummm it doesn't sound good but it might not be an engine about to die related problem. It could be a dodgy gauge connection / even a dogy gauge.

The problem is as you say that you can't really do all that much to check or correct for yourself.

The only thing that I would do is have a look at the blow by when the engine is cold and hot. If it chuffs like an old steam locomotive then I'd be inclined to believe the oil pressure readings - but this doesn't mean because there's not much blow by there's no problem...


All in all it has got to come down to price and whether you can afford to have a new to you car not working for a while (whilst you fix it). This doesn't sound like a good one for someone who needs to drive the work for the next 10 months.

If the rest of the car is as good as you say it is and buying it fits in with your "personal situation" then I'd take a punt - an engine is an easy fix compared with structural problems.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Could also be a problem with the rubber on the oil suction cup. The four fingers of that rubber can wear off, especially if the oil pan has taken a hit, making it difficult to suck the oil out of the pan.

But it could also be a bearing with too much clearance, causing low oil pressure.

Oil pump could also be a problem.

Oil pressure reading and blow-by are not necessarely connected. You can have perfect oil pressure and lots of blow-by. Oil pressure is registered against the bearings of the crankshaft and camshaft and other oil holes. A loud diesel rattle is not necessarely related to oil pressure.

Hard to be sure of anything until you get into it. The replacement engine could have been of much greater milage than the one that failed for example. Boils down to price of the car in my mind. Little or no blowby would be nice as well on that engine but not an absolute indicator of that much with this kind of situation.

The current owner may let you check the simple stuff that might be causing low oil pressure. If it was an electric oil gauge circuit I would be happier as sensors are wear items. Unfortunatly you are a direct oil pressure to gauge feed I believe.

If you are thinking of buying the car you should assume the engine needs total rebuld. A benz has to be pretty tired for the oil pressure to be low...if it has decent oil.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

You could open the oil fill cap and see if oil is being thrown around the cam. The rapid fluctuation of the gauge is a known problem and MB came up with a fix which is a small device placed inside the oil line. There's a thread on here somewhere with pictures of someone installing the device. If the engine has been exhibiting zero oil pressure for a while and it's still running, I'd suspect a problem in the measuring device. I don't recall people with bad rod knocks mentioning a lack of oil pressure so I think it would take a REALLY badly worn engine to register zero on a well functioning gauge. You could unscrew the oil line at the filter when the gauge was registering zero to see if there's pressure or you could pull a gauge and line from a junkyard car and temporarily replace the gauge on this one to see if the reading changes.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

You could take a chance, make a real low ball offer and at worst have a cheap parts car but if you can fix it.....I'm no master mechanic but if the engine has really had that low oil pressure for long, wouldn't it be toast by now? If the car is nice, well kept and no rust, thats worth allot

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

It could be almost nothing or at the same time it could be indicating serious wear. Existing wear tends to increase faster if it is well underway. Sometime on many things I cut a deal that is dependant on what the true situation is.

This does require two honest individuals though if possible. For example one price paid now and another if the issue is minor in nature. The balance to be paid if the issue turns out to be minor in nature.

That would give more insurance to both parties but I would make the offer low enough ($450 maybe) so if the engine was toast, its OK because a good body is valuable IF the buyer can rebuild or swap an engine and if the rest of the car is truly clean/no rust. This only works if you have room, time, and a desire to ignore your MB addiction

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

I did not read the other threads close so someone may have mentioned this.

Ask the Seller if He would let you replace the 2 O-rings at bottom of the Stem on the Oil Filter Housing Cap. They could be the cause of the erratic hot Oil pressure readings.

Unforunately everyone has their own idea what a rebuilt Engine is.

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84 300D, 82 Volvo 244Gl Diesel