More problems with my 240D
 

So, the situation I'm in is as such.

I was driving home on the highway, when I noticed my oil pressure was rather low (at about 0.5/3), and about 10 mins later, the car started to make a knocking noise. I began to pull over, and the car stalled, so I had to get it towed home. I was not expecting this from what is supposed to be supremely reliable car.

So, now there is no compression in the engine when it cranks. What the hell happened? What do I do?

I suspect either the oil pump has blown, or the oil pan has been leaking (unlikely, as there was no pool of oil under the car whenever I was parked, so I suspect it had to be something that has been leaking while the oil was moving around the engine, i.e. under pressure).

How far up **** creek am I?

That's bad. Did you check the oil level? You most likely ran it low on oil. How long since you last changed or checked it?

The engine is probably toast.

"Supremely reliable" yes, but only if it is maintained Its not a magic car that will just run forever with 0 care or maintenance.

First, for those reading, if you ever see your oil pressure drop from 3 bar when the car is moving and your foot is on the pedal at all, pull over immediately, you can destroy your engine in a hurry at highway speed with no oil pressue.

Chances are you've done some pretty bad damage. If you have no leaks then the only way you can loose oil is if you have blow by. Which means you've been burning oil, and slowly loosing oil. Check your oil level, then I would drain the oil and loose for metal shaving.

It sounds like you've made it all the way to the end. :(

It is a hard lesson to learn but you saw the warning and ignored it. No Engine I know of will last long with extremely low/no Oil Pressure at high rpms.

If you have Oil in the Pan it could be the Oil Pump Drive Failed (Chain, Chain Tensioner or Gears) or something happend inside of the Oil Pump to the Pressure Relief Valve or spring (I have read of problems in this areas on this forum).

If misery loves company; in the past I tried to solder the Seam on a Radiator Tank; only to have the Seam open up on the Freeway in heavy traffic.
By the time I got it off of the Freeway it was too late and I had that Knock also; due to wiped out bearings.
The good thing is it was not a Mercedes.

A lot of people never check there oil level either. That can be costly. I tell members of my family if ever a red light comes up on the dash to stop the car right there and then in a safe way.

Then try to contact me or if you cannot call a tow truck. Both approaches are more cost effective than the alternatives. If this is not done most would drive with a warning light illuminated and tell me why they thought they should continue.

Sure it may just be the alternator dropped out or whatever. I also reinforce and stress the ideal of well it will probably be okay does not apply to you. I do not want to hear it.

Now no compression the posters engine is possibly gone. It could have been too late when you first noticed the low oil pressure. This you will never know.This is why I like to see a higher pressure oil warning or two stage audio device installed. Although a low pressure that trips on at about five pounds pressure is far better than nothing.. Did you check your oil cooler hoses for any leakage?

I watch the oil pressure gauge like a hawk. I'm also tempted to install a low pressure alarm which this site thankfully has a DIY on how to do.

I have a couple of oil leaks so I check my oil pretty religiously. My motor mounts as far as I can tell are original so I take the time to see if there is a good amount of space between the power steering belt and the oil cooler lines. My worst fear is my car becoming a parts car in a matter of seconds because of me not watching my gauges.

I feel terrible for you Stuart. If you're savvy with pulling engines maybe you can fit in a donor from another car. Otherwise there isn't much one can do at this point.

I'm very sorry for your lose :(

This does not affect what has been said... which I agree with..
but as a technical side note... on some of our engines the oil pressure valve is screwed into the back of the oil pump ... so it CAN fall out ... and cause a low oil pressure situation which is easy and cheap to fix..( but fast stopping of the engine as has been described is critical ).
IF this were to happen to you instead of just putting that one back into the back of the oil pump and locktiteing it in... you should check for the latest recommended version as about three versions are available....differing I believe in the pressure readings they produce....

Possible causes of loss of compression on all cylinders could be caused by; catastrophic head gasket failure on all cylinders, holes in all pistons, Piston Rings stuck in grooves in every piston, severe cylinder scoring in all cylinders, valve(s) bent / burned / adjusted too tight / seized in guides / in all cylinders, etc.

All and all the knocking you heard is not a good sign. If you are lucky it was the sound of the piston pushing the exhaust valve shut!!:eek:

Take an oil sample from the pan and look for metal. Take the valve cover off and see what it looks like under there. Is it dry?, colored BLUE?, do the valves move freely?, how tight are they?

If the cylinders are trashed there will be plenty of evidence in the oil. If the oil is not too scary perhaps you wiped out the valvetraine from the low pressure, (the cam followers could be stuck or the valves stuck in the guides). The flow of oil is restricted to the upper end so it it would be the first to go. I would think the cam would seize in the towers before the valves would stick if not lubricated, but there is always is hope.

The immediate stopping becomes an issue of then reaching help. One easy way is to throw a $20 Tracfone in the glove box. Ive been in some pretty remote places with mine and have yet in the boonies not had a signal. You just have to remember to renew it every 90 days for another $20. Just add a lighter charger and its good to go.

Excellent help for some of our senior friends too.

Yup, if there is anyone left who doesn't have at least one phone with them 24/7 they should have one in the car.

Just to possibly make the OP feel a little better...
the 240d engine can be resleeved and repistoned for a WHOLE lot less money than a turbo engine... it does not have the annular oil ring pistons needed to keep the turbo engines cool.. so they cost way less to purchase....
Of course, finding a good junk yard engine may be a lot less expensive and last a long time.. or it could give you the leeway to take out this engine and take your time rebuilding it while driving around with the junk yard engine...
Until you take the engine apart you can not really tell how many things you need to replace...